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Item Embargo Diversity and species overlap of Botryosphaeriaceae on some trees of Anacardiaceae in disturbed and undisturbed ecosystems in South Africa(2025-05-16) Ramabulana, Elelwani; Ogola, J. B. O.; Kunjeku, E.; Coetzee, M. P. A.; Slippers, B.The Botryosphaeriaceae are common and diverse on native and non-native plants. It has been established that the ability of Botryosphaeriaceae fungi to exist in healthy plant tissues as endophytes facilitates their global movement during the international trade of plants and plant products. It is important to understand whether fungi in the Botryosphaeriaceae have a restricted host range or a limited geographic distribution once introduced into new areas, and how ecosystem disturbances through human activities influence species diversity and distribution of fungi in the Botryosphaeriaceae. The current study explored Botryosphaeriaceae species diversity on native and non-native tree species of Anacardiaceae found in disturbed and undisturbed ecosystems, as well as species overlap of the Botryosphaeriaceae as endophytes and as pathogens in asymptomatic and symptomatic tissues of these trees. In addition, the genetic diversity and population structure of N. parvum, the dominant species occurring on asymptomatic mango fruit were assessed. These questions were addressed by sampling three tree species of Anacardiaceae, namely Sclerocarya birrea (marula), Mangifera indica (mango) and Lannea Schweinfurthii (false marula) in disturbed and undisturbed ecosystems in the Limpopo and Mpumalanga provinces, South Africa. The ecosystem disturbance study identified 11 species of Botryosphaeriaceae, namely Diplodia allocellula, Dothiorella brevicollis, Dothiorella dulcispinae, Dothiorella viticola, Lasiodiplodia crassispora, Lasiodiplodia exigua, Lasiodiplodia gonubiensis, Lasiodiplodia mahajangana, Neofusicoccum parvum, Oblongocollomyces ednahkunjekuae and Oblongocollomyces sp. 1 occurring on native and non-native Anacardiaceae in disturbed and undisturbed ecosystems. Ten of the 11 species were identified on trees in undisturbed ecosystems, while three were identified on trees in disturbed ecosystems. Lasiodiplodia crassispora and L. mahajangana were generalists on trees in disturbed and undisturbed ecosystems. The results from this study also indicated the ability of some species to cross-infect native and non-native Anacardiaceae growing next to each other. For example, N. parvum isolates occurred on both S. birrea (a native species) and M. indica (a non-native species) trees adjacent to each other in disturbed ecosystems. An investigation on species occurrence of the Botryosphaeriaceae as endophytes and as pathogens on the Anacardiaceae identified 12 species of Botryosphaeriaceae, D. allocellula, Dothiorella brevicollis, Do. dulcispinae, Do. viticola, Lasiodiplodia crassispora, L. exigua, L. gonubiensis, L. mahajangana, L. pseudotheobromae, Neofusicoccum parvum, Oblongocollomyces ednahkunjekuae and Oblongocollomyces sp. 1 in asymptomatic and symptomatic tissues. Dothiorella dulcispinae, L. exigua, L. gonubiensis, Oblongocollomyces ednahkunjekuae and Oblongocollomyces sp. 1 were exclusive to asymptomatic Anacardiaceae, while D. allocellula, Do. brevicollis, Do. viticola, L. crassispora, L. mahajangana and N. parvum occurred in asymptomatic and symptomatic Anacardiaceae indicating the ability to occupy healthy plant tissues as latent opportunistic pathogens on these trees. The N. parvum population genetics data was assessed based on nine microsatellite markers. This study indicated that the N. parvum population consists of three distinct genetic clusters characterized by high levels of genetic diversity. The three clusters were not correlated to host or geographic location indicating the lack of barrier on the movement of the fungus between the hosts and locations sampled. The study highlights the potential of mango fruit to serve as a source of international spread of Botryosphaeriaceae, especially of N. parvum.Item Embargo Effect of biofertilizers on phosphorus nutrition and grain yield of des chickpea (Cicer arietinum L.) grown in different agro-ecologies(2024-09-06) Mashishi, Sina; Ogola, J. B.O.; Odhiambo, J. J. O.; Maseko, S. T.South African soils are predominantly acidic and have high levels of Al and Fe, giving a higher P sorption capacity and low P levels. Consequently, soil fertility has become a major constraint in South Africa’s farming, thereby threatening crop production and food security. Literature reveals, however, that biofertilizers have the potential to improve crop growth, grain yields and, acid and alkaline phosphatase activities in both the plant tissue and soil. Nonetheless, there is scant information about the biofertilizers’ effects on their co-application with rhizobium inoculation as most of the studies focused on the sole application of the biofertilizers such as Bontera, Kelpak, Mycorrhiza, and Rhizobium inoculation. This study evaluated the biofertilizers’ effects on the phosphorus accumulation in the rhizosphere soil, the acid and alkaline phosphatase activity in the rhizosphere soil and, the two chickpea genotypes’ growth and yields under different environments. In 2019, three field experiments were conducted in three locations, namely Thohoyandou, Syferkuil, and Sikhwahlane, and two more were done at Thohoyandou and Syferkuil in 2021. The treatments consisted of a factorial combination of six biofertilizer levels (Mycoroot, Kelpak, Rhizobium inoculation, Kelpak+Rhizobium inoculation, Mycoroot+Rhizobium inoculation, zero control) and two chickpea genotypes (Accession 3 and Accession 7). These were arranged in a three-time replicated randomised complete block design. The intercepted radiation’s (IR) proportion was measured using the AccuPAR LP-80 ceptometer at Thohoyandou in 2019 and 2021. The chlorophyll content was measured at vegetative and reproductive stage using a chlorophyll meter (CCM-200 PLUS, Opti-Science) at Thohoyandou and Syferkuil in 2021. The stomatal conductance (gs) was measured using a portable porometer (AP4 DELTA-T Device) at the vegetative and reproductive stage at Thohoyandou in 2021. The normalised different vegetation index (NDVI) was measured using the portable GreenSeeker at the vegetative stage at Thohoyandou and Syferkuil in 2021. The chlorophyll fluorescence was measured at the flowering stage using the portable chlorophyll fluorometer at Thohoyandou, Syferkuil, and Sikhwahlane in 2019; and at Thohoyandou and Syferkuil in 2021. The acid and alkaline phosphatase activities were measured at the flowering stage at Thohoyandou, Syferkuil, and Sikhwahlane in 2019, and at Thohoyandou and Syferkuil in 2021. The inorganic phosphorus was measured at the flowering stage at Thohoyandou and Syferkuil in 2021. The yield and yield components (pod weight, shoot biomass, and harvest index) were measured at the harvest maturity stage at Thohoyandou, Syferkuil, and Sikhwahlane in 2019, and at Thohoyandou and Syferkuil in 2021. Data were analysed for variance (ANOVA) using the STATISTIX (2017) version 10.0. The Tukey’s honestly difference (HSD) test was used to separate the means that were significantly different (P≤0.05). The Pearson correlation was used to test the linear association’s strength between the parameters studied. The biofertilizers significantly increased the intercepted radiation’s proportion (%IR) at Thohoyandou in 2019 and 2021. The Kelpak sole and in combination with the rhizobium inoculation on 61DAE (86.71) and 75DAE (85.10) recorded the highest %IR in 2019 cropping season. The rhizobium inoculation recorded the highest %IR at 47DAE (50.17) & 83DAE (80.67) and the Kelpak+Rhizobium inoculation recorded the highest %IR at 61DAE (54.33) & 75DAE (68.67) in the 2021 cropping season. The genotype had no significant effect on %IR in both seasons but the interaction between M x accession7 gave the greatest proportion of the intercepted radiation in 2019. The chlorophyll content was significantly increased by the biofertilizers at Thohoyandou (clay soil) only in 2021 with the Kelpak combined with rhizobium inoculation recording the greatest chlorophyll content (2.13-3.10) in all measurement dates. However, the genotype affected the chlorophyll content at 74DAE with accession7 recording the highest chlorophyll content compared to accession3. However, the interaction between the biofertilizer and the genotype had no significant effects on the chlorophyll content in all sites. The stomatal conductance was significantly affected by the biofertilizer application with K+R recording the highest gs at 42DAE (529.25) and M+R recording the highest gs at 56DAE (473.08) at Thohoyandou in 2021. Both the genotype and interaction between the biofertilizer and the genotype significantly affected the gs at 70DAE with accession3 recording the highest gs compared to accession7, and the Mycoroot x accession3 recording the highest gs. The normalised difference vegetative index was significantly increased by the biofertilizer application at 28DAE & 42DAE at Syferkuil only (sandy soil) with Mycoroot and K+R recording the highest NDVI at 28DAE (0.56) and rhizobium inoculation and M+R recording the highest NDVI at 42DAE (0.68). Neither the genotype nor the interaction between the biofertilizer and the genotype had a significant effect on the NDVI in all sites. The biofertilizer’s application significantly affected the acid and alkaline phosphatase activities in all sites except at Syferkuil in 2021 where the biofertilizers had no significant effect on the alkaline phosphatase activity. The co-application of K+R gave the highest APase at Syferkuil (sandy soil) and Sikhwahlane (loamy soil) in 2019, while at Thohoyandou (clay soil) the co-application of M+R gave the highest APase. In 2021, the co-application of K+R gave the highest APase at Syferkuil and Thohoyandou. The alkaline phosphatase activity was higher with the application of rhizobium inoculation at Syferkuil and Thohoyandou in 2019, and higher with the co-application of M+R (13.03) in Sikhwahlane in 2019. However, the zero control gave the highest AlkPase activity (74.14) at Syferkuil in 2021. At Thohoyandou (2021), however, the Kelpak’s application recorded the highest AlkPase activity (56.81). Inorganic phosphorus was significantly affected by the biofertilizers in both sites. The co-application of K+R recorded the highest inorganic phosphorus at Syferkuil and the sole Kelpak (15.16mg/kg) gave the highest inorganic phosphorus at Thohoyandou in 2021. The genotype had no significant effect on the APase and AlkPase activities but significantly affected the inorganic phosphorus at Syferkuil with accession3 (55.61mg/kg) recording the highest Pi compared to accession7. The interaction between the biofertilizer and the genotype affected the APase and inorganic at Thohoyandou, and only the Pi at Syferkuil in 2021. Among the various biofertilizers used at Thohoyandou, the rhizobium inoculation recorded the highest quantum yield of PSII (0.24 to 0.33) in 2019. The biofertilizers, however, significantly affected the PSII, Fv/Fo, and Fv/Fm at Syferkuil in 2021 with the rhizobium inoculation exhibiting the highest PSII, Kelpak exhibiting the greatest Fv/Fo, and the sole Mycoroot and Mycoroot combined with the rhizobium inoculation exhibiting the strongest Fv/Fm. Among the biofertilizers administered at Thohoyandou, the Kelpak and rhizobium inoculations gave the highest PSII, and the Kelpak sole gave the greatest Fv/Fo. The genotype significantly affected the minimal fluorescence (Fo) in Sikhwahlane in 2019. It was pronounced in accession7 than in accession3 and the genotype affected the Fv/Fm at Syferkuil and was more pronounced in accession7 than in accession3. In 