Jay Prakash Verma

Potassium Solubilizing Microorganisms for Sustainable Agriculture

The potassium solubilizing microorganisms (KSMs) are a rhizospheric microorganism which solubilizes the insoluble potassium (K) to soluble forms of K for plant growth and yield. K-solubilization is carried out by a large number of saprophytic bacteria (Bacillus mucilaginosus, B. edaphicus, B. circulans, Acidothiobacillus ferrooxidans, Paenibacillus spp.) and fungal strains (Aspergillus spp. and Aspergillus terreus). Major amounts of K containing minerals (muscovite, orthoclase, biotite, feldspar, illite, mica) are present in the soil as a fixed form which is not directly taken up by the plant. Nowadays most of the farmers use injudicious application of chemical fertilizers for achieving maximum productivity. However, the KSMs are most important microorganisms for solubilizing fixed form of K in soil system. The KSMs are an indigenous rhizospheric microorganism which show effective interaction between soil-plant systems. The main mechanism of KSMs is acidolysis, chelation, exchange reactions, complexolysis and production of organic acid. According to the literature, currently negligible use of potassium fertilizer as chemical form has been recorded in agriculture for enhancing crop yield. Most of the farmers use only nitrogen and phosphorus and not the K fertilizer due to unawareness that the problem of K deficiency occurs in rhizospheric soils. The K fertilizer is also costly as compared to other chemical fertilizers

Consequence of phosphate solubilising microbes in sustainable agriculture as efficient microbial consortium: A review

Phosphorus is an essential nutrient for plant growth and yield. Currently, phosphorus fixation in soil is a major problem throughout the world as available phosphorus in soil is highly reactive with cationic elements to form complex compounds. Rock phosphate is one of the cheapest fertiliser and most abundant; however, its direct application in soils is not much effective for the availability of phosphorus to plant growth due to its low reactivity. Further, phosphorus is present as a fixed or complex form in soils, which is unavailable for plants. Phosphate solubilising microbes (PSMs) have potential to solubilise the complex form of phosphate in the available form of phosphorus to plants. PSMs have different mechanisms for solubilisation of phosphate by producing various acids and enzymes. Other mechanisms of phosphate solubilisation and mineralisation follow chelation and immobilised cell technology. All such phosphate solubilisation mechanisms by PSMs have been discussed in this article. The current need to develop genetically modified PSM as efficient PSMs strains for sustainable agricultural production is also discussed in the present review. The PSMs is known as effective biofertiliser for enhancing the plant growth, yield and nutrient content in crops as well as improve the soil fertility under sustainable agriculture. The main aim of this review was to elaborate the phosphate solubilising activities and their consequences for sustainable agriculture.