Effect of Tile Drain Spacing on Nitrate Losses, Heavy Clay Soil Properties and Wheat Crop Productivity in Egypt

Three field experiments were established at EL-Serw Agricultural Research Station, the Agricultural Research Center, Damietta Governorate, Northeast Delta Egypt, during three winter seasons from 2016 to 2019 to investigate the effect of subsurface drainage system on some soil properties, wheat productivity and nitrate loss from the soil under this study. The experiments were conducted in a randomized complete block design with three replicates. The subsurface drainage lines were divided into three spacings of 15 m, 30 m and 60 m, separated by a buffer zone and installed at a depth of 1.5 m and a slope of 0.1%. The results displayed that reducing drainage distances to 15 m led to decrease ground water level and its salinity, improve of the physical and chemical soil properties. As for promoting the yield and its components, as well as N-uptake of plant and Nitrogen application efficiency (NAE) of wheat plants was realized with narrow spacing compared to wider spacings. Regarding the N-available content of the soil and the loss of nitrates by leaching into the groundwater, they decreased with the reduction of the subsurface drainage spacings, so the nitrogen fertilizer application rate should be divided into 3 doses reduced nitrate losses by leaching. Finally, narrow spacing between tiles drain tends to improve the physical and chemical properties, lower the water table level, and increase production and (NAE) to the wheat crop.