The effect of agricultural management on soil microbial necromass: A hierarchical meta-analysis

Abstract

Microbial necromass is crucial for soil organic carbon (SOC) sequestration and stable carbon pools. The impact of various combinations of agricultural management systems on microbial necromass is poorly understood and merits investigation. In the present study, we compiled 63 global studies comprising 344 observations and used a hierarchical meta-analysis to assess the effects of tillage systems, cropping systems, fertilization systems, and cover crops on microbial necromass. Our meta-analysis revealed that tillage systems and cropping systems lowered the total microbial necromass by 16.4 % and 3.9 %, respectively while fertilization systems and cover crops raised the total microbial necromass by 21.7 % and 25.3 %, respectively. We observed that crop rotation and cover crops mitigated the negative effects of tillage on microbial necromass. No-tillage and fertilization enhanced the negative effects of crop rotation on microbial necromass. No-tillage and cover crops when combined with fertilizer management, jointly increased total microbial necromass but depleted bacterial necromass. Cover cropping under crop rotation effectively restored the soil amino sugars. PiecewiseSEM and multivariate analyses disclosed that the initial SOC content and the mean annual temperature are key factors affecting the changes in the soil amino sugar profile under different agricultural management systems. Crop rotation systems are generally more effective in areas with better soil fertility and higher mean annual temperatures. In regions with abundant rainfall, tillage has a strong negative effect on soil microbial necromass. To minimize the consumption of microbial necromass, cropland management should integrate diverse practices rather than solely considering local climate and soil conditions.