Anaerobically mineralized nitrogen within macroaggregates as a soil health indicator

Aggregate mass and carbon stocks in a paddy soil after long‐term application of chemical or organic fertilizers

“…Crop roots and applied fertilizers mainly accumulate at 0–10‐cm depth; however, some crop residues and basal fertilizer can reach the 10–20‐cm depth as a result of plowing and leaching of dissolved organic matter (Baker et al, 2007; Bronick & Lal, 2005; García et al, 2021; Peng et al, 2010; Veenstra & Lee, 2015). Thus, explaining why the mass and the C concentration of LM, SM and their fractions decreased with soil depth overall (Figures 1–6).…”

“…Although inter-SC and intra-SC within LM and SM are more persistent than is free-SC (Lal, 2018;Six, Conant, et al, 2002), the trends in C concentrations in inter-SC and intra-SC within LM and SM amongst the four treatments in our study were closely related to the change in the mass of microaggregates within LM and SM (Figures 3-6c). Crop roots and applied fertilizers mainly accumulate at 0-10-cm depth; however, some crop residues and basal fertilizer can reach the 10-20-cm depth as a result of plowing and leaching of dissolved organic matter (Baker et al, 2007;Bronick & Lal, 2005;García et al, 2021;Peng et al, 2010;Veenstra & Lee, 2015). Thus, explaining why the mass and the C concentration of LM, SM and their fractions decreased with soil depth overall (Figures 1-6).…”

“…The combination of chemical and organic fertilizers can further increase SOC concentrations as the result of additional exogenous C sources together with the various mineral nutrients present in organic fertilizers (Qiu et al, 2016; Sarker et al, 2018; Watts et al, 2010). Although the appropriate use of chemical fertilizers or the combination of chemical and organic fertilizers maintains or increases SOC stock (Qiu et al, 2012, 2016; Zhao et al, 2018), other management practices such as waterlogging or tillage conditions in paddy soil can affect the subsoil environment (Baker et al, 2007; García et al, 2021; Veenstra & Lee, 2015). For example, these practices can increase the risk of surface nutrient run‐off and the leaching of dissolved organic matter or nutrients (Hua et al, 2017; Shi et al, 2020).…”