Abstract

With changing climate and introduction of new varieties over time, it is imperative to revisit the nitrogen fertilizer dose for optimum rice yields. Increasing prices of N has also necessitated the calculation of economics of N use. To achieve these objectives, a number of field studies were conducted on fine rice to determine its response to increasing nitrogen doses in Rice-Wheat and Central zones of Punjab Pakistan for four years from 2017 to 2020. During the first two years of study (2017 and 2018), seven doses of N (0, 28, 56, 84, 112, 140, 168 kg ha-1) were tested at different locations. Half of nitrogen was applied to soil at transplanting and remaining half was applied about 30 to 35 days after transplanting. Phosphorus and potash were applied to soil at transplanting uniformly @ 90 and 60 kg ha-1 to all treatments except the check (No fertilizer). Increasing nitrogen levels upto 140 kg ha-1, a significant increase in paddy yield was observed. However, further increase in N level did not result in any increase in yield; rather it decreased paddy yield. Agronomic efficiency and partial factor productivity of N decreased with increasing doses of N and it was reduced to 9.3 and 30 respectively at N level of 140 and 168 kg ha-1. Economic analysis of N use on fine rice showed decreasing marginal rate of return (MRR) with increasing doses on N and it was 5.0 and 2.5 respectively for Rice-Wheat and Central zones at 140 kg N ha-1. Above this level of N, the MRR became negative. Therefore, it was concluded that soil application of 140 kg N ha-1 was the most optimum dose for obtaining an economic yield for current scenario for fine varieties of rice. The outcome of this study will help formulating nitrogen fertilizer recommendation of fine rice.