免耕覆膜增加中度盐碱土团聚体有机碳和微生物多样性

不同粒级泥沙流失特征研究可揭示坡面侵蚀机理，表征土壤养分流失状况；而现有研究缺少对不同粒级泥沙流失速率及流失比例的过程性研究。为此，该研究基于连续汇流冲刷试验，研究汇流冲刷次数和坡度对黑土坡面不同粒级泥沙流失特征的影响。试验处理包括6次连续汇流冲刷（1 L/min，每次历时60 min）和2个黑土区典型坡度（5°和10°）。结果表明，汇流冲刷次数对不同粒级泥沙流失速率及比例的影响较坡度的影响明显。试验条件下，<0.25 mm泥沙流失比例最大，其次为1～2、2～5、0.5～1、0.25～0.5、>5 mm泥沙流失比例。随着汇流冲刷次数的增加，<0.25 mm泥沙的平均流失速率由1 965.7～6 698.4 g/(m2·h)显著减小为59.5～80.0 g/(m2·h)，该粒级泥沙流失比例亦总体呈现减小的趋势，而1～2 mm泥沙流失比例总体呈现增加的趋势，二者作为侵蚀泥沙的主体，其变化具有明显规律性。因此，<0.25 mm和1～2 mm泥沙流失特征应作为黑土区土壤侵蚀研究的重要部分，进而指导防治措施的布设；同时，建议采用适宜的覆盖措施防治黑土坡面细小颗粒泥沙的流失。

Increasing soil organic carbon in aggregates and microflora diversity in moderate salt-affected soils through no till combined with plastic film mulching

Abstract: In a 5-year field experiment, four treatments including the conventional tillage with no mulching (CT), conventional tillage with plastic film mulching (CTP), no-tillage with no mulching (NT), and no-tillage with plastic film mulching (NTP) were carried out to study the effects of different tillage methods on the moderate saline soil, such as the soil water and salt distribution, soil structure, aggregate organic carbon, and microflora. The results showed that in the fifth year of the experiment, the average water content of no-tillage treatments (NT and NTP) increased by 5.60% (before spring irrigation), 5.10% (after spring irrigation) than that of the tillage treatments (CT and CTP) in the 40-60 cm soil layer. Before spring irrigation, the average salt content of no-tillage treatments in the soil layers of 0-40 cm decreased by 36.53% (NT) and 11.66% (NTP), compared to that of the tillage treatments of CT and CTP. But after irrigation, the average salt of no-tillage treatments was lower than that of CT by 25.27%, whereas higher than that of CTP by 13.15%. After harvest, the accumulation rates in the soil layers of 0-20 cm under the CT, CTP, NT and NTP treatments were 99.16%, 26.33%, 21.18% and -6.26%, while the accumulation rates in 0-20 cm layers were 48.89%, 55.14%, 4.71% and 3.64%, respectively. These values indicated that the desalination occurred in the soil layer of 40-60 cm, in which the salt accumulation was observed in the no-tillage treatments, because both tillage treatments caused more salt to move up to the tillage layer. After harvest, the average content of macro aggregate (>0.25 mm) in the layers of 0-40cm under the NT and NTP was significantly higher by 53.41% than that of the tillage treatments, whereas the content of macro aggregates (>1 mm) under the NTP was higher by 40% than that of NT. Moreover, soil organic carbon in 0-40 cm layers?under NT, NTP treatments significantly increased by 16.44%, 15.48% than that of CT, CTP, respectively. There were also a great increase in the amount of soil bacteria, antinomies and fungus in the NTP after harvest. The correlation analysis demonstrated that the amount of the bacteria was negatively correlated with the salt content of soil, but positively correlated with the macro aggregate (>0.25 mm) and the soil organic carbon. The amount of antinomies was negatively correlated with the salt content of soil. The data from the high-throughput sequencing technology also showed that the Shannon index under the NTP treatment was higher than that under the CT and CTP treatments. Meanwhile, the factor analysis showed that the community changes 50.9% in the soil organic carbon and 29.4% in macro aggregate (>0.25 mm), indicating both were main environmental factors on the soil bacterial community structure. The no-tillage with plastic film mulching can contribute to the salt accumulation, the improvement of soil structure, the increase SOC sequestration, and microbial diversity, and therefore can serve as a promising approach to increase the soil fertility in Hetao Irrigation regions of China.