Increased rice production is required to meet rising demands, but additional production should come from the sustainable intensification of existing farmlands to minimize the undesirable effects to the environment. Nitrogen (N), phosphorus (P) and potassium omission plot experiment in rice was conducted on 36 famers’ field during 2011 and 2012 in Nawalparasi district of Nepal to quantify the indigenous nutrient supply (INS) and formulation of site specific nutrient management (SSNM) nutrient dose, and SSNM dose was formulated and evaluated on seven farmers’ field during 2013. N application rates were further fine-tuned by applying N fertilizer based on the crop nutrient status and crop demand using a leaf color chart (LCC). Yield responses to fertilizer application followed the order of N > > P ≥ K. Mean grain yields in the nutrient omission plots increased in the order of 0 kg N ha-1 (3.63 t ha-1) < < 0 kg P ha-1 (4.81 t ha-1) ≤ 0 kg K ha-1 (4.82 t ha-1) and the resultant indigenous N, P and K supplying capacity of the soil were 53, 29 and 84 kg ha-1.  With the SSNM approach, rice yield increased by 37% (1.73 t ha-1) than the current farmers’ fertility management practice (FFP). SSNM harmonized uptake of major nutrients, increased panicle numbers, decreased ineffective tillers, and increased thousand grain weight.  SSNM significantly decreased average N application rate by 4% and P2O5 application by 28% while K2O application rate increased by 80% and increased yield by 6% as compared to recommended NPK. Further, LCC improved the grain yield by 5% (310 kg ha-1) with the same amount of N application. It shows SSNM and LCC are the appropriate N management strategies, while appropriate K management strategies are urgently required to maintain the K content of the soil.

 

Keywords: Indigenous nutrient supply, Nitrogen use, Nutrient uptake, Site-specific nutrient management