Effects of different groundwater depths and salinities on evapotranspiration, yield and quality parameters of wheat

This study was conducted to evaluate the effects of 3 different groundwater depths (30, 55, and 80 cm) and 4 different groundwater salinities (0.38, 2, 4, and 8 dS/m) on evapotranspiration, yield, quality parameters, soil salinity, and temporal changes of antioxidant enzymes (Superoxide dismutase (SOD), Catalase (CAT), Glutathione Reductase (GR), Glutathione-S-transferase (GST)) of wheat crops in 2018 and 2019 under rain shelter area. The experimental trials were laid out in a randomized complete block design with 3 replications in lysimeters. In both years of the study, evapotranspiration, yield, water use efficiency, 1000-grain weight, plant height, grain number per spike, stomatal conductance, and spike length increased with increasing groundwater depth. However, evapotranspiration, yield, and quality parameters were found to decrease with increasing groundwater salinity. The highest yield and evapotranspiration values were found to be 963.3 kg da-1 and 630.12 mm in 2018 and 886.83 kg da-1 and 550.12 mm in 2019, respectively. Water use efficiency values varied between 1.49-1.65 kg m-3 in 2018 and between 1.18-1.73 kg m-3 in 2019. The highest soil salinity values were obtained at a groundwater depth of 30 cm, while the lowest values were obtained at a groundwater depth of 80 cm. Antioxidant enzyme activities differed significantly according to groundwater depth and groundwater salinity. In addition, GR enzyme activities were strongly and negatively correlated with plant height, 1000-grain weight, stomata conductance, and hectoliter weight. In contrast, no correlation was found between SOD enzyme activities and yield and quality parameters. Accordingly, it is recommended that GR enzyme changes be considered in predicting the damage that may occur in pandas wheat plant morphology and physiology under saline groundwater conditions to minimize grain yield and quality losses. Under controlled drainage conditions, groundwater can be kept constant at a depth of 55 cm and at 0.38 dS/m to increase the contribution of groundwater to wheat crops. However, as groundwater salinity increases, it is recommended that groundwater depth be kept constant at 80 cm or deeper for sustainable agricultural production.