Studies On Saving Water Mechanism And Effect Of Different Conservation Tillage On Corn-wheat Two Crops A Year Farmland

Farming system of double cropping system in north china plain is mainly winter wheat summer corn cropping system, annual rainfall displays, that concentrating precipitation is From 7 to 9 Months and less precipitation appears in winter and spring, the increase of drought occurrence in wheat growth periods, water shortage and distribution unequally has already hindered greatly agricultural sustainable development of these regions. So efficient and permanent utilization to natural rainfall through the medicum of the fired technical measures is a way to breaking through the bottlenecks in agricultural water resources. people pay more and more attention to conservation tillage with water-holding property, which is a mean to to achieve aforementioned objectives. compared with conventional tillage, conservation tillage can decrease soil loss, increase of rainfall infiltration, increase soil moisture and so on. But these studies focuse on soil, the study for soil-crop has hardly been reported before, and they study tillage measure and straw measure as a whole, but the study for tillage measure and straw measure respectively has hardly been reported before. So in the semi-humid areas, this experiment study soil-crop water variation and yield of winter wheat under different conservation tillage systems systematically, providing theoretical basis and technical support for popularization of local conservation tillage technology. 1. Effects of conservation tillage on Soil Physical CharacteristicsThe results show that, in 0-30cm soil layer, bulk density of PZ was large and porosity was small. The bulk density of PS was small and porosity was large, especially in winter wheat harvest time. With the increment of the depth of soil layer, bulk density of PH and PR was larger and porosity was smaller, relating to tilth depth.The soil evaporation, leaf transpiration rate and Surface Infiltration of PS was highest, surface runoff was lowest, relating to porosity of PS.From sowing period of winter wheatto jointing stage, water content variation was caused by evaporation and irrigation, and the effect of moisture conservation about PR and PH was best. From jointing stage of winter wheat to harvest time, water content variation was caused by evaporation and rainfall, and the soil water content of PR and PZ was higher and the soil water content of PS, PH and PC was lower. There is a rainfall in the later grain-filling stage of wheat, and the rainwater harvesting efficiency of PS, PZ and PH was lower. During the growth season of summer maize, different treatment had unoriented effect for soil water content because it was effected by frequent rainfall and evaporation.Tillage measure had significant influence on soil bulk density, porosity and direct acting factor about soil water content, and it played a dominant role. Before jointing stage of winter wheat, straw factor played a dominant role on soil water content. During the rapid growth season of winter wheat, tillage measure played a dominant role. straw factor played a dominant role on soil water content after rainfall. During the growth season of summer maize, tillage measure and straw factor all played dominant roles.2. Response of crop to conservation tillageThe results show that, the bleeding amount of PS was was maximal, PZ and PR were lower than CK, showing that the root of PS had good ability of water uptake. In the filling stage, the saturation deficit of leaf of PS was lowest, the saturation deficit of leaf of PR and PZ was higher than CK. Leaf water potential of PS and PH was lower than CK. PS, AS and PH had good photosynthesis electronic transferring ability, high photosynthetic rate and yield.The law of correlated drought index of leaf wasn't inconsistent with the law of soil water content, but was inconsistent with the law of bleeding sap amount of root, showing that the absorbing of water directly affected water use efficiency.On the study basis of our team, only through effects of conservation tillage on Soil Physical Characteristics and response of crop to conservation tillage, PS had advantages in all indexes in three years. So PS could popularize and apply on local substituted conventional tillage, but it's long-term effect needed further study.