砂质海涂含粉砂量高,土体板结,返盐迅速,表层土壤含盐量高.围后直接种植旱作生苗困难,垦种效果极差.垦种初期一般棉花亩产仅十余斤.如果采用先水后旱的利用方式,在垦种初期进行种稻改良,不仅加速土壤脱盐,并且当年可以获得较高的产量,当形成一定厚度的地下水淡化层后,即可回种旱作,待土壤返盐到影响旱作物生长时,又回种水稻,反复轮种多次,可以达到稻棉高产稳产的目的.实践证明,水旱轮作是加速新围砂质海涂改良利用的有效措施.但是种稻几年后才能回旱,回旱时间多久,这是需要探讨的砂涂农业生产问题.一般认为种稻年限愈长,土壤脱盐深度愈深,改良效果愈好.但长期种稻,用水量大,而水源又不足,加之经济效益比棉花低,不能充分发挥砂涂的生产能力.如果种稻年限 Sandy seaborne contains high silt, soil compaction, rapid return of salt, surface soil salinity is high. The direct cultivation of dry seedlings around the periphery is difficult, the effect of reclamation is very poor. Reclamation early general cotton yield only ten If the use of water and drought after the first use of reclamation, planting early rice improvement, not only accelerate the soil desalination, and then get a higher yield, when the formation of a certain thickness of the groundwater desalination layer, you can back to drought To return the salt to the soil to affect the growth of dry crops, but also back to the rice, repeated rotation many times, you can achieve the purpose of high and stable yielding rice. Practice has proved that the rotation and drainage is to speed up the improvement of the new permafrost Effective measures.But a few years after the paddy to drought, drought time, which is the need to explore the problem of sand coating agricultural production is generally believed that the longer the growing rice, the deeper the soil desalination, the better the better, but the long-term Rice, water consumption, and insufficient water, combined with low economic efficiency than cotton, can not give full play to sand production capacity. If the rice years