Plant growth promoting rhizobacteria as potential enhancers of nutrient quality in leaf litter composts

The investigation to assess the potential of the biofertilizer consortium, plant growth promoting rhizobacteria (PGPR) mix I in enhancing the nutrient value of leaf litter composts was conducted at College of Agriculture, Vellayani, Kerala during March to November 2018. Leaf litters of cashew (Anacardium occidentale) and mango (Mangifera indica) were composted separately adopting different methods, cocomposting with poultry manure, glyricidia + earthworms, composting inoculum + earthworms and natural decomposition and incubated with PGPR mix I and rock phosphate. Results of the study revealed the nutrient contents in litter composts increased with the biofertilizer treatment (1.52 to 2.43% N, 0.55 to 2.02% P and 0.23 to 0.67% K in mango and 1.16 to 2.05, 0.48 to 1.88 and 0.15 to 0.65% in cashew), lowered C: N ratio and lignin content. Significant variations were observed with the different composting methods and mango litter composted with glyricidia leaves and earthworms followed by PGPR incubation was found to be superior. The pH was brought to near neutrality and microbial counts were considerably higher with the favourable niche created with composting and biofertilizer incubation rendering it a valuable nutrient input in crop production.