华北地区地膜残留及典型覆膜作物残膜系数

为阐明华北地区残膜污染现状及当年地膜残留系数,2008-2011年采用问卷调查及样方检测方法对华北地区主要作物的地膜残留状况进行系统调查,在此基础上2011-2014年通过定点试验监测方法研究典型覆膜作物(花生、棉花)的地膜残留系数。结果表明:华北地区土壤耕层地膜残留强度分布范围为0.2~82.2 kg/hm2,其平均值为26.8 kg/hm2。区域内不同作物和不同省份间地膜残留强度存在显著差异(P0.05),花生和棉花地膜残留强度较高,分别为32.0和31.8 kg/hm2;华北地区所有省份中,河北省农田地膜残留强度最高,为36.8 kg/hm2。2011年,华北地区农田地膜残留总量为14.8万t,其中地膜残留总量居前3位的作物是蔬菜(5.5万t)、棉花(3.9万t)、花生(3.0万t),占残膜总量的83.8%。3 a的地膜残留系数定点监测试验结果表明,花生和棉花的地膜残留系数分别为9.7%和14.3%,如果一直沿用目前的地膜使用模式,预计到2021年,花生地和棉田的地膜残留强度将会达到69.1和70.4 kg/hm2,超过国家农田残膜限值标准,成为残膜污染区域。研究可为华北地区残膜防治提供参考。

Characteristics of residual mulching film and residual coefficient of typical crops in North China

Plastic films have been used extensively as mulching for crops in modern agriculture, and remarkably improved crop yields in the past decades. However, the vast amount of residual plastic films results in serious pollution in the arable land. In order to expound the status of residual films and the residual coefficient of mulch in typical croplands in North China, the amounts of the residual films were studied by using the methods of farm survey with questionnaires and quadrat sampling in 124 study sites from 2008 to 2011 in Beijing, Tianjin, Hebei, Shandong, Shanxi, Henan, Inner Mongolia. During questionnaire survey, the relevant status of mulching application including soil characteristics, crop type, mulching time and recovery method etc. was investigated. Based upon this, the residual coefficient of typical crops (peanut and cotton) was calculated through the methods of field monitoring from 2011 to 2014, by determining the amount of residual film before and after test. The results showed that the amount of film mulch residue in North China fields ranged from 0.2 to 82.2 kg/hm2, with an average value of 26.8 kg/hm2. Among the surveyed sites, 4.8% of fields presented a greater mulch residual volume than the national film residue standard (65 kg/hm2), and 16.1% of fields showed a residual film amount approaching this threshold. The residual amount was significantly different (P<0.05) between different crops and provinces. The residual amount of mulch film in peanut and cotton field was highest, reaching 32.0 and 31.8 kg/hm2, respectively. The high residue film in peanut and cotton field was caused by different reasons. For peanut, it was attributed to the small mulching thickness which was mostly less than 0.005 mm, while for cotton the reason was the long mulching time. Meanwhile, Hebei was the one with the most residual mulching film (36.8 kg/hm2), because of the large proportion of peanut and cotton fields. In the year of 2011, the total amount of residual film in North China was 1.5×105 t. Vegetables, cotton and peanut field had great contributions to the total amount of residual film in this region, and the amount of residual film was 5.5×104, 3.9×104 and 3.0×104 t, respectively. Three years of residual coefficient test showed that the residual coefficient of peanut and cotton were 9.7% and 14.3%. If the present mulching pattern was carried on, the quantity of residual film in peanut and cotton fields would reach up to 69.1 and 70.4 kg/hm2 in 2021, becoming polluted areas that exceed the national standard of film residue. Although the pollution of residual film was not serious at present, it will become a significant issue if no measure was taken to solve it. It is in urgent need to elevate mulch film standards, develop biodegradable mulch film and enhance mulch film recycling. This study will eventually contribute to promoting effective control and management of residual mulch pollution in North China.