Effects of residue management and nitrogen fertilizer rates on accumulation of soil residual nitrate and wheat yield under no-tillage system in south-west of Iran

Conservation tillage, residue management and optimizing nitrogen (N) fertilization are important strategies for soil and water conservation and sustainability of agricultural systems. In order to evaluate the effects of various residue management methods and N fertilizer rates on some soil quality indicators, accumulation of residual soil nitrate, and wheat yield under no till system, a split-plot experiment was arranged in a randomized complete block design with three replications. Main plots were three residue management methods, including retaining (R.M1), removing (R.M2) and shredding (R.M3) of corn residues. The subplots consisted of four N fertilizer rates, 100 (N1), 150 (N2), 200 (N3), and 250 (N4) kg N ha-1 from urea source. The results showed that soil organic carbon and total N in R.M1 and R.M3 treatments increased at the depth of 0e15 cm as compared to R.M2. The maximum accumulation of soil nitrate was observed in R.M1 x N4 and R.M3 x N4 interactions at the soil depth of 60-cm. The results of this study showed that R.M1 x N3 and R.M3 x N3 interactions had a greater impact on wheat yield than the sole effect of R.M1 or R.M3. According to our findings, application of 200 kg N ha-1 in combination with R.M1 which had once less tractor passing for mechanical shredding than R.M3, can contribute effectively to improve soil quality indicators, control soil residual nitrate and subsequently produce more wheat grain yield in the south-west of Iran.