2019’s cropping season, the biofertilizers increased the pod weight and grain yields at Thohoyandou to above-ground biomass and grain yield at Syferkuil, and pod weight to above-ground biomass and the grain yield in Sikhwahlane. In both sites in 2021, the biofertilizers increased the above-ground biomass, harvest index, and grain yield. Accession7 gave the highest value of pod weight at Syferkuil’s cropping season in 2021. The interaction between the biofertilizer and the genotype had no significant effect on the grain yield and yield components in all the locations and in both cropping seasons. Therefore, this makes the biofertilizers an effective tool for increasing the chickpea’s yield in these regions.Item Embargo Effect of biochar derived from different feedstocks on nitrogen retention availability, and uptake by a maize crop(2024-09-06) Khethani, Thakhani; Odhiambo, J. J. O.; Lusiba, S. G.Nitrogen (N) is an essential nutrient for most crops and can be provided directly by fertilisation or indirectly through atmospheric deposition, fixation, all of which can then be converted to nitrate through mineralization and nitrification. Incomplete N utilisation by crops leaves residual soil nitrate, which is water soluble and susceptible to leaching into groundwater, particularly in regions dominated by light-textured sandy soils with low WHC. Application of biochar (BC) can potentially have a significant impact on nitrogen retention and availability. BC is a charcoal-like substance that’s made by burning organic material from agricultural and forestry wastes (also called biomass) in a controlled process called pyrolysis. Biochar can increase organic matter content, act as a liming agent, add basic cations and micronutrients, improve water holding capacity, and release nutrients gradually to the growing plant. This study evaluated the effect of BC derived from different feedstock on nitrogen retention and availability. Two experiments’, laboratory (column leachate) and nursery experiments were conducted at the University of Venda Soil Science Laboratory and the School of Agriculture Experimental Farm, respectively. The treatments in both experiments 1 and 2 consisted of a factorial combination of BC from three different feedstocks (acacia, hay, and poultry litter) and three BC application rates (0%, 1%, and 2%). In experiment 1, the levels of NH4+ and NO3- leached from and retained in the soil were determined in the laboratory experiment before and after 70-day leaching period. The columns were first filled with three kilograms of the soil-BC mixture based on the previously mentioned treatments, giving rise to an initial bulk density of roughly 1.5 g/cm3. A single fertiliser application with 100 mg of solutioned ammonium nitrate (NH4NO3) was applied to each column. The fertilizer was applied to each column's surface in uniform drips after being diluted in 5 millilitres of distilled water. In the laboratory, the columns were maintained at room temperature, or roughly 23 °C. Every two weeks, 200 ml of distilled water was added to each column through a funnel that was placed above the center of each column. To aid in the dispersal of the water drips, filter papers were placed on the soil surface of the columns. Columns were allowed to drain freely during the leaching process, and all leachate samples were collected in foil-wrapped Erlenmeyer flasks to minimize evaporative loss. For 10 weeks (seventy days), columns were leached every two weeks. Every two weeks, the leachates were collected and chilled before analysis to minimize the growth of algae. Leachates were collected every two weeks, and the pH and electrical conductivity (EC) were measured. The leachate samples were then filtered through Whatman No. 42 filter paper to measure the amounts of nitrite (NO3-) and ammonium (NH4+). In experiment 2, which was conducted in a nursery, 5 kg of soil was placed in pots measuring 25 cm in height and 25 cm in diameter. Maize (Zea mays L.) was used as a test crop and harvested 56 days after planting. xviii The measurements made in this experiment were dry matter (kg) and nitrogen uptake (kg/ha). A uniform application of nitrogen fertilizer (LAN) at a rate of 100 kg N/ha was given to each pot. The soils were treated with BC as per the stated application rates and ammonium nitrate fertilizer one week prior to planting. The treatments were arranged in a completely random design (CRD) The pots were wetted to 60% field capacity (FC) and allowed to dry out for 24 hours prior to planting. Three maize seeds were planted in each pot. After watering, the pots were filled to 60% of their field capacity (FC). After being allowed to develop for a maximum of eight weeks (56 days), maize crops were collected, dried, weighed, ground, and the N content determined. In experiment 1, the current study's findings show that using BC can significantly reduce the leaching of highly mobile nutrients like NH4+ and NO3-. The total amount of leachates collected increased by 46% and 42% at the 1% and 2% biochar application rates, respectively. The amount of ammonium and nitrate retained increased by 1.62% and 16.2% at a 2% rate of application, respectively. In comparison to the control, where no BC was added, BC significantly reduced ammonium leaching at 1% on days 56-70 and 2% (w/w) in BC-amended soils. Biochar increased EC in all BT and retained NH4+ and NO3-. In experiment 2, this study has shown that feedstock type significantly affects biomass accumulation and N uptake. Biomass yield and N uptake increased in the order poultry litter > acacia > hay. Increasing biochar rates from 0 to 2% increased biomass accumulation and N uptake. In summary, biochar type and rate of application have a potential effect on N leaching and retention in the soil, as well as the biomass and N uptake and therefore these factors should be considered when biochar is used as a soil amendment, especially for N management in agricultural systems.Item Embargo Evaluating rhizosphere soil microbes, grain yield and nutritional composition of two legume species in farmers' fields in four Municipalities of Vhembe district.(2024-09-06) Matidze, A.; Ogola, J. B. O.; Mokgehle, S. N.; Araya, H. E.Despite the nutritional value and the amounts of N that legumes contribute to the soil, few studies have evaluated rhizosphere soil microbes, grain yield and nutritional composition of indigenous legumes in the fields of South African farmers. To explore the variations in grain yield, rhizospheres soil microbes and nutritional composition in Bambara groundnut and cowpea species, this study evaluated two legume species under five farmer's fields conditions at four locations (Thulamela, Musina, Makhado and Collin Chabane) in the Vhembe district regions of Limpopo province, South Africa during the 2021/2022 summer cropping season. Ten of each Bambara groundnut and cowpea were sampled at 75% physiological maturity from each farmers’ field to determine growth yield and yield components, nutritional composition, and mineral content variations. Ca, K, Mg, Na, B, Cu, Fe, Zn, and protein levels were determined in ground pods and leaves. The rhizosphere soil samples were from 15 cm soil depth. Soil microbial diversity was determined using Carbon Source Utilisation Profiles (CSUP) BIOLOG™ GN2 plates. The abundance and richness of the soil microbes were also determined using the Shannon-Weaver and Evenness diversity indices. The collected data showed significant (p≤0.05) differences in plant dry matter (DM) yield, number of pods, pods dry weight and number of nodules from different farmer’s fields. The high temperature reported in Musina, which exhibited higher growth and yield for Bambara groundnut compared to the other municipalities, indicates the different sites' climatic conditions. A positive correlation was observed between monthly maximum temperature and dry matter for Bambara groundnut (r2 =0.33) and cowpea (r2=0.30). In Makhado municipality, the data showed increased dry matter (144.3 g/plant) and the least in Musina (68.3 g/plant). The legume species studied exhibited differences in the grain protein fractions' profile and grain mineral content. The two species grains showed considerable significant variation for the following nine mineral contents (mg/g dry matter) obtained for the micro minerals of Bambara groundnut Na 897 mg/kg, Fe 534 mg/kg and Zn 35 mg/kg. Cowpea Na 219 mg/kg, Zn 45 mg/kg, and B 31 mg/kg, and for the macro minerals: Bambara groundnut K 1.55 mg/kg, Ca 0.16 mg/kg, Mg 0.21 mg/kg, P 0.26 mg/kg. Cowpea K 1.30 mg/kg, Ca 0.21 mg/kg, Mg 0.25 mg/kg, and P 0.36 mg/kg. The significant difference in Shannon Weaver Diversity Index (H’) (i.e., the ability of the microbial community to degrade more or fewer types of carbon sources at a threshold ODi value ≥ 0.25) was observed for samples in cowpea species under Makhado location, which could degrade more types of carbon sources. Statistically significant utilisation was detected for all five groups of carbon sources. The microbial communities detected the highest AWCD for utilising all carbon sources (carbohydrates, carboxylic acids, amino acids, polymers and amines). This soil diversity and richness is an indicator of the quality of the soil to increase crop yields and agricultural production. Additional research is needed to determine the microbial diversity and activity yield variations, nutritional composition, and mineral elements of Bambara groundnut and cowpea species.Item Open Access Investigations of various agro-wastes as substrates for cultivation of oyster mushrooms (Pleurotus ostratus (Jacq: FR) P. Kumm And Pleorotus pulmonarius (Fr.)(Quel)(2023-10-05) Matidza, Takalani Lorreta; Mchau, G. R. A.; Adesoye, P. O.This study was conducted to assess the effects of various agro-waste substrates on the production of oyster mushrooms (P. ostreatus and P. pulmonarius). The substrates utilised in this research were banana pseudo-stems (BP), macadamia husks (MH), macadamia nutshells (MnS) and maize stalks (MS) as control. The experimental design used in study 1 was a complete randomized design (CRD) for chemical constituents with 3 replications (rep) and 2 bags per rep. In contrast, the experimental design on study 2 was factorial in a complete randomized design comprised of mushroom growth and yield replicated thrice and bags duplicated per rep. Study 3 was nutritional compositions replicated three times, having 2 bags per rep. The maximum pH was observed on MS and the minimum was obtained on MnS. Severe infections by Trichoderma species were observed from PO Pleurotus ostreatus (PO) and Pleurotus pulmonarius (PP) on MnS, and as a result, no fruiting bodies were formed. The growth in terms of the number of days to colonization (DC) was delayed on MH when compared to others. The yield was significantly superior on MS 75.73 and 94.40 g during March to May 2019 in terms of fresh weight (FW). Moreover, the highest yield was observed on MS and BP at 120.19 and 92.63 g from P. ostreatus and P. pulmonarius respectively during June to August 2019. The superior biological efficiency) (BE) was attained from mushroom grown on MS during March to May 2019 whereas on MS and BP was during June to August 2019. The least FW and BE was observed from P. ostreatus and P. pulmonarius grown on MnS. The maximum crude protein (CP) was obtained from PO and PP on MH. Mushrooms are enriched in potassium (K), and the maximum amount was found on MS when compared to others from both Pleurotus species. Therefore, MS and MH were best selected to produce Oyster mushrooms.Item Open Access Effect of water stress and soil texture on growth, yield and quality attributes of potatoes (Solanum tuberosum L.)