No-tillage and soil physical environment

Implications of no-till (NT) management on soil C dynamics, soil fertility, and crop yields have been discussed, but an up-to-date synthesis of NT impact on soil physical properties based on a comprehensive compilation of global published studies is not available. Yet, an understanding of changes in soil physical properties after NT adoption is important to manage soils, agricultural production, and environmental quality. We compared data on soil physical properties among NT, reduced till (RT), and conventional till (CT) systems, discussed factors influencing tillage system effects, and underscored research needs. No-till had mixed effects on soil bulk density and penetration resistance but reduced Proctor bulk density (compactibility) by 4 to 13% in the 0 to 15 cm depth, suggesting that NT can reduce the susceptibility of the soil to compaction. No-till increased wet aggregate stability by 1 to 97%, water infiltration by 17 to 86%, and available water by 44%. It reduced or had no effect on soil temperature during the growing season but increased soil thermal conductivity. The latter indicates that NT can increase the soil's ability to conduct heat. No-till induced some slight water repellency, which can reduce soil aggregate slaking and enhance C storage. However, NT had no consistent effects on saturated hydraulic conductivity, soil consistency, and shear strength. Reduced till effects on soil properties were intermediate in values between NT and CT. No-till benefits for reducing compaction risks and improving structural quality increased in the long term. Changes in soil physical properties appear to be mainly confined to the upper 10 cm depth. Reviews on NT and soil C have also concluded that NT can cause stratification of soil organic C in the upper 5 or 10 cm depth. Thus, NT-induced increases in near-surface ( <10 cm depth) soil organic C concentration most likely improved wet aggregate stability and available water capacity, and reduced compactibility. One-time tillage of NT soils does not seem to negatively affect soil physical properties. Addition of companion practices (i.e., cover crops, C amendments) can enhance NT performance. Overall, NT management can have positive effects on soil physical properties with the extent depending on soil textural class and management duration.