ABSTRACT Straw incorporation (SI) increases soil organic carbon (SOC) and soil total nitrogen (STN). However, the differences in soil C and N fractions between the maize cropping and fallow systems under different SI rates in the black soil region of Northeast China remain unclear. In a 6‐year experiment, we examined these two systems by using circular frames with five annual SI rates (0, 9.2, 18.4, 27.6, and 36.8 Mg ha −1 ) to investigate their effects on soil C and N fractions and storage potential. SI significantly enhanced the SOC and STN concentrations in both systems. Compared to fallow, continuous maize cropping resulted in higher depletion of oxidizable organic C (EOC) and amino sugar N (ASN). However, it maintained greater light fraction organic C (LFOC), particulate organic C (POC), and hydrolyzable unknown N (HUN) concentrations in the 0–15 cm soil layer. Fallow increased the soil C:N ratio and exhibited higher average annual C and N sequestration rates (0.70 and 0.01 Mg ha −1 year −1 , respectively) compared to the maize cropping system. However, increasing SI rates did not significantly affect the transformation efficiency of straw‐derived nutrients. Conventional SI rates in continuous maize cultivation led to soil C and N losses, while higher SI rates and fallow management effectively retained nutrients. Thus, to prevent concurrent losses of soil C and N pools under continuous maize cropping in the 0–30 cm soil layer under current soil conditions, an annual input of at least 6.8 Mg C ha −1 year −1 and 0.2 Mg N ha −1 year −1 is recommended.
Zhang et al. (Sun,) studied this question.