Water productivity of soybeans under regulated surface and subsurface drip irrigation conditions

Increasing population, pollution of current natural resources, global warming and climate change are increasing pressure on water resources. To maintain the food security of the increasing population, it is essential to increase sustainable agricultural production and to use current limited water resources optimally. In this study, the effect of surface drip (SDI) and subsurface drip (SSDI) irrigation methods on water productivity, yield and quality characteristics of soybeans were evaluated. The study was carried out in Bati Akdeniz Agricultural Research Institute located in Antalya, Turkey. To evaluate the performance of the SDI and to compare it with the SSDI, an experiment was conducted based on a randomized blocks design with two factors: irrigation method (SDI and SSDI) and irrigation levels defined as the percentages of available water capacity of the soil profile (100%, 80%, 60%, and 0%). Applied water varied between 45-488 mm and 171-541 mm in the SSDI, and between 50-573 and 164-640 mm in the SDI, during 2016 and 2017, respectively. The yield ranged from 1.98 to 5.61 t ha(-1) for SDI and from 2.29 to 6.33 t ha(-1) for SSDI. While the increased amount of irrigation water had a positive relationship with the yield, there was a negative relationship with the oil content and fatty acid composition. The SSDI treatments used approximately 90 mm less water than the SDI without any reduction in yield.