A Nehzati Pghaleh, Sh Zandparsa, A.r Sepaskhah,
Volume 12, Issue 46 (1-2009)
Abstract
Water and fertilizer applications management should be improved due to scarce resources and environmental protection aspects. An analysis of crop yield production and profit maximization was conducted to determine the optimal water and nitrogen allocation. In this study, maize grain yields were predicted for 25 different amounts of irrigation water (350-1700 mm) and 46 different rates of nitrogen application (0-450 kg N/ha) were predicted using MSM (Maize Simulation Model) model. Irrigation water was distributed in growth period based on maize evapotranspiration. 30% and 70% nitrogen fertilization was used 19 and 50 days after planting date, respectively. Based on field operational costs and present market value in Fars province, optimal amounts of applied water and nitrogen were determined in different conditions of maximum yield (Wm and Nm, respectively), maximum profit under limited land (WL and NL, respectively) and maximum profit under limited water (Ww and Nw, respectively). At present market value ( 88 Rls m-3 for water, 1946 Rls kg-1 for nitrogen and 1570 Rls kg-1 for maize grain), the amounts of Wm, WL and Ww were 1336, 1008, 844 mm, respectively, and the amounts of Nm, NL and Nw were 450 kg N ha-1. Because of the low price of nitrogen, the optimum amounts of nitrogen in the analyzed conditions were similar. If the price of nitrogen and water are increased (i.e. 30000 Rls kg-1 N and 1000 Rls m-3 water), the optimum amounts of applied nitrogen and water in the analyzed conditions are changed to 450, 120 and 210 kg N ha-1, and 1336, 899 and 874 mm, respectively.
