Plant Response to Novel Organo-mineral Fertilizers Based on Selective Enrichment of P- and K-Solubilizing Microorganisms in Soil

Increasing fertilizer demands and dwindling mineral reserves warrant sustainable alternatives for plant fertilization. Organo-mineral fertilizers (OMFs) based on indigenous materials which are unutilized commercially are a possible option. The study describes the effect of novel OMF of phosphorus (OMF-P) and potassium (OMF-K), developed respectively from insoluble low-grade rock phosphate and feldspar on plant growth. The experiment was conducted in a glass chamber partitioned into two blocks, one with soil and the other with soil supplemented with 1% OMF-P or 1% OMF-K. Pearl millet plants were grown in the chambers for 45 days and the roots and soil from different chamber blocks were separated and analyzed. Root volume, fresh and dry weights, average root length, diameter and number of root tips were significantly increased with OMF-P/OMF-K and plants showed improved growth and plant height. The release and availability of P/K in soil was confirmed with isolations of P- and K-solubilizing fungi from the blocks with OMF along with significantly higher values of available P (0.006 mg g −1 ) and K (0.01 mg g −1 ) recorded from these blocks compared to control chambers. Moreover, the OMF prills did not exhibit any adverse effects on the plants and on soil microflora. The release of soluble P and K from the OMF is attributed to the presence of P and K solubilizers in soil, since conditions favourable for their selective enrichment are created. The OMF prills developed could address issues of deteriorating mineral reserves and associated environmental degradation, besides providing a sustainable management option.