(2023-10-05) Hlatshwayo, Cypriel Mfundo; Mzezewa, J.; Odhiambo, J. J. O.Potato (Solanum tuberosum L.) is an annual dicotyledonous tuber herbaceous crop. The crop is relatively susceptible to water stress when compared to other major field crops. Soil texture plays a pivotal role in the correlative relationship between climate, soil, and vegetation, which are dependent on soil moisture dynamics and in correlation to vegetation water stress. This study investigated the effects of water stress and soil texture on potato growth, yield, and quality attributes. The pot experiment was conducted during the 2021(spring)/2022(winter) cropping seasons in a plastic tunnel at the University of Venda (UNIVEN) Experimental Farm situated at Thohoyandou. The experiment was laid out in a Completely Randomized Design (CRD) with two potato cultivars (Mondial and Bp1), three soil textural classes (clay, sandy clay loam, sandy loam), and three water stress levels (30%FC (field capacity), 60%FC,100%FC) with three replicates making a total of 54 experimental units (polyethylene pots). Data collected was subjected to ANOVA using Minitab 21. Water stress × soil texture interaction had a significant (p<0.05) effect on plant height at 51 DAP (days after planting) to 72 DAP, and from 44 DAP to 86 DAP during the 2021/2022 cropping seasons, respectively. The interaction of water stress and soil texture had a non-significant (p>0.05) effect on leaf area. Water stress × soil texture interaction had a significant (p<0.05) effect on stem diameter at 93 DAP, and 65 DAP during the 2021/2022 cropping seasons, respectively. There was no significant (p>0.05) interaction effect between water stress and soil texture on marketable potato yield during the 2021 cropping season, but the interaction had a significant (p<0.05) effect during the 2022 cropping season. This study suggested that severe water stress (30%FC) could be adopted for potato cultivation in winter season. The tuber sizes and shapes produced during the 2021 cropping season were observed to be smaller (<55mm) and short-oval (1.10 to 1.29) to oval (between 1.30 and 1.49). However, during the 2022 cropping season tuber sizes and shapes obtained larger tuber sizes (≥75mm) and long oval (between 1.50 and 1.69) to long (≥1.70). The specific gravity (1.05 -1.07) was suitable for the potato tubers to be used for processing. The skin colour of the Bp1 and Mondial cultivars were yellowish, while flesh colours were light yellow making them suitable for consumers and the market. Therefore, the results suggest vi that 30%FC irrigation water level can be economical for production during the winter season in semi-arid region regardless of the soil texture type (clay, sandy loam, and sandy clay loam).Item Open Access Using genotypic diversity to enhance climate resilience of peanut cropping in Limpopo Province(2023-10-05) Mulaudzi, Ntakadzeni Rose; Odhiambo, J. J. O.; Brancho-Mujica, G.Groundnut or peanut (Arachis hypogaea L.) is mostly grown by small-holder farmers in semi-arid regions of sub-Saharan Africa, particularly South Africa. As with other crops, not all groundnut cultivars respond equally well to the various climatic conditions in the South African province of Limpopo due to different environmental factors. Abiotic stress factors such as drought, extremely high temperatures, unpredictable and insufficient rainfall with annual variation that cannot be accurately predicted are limiting groundnut production in South Africa. In order to increase groundnut production, it is necessary to design properly the management practices, such as season and site-specific exploitation of cultivar x location x management (C x L x M) interactions, which will minimize the impact of the low rainfall and high temperature that characterize the production, particularly in Limpopo Province. The objective of this study was to assess the effects of groundnut cultivar on groundnut performance, soil water use and mineral nitrogen levels under different climatic conditions in Limpopo Province. A further objective was to validate the performance of Agricultural Production Systems Simulators (APSIM) model to predict the observed yields of groundnut cultivar yields under variable environmental and climatic conditions in Limpopo Province. Field experiments were conducted at two locations, the University of Limpopo (Syferkuil farm) and the University of Venda experimental farm during the 2018/2019 and 2019/2020 growing seasons. The experiments were laid out in randomized complete block design (RCBD) consisting of four treatments (groundnut cultivars: Kwarts, Sellie, Opal and Oleic) replicated four times to give a total of 16 plots each measuring 4 m × 3 m (12m2). Soil mineral nitrogen and dry biomass were determined at 50 % flowering and harvest maturity. Grain yield was collected at maturity and soil water content was determined every two weeks during the growing period using the gravimetric method. The APSIM-groundnut model (version 7.10) was used to simulate groundnut cultivars grain yield and biomass production to assess the risks associated with different climate conditions on the yield production of groundnut crops. The results obtained from this study showed that the groundnut cultivar influenced measured parameters (grain, nodulation and yield components) at both locations, whereas the effect of cultivar on biomass, soil moisture and mineral nitrogen was significant only at Syferkuil site. There was a significant difference in the cultivar and cultivar x location interaction on pods and seeds yield, harvest index and shelling percentages. Sellie produced a higher seed yield at Univen, while at Syferkuil Oleic produced the highest seed yield. The cultivar Opal performed well while Kwarts produced low yield in both seasons and locations. Irrespective of cultivar performance, Syferkuil produced less biomass and grain yield compared to Univen due to prolonged dry conditions over the seasons. The results further showed significant variation in soil water content at different depths among the cultivars and soil water content increased with soil depth. Cultivars with high biomass had high soil water content than those with low biomass at all soil depths. It was notable that cultivars with higher biomass showed a higher level of NO3--N and NH4+-N at all depths. At Univen, the soil NO3--N and NH4+-N levels increased at harvest while at Syferkuil NO3--N and NH4+-N decreased at harvest. The results demonstrated the benefits of soil moisture content on groundnut growth and soil mineral nitrogen. APSIM-model showed some capabilities of simulating groundnut grain and biomass yield in response to groundnut cultivar and different environments over the two locations that were simulated in both seasons. Therefore, in these locations, the APSIM model might be a helpful tool for predicting groundnut productivity.Item Open Access Conservation agriculture and slope position effect on selected soil physical properties of a Vertisol at Tshivhilwi in Limpopo Province(2023-10-05) Tshilonga, Mushe Moses; Mzezewa, J.; Odhiambo, J. J. O.Conservation agriculture (CA) is a production system that involves three principles which are minimal or zero tillage, crop rotation and mulching with plant residues. CA improves soil physical properties resulting in soil fertility improvement. However, there are relatively few studies that have documented the benefits of CA on soil physical properties of vertisols. A study was conducted to determine the influence of CA and slope position on soil bulk density (BD), total soil porosity (Vf), soil aggregate stability (AS), soil water holding capacity (WHC), soil organic carbon (SOC), soil electrical conductivity (EC), infiltration rate (IR) and cumulative infiltration (CI) of a vertisol, at Mutanga Wa Ndodzi Agricultural Co-operative at Tshivhilwi village where CA has been in practice since 2013. The farm practices CA with crop rotation. The field used for CA was tilled once in 2013 using a mouldboard plough. Mulching is done using maize stalks. After planting fertilizer was applied based on crop requirement. One set of soil samples were collected from a field under CA while another set was collected from a field under natural grass (control) which is located directly opposite the CA field. Soil samples were collected 10 m apart from 0-10 and 10-20 cm depths along the transects which were at, 10 m apart. A core of diameter of 5 cm and height of 5 cm was collected to determine soil BD. SOC was determined using the modified Walkley-Black wet oxidation procedure. EC was measured with glass electrode professional EC meter in 1:5 ratio soil water suspension. Soil AS was determined using wet sieving method. Soil particle density was determined using a pycnometer bottle after which the bulk density and particle density of the soil were used to calculate soil porosity. Soil WHC was determined by saturating with water 25 g of oven-dried soil in a glass funnel and its water holding capacity determined by gravimetric method. Management and slope position interaction had a significant effect at 0-10 cm and 10-20 cm soil depth with lower BD at the CA site lower slope position at 0-10 cm soil depth. SOC was significantly higher on lower and middle slope of CA than natural grassland (NG) site. The CA site x recorded higher EC at the middle and lower slope positions compared to NG site. Higher AS was observed at the CA site than NG at all slope position at 0-10 cm soil depth, at 10-20 cm CA site recorded higher AS at the lower and middle slope. Vf was significantly higher at the CA site than NG site at all slope positions, CA lower slope was associated with higher Vf followed by middle and summit slope. CA site exhibited a higher WHC than NG site at all slope positions, CA middle lower slope positions had the highest WHC. Interaction effect was observed on final IR however, the significant difference between the two-management system was observed at lower and middle slope. Conservation agriculture and slope position interaction in this research resulted in significantly higher BD, SOC, EC, AS, vf and WHC but had no effect on BD middle slope and summit slope positions at 0-10 cm, SOC summit and lower slope positions at 10-20 cm soil depth, EC summit slope at 0-10 cm, vf at summit and middle slope at 10-20 cm soil depth and WHC lower slope lower slope position at 10-20 cm soil depth. According to the findings of this study, practicing conservation agriculture in various slope positions could be recommended to improve soil properties (bulk density, soil organic carbon, soil electrical conductivity, aggregate stability, total soil porosity, water holding capacity and infiltration rate) of a Vertisol.Item Open Access Evaluating the Effect of Intercropping Maize (Zea mays L.) with Different Lablab (Lablab purpureus L.) Cultivars on Yield, Soil Water Content and Soil Nitrogen in Dry Environments of Limpopo Province using APSIM Model(2023-10-05) Thaba, Rebotile Sophy; Odhiambo, J. J. O.; Bracho-Mujica, G.Smallholder maize production systems are characterized by continuous maize monoculture production, which often leads to soil degradation, nutrient depletion and increased risk of pests and diseases. The cropping system is characterized by low yields that continue to decline due to soil degradation and increased temperatures coupled with poor rains. The integration of drought tolerant crops, such as lablab, into predominantly maize monoculture systems presents a better alternative to maize monoculture. Lablab is native to Africa but remains overlooked in many countries including South Africa, due to lack of information and access to seeds. Crop models, such as APSIM, are useful decision-making tools for investigating crop adaptability to various climates, management, and cropping systems. The objective of this study was therefore