Management of nitrogen fertilizer, irrigation and plant density in onion production using response surface methodology as optimization approach

Abstract

Response surface methodology (RSM) is defined as a collection of mathematical and statistical 
methods that are used to optimize a product or a process. In order to determinate optimum levels of 
nitrogen (N), water volume and plant density of onion (Allium cepa L.), and field experiment was carried 
out according to a central composite design as RSM in Azarshahr County, East Azerbaijan Province, 
Iran –repeated over two years (2011 and 2012). The treatments were designed based on low and high 
levels of N, irrigation and plant density as independent variables. Furthermore, bulb yield, N losses, N 
uses efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full 
quadratic polynomial model. Optimum rates of N, irrigation and plant density was suggested to achieve 
the target range of response variables based on three scenarios: Economic, environmental and eco
environmental. The results showed that increasing of N fertilizer up to 160 kg N ha-1 led to increase in 
bulb yield. The amounts of 93.48 kg N ha-1 , 8930 m3 water ha-1 and 42.67 onions m-2 was found to be the 
optimum conditions for eco-environmental scenario. In general, it seems that resource use based on 
eco-environmental scenario may be the most favorable cropping strategy in onion production.