Long-term effect of integrated nutrient management of properties of typic ustochrept after 23 cycles of an irrigated rice (Oryza sativa L.) - wheat (Triticum aestivum L.) system

A field experiment with rice at the Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana, India under a rice-wheat system was conducted to study the long-term effect of integrated nutrient management (INM) on physicochemical and microbiological properties of soil after 23 cycles of a rice-wheat cropping system. The experiment comprised 14 treatment combinations viz., N, P and K fertilizer application as individual component and use of chemical fertilizers in conjunction with different organic sources to substitute 25% to 50% N through farm yard manure (FYM), wheat cut straw (WCS), and green manure (GM) with Sesbania aculeata. The experimen-tal treatments were replicated three times. GM, WCS, and FYM improved the physical properties of soil like water-holding capacity, penetration resistance, and bulk density. The integrated nutrient management technique resulted in a positive influx of nutrients by increasing organic carbon content, available nitrogen, phosphorus, and potassium varying from 0.390 to 0.543%, 171.7 to 219.3 kg ha^-1, 20.5 to 43.3 kg ha^-1, and 124.6 to 148.9 kg ha^-1, respectively. Also, NO₃-N and NH₄-N and DTPA-extractable Zn, Cu, Fe, and Mn content showed significant improvement in the soil with the addition of FYM, WCS, and GM. These three organic sources of nutrition along with chemical fertilizers helped to improve infiltration rate, available soil moisture, labile C, and microbial count. However, there was a decrease in bulk density, soil strength, pH, and EC of soil with the application of FYM, WCS, and GM in conjunction with chemical fertilizers as compared with chemical fertilizer application alone.