Soil micro-organisms play a pivotal role in food production through their significant effects on nutrient transformation and release, soil organic matter and carbon dynamics, and biotic and abiotic stress tolerance to plants. The microbial consortia (MC) are mixtures of two or more microbial species/strains, living together symbiotically. Generally, a consortium of micro-organisms performs better than the inoculum of single microbial species. The MC, specifically plant growth-promoting rhizobacteria and biofilm biofertilizers can be used in non-legume cereal crops grown in a large area of the world. The MC may help in solubilization of plant nutrients from the soil native pool, production of beneficial substances (siderophores, hormones, etc.) for better root growth of non-legume crops and reduction in plant growth retarding hormone(s). The MC research focuses/encompasses, mainly legume crops, although there are prospect and substantial evidences of their use in non-legume crops. Reports indicate that the use of MC can enhance micronutrients, total organic carbon and N in soil. They could fix N, solubilize P and K, improve soil physico-chemical properties and act as phyto-stimulator. Globally, almost 50% of the total N, P and K used in crops are consumed by cereal crops, which are heavy feeder with high yield potential. Integration of MC with chemical fertilizers provides enormous scope for increasing nutrient-use efficiency in accordance with harmonious improvement in crop yield and soil health. The MC as a component of integrated nutrient management in non-legume cereal crops would considerably reduce the demand and use of mineral fertilizers and cost of cultivation and save nutrient for use in other crops of economic importance. They are low-cost and eco-friendly options and can improve soil health vis-a-vis enhancing productivity of non-legume crops.

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Potassium (K) is essential for plant growth and vital for soil health. However, despite high crop demand, K fertilization continues to be ignored or severely inadequate in Indian agriculture. Over time, this could lead to severe depletion of soil K reserve, irreversibly alter K-bearing minerals, and adversely affect soil fertility and crop productivity. Hence, we should comprehensively assess the alarming situation of soil K mining in India and come up with appropriate solutions. Keeping the above in mind, here we review the soil K pools concerning plant availability, their contents in major soil orders of India, reasons and status of soil K mining under major crops and cropping systems in India, and the impact of long-term K mining on soil K pools and clay minerals. We also address various aspects of sustainable K management in agriculture and suggest future action courses focusing on India. Our main findings are: (i) farmers in India mainly apply nitrogen and phosphorus, but little or no K; consequently, (ii) net K balance continues to be negative for most crops and cropping systems across India (e.g., -3.29 million tonnes [Mt] in 2000-01, -7.2 Mt in 2015-16); (iii) long-term K mining primarily depletes the exchangeable and non-exchangeable K pools in soil, and alters clay minerals to various extents; and (iv) the existing K fertilizer recommendations need an upward revision. We further enlist indigenous non-conventional alternatives of K fertilizers to meet the agricultural K demand. This is the first comprehensive review to simultaneously address the ongoing soil K mining in India, its impact, and its potential mitigation strategies. The points raised here would help reduce soil K mining, plan research work, and make policy decisions on K fertilization and residue management with the ultimate goal to prevent soil health deterioration and ensure sustainable crop production.

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