Effect of Long Term (≈19 Years) Fertilization and Manure Practices on Yield and Soil Quality in Intensive Rice Cultivation on Inceptisol

Abstract

A 19 year old field experiment was conducted to systematically evaluate the long-term impacts of various combinations of chemical fertilizers and organic manures on the yield-related attributes, physical, chemical, biological properties of post-harvest soil samples. The study implemented treatments comprising graded doses of NPK fertilizers, farmyard manure (FYM), supplemental zinc, sole N or P applications, control and fallow. Results unequivocally demonstrated that FYM, especially in conjunction with recommended 100% NPK (NPK+FYM) imparted profound improvements in soil health indicators compared to control and sole chemical treatments. The lowest bulk density (1.32 Mg m-3) and highest pore space (50.22%) were achieved with FYM, reflecting a well-aerated, low-compaction soil structure ideal for root development. Organic carbon (OC%) peaked at 1.18% under sole FYM application treatment and remaining available nitrogen (189 kg ha⁻1), phosphorus (35.43 kg ha⁻1) and potassium (422 kg ha⁻1) and Micronutrients such as Fe (18.8 ppm), Mn (9.54 ppm), Cu (2.61 ppm), and Zn (2.58 ppm) were also elevated in 100% NPK+FYM treatments, supporting both crop nutrition and soil microbial function. Biological health was best under FYM treatment with dehydrogenase activity (4.21 µg TPF g⁻1 day⁻1) and microbial counts peaking (bacterial counts 23.88 × 10⁶ cfu g⁻1, Actinomycets 6.21× 10-4 and Fungi counts 7.68 × 10-3), while the control consistently recorded the lowest values for all properties measured. These improvements translated directly into superior rice straw and biomass yields, consistently highest with the integrated 100% NPK+FYM regime. The study thus strongly recommends integrated nutrient management, especially the inclusion of FYM with balanced fertilization, as essential for sustaining soil quality, nutrient cycling and crop productivity in intensive Indian rice cropping systems. The findings are corroborated by recent multi-location long-term research across major rice-producing zones of India, highlighting the ecological and agronomic superiority of integrated fertilization for long-term agricultural sustainability.