A holistic framework integrating plant-microbe-mineral regulation of soil bioavailable nitrogen

Abstract

Soil organic nitrogen (N) is a critical resource for plants and microbes, but the processes that govern its cycle are not well-described. To promote a holistic understanding of soil N dynamics, we need an integrated model that links soil organic matter (SOM) cycling to bioavailable N in both unmanaged and managed landscapes, including agroecosystems. We present a framework that unifies recent conceptual advances in our understanding of three critical steps in bioavailable N cycling: organic N (ON) depolymerization and solubilization; bioavailable N sorption and desorption on mineral surfaces; and microbial ON turnover including assimilation, mineralization, and the recycling of microbial products. Consideration of the balance between these processes provides insight into the sources, sinks, and flux rates of bioavailable N. By accounting for interactions among the biological, physical, and chemical controls over ON and its availability to plants and microbes, our conceptual model unifies complex mechanisms of ON transformation in a concrete conceptual framework that is amenable to experimental testing and translates into ideas for new management practices. This framework will allow researchers and practitioners to use common measurements of particulate organic matter (POM) and mineral-associated organic matter (MAOM) to design strategic organic N-cycle interventions that optimize ecosystem productivity and minimize environmental N loss.

Persistent soil carbon enhanced in Mollisols by well-managed grasslands but not annual grain or dairy forage cropping systems

“…Higher PPO activity in MSW and MOA and higher PER activity in MOA ( SI Appendix , Table S7 and Fig. 3 A and B ) indicated faster SOM decomposition in these low fertilizer-input systems than high fertilizer-input systems and Pasture, suggesting that microbial necromass or MAOM may be subject to quick mineralization in these systems ( 36 , 37 ). Similar to most cropped soils, these soils have very little POM, indicating that MAOM might be an important source of nutrients ( 38 ).…”

Soil microbes influence nitrogen limit on the plant biomass of the alpine steppe, North Tibet

“…These results suggested soil fungi also contribute to enhance activity of phosphatase except for plant increasing activity of phosphatase (Ryan et al 2014 P addition will increase N absorption of plant according to N:P stoichiometry. However, the inorganic N concentration is low in alpine grassland (Zhou 2001), the inorganic N pools in soil was determined how much organic N feeds into and supplies the inorganic N pool (Daly et al 2021). In present study, N content in leaf and soil AN in the P treatment were the same as those in the CK treatment (Table 3, Table S2), which suggested the N de cit of plant due to P addition was alleviated.…”

Advancing the science and practice of ecological nutrient management for smallholder farmers

“…Thus, the environmental context, management history and the current management regime determine the balance between decomposition and SOM formation/ stabilization. Over the past decade, major discoveries have fundamentally altered our understanding of SOM biogeochemistry (Kuzyakov and Xu, 2013;Lavallee et al, 2020;Liang et al, 2020;Daly et al, 2021).…”