to assess the performance of maize and lablab under sole and intercropping systems and to evaluate the capability of APSIM to simulate crop yields in dry environments of Limpopo province, South Africa. Field experiments were conducted at the University of Limpopo Experimental Farm (Syferkuil) (2018/2019) and at University of Venda Experimental Farm (Univen) (2018/2019 and 2019/2020). Treatments consisted of maize cultivar (DKC-2147) and three lablab cultivars (DL-1002, Rongai (brown) and Q-6880B) planted as sole crops and intercrops. The treatments were laid out in a randomized complete block design with three replicates. Maize and lablab dry biomass (roots and shoots) and grain yield were assessed. Biomass was evaluated at respective flowering and harvest maturity dates for lablab and maize. Harvest index (HI) and land equivalent ratio (LER) were determined from shoot biomass and grain yield collected at harvest maturity. Soil mineral nitrogen (SMN) and soil water content (SWC) were determined at different maize growth stages. Biomass and grain yield of maize-lablab intercrops was evaluated using APSIM and observed data collected from the field experiments. Data obtained was subjected to analysis of variance using the general linear model procedure of Statistix software version 10.0. Means were compared using critical values of comparison at a 5% level of significance. Intercropping maize with lablab reduced maize roots biomass at Syferkuil by 10% and increased shoots biomass and grain yield by 17% and 19% at Univen in 2018/2019 and 2019/2020, respectively. Lablab cultivars had no effect on LER in both sites. DL-1002 and Rongai had roots and shoots biomass of 117-143% and 212-250%, respectively, greater than Q-6880B at flowering. Cropping system significantly affected lablab grain yield, root and shoot biomass at flowering and harvest, and HI. Intercropping reduced roots biomass, shoots biomass, grain yield and HI of lablab cultivars by over 50% compared to monocropping. Cropping system was highly influential on SMN and SWC, and the highest concentration of SMN was observed in maize monocropping at flowering and, lablab monocropping and vi maize/lablab intercrops at harvest. Generally, the levels of SMN were greatest in the topsoil depth (0-15 cm). Maize-lablab intercropping had no effect on SWC at both sites. Sole lablab increased SWC by over 13% across locations. Contrary to SMN, SWC was highest at lower soil depth (30-60 cm). APSIM model accurately simulated maize grain yield and shoot biomass. However, the model had difficulties in simulating lablab grain yield and shoot biomass, with overestimations and underestimations of 4-132% and -49.9-98.6% for biomass and grain yield, respectively, across the sites. The highest overestimations were observed for maize-lablab intercropping. The results of this study showed that intercropping maize with lablab has the potential to sustain maize yields with minimal inputs. Intercropping significantly reduced lablab yields at both locations, however, the biomass and grain yields obtained improved overall productivity of the intercropping system. Results of SMN and SWC support the potential of lablab use to improve soil N and conserve SWC. APSIM was able to simulate maize shoots biomass and grain yield but highly overestimated and underestimated lablab shoots biomass and grain yield. This suggests limited capacity of APSIM-lablab to simulate lablab biomass and grain yield under rainfed conditions in the dry areas of Limpopo province, thus the need for further research. Overall, intercropping maize with lablab showed positive results in maintaining and increasing maize yields over time at Univen, demonstrating that maize-lablab intercropping is a viable system to integrate into maize cropping systems to improve maize yields and land productivity in Limpopo province.Item Open Access The effect of various selected shade nets on field-grown bush tea’s physicochemical and antioxidant properties (Athrixia phylicoides DC.)(2023-10-05) Ramenu, Khuthadzo; Mchau, G. R. A.; Ramphinwa, M. L.; Mashau, M. E.Bush tea (Athrixia phylicoides DC.) is an indigenous herbal tea plant in South Africa with medicinal potential. Various parts of this plant are used to make herbal infusions and have been used traditionally for different purposes, including treating other diseases owing to the presence of pharmacologically active metabolites and antioxidants that are believed to be the active ingredient in the plant. However, knowledge of the manipulation of agronomic practice to enhance the accumulation of physicochemical antioxidant properties is not yet present. Therefore, this research was aimed at evaluating the effects of various shade nets colours and light intensities on the physicochemical, polyphenols and antioxidant activities of field grown bush tea leaves. The field experiment was conducted during the 2018 and 2019 autumn seasons at the University of Venda, School of Agriculture. Three replicates of the experiment were conducted using a Randomized Complete Block Design (RCBD) with three distinct degrees of light intensity (i.e., 40%, 50%, and 80%), three shade nets (specifically, black, green, and white) and full sunshine (control, 100%). The individual plots were each 4.8 m x 4.8 m in size. There were 24 plants per plot, with each plot having four plant rows spaced 1.2 m apart and 0.75 m apart within each row. When necessary, a drip watering system was applied to irrigate the plots except during rainy periods. When necessary, weeding was done manually using a hand hoe throughout the cropping seasons. To protect the plants from termites, methamidophos was sprayed at a concentration of 10 mL per 20 L immediately following each weeding session. At the end of the season, the leaves were harvested by cutting the base of the stem and placed inside brown paper bags and stored in the shade at room temperature to allow shade drying process as it is the best method for retaining bioactive compounds and phytochemicals. The leaves were detached from the stems after drying, by the process of threshing and the leaves were ground using the Retsch miller machine. The parameters such as moisture, ash, dry matter, vitamin C, and colour attributes (a*, b*, c*, H° and ΔE) were analysed. In addition, parameters such as chlorophyll content a, chlorophyll content b, total chlorophyll content (TCC), total flavonoid content (TFC), total phenolic content (TPC), as well as antioxidant activities following ABTS and FRAP methods were analysed using a spectrophotometer. For each treatment, the samples were analysed three times. Analysis of variance was conducted in all the collected data using the statistical package SAS version 9.4 statistical software and student’s t-LSDs (Least Significant Differences) were computed at 5%, comparing the means of substantial source effects at a considerable level. The analysis of Pearson's Correlation Coefficient was used to establish the association between the climatic factors and nutritional compositions, polyphenols, antioxidants activities, chlorophyll contents and colour attributes of bush tea. The results revealed that different shade nets colours and light intensities significantly (p <0.0001) influenced the nutritional compositions (moisture, ash, dry matter, vitamin C), polyphenols (TPC and TFC), antioxidants activities (ABTS and FRAP) and physicochemical properties (colour attributes, chlorophyll a, chlorophyll b, and TCC) of field grown bush tea in both years 2018 and 2019. Black shade net colour had a noteworthy influence on total chlorophyll content, chlorophyll a content, and chlorophyll b content. In contrast, green shade net influenced on H° values and the white shade net on TFC. In contrast, the use of shade nets colours had no effects on dry matter (92.86%), vitamin C (3.03 mg AA/100g), or colour attributes [b* (20.65) and c* (20.65)] values of bush tea as they were highly significant at control. The use of 80% light intensity, significantly influences the moisture content, chlorophyll a, chlorophyll b and total chlorophyll content and H°. However, control had a higher influence on dry matter, vitamin C, b*, c* and FRAP results. A very strong, strong, and moderate positive correlation was observed between the climatic factors and nutritional compositions, polyphenols, antioxidants, and chlorophyll contents of field-grown bush tea, under the influence of shade nets colours and light intensities during autumn 2018 and 2019. However, colour attributes: a*, b* and H° resulted in weak/ no correlations. This study is the first to demonstrate different shade nets colours and light intensities as the key factor of accumulating of chlorophyll contents and antioxidants in field-grown bush tea plants. The use of a black shade net together with 80% light intensity resulted in being the best treatment to promote the accumulation of antioxidants compared to other treatments. And it is evident that black shade net together with 80% light intensity was of significant influence after control (100% light intensity). Future studies will be to determine the regulatory effects of shade treatments on the biosynthetic pathway of flavonoids and the accumulation pathways of chlorophyll contents under the shade nets treatment.Item Open Access Selection of Efficient Indigenous Rhizobia Inoculants for the Production of Selected Tropical Legumes in Limpopo Province (South Africa)(2023-10-05) Nemaembeni, Phethani Muofhe; Gwata, E. T.; Phalane, F. L.; Maphosa, T. M.Tropical legumes are important food crops for human and animal nutrition as well as the improvement of soil fertility. In Southern Africa, tropical legumes are cultivated mostly by smallholder farmers partly because of their ability to thrive in poor soils and adverse weather conditions. Tropical legumes are useful in these cropping systems because of their ability to fix nitrogen (N) thus minimizing the necessity for chemical nitrogenous fertilizers. Soil rhizobia (as bio-inoculants) can enhance the productivity of these legumes through the improvement of soil fertility. However, both the compatibility and competency of individual rhizobial strains is important for attaining optimum crop productivity. Therefore, it is imperative to identify the best efficient rhizobial strain x legume genotype combinations for successful nodulation and optimum legume yield for the benefit of resource-limited farmers in smallholder farming systems and end-users. The aim of this study was to improve the productivity of tropical legumes. The specific objectives of the study were to (i) determine efficient rhizobial strains that combine with tropical legume species to produce optimum crop productivity and (ii) determine efficient tropical legume species x rhizobial genus combinations that produce optimum crop productivity. The study consisted of two experiments both of which were carried out at the Agricultural Research Council (ARC), Plant Health and Protection (Pretoria) greenhouse and laboratory facilities (25° 61’ 547” S, 28° 36’ 435” E). The conditions in the greenhouse were set at a 14 h day temperature of 28° C and 10 h night temperature of 15 °C. In the first experiment, four tropical legumes (pigeonpea; soybean; tepary bean; bambara groundnut) were used in the study. At planting, each legume species was inoculated separately with each of 15 rhizobial strains and allowed to grow for six weeks after which a range of N fixation variables were evaluated. The experiment was laid out in a split plot design with legume species as the main factor and rhizobial strain as the sub-factor. The quantitative data sets on leaf color score (LCS), nodule dry weight (NDW), shoot dry weight (SDW) and root dry weight (RDW) were subjected to standard analysis of variance (ANOVA) procedures and GGE biplot analysis. In the second experiment, three tropical legumes and four rhizobial strains (each from a distinct genus) which were selected from experiment 1 were used. A split-split plot design with the rhizobial strain as the main factor, legume species as the sub-factor and legume variety as sub-sub factor with two replications was used and the data sets of the N fixation variables were analyzed following the same procedure as described above. The results showed that there was variation in legume species x rhizobial strain compatibility and the pattern of root nodulation varied within the legume species depending on the specific strain used. Tepary bean nodulated poorly with most of the rhizobial strains. There were significant differences among the legume species for all the traits that were measured. However, there were no significant (P < 0.05) differences among the rhizobial strains for NDW, RDW and SDW. The highest NDW (0.05 g) and SDW (0.42 g) were attained by bambara groundnut. The mean LCS for the trial was (19.26) while the highest (23.65) and lowest (14.23) LCS were associated with the rhizobial strains Bradyrhizobium elkanii (R4) and Phyllobacterium leguminum (R11), respectively. Among the Paraburkholderia species, the rhizobial strain Paraburkholderia phenolyruptix (R1) was associated with the highest (22.08) LCS. The results also revealed that the rhizobial strains Rhizobium leucaenae (R8) and Rhizobium sp (R6) induced the highest (20.89) and lowest (15.24) LCS, respectively. However, the rhizobial strain Bradyrhizobium elkanii (R14) which attained a relatively high LCS, was associated with the heaviest NDW among all the strains. In contrast, there were detectable nodules associated with four rhizobial strains. Two distinct rhizobial species, namely Paraburkholderia sp (R2) (designated N362) and Bradyhizobium lupini (R5) were associated with the heaviest shoots across the legume species. In contrast, the control strain achieved the lowest (0.25 g) SDW. In addition, all the three strains from the genus Paraburkholderia and the single strain from the genus Phyllobacterium as well as all the five from the genus Bradyrhizobium (R4; R5; R12; R13 and R14) were associated with significantly (P< 0.05) heavier SDW than the control. The results also revealed highly significant (P < 0.01) positive correlations between the LCS and NDW. However, the LCS was negatively but significantly (P < 0.05) correlated with the RDW. In addition, there were highly significant positive correlations between the SDW and each of NDW and RDW. The variety x legume species interaction was highly significant (P < 0.001) for all the attributes that were measured except for NDW. Inoculation with Bradyrhizobium sp (33a-PP4) showed varietal differences in the pattern of N fixation indicators in bambara groundnut and pigeonpea. Nonetheless, some of the soybean varieties formed no nodules after inoculation with the Paraburkholderia sp and Phyllobacterium leguminum strains. Similarly, soybean responded poorly to inoculation with Rhizobium sp. (34a-PP5) and Bradyrhizobium sp (33a-PP4). In pigeonpea, all the four varieties that were used in the study showed similar LCS values. The SDW was used for determining the ideal rhizobial genus and legume species by applying the GGE biplot method in which the legume species and rhizobial strains were coded as environment scores and genotypes scores, respectively. The GGE biplot analysis indicated that 60.0% of the rhizobial strains were distributed in the top left quadrant but none in the bottom right quadrant. The rhizobial strains ‘R2’ (Rhizobium sp; 34a2-PP5) and ‘R1’ (Paraburkholderia sp; N362), were positioned far away from the origin suggesting that they uniquely influenced the legume species. The biplot analysis also revealed that the legume species (coded as environment scores), particularly ‘E1’ (pigeonpea) and ‘E2’ (soybean), were separated by acute angles between them and grouped in the same top right quadrant. In contrast, the remainder of the pairs of legume species were separated by obtuse angles with each suggesting that they were negatively related to each other in terms of the SDW trait. The legume species ‘E3’ (tepary bean) showed the shortest absolute projection suggesting that it was the most stable in performance across the rhizobial strains. In determining the ‘which- won where’, the biplot analysis explained 95.23% total variation of which PC1 and PC2 accounted for 84.41% and 10.82%, respectively. The results also revealed that among the rhizobial strains (depicted as genotypes) on the vertices of the polygon ‘R2’ (Rhizobium sp; 34a2-PP5) and ‘R4’ (Bradyrhizobium elkanii; 33a-PP4), performed best with pigeonpea (E1) and soybean (E2), respectively (Fig. 10). Bambara groundnut (E4’) showed the longest vector, suggesting that it had a high discriminating ability. The rhizobial strain ‘R2’ (Rhizobium sp; 34a2-PP5) was positioned in the innermost concentric circle, thus representing the ideal and most stable strain for SDW among the strains. The study findings provided new information in the patterns of N fixation among a set of tropical legumes that were inoculated with distinct rhizobial genera. The information will be useful in future for formulating bio-inoculants that may improve legume productivity in Limpopo Province (South Africa) where all the legume species that were used in this study are cultivated. The validation of the symbiotic efficiency of Bradyrhizobium elkanii (33a-PP4) and Phyllobacterium leguminum; 31b-PP4) with more diverse bambara groundnut germplasm will be merited.Item Open Access A Study of the Genetics of Root Nodulation in Pigeonpea (Cajanus cajan) Using Indigenous Rhizobia(2023-10-05) Phalane, Francina Lebogang; Gwata, E. T.; Mchau, G. R. A.; Hassen, A. I.Pigeonpea (Cajanus cajan) is an important grain legume, which is grown in many African countries largely for human and animal consumption. Leguminous crops such as pigeonpea fix atmospheric nitrogen (N) symbiotically in the root nodules thus elimination of the need for expensive chemical nitrogenous fertilizers. The determination of host plant x microsymbiont combinations that produce optimum crop productivity is important in the pigeonpea value chain. In addition, the characterization of both symbionts is necessary for exploiting the N fixation in tropical legumes including pigeonpea. There is a dearth of information regarding the agronomic performance of pigeonpea and other common legume species such as Bambara groundnut (Vigna subterranea), soybean (Glycine max) and tepary (Phaseolus acutifolius) that are cultivated in South Africa. Therefore, the aim of this study was to evaluate the symbiotic effectiveness of indigenous rhizobia on pigeonpea.. The specific objectives of the study were to: (i) collect rhizobial strains that are associated with root nodulation in pigeonpea from diverse locations across South Africa (ii) perform molecular characterization of the rhizobia that are associated with root nodulation in pigeonpea from diverse locations in South Africa (iii) to sequence the whole genome of a selected rhizobial strain derived from pigeonpea and determine its molecular characteristics and (iv) determine the effectiveness of the rhizobial strains with pigeonpea and other common tropical legume species. In the first objective of the study, forty soil samples were collected from diverse locations across the country and used for inoculating separately the seed of each of five randomly selected pigeonpea genotypes. The pigeonpea plants were raised in a N-depleted growth medium in the greenhouse. A split-plot experimental design with two replications was used in the study. After six weeks of growth, the plants were harvested to isolate rhizobia from the root nodules. Several morphological characteristics of the rhizobial colonies including shape and growth habit (type) were determined. In addition, a range of N fixation variables of the host pigeonpea plants was measured including the nodule dry weight (NDW) and shoot dry weight (SDW) per plant. A variety of the colony morphologies ranging from tiny to medium as well as cream white and large, watery oval colonies was observed. Two hundred and eighty putative pigeonpea rhizobial strains were obtained from the root nodules of the plants. Based on their morphological characteristics on YMA-CR, nutrient agar and peptone glucose agar, the isolates were deposited into the South African Rhizobium Culture Collection gene bank. There was ˃40.0 % difference in the number of nodules between ‘Genotype-5’ and ‘Genotype-4’ but the difference in NDW between the two genotypes was ˃80.0 %. In contrast, the heaviest dry shoots (0.4513 g) that were attained by ‘Genotype-3’, weighed 52.0% more than the lightest dry shoots that were observed for ‘Genotype-4’. The results indicated that the soil samples contained diverse rhizobial isolates with distinct morphological characteristics and significant differential N fixation ability of the pigeonpea genotypes suggesting that there was a potential to select for optimum host genotype x rhizobial strain combinations for N fixation in this legume species. In the second objective of the study aimed at the molecular characterization of the rhizobial strains derived from pigeonpea, two housekeeping bacterial genes (namely 16S rRNA and recA) were used to identify each rhizobial strain to the species level. In addition, the phylogenetic relationships among these rhizobial strains were determined. The results showed that 56 strains were confirmed as rhizobia and deposited into the national rhizobia collection bank. Two primers successfully amplified both the Rhizobium strain (30bp3) as well as several Bradyrhizobium strains (16a2p3, 15bp3, 11a2p3, 13bp3, 33ap4 and 19a1p3). Two novel genera of rhizobia (Phyllobacterium and Paraburkholderia), were associated with root nodulation in pigeonpea. There was a considerable variation in the size of the sequences of both the 16S rRNA and recA genes among the rhizobial isolates. The sequences of the 16S rRNA genes across the four genera averaged 1015.73 bp. The 16S rRNA Rhizobium phylogenetic tree showed that the rhizobial isolates obtained from pigeonpea were dispersed in six different clusters and grouped with several type species of the genus Rhizobium including R. tropici with a high (77.0%) similarity grouping. The 16S rRNA based phylogenetic tree showed that the novel Paraburkholderia rhizobial isolate ‘30a2p3’, grouped with several type strains including P. rhizosphaerae (with a similarity grouping >50%) but in the recA based phylogenetic tree, the same isolate was grouped in Cluster IV with 93.0% similarity grouping. The study concluded that the sequences of the two genes (16S rRNA and recA) of the isolates from pigeonpea could provide sufficient phylogenetic information about the isolates up to the species level and confirmed that this legume is promiscuous in diverse soils from South Africa. The objective focusing on the whole genome sequencing of a selected rhizobial strain derived from pigeonpea to determine its molecular characteristics selected the rhizobial strain 10ap3 (SARCC-755) (that was originally derived from pigeonpea in the trapping experiments). Upon DNA from the strain, the DNA libraries were prepared using the Nextera protocol (Illumina, USA) and paired-end (300bp x 2) sequenced on a MiSeq (Illumina) sequencer at the Biotechnology Platform, Agricultural Research Council-Onderstepoort Campus (Pretoria, South Africa). The genome was a large circular chromosome (6,297,373 bp) and containing the overall G + C content of 60.0%. The total number of genes in the genome of the strain was 6,013 of which 99.13% were coding sequences. However, only 5,833 of