Is it necessary to adjust nitrogen recommendations for tillage and wheat residue management in irrigated sweet corn?

Conservation tillage practices have gained interests. A 2-year field study (2014-2015) was conducted to evaluate four N rates (0, 69, 138, and 207 kg N ha(-1)) effects on irrigated sweet corn (Zea mays L.) grown with or without wheat (Triticum aestivum L.) residue removal and conventional (CT), reduced (RT), or no-tillage (NT) practices near Shiraz, Iran. After 2 years, maximum marketable yield occurred at 156 and 159 kg N ha(-1) under CT and NT, respectively, while yield was tended to be increased with increasing N rates under RT. Increasing N rate increased total plant N uptake, shoot, and grain N accumulation. The lowest nitrogen use efficiency (NUE) was obtained under NT, while RT and CT either showed similar effects or RT was superior over CT. Soil total N was greater under CT and residue retention showed 18% and 14% higher N concentration than residue removal in 2014 and 2015, respectively. Soil organic matter was the highest (2.59%) under RT with residue retention and 138 kg N ha(-1). Conservation tillage needs more N rather than CT during transition from conventional to conservation agriculture practices, but it is based on the short-term results and evaluation of long-term experiment is highly recommended.