Assessing the efficacy of different formulations of organic granules immobilizing Azotobacter chroococcum and Bacillus subtilis on productivity and yield of wheat (Triticum aestivum L.) at different water regimes

Abstract

Microbial biofertilizers can be effective alternatives to fulfil plants' nutritional requirements as chemical fertilisers are considered unsustainable and a threat to environmental and health concerns. However, farmers hardly adopt these bioinoculants due to the uncertainty of their effectiveness in field conditions. In this study, we used porous dry organic materials obtained from biodegradable nontoxic agro-waste and process byproducts from agro-based industries which can act as a suitable carriers and protect the microbes during storage, marketing and field application. In this study, we created various formulations for Azotobacter chroococcum and Bacillus subtilis by combination presmud, cow dung manure as the organic matrix and jaggery, molasses, and serous gum as the binder and clay as the stabilizer.  Azotobacter chroococcum and Bacillus subtilis increased straw and grain yield in wheat (Triticum aestivum L.) over the unimmobilized biofertilizers and other used matrixes and binders in irrigated as well as water stressed cropping conditions.  The immobilized biofertilizers significantly increased soil fertility and nutrient availability compared to the unimmobilized PGPRs. The formulation IBF-VI showed a 35.9 and a 61.21% increase in grain and straw yields, respectively, over unimmobilized PGPRs. Interestingly, the biofertilizers immobilized in the organic matrix have supported similar grain and straw yield recorded for the synthetic chemical fertilizer’s urea and DAP. The performance of selected immobilized biofertilizers was further examined at various water regimes to measure their efficacy in wheat growing under water stress. The studies show that immobilizing microbial biofertilizers in sugar mill waste press mud and molasses for granule production improves the performance of the microbial biofertilizers. These compounds are abundant and inexpensive locally, and small-scale entrepreneurs can supply them on a small scale. The findings provide a new potential for producing and marketing customised effective microbial bio-fertiliser formulations in rural areas using small industrial setups.