the genes were associated with proteins that could be assigned to specific functions. Several important genes that were found on the genome, included the genes for N metabolism, stress response, phosphorus metabolism and iron acquisition as well as adenosine monophosphate nucleoside for purine conversion. The nodulation gene (nolR), which functions as a DNA binding transcription factor was located on contig 12. Precursor genes for purine synthesis, for instance, inosine-5-monophosphate and adenylosuccinate, which are also responsible for nodule formation, were also present on the genome. The results showed that the genome of this strain (Rhizobium tropici SARCC-755) does not contain common nod and nif genes suggesting that an alternative pathway involving a purine derivative was involved in its symbiotic association with pigeonpea. The genome also possessed some genes that are associated with abiotic stresses and mineral nutrient acquisition thus making it a candidate for future formulation of commercial inoculants especially when considering its high symbiotic efficiency with pigeonpea. In the fourth study objective, which focused (i) on determining the relative performance of individual tropical legume species when inoculated separately with each of the specific rhizobial strains that were previously derived from pigeonpea, (ii) quantify the magnitude of the effects of interactions between the host tropical legume species x rhizobial strain on a range of N fixation variables and (iii) identify the winning (superior) rhizobial strains with the specific test legume species. Thirty-six rhizobial strains which were previously isolated from pigeonpea root nodules were used in the study. There was at least one strain representing each of four distinct rhizobial genera namely Bradyrhizobium, Paraburkholderia, Phyllobacterium and Rhizobium. The experiment was laid out as a split plot design with legume species as the main factor and rhizobial strain as the sub-factor. Each treatment was replicated twice. The data sets of several N fixation variables including NDW and SDW were measured and subjected to the analysis of variance and Pearson’s correlation analysis using SAS statistical software (version 9.3) followed by mean separation using LSD test at the 5.0% probability level. Further analysis using the GGE biplot model was carried out to understand better the relationship between the host plants and the microsymbionts. For objective (i) of the fourth study, three healthy seeds of each legume species were planted in a plastic pot filled with 1.65 kg sterile river sand saturated with Hoagland solution. At seven weeks after germination, each plant was harvested and gently washed with tap water before detaching the nodules carefully from the roots. Similarly, the shoot was separated from the roots for each plant prior to oven drying all the harvested plant parts at 70o C for 48 h followed by weighing to determine the dry weights. The results showed marked variability in the responses of the legume species to inoculations with individual rhizobial strains. Tepary bean showed poor nodulation as indicated by the chlorotic plants which contrasted sharply with those of Bambara groundnut. Pigeonpea responded differentially to each individual rhizobial strain resulting in marked differences in the nodule load per plant. Some rhizobial strains, (for instance, Rhizobium strain ‘26a-PP3’) induced profuse nodulation in Bambara groundnut but not in the other legume species. The principal component (PC) analysis showed that the first two principal components accounted for 78.74% of the total variation. Four N fixation variables, including the NDW and SDW, were moderately associated with PC1. The GGE biplot of the rhizobial strain x legume species interaction for NDW explained 82.44% of the total variation. For NDW, the environments represented by E3 (soybean) and E4 (pigeonpea) were positively correlated since their vectors were separated by an acute angle. However, E1 (Bambara groundnut) and E3 (soybean) were negatively correlated since they were characterized by an obtuse angle between them for the SDW. The ‘which-won where’ biplot for NDW explained 82.44% of the total variation of which PC1 and PC2 accounted for 50.40% and 32.04% of the total variation, respectively. Two rhizobial strains on the vertices of the polygon (Rhizobium sp. 36a-PP5) and (Rhizobium sp. 26a2-PP5) performed best with Bambara groundnut (E1) and soybean (E3), respectively. E3 (soybean) consisted of the longest vector line suggesting that it possessed a high discriminating ability. Two rhizobial strains, namely, (Rhizobium sp.; 33a-PP2) and (Rhizobium multihospitium; 37a-PP4) were identified as ideal for RDW and SDW, respectively. The biplot analysis also revealed that for SDW, E1 (Bambara groundnut) and E4 (pigeonpea), in that sequence, were plotted closet to the epicentre. The GGE biplot analysis also revealed that both pigeonpea and Bambara groundnut provided the most ideal symbiotic activity for NDW but tepary bean lacked the discriminatory ability for NDW. Further testing and validation of the symbiotic activities of the rhizobial strains identified in this study in field trials on diverse legume species and in multiple agro-ecological locations is recommended. It will also be desirable to identify new bio-inoculants for improving tepary bean productivity.Item Open Access Variation in Drought Tolerance Attributes Among Tepary Bean (Phaseolus acutifolius) Germplasm(2023-05-19) Nong, Refilwe Aljareau; Gwata, E. T.; Gerrano, A. S.Tepary bean (Phaseolus acutifolius A. Gray) is an important food legume which originated from South America. In South Africa, it is cultivated by smallholder growers mainly in the drought prone Sekhukhune District of Limpopo Province. Currently, there are no significant breeding efforts aimed at cultivar development of this crop and it remains under-utilized despite the potential of the crop. Therefore, this study evaluated drought tolerance and growth attributes of the tepary bean emphasising on the leaf proline content that are associated with drought tolerance directly or indirectly. The study also determined the drought tolerance and growth relationships as well as identified potentially superior genotypes of tepary bean. The germplasm was evaluated before and after the soil moisture stress treatment which was imposed on the trial by withholding water for 21 days. A 6 x 7 rectangular lattice design replicated three times was used for evaluating 42 genotypes. The results showed that prior to soil moisture stress, there were significant (P<0.05) differences among the 42 genotypes for all the six phenotypic parameters that were measured. The highest (1.05 μmol/g dry weight) and lowest (0.32 μmol/g dry weight) leaf proline content (LPC) were observed for genotypes ‘Ac-35’ and ‘Ac-9’, respectively. The trial mean for proline was 0.69 μmol/g dry weight. The genotype ‘Ac-42’ attained the highest (27.85) leaf chlorophyll content (LCC) which was 48.94% higher than the check genotype (‘Ac-34’). The genotype ‘Ac-33’ achieved almost two-fold higher relative water content (RWC) (84.72%) than genotype ‘Ac-11’ which recorded the lowest (43.12%) RWC. The highest (68.70 mmol m-2s-1) stomatal conductance (SC) was three-fold more than for the check genotype (19.90 mmol m-2 s-1). At least four genotypes (‘Ac-6’, ‘Ac-7’, ‘Ac-22’ and ‘Ac-28’) attained significantly (P < 0.05) greater stem height (SH) than the trial mean (28.63 cm). After the soil moisture stress treatment, the results revealed that the LPC ranged from 1.26 to 0.36 μmol/g dry weight that were observed for genotype ‘Ac-35’ and ‘Ac-9’, respectively. The LPC showed a positive but not significant (P > 0.05) correlation with each of the other remaining attributes both before and after the moisture stress treatment. Similarly, after the soil moisture stress, the LCC maintained a highly significant (P < 0.01) positive correlation with the RWC but a negative correlation with the SH. In both soil moisture conditions, there was no discernible correlation between the SD and the SH. In general, the soil moisture stress lead to a variable increment in the LPC among the genotypes. An independent samples t-test which was used to determine the significance of the change in LPC showed that there was a highly significant (P < 0.00019) difference between the measurements of this amino acid before and after soil moisture stress. The results also showed a reduction in LCC during the soil moisture stress period but there was no clear pattern of the influence of the soil moisture stress on both the SC and RWC. The principal component analysis showed that before the soil moisture stress, the first two principal components accounted for 45.49% of the total variation and three traits (SC, LPC and SH) were highly associated with PC1. In addition, SC contributed the most variation for this component. However, PC2 was highly associated with LPC and RWC. In contrast, PC3 was dominated by SH. The results also showed that after the soil moisture stress, the first two principal components accounted for >50.0% of the total variation. The LPC and SH were highly associated with PC2 but PC3 was dominated by both LCC and SD. In the biplot analysis four genotypes (‘Ac-2’, ‘Ac-19’, ‘Ac-30’ and ‘Ac-41’) were clustered around the origin prior to the moisture stress treatment while five genotypes (‘Ac-3’, ‘Ac-9’, ‘Ac-11’, ‘Ac-28’ and ‘Ac-35’) were distinct and positioned far away from the origin. The genotypes in the right top quadrant (including ‘Ac-4’, ‘Ac-6’, ‘Ac-7’ and ‘Ac-28’) were associated and characterized by high leaf proline, high degree of stomatal opening and tall shoots. The tallest shoots were associated with the genotypes that were grouped in the left top quadrant while the remainder of the genotypes were characterized by thick stems and grouped in the left bottom quadrant. The tepary bean genotypes were grouped into three main clusters with the majority of the genotypes (64.28%) grouped in cluster III. Cluster I consisted of only seven genotypes including ‘Ac-40’ (which was associated with high LCC) as well as ‘Ac-2’, ‘Ac-35’, and ‘Ac-37’ (which were characterized by both LPC and RWC). The check (genotype ‘Ac-34’) was grouped in cluster III in a sub-cluster with genotype ‘Ac-20’. This study discusses the implications of the observed variability among the tepary bean genotypes for these phenotypic attributes and growth parameters. There will be merit in validating these results on a field basis together with grain yield evaluation and genotyping over multiple locations and seasons to determine elite germplasm that breeders and growers can utilize.Item Open Access Variation in Root Nodulation Traits among Parental Genotypes and Segregating f 2 Pigeonpea Plant Populations(2023-05-19) Mthombeni, Tinyiko; Gwata, E. T.; Gerrano, A. S.Pigeonpea (Cajanus cajan L. Millsp.) is an important grain legume that originated in the Indian sub-continent. In South Africa, it is grown either as single plants or as a hedge, mainly in Kwazulu-Natal, Limpopo, and Mpumalanga Provinces. The crop provides highly nutritious food for human consumption and fixes considerable amounts of atmospheric nitrogen (N) thus contributing to the improvement of soil fertility. Root nodulation in pigeonpea is an integral part of the symbiotic process that results in N fixation thus contributing to the productivity of the crop. Currently, there are no reports that determined the genetics of root nodulation in pigeonpea. Therefore, this study was designed to determine the mode of inheritance for selected root nodulation traits. The experiment was conducted in a greenhouse at the Agricultural Research CouncilPlant Health and Protection (ARC-PHP). The average day