Conservation tillage increases nutrient accumulation by promoting soil enzyme activity: a meta-analysis

The conservation tillage i.e. reduced tillage (incl. no tillage and minimum tillage) and straw return, plays an important role in the promotion of sustainable agriculture. However, comprehensive cognition is still weak on how conservation tillage improves soil.

Here, we collected 7613 paired observations from 308 publications to reveal the improvement of soil by conservation tillage in perspective of coupled soil nutrients and soil functional enzyme activities.

(1) Conservation tillage had positive effect on soil organic matter, total nitrogen, total phosphorus, total potassium, dissoluble organic carbon, available nitrogen, ammonium nitrogen, available phosphorus, available potassium, microbial carbon, and microbial nitrogen (7.44–30.56%) via promoting soil enzyme activity, while significantly reduced nitrate nitrogen (-11.55%), and this effect was more concentrated in soil surface. (2) The accumulation of soil nutrients under conservation tillage was closely related to the soil functional enzyme activities with slope ranges from -0.07 to 0.94. The complexity of coupling and cycling among soil elements caused single soil functional enzyme and the accumulation of multiple nutrients were intensively related. (3) Soil depth contributes to differentiation of soil nutrients accumulation and is influenced by the type of tillage and crop. Besides, geography, climate and initial soil properties had limited moderating effects on nutrient response to conservation tillage.

Overall, conservation tillage promotes nutrient accumulation by improving the soil biochemical environment to enhance soil enzyme activity. This could effectively improve soil fertility and biochemical environment for sustainable agricultural development. The research could provide valuable references for sustainable agricultural management.