Effect of No-Tillage, Water Tension, and Nitrogen on Soil Nitrate Movement and Corn Yield in the North of Khuzestan

The objective of this study was to evaluate the effect of different levels of irrigation and nitrogen fertilizer on nitrate movement, yield, and water use efficiency (WP) of corn in no-till planting method. The research was conducted in two years as a randomized complete block design arranged in a split block treatment design with three replicates in the Safiabad Agricultural Research Center. Irrigation treatments amounts of 50%, 75%, and 100 % of crop water requirement (I₁, I₂, and I₃) were allocated to the main plots, and three levels of nitrogen i.e. 150, 225, and 300 kg ha^-1 (N₁₅₀, N₂₂₅, and N₃₀₀) were in the sub plots.  The average corn yield of 5 t ha^-1 showed that summer corn no-till planting in wheat residue without any tillage practice was applicable in Khuzestan climate conditions. Irrigation treatments had a significant effect on corn yield (p<0.01), such that the maximum yield (5.5 t/ha) was obtained from I₃ with 1037 mm applied water, and minimum yield (4.2 t/ha) was from I₁ with 786 mm of water. Nitrogen had significant effect on yield (p<0.05) and protein percent (p<0.01), such that the N₃₀₀ treatment had the maximum yield of 5.4 t/ha with a protein percent of 10.1%.  In all treatments, fertilizer was leached within 0-30 cm soil layer, while nitrate concentration in deeper layers was 30-50% of the surface layer. However, in deeper layers, nitrate concentration variation in the same fertilizer treatment was not much.