and night temperatures in the greenhouse were 28°C and 15°C- respectively, with 14 hours of daylight. A randomized complete block design with two replications was used to set up the experiment. Six pigeonpea genotypes were used in the study together with thirty-six rhizobia strains originating from soil that was collected from diverse locations across South Africa. The nodulation variables which were measured included leaf chlorophyll content (LCC), shoot dry weight (SDW), root dry weight (RDW) and nodule dry weight (NDW). The data sets for each of these quantitative variables were subjected to the analysis of variance followed by mean separation using the least significant difference at the 5% probability level using statistical software (Statistix 10.0), and subsequently to analysis of goodness of fit test using standard Chi-square procedures for various Mendelian ratios. The results revealed that the method which was employed to phenotype both the parental genotypes and the F2 progenies was effective and enabled a distinction between the phenotypic classes among the treatments hence a rapid, simple technique to identify contrasting parental genotypes for specific nodulation traits for use in the subsequent genetic study. The GGE biplot analysis revealed that the rhizobial strains 'R24', 'R28', 'R31' and 'R34' were clustered around the origin. In contrast, the rhizobial strains 'R7', 'RB', 'R10', 'R27' and 'R29'were positioned far away from the origin. The biplot also indicated that the pigeonpea parental genotypes (coded as environment scores), 'Gen-1' (E1 ), 'Gen-2' (E2), 'Gen-3' (E3) and 'Gen-5' (ES) were separated by acute angles between them and grouped in the same quadrant. The 'which-won where' biplot explained 56.05% total variation of which PC1 and PC2 accounted for 29.40% and 26.65% of the total variation, respectively. The results also revealed that the rhizobial strains (depicted as genotypes) on the vertices of the polygon 'R 1 0', 'R 11 ', 'R27' and 'R3S' performed best with the pigeonpea parental genotypes (depicted as environments) 'Gen-2' (E2), 'Gen-S' (ES), 'Gen-4' (E4) and 'Gen-6' (E6), respectively. The genotype 'Gen-S' (ES) showed the longest vector line, suggesting a high discriminating ability. The frequency distribution curve for the F2 plant population that was derived from the cross Pa x P1 showed approximately a normal distribution curve but with a slight skew to the right suggesting the presence of epistatic gene action for the LCC trait. The segregation ratio of 9 high:7 low chlorophyll content in the cross P4 x P2 (P-04-SST x P-02-DC) suggested duplicate recessive epistasis in which there is complete dominance at both gene pairs; but, when either gene is homozygous recessive, it masks the effect of the other gene. For SDW, the results also confirmed that the 9:7 ratio was the best fit. The segregation pattern, based on the LCC, of the F2 population in the cross P-04-SST x P-02-DC, best fitted the 9:7 ratio. The results showed that the 9:7 ratio was generally predominant for the traits that were studied thus indicating a high probability that more than one gene, with epistasis are involved in their genetic control. The LCC showed a weak negative correlation with each of NDW and SDW in the F2 progenies that were derived from P-04-SST x P-02-DC. However, there was a positive but weak correlation between NDW and SDW in this set of progenies. In contrast, there was a highly significant (P < 0.01) positive correlation between NDW and SDW in 'cross 2'. The LCC was positively correlated to both NDW and SDW in the F2 progenies that were derived from the cross involving Pax P1. It is recommended that future studies should include the determination of heritability values that can be used in breeding programs aimed at the genetic improvement of N fixation in pigeonpea. It may also be necessary to combine classical Mendelian genetics with modern genomics tools to gain a better understanding of the complex nature of N fixation in pigeonpea as well as its genetic manipulation.Item Open Access The study of phenophases of Lantana camara in some parts of Makhado Municipality; Limpopo Province, South Africa(2023-05-29) Kwinda, Aluwani Ndanduleni; Ligavha-Mbelengwa, M. H.; Tshisikhawe, M.P.A few strategies have been utilized in plant phenology to observe the starting date of the life cycle events and the basic temperature for development and improvement of perennial plants. The study of phenophases on plant species required clear observations, interpretations and the recording of the plant yearly life cycle that can be characterized by the start and the end of each stage. According to the USA National Phenology Network, phenophases generally have a duration of a few days or weeks depending on the type of plant species. This study considered the various phenophase events of Lantana camara, an alien invasive shrub which poses a major threat to the biodiversity by suppressing the growth of indigenous species in the ecosystem as observed in some parts of Makhado Municipality. This study aimed to determine when different phenophase events of L. camara occurred, compared the duration of lifespans of each reproductive phase and established relationships between different phenophase events of the plant. The study was done by conducting field observations using digital repeat photography method on monthly basis for 12 months in some parts of the Makhado Municipality, Limpopo Province. The study areas were Ha-Mashau, Doli village and Elim. Observations were done randomly once or twice a month to observe as to when the life cycle events of Lantana camara begin and end. Findings showed that there was variation amongst phenological events of Lantana camara at both the study locations that were visited. Lantana camara did not carry leaves, flowers, and fruits for equal periods of times. This variation between phenophases was thought to be caused by environmental factors acting on the plants such as daily temperature, amount of rainfall, and soil moisture content amongst other factors at these locations.Item Open Access Biochar and Poultry Litter Effects on Maize Growth, Nutrient Uptake and Selected Soil Biological Activities in Different Soil Types(2022-07-15) Ntsoane, R. L.; Odhiambo, J. J. O.; Kutu, F. R.; Kutu, F. R.South African soils contain lesser percent organic carbon content compared to soils from many parts of the world. The loss in organic carbon content reduces soil fertility and drives an ever increasing demand for the use of soil amendments to enhance soil fertility. The study consiststed of a greenhouse pot experiment and a laboratory incubation experiment. The objective of a greenhouse study was to assess the effects of biochar and poultry litter application on maiize productivity under different soil types. Treatments consisted of different soil types and amendments of biochar and poultry litter. Soils were collected from four sites (Mutshenzheni, Rambuda, Tshiombo Irrigation and Tshiombo Madzivhandila) representing different soil types (Westleigh (We1), Hutton (Hu), Westleigh(We2) and Shortlands (Sd), respectively. Soils were amended with biochar and poultry litter. The amendments consisted of various mix ratios of biochar (BC) with poultry litter (PL) as treatments, which are namely, BC0PL0, BC100PL0, BC75PL25, BC50PL50, BC25PL75, and BC0PL100. Soil amendments were applied at different rates of 0- 5 t ha-1 PL and 0- 40 t ha-1 BC. Treatments were laid out in a completely randomize design (CRD) and replicated three times. Biochar and poultry litter application exerted no significant difference on soil pH of We2, Sd, and Hu soils. However, the effect of biochar and poultry litter application was significant at soil We1. In contrast, application of biochar and poultry litter had no effect on soil total N of soil We1, We2, and Hu and was significant on soil Sd. The results of this study showed that application of biochar and poultry litter treatments had no significant effect on both the maize growth and nutient uptake at early stages ( Week 1 and Week 2). However, the application of biochar and poultry litter treatments had a significant difference ( p ≥ 0.001) on maize growth and nutrient uptake at a later stage ( Week 3 to Week 6). Therefore, there is a potential to ameliorate fertility constraints in agricultural soils using biochar combined with poultry litter. Though biochar possesses some essential elements required for plant growth, sole application reduces its efficiency with its effectiveness confirmed only when applied in combination with organic-based materials such as poultry litter. The laboratory incubation experiment assessed the effects of different biochar rates on soil chemical and bio-quality parameters. Each treatment consisted of a 200 g of soil (We1, Hu, We2 and Sd) homogenously mixed with biochar amendments (0, 10, 20, and 40, t ha-1). The treatments were laid in a completely randomize design (CRD) and replicated three times. Soil sampling was done on day 0, 30, 60, 90, and 120, and samples were analyzed for soil available P and N and bio-quality parameters namely microbial biomass nitrogen, microbial biomass carbon, urease, alkaline and acid phosphatase, β glucosidase, soil organic carbon, and dehydrogenase activity. The results of the study revealed various responses of soil bio-quality parameters and selected soil chemical properties after biochar and poultry litter application. Thus, the effects of biochar rate, incubation days and soil type on soil enzymes and other bio-quality parameters elicited an understanding on microbial activity and soil enzymes mechanism . Therefore, a prolonged study (more than 120 day) is required to evaluate the effects of incubation days, biochar rate and soil type effect on soil nutrients and bio-quality parameters.Item Open Access Soil texture and mineralogy influence on the productivity of selected tropical legumes(2022-07-15) Mashaba, Lacaster Themba; Wakindiki, I. T. C.; Gwata, E. T.Cowpea (Vigna unguiculata) and tepary bean (Phaseolus acutifolius) are essential legumes which provide food for many people in South Africa. However, the productivity of these major tropical legumes in Limpopo Province is low partly because of poor soil fertility and soil degradation. This study aimed to determine the productivity of tropical legumes (cowpea and tepary bean) in different soils in Limpopo Province. Two pot experiments were conducted at the University of Venda experimental farm. The experimental design was a Completely Randomized Design (CRD) arranged in a 2 × 4 factorial treatment structure replicated three times. The aim of the first experiment was to determine the effect of soil types on nodule dry weight (NDW), root dry weight (RDW) and above-ground biomass (ADB) of the legumes. Modified plastic pots (2.0 L) were used for planting the legumes. The second experiment was aimed at determining the effect of soil types on productivity variables including the number of branches per plant (NB), plant height (PHT), plant vigour (PV), number of pods per plant (NPP), number of seeds per pod (NSP), pod length (PL), pod weight per plant (PWT) and seed weight per plant (SWTP) of the two legume species. Similarly, 5.0 L plastic pots were filled with soil (4.5 kg) and used for sowing the seed of legumes. Soil type had highly significant (P≤0.001) effects on NDW, ADB and RDW of legume species. The highest NDW (0.2133 g), ADB (3.6767 g) and RDW (2.1067 g) of cowpea was observed on the Leptsols. There were no nodules in tepary bean. For tepary bean, the highest ADB (1.6933 g) was observed in Leptsols whereas, the highest RDW (0.7433 g) was observed in Luvisols. In the second experiment, the results showed highly significant (P≤0.001) effects of Luvisols, Leptsols, Ferralsols