Response of nitrate leaching to no-tillage is dependent on soil, climate, and management factors: A global meta-analysis.

No tillage (NT) has been proposed as a practice to reduce the adverse effects of tillage on contaminant (e.g., sediment and nutrient) losses to waterways. Nonetheless, previous reports on impacts of NT on nitrate ( ) leaching are inconsistent. A global meta-analysis was conducted to test the hypothesis that the response of leaching under NT, relative to tillage, is associated with tillage type (inversion vs non-inversion tillage), soil properties (e.g., soil organic carbon [SOC]), climate factors (i.e., water input), and management practices (e.g., NT duration and nitrogen fertilizer inputs). Overall, compared with all forms of tillage combined, NT had 4% and 14% greater area-scaled and yield-scaled leaching losses, respectively. The leaching under NT tended to be 7% greater than that of inversion tillage but comparable to non-inversion tillage. Greater leaching under NT, compared with inversion tillage, was most evident under short-duration NT (<5 years), where water inputs were low (<2 mm day ), in medium texture and low SOC (<1%) soils, and at both higher (>200 kg ha ) and lower (0-100 kg ha ) rates of nitrogen addition. Of these, SOC was the most important factor affecting the risk of NO leaching under NT compared with inversion tillage. Globally, on average, the greater amount of NO leached under NT, compared with inversion tillage, was mainly attributed to corresponding increases in drainage. The percentage of global cropping land with lower risk of NO leaching under NT, relative to inversion tillage, increased with NT duration from 3 years (31%) to 15 years (54%). This study highlighted that the benefits of NT adoption for mitigating leaching are most likely in long-term NT cropping systems on high-SOC soils.