长期秸秆还田对褐土农田土壤有机碳、氮组分及玉米产量的影响

基于1992—2022年连续30 a的长期定位试验，研究秸秆不还田（CK）、秸秆覆盖还田（SM）、秸秆粉碎直接还田（SC）和秸秆过腹还田（CM）4种不同秸秆还田方式对土壤有机碳、氮组分和作物产量的影响。结果表明：（1）不同秸秆还田方式均可增加耕层土壤有机碳、全氮及其组分含量；与CK相比，CM处理0~20 cm土层土壤的总有机碳（SOC）、轻组有机碳（LFOC）、微生物量碳（MBC）、水溶性有机碳（DOC）和颗粒有机碳（POC）的含量分别显著增加42.85%、93.51%、80.09%、190.42%和123.38%；土壤全氮（TN）、轻组有机氮（LFON）、微生物量氮（MBN）、水溶性有机氮（WSON）和颗粒有机氮（PON）的含量分别显著增加49.37%、34.26%、69.49%、172.73%和129.29%。（2）各活性有机碳组分与土壤有机碳的比值表现为LFOC>POC>MBC>DOC；各氮组分与土壤全氮的比值表现为LFON>PON>MBN>WSON。（3）CM和SC处理下敏感指数最高的指标为DOC，DOC可作为CM和SC处理早期有机物变化的指示物；SM处理下敏感指数最高的指标为LFOC，LFOC可作为SM处理早期有机物变化的指示物。（4）土壤有机碳、氮组分间均呈显著正相关关系，其中DOC可以较好地反映SOC的变化情况，WSON可较好地反映TN的变化情况。（5）与CK相比，长期秸秆还田均可以显著提高玉米产量，SM、SC和CM处理30 a累计产量分别增加6.38%、7.82%和23.00%。综上，长期秸秆还田是提高土壤有机碳氮组分含量和作物产量的有效耕作措施，以秸秆过腹还田效果最为突出，可在黄土高原旱地玉米种植区域推广。

Effects of long\|term straw returning on soil organic carbon and nitrogen components and maize yield in brown soil farmland

Based on a continuous 30-year long\|term locational experiment from 1992 to 2022, the effects of four different straw return methods including no straw returned to the field (CK), straw mulching returned to the field (SM), straw crushed and directly returned to the field (SC) and straw returned to the field in the overgrowth (CM) on soil organic carbon, nitrogen fractions and crop yields were investigated. The results showed that (1) Straw returning increased the content of soil organic carbon, total nitrogen and its components in the tillage layer compared with CK. The content of total organic carbon (SOC), light group organic carbon (LFOC), microbial biomass carbon (MBC), water\|soluble organic carbon (DOC) and particulate organic carbon (POC) in the soil layer of 0~20 cm of the CM treatment were significantly increased by 42.85%, 93.51%, 80.09%, 190.42% and 123.38%, respectively. The contents of soil total nitrogen (TN), light group organic nitrogen (LFON), microbial mass nitrogen (MBN), water\|soluble organic nitrogen (WSON), and particulate organic nitrogen (PON) increased significantly by 49.37%, 34.26%, 69.49%, 172.73% and 129.29%, respectively. (2) The ratio of each active organic carbon component to soil organic carbon showed LFOC>POC>MBC>DOC; the ratio of each nitrogen component to soil total nitrogen showed LFON>PON>MBN>WSON. (3) The highest sensitivity index under CM and SC treatments was DOC, which could be used as an indicator of the change of organic matter in the early stage of CM and SC treatments. LFOC had the highest sensitivity index under SM treatment and could be used as an indicator of early organic matter changes in SM treatment. (4) Significant positive correlations were found between soil organic carbon and nitrogen fractions, in which DOC better reflected the changes of SOC and WSON better reflected the changes of TN. (5) Compared with CK, long\|term straw return could significantly increase corn yield, and the cumulative yields of SM, SC and CM treatments increased by 6.38%, 7.82% and 23.00%, respectively. In summary, long\|term straw return was an effective tillage measure to improve soil organic carbon and nitrogen fractions and crop yield, and the effect of returning straw to the field was most prominent, which should be popularized in the dryland maize cultivation area of the Loess Plateau.