Influence of inorganic fertilizers and organics on inorganic P, organic P and their fractions in calcareous soil of Bihar under rice-wheat cropping system

A field experiment was conducted at Pusa, Samastipur (Bihar) for assessing the impact of long term application of various organic sources along with different doses of inorganic fertilizers on P inorganic and organic P contents as well as their organic and inorganic P fractions. Under inorganic P fraction, the impact of various sources was assessed on saloid-P, Al-P, Fe-P, Ca-P, dissolved organic-P, humic matter-P, microbial-biomass-P and inorganic-P. The present investigation was undertaken from a long-term experiment in the calcareous soil in split plot design. Based on the experimental data obtained during the investigation, it was noticed that there was increase in yield due to the conjoint application of organics and inorganics can be shown as : compost + crop residues>compost> crop residues> no manure. The application of compost @ 20 t ha^-1 + crop residues (@ 100% could save approximately 50% of the recommended dose of NPK. The inorganic P was the dominant fraction of total soil P (up to 88.2%) whereas; organic P fraction was very less (up to 19.7%). The contribution of different inorganic P fractions viz., saloid-P, Al-P, Fe-P, and Ca-P towards total P were recorded as 0.46-1.06%, 0.58-2.47%, 0.54-2.40% and 50.2-70.0%, respectively. The different organic pools of P e.g. organic, humic matter-P, dissolved organic-P, microbial biomass-P were significantly influenced by the application of organic sources.