Does occasional tillage undo the ecosystem services gained with no-till? A review

Continuous no-till (NT) is an effective practice to control soil erosion, conserve water, and reduce monetary and energy costs, but it can be challenged by inadequate weed control, soil organic C (SOC) and nutrient stratification, and risks for compaction, runoff, and acidification. Occasional tillage in NT (OT) could be a potential solution to such problems, but the question is: Does OT reduce or undo the beneficial soil ecosystem services from NT? To answer this, we 1) synthesized and interpreted published data on OT impacts in long-term NT systems on erosion, soil properties, crop yields, and other ecosystem services and 2) discussed potential factors that affect OT effects. The limited literature on OT provides important insights. It indicates that OT can increase runoff and sediment loss, reduce losses of dissolved nutrients and pesticides in runoff and have small effects on soil physical properties. Occasional tillage does not generally reduce soil water content needed for the crops nor reduce stocks of SOC, but it reduces vertical stratification of SOC and nutrients. Soil microbial biomass decreases with OT in some cases, but this reduction appears to have limited agronomic significance. Crop yield increases in about 15%, decreases in 5%, and does not change in 80% of cases. Impacts of OT on soils and crops generally lasted <2 yr. Controlled traffic, cover crops, diversified crop rotations, and soil amendments may accelerate soil recovery after OT, reduce the need for OT, and prolong the OT benefits. Tillage method, depth, frequency, and timing, and also soil temperature and water content affect OT performance. More research is needed to better target OT and choose among OT options for benefit optimization. Overall, OT one in 5-10 yr has limited or no effects on soil ecosystem services while reducing compaction and stratification, and aiding weed control as part of integrated weed management.