Trade-off between soil pH, bulk density and other soil physical properties under global no-tillage agriculture

Abstract

No-tillage (NT), here defined as NT with/without residue retention, has been widely used as a sustainable alternative to conventional tillage (CT). In particular, site-specific effects of NT on the soil pH, and soil physical properties including bulk density, total porosity, aggregate size and stability, hydraulic property, available water capacity have been intensively studied within various agroecosystems in the past decades. However, the synthesis of information on a global scale remains lacking. Here, using a global dataset based on 264 publications, effects of agronomic/environmental factors on soil physical properties under NT were quantified by intensive meta-analysis. We found that the effects of NT on soil physical properties are fairly complex, and greatly depend on climate conditions, experimental duration, and soil texture. Specifically, relative to CT, NT increased soil bulk density by 2.3%. Soil bulk density increased by 3.7% during the first 6 years of NT. Meanwhile, NT increased soil penetration resistance by 27.8%; NT decreased soil pH by 1.8%, the greatest reduction took place in silty soils (5.6%) or during a moderate-term NT (6–12 years, 5.0%). Nonetheless, regardless of environmental and agronomic factors, NT improved mean weight diameter and water-stable aggregate by 50 and 36%, respectively. Although NT had no effects on the saturated hydraulic conductivity, it enhanced soil available water capacity by 8.7%. Taken altogether, the trade-offs between observed negative effects such as increased bulk density and decreased soil pH; and positive effects such as improved aggregate size and stability, and soil water availability demonstrate the overall beneficial responses on soil physical property under global NT agriculture. Furthermore, the present study demonstrated that climate conditions (e.g. mean annual precipitation and temperature), and experimental duration appeared to be the predominant factors controlling the response of soil properties to NT application. These results will help design site-specific NT management strategies considering highly informative, and prevalent environmental and agronomic factors within a local environment.