残膜对农田土壤养分含量及微生物特征的影响

【目的】探究残膜对土壤养分含量和生物学特征的影响，明确产生危害的土壤残膜强度限值，为中国残膜污染防治工作提供理论支撑。【方法】于2011—2015年在甘肃张掖设置0（CK）、150 kg·hm^-2（T1）、300 kg·hm^-2（T2）、450 kg·hm^-2（T3）以及600 kg·hm^-2（T4）残膜梯度试验，并测定不同残膜强度下土壤理化性状、微生物量碳氮、微生物群落丰度以及土壤酶活性等关键指标。【结果】残膜对土壤含水量、有机质（SOM）、全氮（TN）、铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）、有效磷（Olsen-P）的影响较大，随着残膜强度的增加，土壤含水量显著增加（P＜0.05），而SOM、TN、NO₃^--N以及Olsen-P显著降低（P＜0.05），NH₄⁺-N则表现出先升高后降低的变化趋势。低残膜强度下，土壤微生物量碳（MBC）和土壤微生物量氮（MBN）含量增加，但高残膜强度（T3和T4）则会显著降低土壤微生物量（MBC和MBN）及微生物群落丰度（吸光值平均变化率、丰富度、Shannon指数、Simpson指数以及McIntosh指数）（P＜0.05）。土壤酶活性随残膜强度的变化趋势同微生物量碳氮含量基本一致，残膜强度为300—450 kg·hm^-2时，土壤中α-葡萄糖苷酶（AG）、β-葡萄糖苷酶（BG）、纤维素酶（CBH）、木聚糖酶（BXYL）以及几丁质酶（NAG）活性普遍较高，残膜强度为600 kg·hm^-2时土壤酶活性显著降低（P＜0.05）。【结论】农田土壤中低量残膜存在下可通过保水作用提高土壤微生物活性及其丰富度，而当残膜强度超过450 kg·hm^-2时，土壤微生物量、微生物群落丰度和土壤酶活性显著降低；同时，长期残膜作用下会降低土壤SOM、TN、NH₄⁺-N、NO₃^--N以及Olsen-P含量，引起土壤养分退化。因此，对于中国地膜残膜污染较严重的地区，应加大残膜防治工作力度，降低残膜引起的土壤退化风险。

Effect of Residual Plastic Film on Soil Nutrient Contents and Microbial Characteristics in the Farmland

【Objective】 The purpose of this study was to explore the effect of residual plastic film on soil fertility and soil microbial characteristics, clarify the risk threshold of residual plastic film in the field and promote effective control and management of residual plastic film pollution in China.【Method】Five residual plastic film gradients were designed in representative farmlands in Zhangye county of Gansu province from 2011 to 2015, including 0 (CK), 150 kg·hm^-2 (T1), 300 kg·hm^-2 (T2), 450 kg·hm^-2 (T3) and 600 kg·hm^-2 (T4). After crop harvesting in 2015, soil physical and chemical properties, microbial biomass carbon and nitrogen, enzyme activity and microbial abundance were monitored.【Result】The amount of residual plastic film had a great effect on soil water content, organic matter (SOM), total nitrogen (TN), ammonium (NH₄⁺-N), nitrate nitrogen(NO₃^--N) and available phosphorus (Olsen-P), in which the soil water content was significantly increased with increasing residual plastic film in field, however the SOM, TN, NO₃^--N and Olsen-P were declined, the NH₄⁺-N was increased and then decreased with the increase of residual plastic film. In the lower residual plastic film treatment, the soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were improved because of soil water content increased compared with CK, however, they were significantly reduced in the high residual plastic film treatments (T3 and T4) (P<0.05). In addition, the soil microbial community abundance (AWCD, richness, Shannon, Simpson and McIntosh) of CK and T1 were significantly higher than that of T3 and T4 (P<0.05). The variation trend between soil enzyme activity and residual plastic film was similar to MBC and MBN, and the activities of α-1,4-glucosidase (AG), β-1,4-glucosidase (BG), Cellobiohydrolase (CBH), β-1,4-xylosidase (BXYL) and β-1,4-N-acetyl-glucosaminidase (NAG) were high in the treatments of 300-450 kg·hm^-2 of residual plastic film, however, they were significantly decreased when the residual in the treatment with plastic film at 600 kg·hm^-2.【Conclusion】In the treatment with lower residual plastic film, the soil microbial activity was improved though increasing soil water content, whereas the soil microbial biomass carbon, microbial biomass nitrogen, microbial community abundance and soil enzyme activity were significantly decreased if the residual plastic film higher than 450 kg·hm^-2. Moreover, the soil organic matter, total nitrogen, ammonium nitrogen, nitrate nitrogen and Olsen-P all reduced with long-term effect of high residual plastic film, and caused soil fertility degradation. It was concluded that management of the residual plastic film should be strengthened in order to reduce the risk of soil degradation, especially in the regions with serious residual plastic film pollution.