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

Abstract

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 N-use efficiency.