Mina Taheri; Vahid Rezaverdinejad; Javad Behmanesh; Fariborz Abbasi; Javad Baghani
Abstract
Water resource deficiency and the necessity of sustainable production in irrigated lands have attracted much attention to water productivity issues. In this regard, analysis, estimation, and preparation of water productivity map are necessary as an influential factor to recognize cultivation potential ...
Read More
Water resource deficiency and the necessity of sustainable production in irrigated lands have attracted much attention to water productivity issues. In this regard, analysis, estimation, and preparation of water productivity map are necessary as an influential factor to recognize cultivation potential in irrigated lands. The aim of this study was to select a proper interpolation method for water productivity and investigate spatial changes in water productivity in Iranian wheat production centers. In this research, 241 field data were used, of which range of water productivity (irrigation water + effective precipitation) was estimated between 0.3 to 2.58 kg.m-3 with the average of 0.79 kg m-3, in 2016-2017 season. Interpolation methods used included Ordinary Kriging, Inverse Distance Method (IDW), and Radial Basis Function (RBF). Cross Validation technic was applied to evaluate methods by statistical measures such as Root Mean Square Error (RMSE), Mean Bias Error (MBE), and Mean Absolute Relative Error (MARE). Interpolation methods evaluation showed that between available procedures, typical Kriging method with exponential semi-variogram model had the most proper condition to prepare wheat water productivity zoning map. The results of the spatial analysis of water productivity confirmed that geostatistics could be used with acceptable accuracy (MBE=0.005) to provide water productivity mapping. Results of Cluster analysis of the effective factors (salinity of irrigation water, soil salinity, and crop cultivar) on wheat water productivity index showed that the areas suitable for wheat cultivation were separated into 13 independent groups (at the 5 percent level), such that the highest and lowest mean water productivity of wheat were observed in group 5 (Mean = 0.84 kg.m-3) and group 10 (Mean = 0.41 kg.m-3), respectively.
h a; f a
Abstract
Optimization of water and nitrogen applicationdecreases production costs, conserves resources, and reduces environmental pollution which occurs as a result of excessive use of these resources. The objective of this study was to optimize applied water and urea in corn fertigation. A field experiment ...
Read More
Optimization of water and nitrogen applicationdecreases production costs, conserves resources, and reduces environmental pollution which occurs as a result of excessive use of these resources. The objective of this study was to optimize applied water and urea in corn fertigation. A field experiment was carried out in furrows, having 165m length and 0.006 m/m slope, in Karaj. The corn hybrid 370 double-cross was planted on June 2008 and 2010. The experiments were carried out according to a factorial arrangementbased on randomized complete block design with 4 replicates. Four levels (0, 60%, 80%, and 100%) of the recommended fertilizer value and four levels (60%, 80%, 100%, and 120%) of irrigation water requirement were applied. Fertilizer treatments were accomplished atfour critical stages of the growth (before cultivation, seven-leaf stage, shooting stage, and flowering stage). In this study, an analysis of crop yield production, cost and revenue functions, and profit maximization was conducted to determine the optimal water and nitrogen use. The results of multiple regression at 5% level showed that the relationship between the grain yield and the amount of each of the inputs of water and nitrogen was a quadratic function (R2=0.83 and ME=15.53%). The optimal level of urea consumption was dependent on applied water. By increasing the amount of irrigation water, the optimum level of fertilizer consumption is increased. When land is limiting, use of full irrigation (940 mm) and 375 kgurea/ha leads to maximum income. When water is limiting, the optimum amounts of applied water and urea were774 mm (77% of water requirement) and 357 kg/ha (90% of urea recommendation), respectively.