Response of tepary bean (phasseolus acutifolius) to vesicular arbuscular mycorrhiza and phosphorus application rates

Thesis (M.Sc. (Agronomy)) -- University of Limpopo, 2023

Tepary bean (Phaseolus acutifolius) is a legume crop cultivated for its high nutritional status and is tolerant to biotic and abiotic stress. It can potentially fix atmospheric nitrogen (N), reducing the need for chemical fertilizers. The current study aimed to evaluate how vesicular-arbuscular mycorrhiza and phosphorus application rates influence tepary beans' growth, yield components, and biological nitrogen fixation. The experiments were carried out simultaneously at Syferkuil and Ga-Molepo during the 2020/2021 summer growing season. The field experiment was laid out in a split-plot design with four replications. Treatment factors were phosphorus (P) and vesicular-arbuscular mycorrhiza (VAM). Phosphorus was the main factor with five treatment levels (0, 20, 40, 60, and 80 kg/ha P), whereas VAM was the sub-factor with two levels (inoculated with 50 kg/ha and uninoculated). Growth and yield parameters were measured, and the amount of nitrogen fixed was determined. Soil samples were collected before planting and after harvest to determine the chemical composition of the soil. The collected data were subjected to ANOVA at a 5% significance level. Selected parameters such as the number of days to 50% emergence and plant height were significantly affected by P application. Pod length was influenced considerably by the VAM application. A significant impact on plant height, chlorophyll content, pod weight and grain yield was observed between the two locations. The 60 kg/ha P application resulted in the highest plant height as compared to the application of 80 kg/ha P. The reason could be that the P requirement was already met. The interactive effects of 60 kg/ha and VAM inoculation increased the pod length. This could be due to the fact that organic fertilizers contain plant nutrients, growth-promoting substances, and beneficial microflora when combined with inorganic fertilizers, which provide favorable soil conditions to improve nutrient use efficiency. Dry matter, Percent N derived from the atmosphere (%Ndfa) and N fixed increased with an increase in P application, except for 0 kg/ha and 20 kg/ha P for %Ndfa and N fixed, respectively. The δ15N value decreased with an increase in P application. Application of 80 kg/ha P fixed the highest amount of N at both locations. The findings of this study demonstrated that the application of P and VAM was effective on the growth, yield components and N fixation of tepary bean.

Department of Agriculture, Land Reform, and Rural Development