Carbon emissions and priming effects derived from crop residues and their responses to nitrogen inputs

Crop residue-derived carbon (C) emissions and priming effects (PE) in cropland soils can influence the global C cycle. However, their corresponding generality, driving factors, and responses to nitrogen (N) inputs are poorly understood. As a result, the total C emissions and net C balance also remain mysterious. To address the above knowledge gaps, a meta-analysis of 1123 observations, taken from 51 studies world-wide, has been completed. The results showed that within 360 days, emission ratios of crop residues C (ER) ranged from 0.22% to 61.80%, and crop residues generally induced positive PE (+71.76%). Comparatively, the contribution of crop residue-derived C emissions (52.82%) to total C emissions was generally higher than that of PE (12.08%), emphasizing the importance of reducing ER. The ER and PE differed among crop types, and both were low in the case of rice, which was attributed to its saturated water conditions. The ER and PE also varied with soil properties, as PE decreased with increasing C addition ratio in soils where soil organic carbon (SOC) was less than 10 parts per thousand; in contrast, the opposite phenomenon was observed in soils with SOC exceeding 10 parts per thousand. Moreover, N inputs increased ER and PE by 8.31% and 3.78%, respectively, which was predominantly attributed to (NH4)2SO4. The increased PE was verified to be dominated by microbial stoichiometric decomposition. In summary, after incorporating crop residues, the total C emissions and relative net C balance in the cropland soils ranged from 0.03 to 23.47 mg C g-1 soil and 0.21 to 0.97 mg C g-1 residue-C g-1 soil, respectively, suggesting a significant impact on C cycle. These results clarify the value of incorporating crop residues into croplands to regulate global SOC dynamics and help to establish while managing site-specific crop return systems that facilitate C sequestration. 农田壤?残衍残(PE?.?普遍,驱氮(N?.净衡??.鸿沟?511,123 荟萃.:残(ER?0.22%-61.80%?残PE(+71.76%?.?残衍贡(52.82%?PE 贡(12.08%??ER.ERPE 残?稻残衍ERPE?处C/N 饱.ERPE 壤??PE 壤(SOC?10 parts per thousand 壤残添?SOC10 parts per thousand 壤.?N 农田壤ERPE8.31%3.78%??(NH4)2SO4NERPE.PEN 微.?残壤壤0.03-23.47 毫?净衡壤残0.21-0.97 毫?残壤著.残农田节SOC?且固田. The generality, driving factors, and responses to nitrogen inputs of carbon emissions and priming effects (PE) derived from crop residues were investigated. The results showed that within 360 days, emission ratios of crop residues C ranged from 0.22% to 61.80%, and crop residues generally induced positive PE (+71.76%). In summary, after incorporating crop residues, the total C emissions and relative net C balance in the cropland soils ranged from 0.03 to 23.47 mg C g-1 soil and 0.21 to 0.97 mg C g-1 residue-C g-1 soil, respectively, suggesting a significant impact on C cycle.image