地膜覆盖和残留对玉米田土壤线虫群落的影响

Plastic film mulching is one of the important measures to increase production of crops, has been widely applied in production. However, recovery and degradation of plastic film are difficult, which cause enrichment of and pollution of residual plastic film. Residual plastic film will affect not only the physical and chemical properties of the soil but also the growth of crops. Soil nematode communities, whose characteristics can reflect the environmental condition of soil, has been widely used as indicator organism in agricultural ecosystems. Corn has become the most widely cultivated crops in China. Plastic-film corn area accounts for more than 40 percent of corn planting area in the east of Inner Mongolia. The increase of plastic-film corn area certainly has resulted in continuous cropping of corn, which leads to plastic film pollution. In order to explore the plastic film pollution and the effect of residual plastic film on the soil nematode communities, and to further analyze the relationship between the distribution of nematodes and soil properties，this project will first study plastic film distribution in the soil, the relationship between film mulching cultivation and soil nematodes communities, and then analyze the indicator function of soil nematodes on residual plastic film and soil environmental changes. The aims of this project are ① to accurately detect the pollution degree, ②to objectively evaluate the negative impact on residual film pollution and③ to provide the scientific basis for corn film mulching cultivation technology extension and plastic film pollution control.

地膜覆盖栽培是农作物增产的重要措施之一，在生产中得到了广泛应用。但由于地膜回收困难且不易降解，容易在土壤中富集，造成残膜污染。残留地膜不仅会影响土壤理化性质，而且还会影响作物的生长发育。线虫群落能够反映土壤环境状况，并且已经成为农业生态系统中重要的指示生物。目前，玉米是我国第一大作物，也是内蒙古东部地区的主要粮食作物。该区覆膜玉米面积占40%以上，覆膜玉米面积的不断增加势必造成连作现象的发生，导致残膜污染成为亟待解决的问题。为了分析该区残膜污染情况以及地膜残留对土壤线虫群落的影响，本项目以覆膜玉米田和模拟试验小区为对象，研究残膜在土壤中的分布规律，评价残膜污染程度，探讨覆膜栽培及地膜残留与土壤线虫群落特征的关系，揭示土壤线虫对覆膜、残膜污染及土壤环境变化的生物指示作用，为准确推断残膜污染程度、客观评价地膜残留给土壤带来的负面影响以及合理推广玉米覆膜技术和残膜污染治理提供科学依据。

在我国玉米种植区域，覆膜连作已成为重要的玉米种植方式。通过对不同覆膜年限玉米田和残膜梯度模拟实验田的土样进行分析，结果表明：土壤表层地膜残留量占总量的60%以上；随着覆膜连作年限的延长，残膜量和破碎化程度均显著增加，残膜在土壤中平均年增加量为38.80 kg/hm²。覆膜连作显著影响了土壤线虫总数和属数，显著影响了植物寄生线虫、Pp2、Ba3功能团的数量和相对丰富度，同时又显著影响了线虫的17种生态指数和土壤的11种理化性质（P<0.05）。玉米的生育时期显著影响了线虫总数，显著影响了食真菌线虫、食细菌线虫、捕食杂食线虫、cp3-5类群、Pp2、Fu3、Fu4、Ba2、Ba3、Om4功能团的数量和相对丰富度；生育时期还显著影响了土壤有机碳、全氮、全磷、全钾、阳离子交换量、pH值、含水量、容重、孔隙度。土层对玉米成熟期植物寄生线虫和cp3-5类群数量、香农多样性指数、均匀度指数、优势度指数、通路指数、总成熟度指数、结构指数和基础指数等均产生了显著影响（P<0.05）。在模拟试验中，营养类群、生活史类群和功能团的数量和相对丰富度，线虫总数，线虫属数以及生态指数均对残膜梯度的变化存在显著的响应（P<0.05）；线虫数量的最低值多出现在覆膜连作4年的土壤中，如线虫总数、植物寄生线虫数量、食真菌线虫数量、cp1-3类群数量、Pp2、Pp3、Fu2、Fu3、Fu4、Ba1功能团数量；数量和丰富度及生态指数等指标的极值多出现在360 kg/hm²处理中。依据线虫群落分布特征、土壤理化性质的变化和地膜残留情况可以看出，土壤中残膜量随着覆膜连作年限的增加而增加，残膜量的增加显著影响了土壤性质和土壤线虫群落特征；所以线虫可以作为覆膜玉米田土壤状况的指示性生物。