Soil nitrogen status can be improved through no-tillage adoption particularly in the surface soil layer: A global meta-analysis

United Nations 'Sustainable Nitrogen Management' (UNEP/EA.4/L.16) resolution calls for adopting best practices for recovery and recycling of N. Bulk of the soil N stock is in soil organic matter (SOM) form. The stabilization of SOM following conversion to no-till practice will, therefore, regulate N flux and storage in soils. To realize the no-tillage (NT) effect on soil N, a global meta-analysis was conducted with 2,268 pairs of data points from 327 peer-reviewed articles. Increases of 21 and 16% in total N concentration and N stock, respectively, were noted under NT compared to conventional tillage (CT) in the surface soil layer (0-10 cm). However, no such changes were accounted for down the profile. Continental and temperate climates recorded significant gains in total N in NT while the effect was negligible in tropical and dry climates. Soil N increased in NT irrespective of soil texture; coarser the texture, marginally higher was the gain. An incremental rise in soil N was evident with an increase in the duration of NT adoption. The cereal-cereal and cereal-legume rotations had marginal advantages with NT over other cropping systems. The surface 0-10 cm layer recorded the largest N stock under NT, which remained similar down the depth. A decrease in soil pH was noted with conversion to NT practice, but soil electrical conductivity was comparable with CT. No-tillage favoured the soil N and as a consequence, fertilizer-N use under no-till condition, must take into account of the potential N release from SOM for achieving higher Nuse efficiency.

Automated summary

This study conducted a global meta-analysis and found that no-tillage (NT) farming can increase soil nitrogen concentration and stock, especially in continental and temperate climates. Soil texture has a minimal impact on the effects of NT, while the duration of NT adoption can further enhance soil nitrogen content. The choice of crop rotation also influences the NT effect. No-tillage farming benefits soil nitrogen, but potential nitrogen release from soil organic matter should be considered when applying fertilizer nitrogen under NT conditions.