辽西半干旱区不同类型可降解地膜的生命周期与生态效应评价

Plastic film mulching (PE) effectively improve the growth and development conditions of crops, resist the adverse environment, and make high use efficiency of light, heat, water and nutrients to achieve high yield and high quality of agricultural products. Due to the undegradable feature, plastic film will bring soil pollution and deteriorate soil quality. It is an ideal way to solve this problem by using biodegradable mulch instead of ordinary plastic mulch. However, the comparison of degradation characteristics of different types of biodegradable mulch and the study on comprehensive impact of biodegradable mulch on crop growth and soil quality are still lacking. This project will be conducted in Fuxin, semi-arid area in Liaoning province to investigate the following issues: 1) to reveal degradation and accumulation process of biodegradable plastic films by measuring its degrading rate, residue amount and distribution; 2) to evaluate the effect of biodegradable mulch on growth and development, yield and quality of maize;3) to clarify the effect of biodegradable plastic film application on soil quality through measurement of soil physical, chemical and biological properties. These results will provide scientific base for the screening and application of biodegradable plastic films in semi-arid area in Liaoning province.

地膜覆盖栽培可以有效改善农作物生长发育条件，抵御不良环境，充分利用有限的光、热、水和养分，实现农产品的高产优质。但普通塑料地膜的难降解性导致其在土壤中大量积累，严重污染土壤，降低土壤质量。利用可降解地膜代替普通塑料地膜是解决这一问题的理想途径。然而，关于不同类型可降解地膜的降解特性对比，以及可降解地膜覆盖对作物生长发育、土壤质量的综合影响研究尚属缺乏。本项目以农业部阜新农业环境与耕地保育科学观测实验站为平台，具体开展以下研究：监测区域土壤中不同类型地膜的降解情况、残留数量及分布，揭示不同地膜的降解过程和累积特性；通过调查和测定不同类型地膜覆盖下玉米的生长发育情况和氮、磷等养分吸收利用情况，探明可降解地膜对玉米生长发育、产量和品质的影响；测定覆膜后土壤物理、化学和生物学指标，评估不同降解地膜覆盖对土壤质量的影响。项目研究结果将为实现辽西地区可降解地膜的筛选和推广应用提供科学依据。

地膜连续覆盖会导致残膜在土壤中大量积累，利用可降解地膜代替普通塑料地膜是解决残膜污染的理想途径之一。本项目采用田间试验与室内分析相结合的方法，系统研究了半干旱区域不同类型地膜的降解过程和累积特性，阐明了可降解地膜对玉米生长发育和土壤质量的影响，筛选出了较适于区域玉米覆盖栽培的可降解地膜类型，主要结论如下：（1）两种可降解地膜（添加剂型降解膜和全生物降解膜）的降解进程相似，均从覆盖后第58天开始出现明显降解，普通地膜几乎无降解。随着覆盖时间的延长，可降解地膜的水蒸气透过量显著增加，力学性能（最大负荷、拉伸强度和断裂标称应变）显著下降，尤其是全生物降解膜变化明显，且膜面微观形态和化学结构变化显著，普通地膜各项指标变化不明显。添加剂型降解膜和全生物降解膜的当季降解率分别为37.4%和47.8%，降解残片以小于4cm2和4~25cm2的中小规格为主。覆盖2年后，表层土壤中普通地膜、添加剂型降解膜和全生物降解膜的残块数分别为277万、259万和236万片/hm2，残膜质量分别为73.6、55.9和 57.6 kg/hm2。（2）普通地膜、添加剂型降解膜和PBAT全生物降解膜覆盖下玉米生育进程大致相同，且不同类型地膜覆盖对玉米株高、茎粗、根系形态、氮磷养分吸收利用和籽粒品质并无显著影响，虽年际间玉米产量各有不同，但处理间产量及产量构成总体上并无显著差异。（3）降解膜覆盖的保温性能略低于普通地膜，且在玉米生长中后期，全生物降解膜覆盖的土壤剖面含量水量低于其它覆膜处理。不同类型地膜覆盖并未对土壤理化性质产生明显影响，基于3种供试地膜的污染土壤短期内均未见对土壤微生物硝化作用产生明显抑制和毒害作用。总之，从产量、降解特性和残留率等方面综合评价，以PBAT全生物降解地膜替代普通地膜应用于辽西半干旱区玉米覆盖栽培更具潜力。