How Do Agronomic Management Practices Affect Soil Nitrogen Mineralization? a Meta-Analysis.

Potential Nitrogen mineralization (PMN) has been positively related to crop yield and proposed as an indicator of soil health. In fertile soils, mineralized N from soil organic matter is the dominant source of N for plant uptake even when N fertilizer is applied. Importantly, N mineralization has been indirectly managed through agronomic practices such as tillage and crop rotations, however, the overall effect remains unknown. In this study, we used meta-analysis to understand how common agronomic management practices including N fertilizer application (organic and inorganic), crop sequence, cover cropping, and tillage system affect PMN. Data were extracted from 54 individual studies published in peer-reviewed journals. Fertilizer addition increases PMN: compared to no fertilizer addition, inorganic fertilizer increases PMN by 27% and manure increases PMN by 57%. Crop diversity also increases PMN: an increase in the number of crops in rotation increases PMN by 27% and a cover crop increases PMN by 49%. On average, tillage has relatively little effect on PMN. However, when type of tillage is compared across depths, chisel plow has lower PMN than no-till in the top soil but higher PMN than no-till at deeper depths. Similarly, when compared in terms of the number of years of tillage practiced, chisel plow has higher PMN in the initial years but after10 and 15 years it has lower PMN than no-till. The conservation crop management practices fertilizer addition, crop rotation with three or more crops in sequence, cover crops and long-term no-tillage increase PMN.