and Fluvisols on PHT, NB, NPP, PWT, SWTP and PV. However, soil type had no significant (P >0.05) effects on PL and NSP. Leptsols was the most productive soil type for cowpea in all the measured parameters when compared to other soil types. The results in both experiments could be attributed due to variations in soil properties. It was concluded that Leptsols is the most productive soil for cowpea. However, field experiments are recommended to validate the results.Item Open Access Chickpea nitrogen fixation, rhizosphere nutrient concentration and contribution of residual nitrogen to improve maize production in response to biochar application in three different soil types(2022-07-15) Lusiba, Siphiwe Gloria; Odhiambo, J. J O.; Adeleke, R.; Maseko, S. T.Soil degradation is a major challenge affecting agricultural production around the world in the twenty-first century. Alternative approaches including the use of biochar and the introduction of legumes that will fix nitrogen though the process of biological nitrogen fixation (BNF) are essential for improving soil quality of current low productive soils, thus increasing crop yields, and maintaining food security while conserving the environment. To address this problem, three experiments were conducted in this study. First, two locally produced biochar from poultry litter and acacia feedstocks were assessed whether they qualify as ‘biochar’ for use as soil amendment according to the international biochar bodies. Secondly, a pot experiment was then conducted to investigate the potential impact of poultry litter biochar (PLB) and acacia biochar (ACB) to improve rhizospheric soil nutrient availability, bacteria abundance and diversity, chickpea growth and total nitrogen fixation in three contrasting soil types. Thirdly, another pot experiment was conducted to determine the contribution of residual N from biochar and N-fixed by chickpea to the following maize crop grown in three contrasting soil type. The treatments consisted of three soil types classified as Fernwood [Arenosol]; Pinedene [Gleyic Acrisol]; Griffin [Helvic Acrisol], sampled from three different smallholder farmers at Dopeni village, Limpopo Province. The two biochars [PLB and ACB] were applied at four application rates of [0% (control), 0.5, 1 and 2% w/w]. The treatments were arranged in a completely randomized design and replicated four times. For the first experiment, chickpea (Cicer arietinum) desi cultivar was inoculated and grown for 65 days in soils with uniformly applied P at 60 kg P/kg in all pots and water maintained at 60% field capacity. For the second experiment, maize (Zea mays) was grown for 95 days in the same soil as chickpea and biochar treatments as well as after harvesting maize that was used as a reference crop. Biochars made from poultry litter and acacia feedstocks meet the International Biochar Initiative (IBI) and European Biochar Certificate (EBC) requirements and qualifies as biochar for use as a soil amendment. Both biochars had C content greater than 50%, with H/C and O/C ratios less than 0.6 and 0.4, respectively, indicating that both biochars are stable for C sequestration and can remain in the soil for about 1000 years. Because poultry litter biochar (PLB) contained more nutrients than acacia biochar (ACB), PLB improved rhizospheric pH, CEC, and nutrient concentration (N, P, K, and Ca) when applied at 0.5-2% in the Griffin and Pinedene soils, resulting in higher biomass production and nutrient uptake of chickpea. In addition, when 2% PLB was applied to those two soils, bacteria capable of fixing N, especially those from the phylum Proteobacteria, were more abundant. Thus, chickpea grown in these soils and at these PLB rates derived more N from the atmosphere, fixed more N, and xvi accumulated more N and C in the shoot, but was less water use efficient. Furthermore, maize grown in 1% residual PLB treatments produced more biomass and accumulated more N and other nutrients than maize grown with 0.5-2% residual ACB treatments. However, when grown after chickpea harvest in residual PLB treatments of 2% in the Griffin and Pinedene soils, maize produced greater biomass and accumulated more N and other nutrients. Application of PLB and ACB at 0.5% in the Fernwood soil was ideal to improve rhizospheric nutrient availability, the abundance of bacteria communities [from the phylum Proteobacteria, Acidobacteria, and Firmicutes which are important for C and N cycling and bioremediation], as well as growth, BNF, and C accumulation of chickpea, including maize growth and nutrient uptake in monocropping or in rotation with chickpea. The greatest variation in relative abundance of bacteria communities and growth of chickpea was due to the substantial change in soil pH and rhizospheric nutrient availability such as N, P, K, and Mg, while biomass production and N accumulation were largely attributed to the improved BNF and C accumulation of chickpea in the clay textured soils. The increased growth and nutrient uptake of the following maize crop in the Griffin and Pinedene soils was attributed to high N inputs through BNF and biochar mineralisation, whereas the variation in bacteria communities, chickpea and maize performance in the Fernwood soil was due to the change in rhizospheric soil pH, P, and K. The findings of this study conclude that biochar made from poultry litter is recommended for use as a soil amendment to improve nutrients and soil quality, although caution should be taken when applied at higher rates (40 t/ha) as it may immobilize N or result in high release of toxic elements. Furthermore, incorporating chickpea into existing maize cropping systems of smallholder farmers and using biochar made from poultry litter will help reduce nitrogen input costs by adding residual nitrogen from biochar mineralisation and through BNF, improving soil quality and maize production. On the other hand, biochar made from acacia feedstock will be excellent for use to improve soil organic carbon and water adsorption, but it should be applied months before planting or supplemented with high organic N and P materials when used as a soil amendment to improve nutrient availability, as it may temporary fix N and P in the soil. When using poultry litter or acacia biochar on a poorly buffered loamy sand soil like the Fernwood, care should be taken to avoid over liming, which can cause nutrient deficiency and negatively affect nutrient uptake. Moreover, to improve chickpea and maize performance in sandy textured, highly leached soils like the Fernwood, biochar should be applied regularly or combined with organic materials to improve soil organic carbon to allow the soil to retain and release nutrients for plant uptake.Item Open Access Assessment of hydro-physical properties of some crusting soils in four different soil form as revealed by micro-focus x-ray computed tomography in Limpopo Province, South Africa(2021-06-23) Mpofu, Khuthadzo Tendani Given; Wakindiki, I. I. C.; Odhiambo, J. J. O.Most of the available knowledge about soil structure degradation through crust formation is limited to two-dimensional geometry. However, soil is a natural three-dimension body. The objective of the study is to assess soil crusting and hydro physical properties in four different soil form by using X-ray Computed Tomography, Characterizing micro-morphometric of crusting soil’s pore system, quantifying soil structure degradation through crusting development and visualizing hydro physical properties in all four-soil form. Micro X-ray Computed Tomography techniques can greatly add value to existing knowledge because they can reveal soil structure in three dimensions (3D). Undisturbed soil aggregates were obtained from two adjacent sampling locations namely Visibly Crusted (VC) and Not-Visibly Crusted (NVC). Four soil forms were studied in Limpopo province, South Africa at Vhembe Region under Thulamela and Collin Chabane local Municipality. Soil form studied are Dundee, located at (Tshamutoro village), Shortlands (Mukula Village), Hutton (University of Venda) and Glenrosa (Ha-Davhana village). The samples were scanned using Nikon XTH 225L micro-focus CT X-ray unit. The scans were reconstructed into three-dimensional volume data set of pore shapes, pore size and porosity among the soils using CT Pro software® and further analysed using VG Studio Max V3.0®. images were acquired after 30 minutes in each scan. The result of the study indicated that total porosity decreases with increase in depth, and the shape of the aggregates were dominated by regular pores that are susceptible to water erosion. Moreover, soil pores inform of mesopores, micropores, and macro pores were recorded using 3D images acquired .By visualizing hydro physical properties using images in 2D and 3D, it was possible to visualize arrangement of aggregates and their sizes helping to understand the erodibility of soil. In conclusion X-ray computed tomography is an effective tool to study the microstructure of soil aggregates.Item Open Access Effects of tillage and mulching on selected soil properties, growth and yield of sunflower (Helianthus annuus L.)(2021-06-23) Selolo, Koena Revonia; Mzezewa, J.; Odhiambo, J. J. O.Excessive and unnecessary tillage without residue retention can degrade the soil’s physical quality, decrease soil organic carbon contents and crop yields. Although the benefits of improved tillage methods and mulching have been reported in literature, little information is available on South Africa and more so on highly weathered soils of the Limpopo province. A study was conducted under dryland conditions at the University of Venda experimental farm, Limpopo province, South Africa. The aim of the study was to determine the effects of tillage and mulching on selected soil properties, growth and yield of sunflower (Helianthus annuus L.). The experiment was laid out in a split plot design with three replications. The experiment was conducted during the 2018/19 and 2019/20 cropping seasons. Treatments consisted of two (2) tillage methods (conventional and minimum tillage) and three (3) levels of avocado leaf mulch (0, 6 and 12 t/ha). The following soil properties were determined: soil organic carbon (SOC), soil water content (SWC), bulk density (BD), infiltration rate (IR), cumulative infiltration (CI) and aggregate stability (AS). Sunflower plant parameters including plant height, leaf area index, dry matter at flowering stage (FS), total biomass at harvest maturity stage (HMS), head diameter, head dry weight, seed weight and grain yield were determined. Minimum tillage resulted in significantly higher SOC, final IR and AS than conventional tillage. Conventional tillage outperformed the minimum tillage with respect to SWC and CI in both seasons. Minimum tillage recorded significantly higher plant height, LAI, head diameter, head dry weight, seed weight and grain yield than conventional tillage. Tillage had no effect on BD, dry matter at FS and total biomass at HMS in both seasons. Avocado leaf mulch application influenced SWC, CI and AS, but had no effect on SOC, BD, final IR, sunflower growth and grain yields. The 6 t/ha and 12 t/ha mulch treatments had significantly higher SWC, CI and AS than no-mulch treatment. Significant interactions between tillage and mulch rate observed on SOC at 42 days after planting (DAP), final IR, CI and AS indicated that the differences in SOC, final IR, CI and AS in the two tillage practices can be explained, in part, by the differences in how the two tillage practices react to different levels of avocado leaf mulch. The results suggested that tillage and mulching could improve sunflower crop yields, soil organic carbon, soil water content, infiltration rate and aggregate stability under the experimental conditions.