长期连作滴灌棉田残膜分布特征及对土壤水分运动和棉花根系生长的影响机理

The problem of residual membrane contamination has attracted great attention of the State Council, people's governments at all levels and scientific research workers. The planting area and total output of cotton under mulch drip irrigation in Xinjiang account for more than 50% of the total amount of the country. However, the research group found that the residual film in long-term continuous cropping cotton field increased by 15.11-18.70 kg/hm2 year by year. The accumulation of residual film in topsoil will not only affect the evolution of soil physical properties and soil water movement, but also directly hinder the growth of cotton root system. The project proposes to monitor cotton fields under plastic mulch drip irrigation for various years (3-21 years) at fixed-points, so as to illustrate the characteristics of accumulation and morphological change of residual film in cotton fields in typical oasis area, to further taking the evolution of soil physical properties as a breakthrough point, the influence mechanism of residual film on soil water movement was clarified through control experiment and undisturbed soil-trough simulation, and the appropriate irrigation control strategy was put forward. Determine the biological characteristics of the initial growth and process growth of cotton, and use mathematical and computer language to build a cotton root growth model and visual analysis. The relationship between residual plastic film accumulation and water movement and root growth response was further analyzed, the cumulative threshold of residual plastic film in long-term continuous cropping drip irrigation was proposed. The mechanism of residual plastic film distribution and morphology on cotton root growth was analyzed and the agronomic restoration strategy was proposed. Expected results provide an important reference for the treatment of residual membrane pollution in drip irrigation cotton fields.

残膜污染问题引起国务院、各级人民政府和科研工作者高度重视。新疆膜下滴灌棉花种植面积及总产量均占全国总量的50%以上；然而课题组调研发现，长期连作棉田残膜以15.11-18.70 kg/hm2的速度逐年递增；残膜在耕层累积，不仅会影响土壤物理性质演变和土壤水分运动，还会阻碍棉花根系生长。项目拟对不同膜下滴灌年限棉田（3-21年）进行定点监测，阐明典型绿洲区长期连作棉田残膜累积和形态变化特征；以土壤物理性质演变规律为突破口，通过控制试验和原状土土槽模拟，阐明残膜对土壤水分运动影响机理，并提出适宜灌溉调控策略；确定棉花初始生长和过程生长生物学特征参数，利用数学和计算机语言构建棉花根系生长模型并进行可视化，解析残膜累积和水分运动与根系生长响应关系，提出长期连作滴灌棉田残膜累积阈值，剖析残膜分布和形态对棉花根系生长的影响机理，提出农艺修复策略。预期成果为膜下滴灌棉田残膜污染治理提供重要参考。

残膜污染问题引起国务院、各级人民政府和科研工作者高度重视。残膜在耕层中累积，不仅会影响土壤物理性质演变和土壤水分运动，还会阻碍棉花生长。项目组采用调查研究和定点监测等手段，明确了绿洲区棉田土壤耕作层中地膜以每年约15.69 kg·hm-2的速率残留，从覆膜起始至覆膜耕作15年，较大的残膜碎片（>25 mg/片）在0～5 cm土壤深度富集较为稳定；经过15年以上的覆膜耕作后，较大的残碎块在翻耕耙地等农田作业下开始碎裂成较小的残膜碎片，其中较小的残膜碎块（<25 mg/片）的累积更加明显，且这部分残膜向深层土壤的下移更加显著。通过使用MATLAB软件结合BP 神经网络模型预测得出，在现有覆膜耕作模式和地膜回收措施不变的情况下，绿洲应用覆膜滴灌30 年棉田残膜密度将达到419.19 kg·hm-2，超出国家残膜标准限值 75.0 kg·hm-2近6倍。通过原状土模拟试验得出，随着残膜量的增加，土壤稳定入渗率和累积蒸发量逐渐减小；当残膜量超过79.2 kg/hm2时，土壤稳定入渗率和累积蒸发量较无残膜土壤显著减小。土壤入渗率模型Kostiakov和累积蒸发量模型Rose同样适用于残膜累积的土壤，但随着残膜量的增加，模型拟合参数的相对均方根误差变大。通过控制试验和模型构建等手段研究得出，覆膜滴灌15年时，棉花叶片Pn蕾期较残膜农田减少5.30%，Tr吐絮期减少15.06%，Gs花铃期减少54.13%，Ci蕾期降低23.58%。棉花根系的根长密度、根表面积密度、根系体积和根系直径亦与土壤残膜量呈显著负相关关系。随着覆膜滴灌年限的增加，残膜量在超过 391.73 kg·hm-2时（覆膜20年）棉花产量受到显著影响。依托本项目，培养研究生3名，发表论文14篇，其中SCI检索6篇；荣获全国农业节水科技二等奖、新疆水利学会科学技术一等奖各1项。