Simultaneous‏ ‏effects of irrigation method and different‏ ‏levels of irrigation water on the ‎canola yield in the semiarid region

Background and Objective: Water is the most important and limiting production factor in agriculture. The rapid decline of groundwater table is threatening sustainable irrigation agricultural development. Considering the limitation of ground water resources and the necessity of optimal use of surface water, the reform of the Irrigation systems is a necessity. Iran is located in one of the driest regions of the world. Based on this, one of the major challenges in providing food for the growing population is the issue of water and proper management of water resources. With the increasing shortage of irrigation water, new irrigation methods for optimal use of water will be more important in the future. Another way to increase water productivity is to adopt deficit irrigation strategies. Deficit irrigation is defined as the use of water less than the plant's water requirement, which has been developed in many countries in order to reduce the amount of irrigation water.
Methodology: This study compares the effects of different irrigation regimes on seed yield and water productivity of canola with three irrigation mathods of furrow, sprinkler and drip whith foure irrigation treatments included 60, 80, 100, and 120 percent of full irrigation amount. For this purposea field experiments was carried out using a split plot arrangement in randomized block design with three replications inTabriz in 2018-2019 and 2019-2020 grwoing seasons. The soil class of the farm is sandy loam. The amount of effective rainfall in the growing season was 278 mm in the first year and 202 mm in the second year.
In each experimental unit of furrow and drip irrigation method, there were 4 rows of planting 8 meters long and in each experimental unit of sprinkler irrigation method there were 6 rows of planting 3 meters long. The distance between planting rows was 50 cm and the distance between plants in each row was 3 to 5 cm, and the seeds were planted at a depth of 1 to 2 cm. Octans autumn hybrid canola seed variety was used for cultivation. Hunter model A12 hidden sprinkler with a spraying radius of 3.7 meters was used for sprinkler irrigation. In this plan, a sprinkler was installed in each corner of the plot, and to prevent interference between the plots, the radius of the sprinkler was adjusted to 90 degrees. For drip irrigation, a strip with an aperture distance of 20 cm and a thickness of 175 microns was used.
In this research, the irrigation timing was applied in the furrow method based on the fixed cycle of 10 days for the area and for drip and sprinkler irrigation cycle of 5 days. The amount of irrigation water in each irrigation round was estimated by measuring the volumetric soil moisture before each irrigation round in the full irrigation treatment, and according to the area of each plot and applying the irrigation efficiency, the amount of water used for each method was obtained. The actual evaporation and transpiration of rapeseed was obtained from the water balance equation. At the end of the growing season, the product of each plot was harvested separately and the weight of dry matter, weight of seeds, weight of 1000 seeds, the amount of yield per unit area and other characteristics were measured and recorded, and the parameters related to water consumption efficiency for each plot were was achieved
Findings: The obtained results showed that regardless of the amount of irrigation, crop yield and other growth indicators were better in drip irrigation than the other two methods, so that the drip method at the level of 120% had the highest amount of yield, weight of 1000 seeds and plant height. The lowest amount of irrigation water is related to the drip method at the level of 60%, and this method reduced the amount of irrigation water by 49% and 21%, respectively, compared to furrow and sprinkler irrigation at the same level. The highest value of water prodoctivity and irrigation water prodoctivity related to drip irrigation was at the level of 60%. At this level, the drip method increased the efficiency of water prodoctivity by 87% and 25%, respectively, compared to the furrow and sprinkler method.
Conclusion: The results of this research showed that the use of modern irrigation methods such as drip and sprinkler instead of the surface methods, in addition to saving the amount of water used, also improves the performance of the product. Also, the application of deficit irrigation techniques in these methods will have less yield loss and increase the water use efficiency compared to traditional methods.