Dry Soil Layer Formation And Soil Water Recharging Of Alfalfa Field On The Loess Plateau Of Central Gansu

Annual evapotranspiration is greater than the precipitation in the loess plateau, and theshallow soil moisture is not able to meet the needs of alfalfa growth, consuming large of deep soilmoisture, so many years of continuously growing alfalfa can easily lead to soil desiccation. Inorder to understand the alfalfa soil dry degree and how to solve the soil dry layer problem, theresearch has set fodder rotation and limited filling tests in Gansu province dingxi city in2011. Wemake clear the features of perennial alfalfa dry soil and evaluate the recovery effect of differentagricultural technology measures on the soil dry layer water by alfalfa soli dry layer identification,formed of dry layer and water dynamics dynamic law. The results show that.(1)After7years and9years research on alfalfa soil moisture has shown that the degree of drysoil of7alfalfa in0-30cm soil is mild dry soil. In the remaining soil, most layers of alfalfa dryingis a serious dry except for the200-250cm levels of soil drying. The soil drying degree of9yearsof alfalfa in0-10cm is not drying, the soil dry in10-30cm soil is mild degree of drying. In theremaining soil, the dry degree in the alfalfa layers is a serious and dry except for the80-140cmsoil layer is mild.(2)The Alternate husbandry study show that the process of Tillage planting potatoes (AP),Plantingmillet (AM) and relaxation (AF) can recovery the dried layer soil moisture, but the extent ofrecovery degree is different. Increasing soil moisture storage capacity2.81mm when continuinggrowing alfalfa in that year’s rainfall is still in0-300cm soil, which is less than the AP, AF andAM all three respectively19%,10%and24%, the order of the magnitude of the increase in soilmoisture storage is AA<AM<AP<AF, significant difference between the treatment. Furtherrestoration of the evaluation results show that, the level recovery of full restoration of soilmoisture in0-110cm, and it shows mild recovery in110-300cm. The processing of rotating grainin0-30cm that the recovery dry soil layers is100%, it is an excellent recovery in30-50cm,in50cm soil, the layer shows differently, particularly80-200cm is no recovery,water restoration ofdry soil layers is full recovery in processing of leisure in0-140cm, in140-170cm water, therestoration of dry soil layers is in excellent performance for recovery, the restoration of dry soillayers in170-300cm-water is characterized by moderate recovery. The soil water restorationworks best for leisure, following by ploughed and planted potatoes. But the overall economic efficiency, tillage planting potato is better.(3)The experimental of limited supplementary irrigation study showed that, the differentirrigation has a certain effect on the soil moisture content, and the processing of irrigation in135mm has increased soil water maximum (97.95mm). Further restoration of the evaluationresults show that, in irrigation treatment of90mm, the0-80cm water restoration of dry soil layersto reach full recovery,80-110cm soil layers for moderate recovery, the recovery of soil moisture in110-140cm is no recovery, it is mild recovery in140-300cm. In processing of135mm irrigationtreatment, it reaches full recovery in0-110cm.It has no recovery ability in110-140cm, and it ismild recovery in140-170cm and200-250cm soil layer. The recovery degree in170-220cm and250-300cm soil layer is slightly recovery. It means that the dry layer recovery significant effect inthe irrigation of7years alfalfa, and the larger irrigation, the better results in a certain range.(4)Comparing the Fodder crop rotation and limited irrigation water saving measures shows thatthe leisure(AF) work best in fodder crop rotation trials, and the amount of restore soil watercorrespond to the irrigation135mm water. The restoration of millet planting soil water isEquivalent to irrigate90mm water, which is access to restore of rotating potatoes planting soilwater is equivalent to irrigate114mm water, the water recovery degree between90mm and135mm in irrigation, and with a high economic efficiency, which is the ideal soil moisturerecovery test.