Optimizing application rate of nitrogen, phosphorus and cattle manure in wheat production: An approach to determine optimum scenario using response-surface methodology

Optimal application rates of inorganic nitrogen (N), phosphorus (P) and cattle manure were estimated using Response Surface Methodology (RSM).A Central Composite Design (CCD) was conducted at field level during 2012-13 and 2013-14 growing seasons.The applied levels of N were 0, 150 and 300 kg N ha -1 in form of urea.The levels used for P fertilizer were 0, 100 and 200 kg ha -1 (P 2 O 5 ) and for cattle manure were 0, 15 and 30 t ha -1 .Both seed yield (SY), biological yield (BY) were measured at harvest time.N loss (NL) and Agronomic N Use Efficiency (ANUE) were calculated based on other measurements.Increasing N and P rates up to 200 kg ha -1 increased SY.Optimization of N, P and manure application amount was based on economic, environmental and eco-environmental scenarios.Under economic scenario, using 145.4 kg ha -1 N, 200 kg ha -1 P and 18.4 t ha -1 manure resulted in 6500 kg ha -1 SY with ANUE of 10.49.For environmental scenario, by N application of 21.2 kg ha -1 , no application of P and applying 16.3 t ha -1 manure, SY and ANUE of 3160 kg ha -1 and 9.08 were obtained, respectively.Using eco-environmental scenario, by applying 144.7 N and 34.3 kg ha -1 P, plus 30 t ha -1 manure, about 4031 kg ha -1 SY and a considerable high ANUE of 16.5 were recorded.The results of this study showed that the privilege of eco-environmental scenario compared to the other scenarios was mainly due to higher ANUE.