Effect of Dificit Irrigation Management in Wheat Different Growth Stages on Its Improvement of Economic Productivity

Optimizing the economic utilization and saving of water resources is a global issue in water resources and its demand management. Also food demand continues to rise with increasing population. Thus, it is necessary to use water resources efficiently in the agricultural sector as the major consumer of water resources in Iran. In relation to economic assessment of agricultural water uses, especially wheat as a strategic and dominant crop pattern, there has been inadequate study in the country and inappropriate attention to this issue. In this regard, it is important to investigate different timing and amount of irrigation, and determine optimum option based on different indices like productivity of yield per unit of input. Therefore, the main aim of this study is to determine the optimal water use in different growth stages and economic assessing of treatments in Shahrekord region, Chaharmahal & Bakhtiari province, Iran. This experiment was conducted in complete block design in Chahartakhte research station, in Shahrekord with dry and cold climate. There are five irrigation treatments included E0, E1, E2, E3 and E4 with the irrigation depth of 100, 85, 70 and 55 percent of wheat evapotranspiration obtain from lysimeter. Crop growth stages were divided into six stages (T1, T2, T3, T4, T5, T6) including germination, tillering, stem elongation, flowering, milky and dough. Deficit irrigation and water stress was applied on only one step of growth season (as an example only T1) and other growth season periods were irrigated based on 100 percent of wheat evapotranspiration. In the current economic assessment study to achieve the best deficit management practices through partial budgeting, the cost ratio for each treatment, net profit, total productivity of water use and profitability in each of the treatments were determined, respecting the price of water and irrigation and other inputs. When the price of water is more than the profit from increased production by changing irrigation management, water and irrigation costs are equal and it is called as profit. After determining the price of water consumption as well as income and production costs, water productivity results and statistical tests were analyzed. SPSS and MSTAT-C statistical software was used for statistical analysis. Then, the best period and the best level of deficit irrigation for the production of wheat were determined and suggested as the optimal level and stage for deficit irrigation application. Investigation of the average cost showed that the maximum net profit was happened in treatments E3 during the tillering (40492 thousand Rials). According to results, the maximum cost ratio was 2.25, related to treatment E4 which was applied in the ripening stage. In general, all treatments have benefit-cost ratios greater than one. E4 treatments applied during the plant to achieve maximum economic efficiency (12.78 thousand cubic meter) and maximum productivity of irrigation water (1.58 kg per ha). According to mean comparison results, E2 treatments had maximum yield equal to 5.25 ton per ha and E4 treatment had minimum yield with 3.85 ton per ha. There was no linear relationship between yield reductions and reducing the irrigation water application. Comparing the average yield resulting from the application of deficit irrigation in different growth periods indicated the period T4 with the lowest yield (4.28 tons per hectare) was the most sensitive period to decreasing the irrigation water. The maximum gross income was gained by E2 (74127 thousand Rials) and the minimum by E4 (58080). The irrigation treatments cost had declining trend, E0 to E4. In all treatments benefit-cost ratio were greater than one. Applying deficit irrigation during the growing period (with the economic productivity of 1.17) is recommended. After it, the treatments of E3 and E4 (with economic productivity 1.09 and 1.01, respectively) and then applying deficit irrigation practices in growing period, T2 and T5 (tillering and pasty), by productivity of 1.049 and 1.092 are suggested. Achieving maximum yield and economic productivity, E2 treatment is recommended. In this treatment with 70% of evapotranspiration, the economic productivity was equal to 1.13; and by applying deficit irrigation during the growing period, the economic productivity was equal to 1.17. Finally, note that it is necessary to identify the critical periods of water stress and be aware of the relationship between crop yield and water use in irrigation. To achieve optimum production in wheat cultivation, efficient use of limited water resources is inevitable