Fertilizer N Economy, Soil Nutrient Status, Water Use Efficiency and Rice Productivity with Real-time Nitrogen Management and Organic Residues under Irrigated and Rainfed Situations

Integrated nutrient management by combining organic and inorganic sources of plant nutrients has been found to improve and sustain soil and food productivity. A field experiment was conducted in a silty clay loam acid Alfisol to investigate the utility of lantana (Lantana spp.) biomass, an obnoxious weed, unfit as cattle feed, and growing abundantly in uncultivated areas, as an organic amendment in rice-wheat cropping system. Soil applications of the freshly-chopped lantana biomass at 15 t ha⁻¹ yr⁻¹ before puddling were initiated in 1999 wet season (ws). Three N management treatments (N applied at LCC=2 and LCC=3, and at recommended rate of 90 kg ha⁻¹) under two water regimes (irrigated vs rainfed) were imposed to rice in 2003. After seven rice-wheat cropping cycles (June 2006), soil organic carbon, available N, Olsen's P and exchangeable K were 1.18%, 378, 42 and 110 kg ha⁻¹, respectively, with lantana addition (M₁), and 1.10%, and 323, 33 and 99 kg ha⁻¹ without lantana addition (M₀), as against initial values of 1.08%, and 314, 22 and 121 kg ha⁻¹. Rice grain yield (2003–2005) increased by 4–21% with M₁ compared to M₀, and 4–13% with LCC = 3 compared to fixed recommended dose of N (RFD). Irrigated rice produced 6% higher yield than rainfed rice. Water use efficiency (WUE) was highest under rainfed condition, with M1 and LCC=3. Nitrogen management using LCC saved 30 and 60 kg ha⁻¹ fertilizer N without and with lantana addition, respectively, over RFD. Thus, real-time N management through LCC= 3 coupled with lantana biomass economized on fertilizer N, and enhanced the rice productivity and WUE under both irrigated and rainfed situations.