微咸水补充灌溉压砂地水盐运移规律及西瓜响应机理

Shortage of water resource is the most key factor to restrain the development of watermelon industry planting with gravel mulch in the arid area in central Ningxia. Utilization of underground brackish water is an effective way to resolve the contradiction between water supply and demand in this region. However,long-term brackish water irrigation might cause soil salinization if without leaching salts practice in arid region. Furthermore,it could affect crop growth and product quality also.Therefore how to safely and efficiently utilize brackish water is the problem to be solved in sustained watermelon production on the field with gravel mulching. Clarification the distibution characteristics and movement of water and salt and the response mechanism of watermelon is the key to solve the problem. This research is to study the effects of thickness and textural composition of gravel layer and the amount of brackish water on the dynamic changes of water and salt ,the effect of brackish water supplementary irrigation on growth, yield and fruit quality through field experiment and soil column simulation.The objectives are to ⅰ) reveal the distribution characteristics and movement of soil salt with gravel mulches under the condition of brackish water supplementary irrigation;ⅱ)calrify the response mechanism of watermelon to brackish water irrigation. Results from this research can provide scientific basis for making and optimizing brackish water irrigation regime and guarantee sustainable development of watermelon industry for local region.

水资源短缺是限制宁夏中部干旱带压砂西瓜产业发展的最关键因素。利用较为丰富的地下微咸水是解决该地区水资源供需矛盾的有效途径，但在无洗盐措施的压砂地上长期使用微咸水灌溉容易引起土壤盐渍化，进而影响作物生长和产品品质。因此，如何安全高效地利用微咸水是压砂西瓜可持续生产中亟待解决的问题，而明确微咸水灌溉条件下压砂地土壤的水盐分布特征及其运移规律和西瓜的响应机理是解决这一问题的关键。本项目通过田间定位试验和土柱模拟试验的方法，分析不同覆砂厚度、砂石级配、微咸水补灌量下土壤水分和盐分的动态变化，揭示微咸水补灌条件下压砂地土壤盐分的分布特征和运移规律；同时，研究微咸水补溉对西瓜生长、产量和品质的影响，阐明压砂地西瓜对微咸水补溉的响应机理。研究结果将为优化和制定压砂地西瓜微咸水灌溉制度提供理论依据，为宁夏中部干旱带压砂瓜产业持续发展提供保障。

本项目通过3年田间定位试验、调查试验和一系列土柱模拟试验研究了微咸水补灌对压砂地土壤水盐运移规律以及西瓜生长、产量和果实品质的影响。研究结果如下，.1）微咸水补灌增加了土壤水分含量和西瓜耗水量，灌溉水入渗深度和西瓜耗水量随灌水量增大而加深和增加，灌水定额为15、30、45 m3/667m2处理的入渗深度分别达到40、80和100cm左右。.2）微咸水灌溉3年后，在盐分本底值高的条件下除了灌水定额为15 m3/667m2处理0-40cm土层土壤盐分增加85.86%外，其他处理0-100cm土层土壤盐分含量有不同程度的降低；0-100cm土层Cl/SO4从2014年灌水前的4.06~5.72降低到2016年试验结束时的1.44~1.52； 15 和30m3/667m2处理0-100cm土层钠吸附比（SAR）分别增加了12.34%和35.21%，而45m3/667m2的处理降低了11.5%。.3) 在盐分本底值低的条件下微咸水灌溉2年0-40cm土层土壤盐分含量随灌水量增加而增加，增加幅度从8.02到85.87%；40-100cm土层盐分含量有降低趋势；30 和45m3/667m2处理0-100cm土层Cl/SO4的比值和SAR分别增大了6.21%、17.34%和48.41%、48.59%。.4）在盐分本底值高且土质为黏壤土的条件下，灌水定额为15 m3/667m2的处理促进了西瓜生长；在降水较多年份除15 m3/667m2处理的产量与CK产量相当外，其他处理的产量低于CK的；在干旱年份，微咸水补灌处理相比CK处理增加了西瓜产量增加幅度在17~61%。在盐分本底值低且土质为砂壤土条件下，灌水定额为30 m3/667m2的处理有利于西瓜生长，与CK处理的西瓜产量相比微咸水补灌处理提高了西瓜产量，提高幅度在32.4~78.6%。.5）与CK相比补灌微咸水对西瓜瓜心可溶性固形物含量无显著影响但是降低了瓜周可溶性固形物含量和瓜液pH值，提高了可滴定酸含量和维生素C含量。.6）田间调查结果表明随着微咸水补灌年限增加，土壤盐分含量不断增加，西瓜产量和果实可溶性固形物含量呈下降趋势。.7）与不覆砂相比，覆砂处理增加了土壤水分入渗深度和土壤水分含量，促进了土壤盐分向下层运移并抑制了土壤盐分表聚。覆砂厚度和砂层级配对土壤水分和盐分分布具有明显的影响。