Delayed nitrogen application after straw and charred straw addition altered the hot moment of soil N₂O emissions

Abstract

The combination of nitrogen (N) fertilization and straw incorporation has complex influences on soil N transformations and derived nitrous oxide (N2O) emissions. This study aimed to reveal the coupled effects of straw returning forms and N fertilizer management on soil N2O emissions. Here, carbon (C) sources with varied availabilities were supplied by different straw returning forms, including straw, charred straw, and combined application of straw and charred straw. The time gaps between additions of exogenous N and C sources were carried out by managing the timing of N fertilization, including N application simultaneous with or delayed after straw return. Soil N2O emissions under different straw returning forms and their response relationships to soil C, N, microbial biomass, as well as soil pH and oxygen (O2) were explored. Co‐application of straw and N fertilizer provided sufficient C and N sources, enhanced the microbial biomass, and consequently increased N2O emissions. Delayed N fertilization could decouple the response of N2O emissions to straw addition, because of constrained N availability and limited pH decline, which decreased the cumulative N2O emissions significantly. Possibly due to straw induced N immobilization coupled with charred straw induced pH elevation, the combined application of straw and charred straw constrained soil N2O emissions compared with straw only application, regardless of N fertilizer management. By shaping the microbial biomass and soil C, N, and O2 dynamics, delayed application of N fertilizer could further enhance the inhibition effect of the charred straw and straw combination on soil N2O emissions. Therefore, the varied straw returning forms and the timing of N fertilization could affect the supply of available C and N, influencing the hot moments of N2O emissions, and the joint addition of straw and charred straw with a few weeks delayed N application could possibly reduce the risk of soil N2O emissions from straw return systems. Such mitigation potential should be evaluated further under field conditions. Highlights Delayed N fertilization attenuated the magnitude of N2O emissions after straw additions. Combination of charred straw with straw mitigated N2O emissions, further enhanced by delayed N fertilization. Soil pH was the chief regulator for N2O emissions under different straw returning forms and N application.

Cover crop residue decomposition triggered soil oxygen depletion and promoted nitrous oxide emissions

“…1 a, 2 a). A recent study by Ye et al 60 , showed that straw residue incorporation affected soil N 2 O and CO 2 emissions by altering the dissolved organic carbon and O 2 content of the soil. A greater association of CO 2 than POXC with N 2 O emissions (Table 4 ), especially under 50% WFPS, highlights that microbial respiration is closely linked to soil CO 2 emissions, while POXC represents net C availability.…”

Wheat straw and microbial inoculants have an additive effect on N2O emissions by changing microbial functional groups

“…Straw decomposition can rapidly consume soil O 2 , leading to the rapid development of anoxic zones at the interfaces of straw and soil (Zhu et al, 2022). O 2 consumption can slow the rate of nitrification (Ye et al, 2023). In addition, straw with a high C/N ratio can serve as an available C source and can promote microbial biomass (Xia et al, 2018).…”

Soil physics matters for the land–water–food–climate nexus and sustainability

“…They found that application of organic amendments generally reduced bulk density of fluvoaquic soil, and increased the field water capacity as well as the amount of water-stable macroaggregates. Ye et al (2023) found that combined application of straw and charred straw would constrain soil N 2 O emissions compared with straw only application, regardless of nitrogen (N) fertilizer management, owning to straw-induced N immobilization coupling with charred straw-induced pH elevation. In addition, delayed N fertilization clearly attenuated the magnitude of N 2 O emissions after straw additions, whereby soil pH was the dominant regulator for N 2 O emissions under different straw returning forms and N application.…”