陕北农牧交错带沙地利用的水资源调控及生态响应

Sandy land treatment and agriculture utilization in ago-pastoral ecotone of Northern Shaanxi Province have formed a considerable scale. Ecological deterioration will happen if excessive sandy land agriculture with great water demand is involved in the environmental fragile zone, and will be accompanied with further water shortage, soil declining and sandy land loss of farming capacity again. It's very important to comfirm a feasible sandy land agriculture scale according to the support of water resource so that sandy land soil quality and environment have sustainable development capacity. Main researches were focused on three points. (1) Based on experiment and analysis, three water saving methods such as mixing arsenic sandstone with sand, improving water irrigation technique and rational farming system, were used to enlarge the support of water resource, and combaniation experimental programs of the three were used to calculated feasible scale of sandy land agriculture under the water resource restriction. (2) Sturcture and water-fertilizer characteristics and there trends of the special synthetic soil by arsenic sand stone and sand were monitored and analyzed, so that relationship between farming methods, irrigation system and soil quality can be revealed, which can help to search the best approach to make sandy land be developed sustainably. (3) Entironment response under sandy land agriculture was inspectd in the course of cultivating years. Relationship between water content in topsoil with soil crust was espacially researched in the unfarming season with bare soil in order to discuss the sand-fixing mechanism of topsoil and the measures to improve. In summary, a water resource regulation pattern on sandy land agriculture and entironment response is put forward and integrated to coordinate development of water-soil resources, to promote soil quality and sustainable development, and to made important attempt on entironment virtuous cycle with the propuse of economic development at the same time.

陕北农牧交错带沙地治理和利用已有规模，当地生态环境脆弱、农业用水量大，若无度开发将带来生态环境恶化，并伴随缺水进一步加剧、土壤质量下降、沙地失耕等。以水定发展，确定适宜的沙地利用规模、保证土地质量与生态协调十分重要。本研究（1）基于实验及理论分析，以沙地改造节水、灌溉节水、保水耕作节水三种手段最大限度地促进水资源支持力的延伸，采用不同的砒砂岩与沙土复合配比、灌溉技术、耕作制度组合方案确定适宜的沙地利用规模；（2）监测复合土壤在持续耕作过程中结构和水肥的变化趋势，揭示耕作方式和灌溉制度与土地质量之间的关系，分析寻找沙地持续利用的有效途径；（3）观测研究沙地农业利用的生态环境响应，以沙地表层固结与水分含量的关系研究为重点对耕作期与休耕期分别研究，探索沙地表层固沙效应的机理与调控措施。综上，集成构建沙地农业利用及生态环境响应的水资源调控模式，实现水土资源协调发展，促进土地质量及生态环境良性循环。

沙漠化、水资源贫乏、生态环境脆弱等三大问题严重地影响着陕北农牧交错带土地利用与农业经济的发展，当地特有的砒砂岩与沙复配成土可作为补充耕地用于农业生产，但若不考虑当地的水资源条件无度地开发沙地农业将引起研究区内缺水问题加剧、生态环境恶化，新补充的耕地因无水可灌而失耕，继而重新沦为荒漠化土地等问题。为此，（1）本项目结合复配工程节水、适宜的灌溉制度节水以及保护性耕作制度节水等三种手段最大限度地挖掘节水潜力，研究如何提高水资源利用效率。通过室内试验和大田试验相结合，研究获得了最佳的复配成土比例、形成了合理的灌溉制度，确立了可行的保护性耕作技术。取得了玉米和马铃薯灌溉分别为16.51%和4.6%的节水效果；（2）提出剩余水资源可利用量的概念，并以沙地剩余水资源可利用量作为沙地农业开发规模的约束条件，以不同类型作物的种植面积为变量，建立沙地农业开发利用优化模型，并针对农牧交错带内的6县（区）分别求解确定了现状年、2020年和2030年三个水平年适宜的沙地农业规模、种植结构和水资源配置方案；（3）以土壤的结构、有机质和N、P、K含量作为关注的主要土壤肥力因素，在项目执行期间对复配土壤的肥力性质进行了持续监测，以分析复配土的成土趋势，由于项目执行期短，监测年份较短，目前N、P、K养分的趋势性不明显，但有机质含量增加趋势明显；（4）以固沙为目标，分析总结了沙地农业利用过程所产生的生态环境响应，从土壤结构与质地、水分含量、抗风蚀和结皮等多个方面探索了沙地表层固沙效应的机理与调控措施。综合上以研究成果，本项目构建了充分考虑土地资源、经济和生态协调发展的陕北农牧交错带沙地农业利用的水资源调控模式，实现了在陕北农牧交错带这一特殊区域内维护生态、资源和经济持续发展的有益探索，也对区域水资源利用、沙地治理、农业经济发展和环境保护等实践措施的提出具有较好的指导意义。