EFFECT OF PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) AND BIOCHAR ON SOIL PROPERTIES AND PERFORMANCE OF COWPEA (Vigna unguiculata (L.)Walp)

Abstract

A screenhouse and field experiment was carried out at Obafemi Awolowo University, Ile-Ife, in 2016 to investigate the effect of Plant Growth Promoting Rhizobacteria (PGPR) on cowpea (Vigna unguiculata) using biochar as a carrier. This was to evaluate the suitability of PGPR as fertilizers, pesticides as well as soil fertility improvement. The experimental design was a randomized complete block design with six treatments, replicated six times. Treatments used were Control, 40 ml biofertilizer (Bacillus thuringiensis, Pseudomonas putida and Klebsiella variicola), biofertilizer (40 ml) + biochar (40 g), biochar (40 g), 60 KgP₂O₅/ha Single Super Phosphate SSP and 2.5% of Lambda Cyhalothrin (Laraforce insecticide). Agronomic data were recorded and post-harvest soil analyses were carried out. The nodulation and plant heights of cowpea plants increased with the application of biofertilizer + biochar and showed about 13% and 53% increase in plant height and number of leaves respectively, over the control for the field experiment. Biofertilizer + biochar showed just about 2% decrease in the number of pods when compared with SSP which recorded the highest number. Biofertilizer + biochar treated soils recorded high microbial respiration with about 41% increase over control soils. Biochar application significantly increased the soil exchangeable K and Mg while the application of biofertilizer alone had a significant effect on Ca and the soil organic matter. The results suggest that PGPR as a potential alternative for chemical fertilizers and pesticides in cowpea production and its combination with biochar is a good technology to be adopted for soil fertility improvement.