拉萨河谷设施农业土壤质量变化及其对生产方式的响应

With economic developing and diet diversification demand rising, agricultural greenhouses have been built rapidly in Lhasa area on the Tibetan Plateau. These greenhouses supplied lots of vegetable for the local people and improved the farmer’s income. However, under high level investment and long-term covered cultivation, the greenhouses operation often lead to some changes in soil quality, such as soil acidification, salinization, nutrient imbalance, etc. However, there are still few studies on Plateau greenhouse’s soil quality change because the greenhouses were built relatively later on Tibetan Plateau than those in eastern areas in China. The environment and ecological system are very sensitive and fragile on Plateau, and it is the “Asia's water tower”, and the influences of environment changes will be more extensive and profound. Therefore, it is necessary to pay more attention to soil quality change in agricultural greenhouse on Plateau..Based on the existing results, the management method of agricultural greenhouses in Lhasa river valley, such as chemical fertilizer type and amount, irrigation method, crop rotation mode will be investigate with questionnaire survey in this study; and soil samples from both inside and outside of these greenhouses and agricultural materials including fertilizer, irrigation water will be collected. The indexes of soil particles composition, organic material, soluble salt, nitrogen, phosphorus, potassium, lead, cadmium, copper, and zinc in these samples will be measured with standard methods. Using the mathematical analysis methods such as comparative analysis, correlation analysis, cluster analysis etc., the soil background quality and its spatial differentiation will be discussed; the rules of soil quality changes in Plateau agricultural greenhouses and their response mechanism to the greenhouses management pattern will be explored; the soil qualities will be evaluated; the potential appropriate area for agricultural greenhouses will be identified; the suggestions and strategies for optimized layout and scientific operation methods for agricultural greenhouses will be put forward to reduce the risks of soil quality changes in plateau agricultural greenhouses. These results will be helpful to promote coordination relationship between agricultural greenhouse and Plateau sensitive environment.

随着高原经济发展和居民饮食多样化需求的提升，西藏拉萨设施农业发展迅速，有利保障了当地蔬菜供应，促进了农民增收。但在长期高投入封闭式生产模式下，设施农业极易导致土壤质量退化。加之高原生态环境敏感，是我国重要生态安全屏障，其土壤质量变化的影响更加广泛和深远。但高原设施农业起步较晚，对其土壤质量变化的研究较少，其土壤质量变化规律及其对生产方式的响应机制仍不清楚，制约了设施农业与环境的协调发展。.本研究系统调查拉萨河谷设施农业生产方式，采集分析设施农业内外土壤及主要农资样品，综合运用对比分析、相关分析、聚类分析等技术方法，研究拉萨河谷设施农业区土壤质量本底及其空间分异；阐释高原设施农业土壤质量变化规律；揭示土壤质量变化对生产方式的响应机理；评价拉萨设施农业区土壤质量状况；辨识设施农业的适宜分布区；从设施农业布局及生产管理方面，提出降低土壤质量风险的高原设施农业调控措施与可持续利用模式。

在长期高投入封闭式生产模式下，设施农地土壤质量极易发生退化。但高原设施农业起步晚，其土壤质量变化规律及其对生产方式的响应仍不清楚。基于此，本研究通过调查采样、实验测试和问卷访谈，分析拉萨河谷设施农地土壤环境本底状况，解析设施土壤环境变化及其空间分异，研究土壤质量变化对生产方式的响应，探讨降低土壤环境风险的高原设施农业调控策略。.项目执行过程中，收集了拉萨2006-2020年谷歌高清影像，解译获取了近15年来的设施农地分布数据。调研了18个典型设施农地分布区，分层采集了662个设施农地土壤样品，513个大田土壤样品。同时获取灌溉水样25份，肥料样42份，农药样8份。分析测定了土壤理化指标以及农资样品的重金属元素含量。调研过程中，同步完成了调查问卷301份，获取了设施农业种植作物类型、倒茬方式、灌溉施肥等生产数据。.研究发现拉萨设施农地集中分布于拉萨河干流和其支流堆龙曲两岸各约1.5km范围内海拔3600∼3700m坡度为2°∼6°的阳坡区。2006-2020年，拉萨设施农地面积年均增长率为4.41%；新增设施农地主要源于耕地，减少多因为建设用地扩张。设施农地整体向稍高海拔和稍大坡度区转移，分布重心向东南方向迁移了4.23km。.与邻近大田耕地土壤理化指标相比，拉萨设施农地土壤pH平均下降了1.12个单位，水溶性全盐上升了24%，氮、磷、钾等养分含量均有所增加，重金属元素富集不显著；海拔3600-3700m表层土壤环境变化相对明显。设施农地土壤质量指数较大田耕地平均降低了16.28%；且海拔越高，下降越明显。土壤盐分、速效钾和镉含量是影响土壤质量的主要因子。土壤酸碱度变化主要受肥料类型和种植年限的影响，土壤盐分受施肥量的影响明显，而土壤养分变化主要受肥料类型的影响。.基于上述研究发现，高原设施农地应优先布局在海拔较低的区域。加强对7年以上设施农地土壤环境的监测；化肥用量可减少20~50%，特别是减少施用高磷复合肥和高腐殖酸肥料。可加大叶类蔬菜的种植，加强轮作换茬，以缓解土壤环境问题。研究结论有望为高原设施农业与环境协调发展提供科学借鉴。