Effect of long-term application of rice straw,farmyard manure and inorganic fertilizer on potassium dynamics in soil

Knowledge of K-dynamics in soils can help devise practices for efficient K management in intensive rice-wheat systems. We studied the effect of long-term application of rice straw, farmyard manure (FYM) and inorganic fertilizer on total K and its distribution among different forms in 60-cm soil profile after 14 years of rice-wheat cropping. The exchangeable, the non-exchangeable and the lattice K respectively comprised 1%, 3–10% and 89–95% of total K in surface soil under different treatments. Application of rice straw and FYM positively impacted total K status of soil and its distribution among different forms. The greatest concentrations of total K, lattice K, exchangeable K and NH₄OAc-extractable K were observed in plots receiving both rice straw and FYM together and the lowest in inorganic fertilizer treated plots. On the contrary, the non-exchangeable K was the highest in inorganically fertilized plots and the lowest in rice straw amended plots. The exchangeable, the water soluble and the NH₄OAc-extractable K decreased with soil depth and did not indicate K movement beyond the rooting zone of the crops. The results showed that incorporation of rice residue in soil, instead of burning, besides reducing environmental pollution led to improved K-fertility of soils.