The agricultural intensification of the last century has to a large extent been fueled by the application of mineral fertilizer. Significant amounts of mineral fertilizer nitrogen (N) are being lost through leaching of mineral N to ground- and surface water, which has devastating implications for the environment. The low efficiency of N use in agricultural soils is to a large extent caused by the decoupling of carbon (C) and N cycles, since mineral N applications take over the role of the microbial community as a regulator of both decomposition and N mineralization. The use of organic amendments emphasizes a more ecosystem-based approach that can optimize agricultural N management by restoring this microbial link between soil C and N processing. We investigated how the chemical composition of different forms of organic amendments impacts the abundance, composition and activity of the soil microbial community and subsequently the ecosystem processes carbon (C) and N mineralization, and ecosystem services microbial N immobilization and plant growth and nutrient uptake.
Results/Conclusions
Addition of organic amendments increased soil microbial biomass, activity and fungal/bacterial ratio and created distinct microbial community compositions, whereby high C:N ratio organic amendments had stronger effects compared to low C:N ratio amendments. Structural equation modelling showed that higher values of soil microbial activity were associated with increased N mineralization rates, increased plant biomass and plant 15N uptake, while microbial 15N immobilization was associated with soil microbial community composition. The outcomes of this study highlight the importance of the chemical composition of organic amendments for finding a balance between plant N uptake, microbial N immobilization and N retention in labile and stable soil pools through the effects on the composition and activity of the soil microbial community. The results provide insights that can be used in designing combined input (nutrient and organic) ecosystem-based nutrient management strategies for a more sustainable agriculture.