Abstract:
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.
