免耕和秸秆还田对东北黑土区土壤团聚体组成及有机碳含量的影响

为解决东北黑土区因不合理耕作导致的土壤结构性状变差及有机碳含量下降的问题,该研究于2015年开始,在黑龙江省哈尔滨市东北农业大学向阳试验基地开展。设置免耕+秸秆还田（NTS）、免耕（NT）、翻耕+秸秆还田（CTS）、翻耕（CT）4种处理,于2018、2019年采集土样,研究免耕措施及秸秆还田对东北薄层黑土区0～10、>10～20 cm土壤团聚体稳定性、土壤有机碳含量、各粒径团聚体内有机碳含量影响。结果表明：2018和2019年0～10、>10～20 cm土层NTS处理>5 mm水稳性团聚体百分比含量及平均重量直径（MWD）显著高于其他3种处理,NTS及NT处理土壤有机碳含量显著高于CTS及CT处理（P?<0.05）,4种处理各粒径水稳性团聚体有机碳含量峰值总体出现在1～2 mm处,NTS及NT处理>5、2～5、1～2 mm有机碳贡献率整体高于CTS及CT处理。研究表明,免耕与秸秆还田有利于薄层黑土坡耕地耕层土壤团聚体稳定性的提高和各粒级下团聚体有机碳的积累,与其他3种处理相比,免耕+秸秆还田效果更佳。

Effects of no-tillage and straw returning on soil aggregates composition and organic carbon content in black soil areas of Northeast China

Abstract: Soil aggregates and organic carbon content are important soil quality evaluation indices. They play important roles in guiding agriculture and ensuring food production safety. In order to solve the problem of deterioration of soil structural properties and decrease of organic carbon content caused by irrational farming in the black soil area of Northeast China, an experiment was carried out in Xiangyang experimental base of Northeast Agricultural University in Harbin since 2015. To study effects of no tillage and straw returning on soil aggregate stability, soil organic carbon content and the soil organic carbon content of the aggregates in 0-10 and 10-20 cm soil layers in the Northeast thin black soil area, four treatments including straw returning with no-tillage (NTS), no-tillage(NT), straw returning with conventional tillage(CTS) and conventional tilliage(CT) were designed. Soil samples were collected in 2018 and 2019. The impact of conservation tillage on the physical and chemical properties of soil was analyzed. The results showed that the percentage content of water-stable aggregates larger than 5 mm and Mean Weight Diameter (MWD) of NTS treatment were significantly higher than those in the other three treatments of 0-10 and 10-20 cm soil layers in 2018 and 2019. Compared with 2018, the percentage content of water-stable aggregates larger than 5 mm of NTS and NT treatments increased to varying degrees in 2019. In 2018, the MWD values of 0-10 cm soil layer ordered from high to low were NTS, NT, CTS and CT. In 2019, the NTS treatment was significantly higher than NT treatment (P<0.05), and no significant difference was found between CTS treatment and CT treatment. In 2018 and 2019, the MWD values of 10-20 cm soil layer ordered from high to low were NTS, NT, CT and CTS, and the difference was significant between treatments (P<0.05). The organic carbon content of soil and organic carbon content in aggregates decreased with the increase of soil depth generally. In 2018, the soil organic carbon content of NTS and NT treatments in 0-10 and 10-20 cm soil layers were significantly higher than those in CTS and CT treatments (P < 0.05). In 2019, no significant difference in 0-10 cm soil layer was found between CT treatment and CTS treatment. In 10-20 cm soil layer of 2019, the contents of soil organic carbon of NTS and NT treatments were not significantly different, and CTS treatment was significantly higher than CT treatment (P < 0.05). In 2018 and 2019, the peak value of organic carbon content of water stable aggregates in 0-10 and 10-20 cm soil layers appeared at 1-2 mm, the organic carbon content of water-stable aggregates smaller than 0.25 mm was the lowest. In 0-10 and 10-20 cm soil layers of 2018 and 2019, the organic carbon contribution rates of water-stable aggregates of >5, 2-5 and 1-2 mm of NTS and NT treatments were higher than those in CTS and CT treatments generally, and those of water stable aggregate smaller than 0.25 mm was smaller than those of CTS and CT treatments. The research showed that no tillage and straw returning were beneficial to stability of soil aggregates and accumulation of organic carbon in different aggregates at sloping farmland of thin black soil. The treatments of no-tillage combined with straw returning had the best effect compared with treatments of no-tillage, conventional tillage and conventional tillage combined with straw returning.