Managing Fertilizer Rates and Tillage Depth to Improve Nitrogen Use Efficiency and Soil Health

Nitrogen (N) fertilizers boost agricultural yields, but N lost from agricultural systems may endanger the ecosystem. The agronomic practices leading to high N recovery with decreased losses without compromising yields need to be identified. Field experiments were conducted for two consecutive wheat growing seasons using three levels of N fertilizers as urea: recommended dose N (134 kg N ha^{− 1}), 25% less than recommended and 25% more than recommended, a control (no N fertilizer), two alternative N sources (calcium ammonium nitrate (CAN) and animal (cattle & buffalo) manure applied with the equivalent of N applied as urea. All N treatments were applied under conventional tillage (0–15 cm) along with the recommended dose of urea under deep tillage (15–30 cm). Higher N fertilizer rates increased grain yield (49% higher than the control), and decreased soil microbial biomass carbon and leucine aminopeptidase activity compared with the control indicated better N utilization efficiency. Nitrate leaching occurred with CAN & urea applications as well as in the deep tillage. Deep tillage improved wheat N recovery and reduced atmospheric reactive N losses. This study indicated that raising N fertilizer rates to improve production may harm soil health and the ecosystem. By boosting N recovery, deep tillage may reduce atmospheric N losses. CAN use lowered wheat production because of low N utilization efficiency, but animal manure enhanced it.