免耕覆膜增加中度盐碱土团聚体有机碳和微生物多样性

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

为阐明免耕覆膜措施在河套灌区中度盐碱地的改土效果,开展了连续5a的田间定位试验,分析了翻耕无覆盖(CT)、翻耕地膜覆盖(CTP)、免耕无覆盖(NT)、免耕地膜覆盖(NTP)4种耕作措施对土壤水盐分布、团聚体有机碳和微生物区系的影响。结果表明:试验第5年春灌前,免耕处理(NT、NTP)0~40cm土壤平均含盐量较CT、CTP分别降低36.53%、11.66%,春灌后较CT处理低25.27%,但较CTP高13.15%(P<0.05),作物收获后0~40 cm土壤含盐量NT较CT、NTP较CTP分别显著降低52.44%、20.65%(P<0.05),免耕和覆膜均能抑制蒸发季节0~40 cm土层返盐。收获后免耕处理0~40 cm土壤>0.25 mm粒级团聚体质量分数较翻耕显著提高53.41%,NTP处理>1 mm粒级团聚体较NT显著提高40%(P<0.05);0~40cm土壤有机碳NT较CT、NTP较CTP分别显著提高16.44%、15.48%,CTP较CT显著提高7.46%(P<0.05)。收获后NTP处理显著提高了0~40 cm土壤可培养细菌、放线菌、真菌菌落数,高通量分析表明NTP处理Shannon指数显著高于CT、CTP处理,土壤有机碳和>0.25mm团聚体质量分数是提高土壤细菌群落多样性的主控环境因子,分别解释50.9%、29.4%的群落变化。总之,免耕地膜覆盖能够改善盐碱土壤结构、增加土壤固碳、提高微生物多样性,可作为河套地区盐碱土壤质量提升的推广措施。

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 0-40 cm 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.