Residual effect of organic amendments (FYM and biochar) and urea types on soil nitrogen dynamics and wheat (Triticum aestivum L.) performance

Abstract

Integrated Nutrient Management (INM), which combines organic soil amendments with synthetic fertilizers, is an important strategy for maintaining soil fertility and crop productivity. The aim of this study was to evaluate the performance of wheat (var. Zinc Gahun-1) and the post-harvest soil nitrogen dynamics under residual effects of organic amendments with varied urea types and rates in Rupandehi, Nepal. A split plot experiment was conducted using Farmyard Manure (FYM) and biochar as main-plot factors and five urea treatments with 100% Neem Coated Urea (NCU), 50% NCU, 100% Prilled Urea (PU), 50% PU and a zero-urea (control) as sub-plot factors. Post-harvest soil total nitrogen (TN%) in topsoil (0-15cm) and subsoil (15-30cm) was evaluated using the Kjeldhal apparatus alongside key agronomic traits. The 100% NCU treatment yielded peak performance with 87.37cm plant height, 202.8 tillers/m2, 43.2 grains/spike and 3.65 t ha-1 while, the control attributed 76.83cm plant height, 184.98 tiller numbers/m2, 35.63 grains/spike and grain yield of 2.36 t ha-1. 50% NCU and 100% PU showed statistically similar performance in almost all variables. Soil total nitrogen correlated strongly to topsoil (0- 15cm) at 0.099% compared to subsoil (15- 30cm) at 0.043%, indicating lower nitrate leaching. However, organic amendments showed negligible statistical differences with slight numerical edge of biochar compared to FYM. Thus, this indicated that farmers in terai of Nepal can effectively reduce the input costs for fertilizers by substituting conventional prilled urea with neem coated urea for similar crop productivity while maintaining organic amendments for long term soil health.