RESEARCH ON MEASURES TO PREVENT SECONDARY SALINIZATION AND FARMLAND CONSERVATION USING MATERIAL AND WATER CIRCULATION IN THE LOWER LOESS PLATEAU AREA

确定的主要盐渍化过程在研究区是由于：1。毛管水上升; 2.使用含盐灌溉水; 3.将凿井挖出的土倾倒在田间并压实; 4.地表地形和排水条件的变化; 5.偶尔的内涝，加速了沉积在底土层中的钠的溶解，随后增加了地下水SAR。导致这些过程的原因是确定的：1。地下水位高，2.地下水矿化度高;溶解盐在土壤下层的沉积，4.下层不透水土层; 5.渠道渗漏损失和农田渗漏损失严重，6.地下水管理不足; 7.排水管理系统不足。地下水埋深较深的威尔斯井经常出现低EC值和高残留碳酸钠（RSC）的现象。因此，在地下水持续利用的情况下，土壤碱化可能会增加。 关于我们 这些威尔斯用来灌溉。根据一系列的研究结果，提出了防止盐渍化过程的一些建议：1。通过设置有效的排水系统降低地下水位; 2.控制田间抛荒盐渍土;管理含盐灌溉水的使用，4.维护和操作排水系统，以履行其功能，5.施用秸秆还田改良盐碱地;在沿着渠和农田周围引入生物排水，以防止内涝。利用黄土高原侵蚀土径流浑水进行秸秆还田的优点是：1。改良盐渍土（通过土壤施肥和淋溶），2.提高土壤肥力，改善土壤物理性质（土壤质地、孔隙度、渗透性）;利用黄土高原侵蚀土壤（有效利用同一流域的物质循环）;减轻渭河和黄河流域的悬移质泥沙。少

The identified main salinization processes in the study area are due to : 1. capillary water rise ; 2. use of saline irrigation water ; 3. dumping and compacting dug soil of well sinking in the field ; 4. variation in surface topography and drainage condition ; 5. occasional waterlogging, which accelerates dissolution of deposited sodium in the subsoil layers, and afterward increases groundwater SAR. Causes bring on these processes are identified : 1. high groundwater table, 2. high groundwater salinity, 3. deposition of dissolved salts in subsoil layer, 4. impermeable soil layer in lower layers, 5. heavy seepage losses through canal and percolation losses in farmlands, 6. insufficient groundwater management, and 7. insufficient drainage management system. Frequent occurrence of low EC value with high residual sodium carbonate (RSC) was observed in wells with deep groundwater table. Thus alkalization of soil is likely to be increased under the continuous utilization of groundwater from … More these wells for irrigation. Based on a series of research findings, some suggestions for preventing salinization processes are proposed : 1. lowering the groundwater table by installing effective drainage system, 2. controlling dumped saline soil in the fields, 3. managing the use of saline irrigation water, 4. maintaining and operating drainage system to fulfill its function, 5. applying warp soil dressing to reclaim salinized farmlands, and 6. introducing biological drainage along canals and around farm lots to prevent waterlogging. Merits of warp soil dressing applying muddy runoff water containing eroded soil from Loess Plateau are identified : 1. improving saline soils (through soil dressing ＆ leaching), 2. improving soil fertility, soil physical properties (soil texture, porosity, permeability), 3. utilizing eroded soils from Loess Plateau (effective use of material circulation in the same watershed), and 4. mitigating suspended sediment load in Wei River and Yellow River Basins. Less