Long-term fertilizer impacts on potassium dynamics in rice-based systems

Abstract

A comprehensive study was conducted to investigate the long-term effects of integrated nutrient management on soil potassium (K) fractions—water soluble K (WSK), exchangeable K (Exc.K), non-exchangeable K (NExc.K), lattice K (Lat.K), and total K (Tot.K)—under rice-based cropping systems at three Long-Term Fertilizer Experiment (LTFE) sites: Maruteru (Andhra Pradesh), Titabar (Assam), and Mandya (Karnataka). Results revealed that integrated application of 100% recommended dose of fertilizers (RDF) with farmyard manure (FYM) at 5 t ha⁻¹ (T5) significantly enhanced all K fractions at Maruteru. In contrast, a treatment combining 50% RDF with 25% FYM-N and 25% green manure-N (T7) showed superior performance at Titabar and Mandya. Across all sites, the contribution of different K fractions to total K followed the trend: lattice K > non-exchangeable K > exchangeable K > water soluble K. The study highlights the pivotal role of balanced fertilization and organic amendments in sustaining soil K reserves, particularly in intensively cultivated rice systems. Continuous omission of K led to significant depletion across all K pools, underscoring the necessity for site-specific and integrated K management strategies to maintain soil fertility and long-term productivity. The variations observed across locations also emphasize the influence of soil texture, organic matter content, and cation exchange capacity on K fraction distribution. The research reinforces that long-term use of organics in combination with fertilizers not only enhances potassium availability but also contributes to improved soil structure and nutrient buffering capacity, ensuring resilient cropping systems under diverse agroecological conditions.