Study On The Relation Between The Economic Property Of Alfalfa And Soil Water Ecological Environment

Alfalfa is an excellent perennial leguminous grass, which is widely planted in the world. Loess Plateau is not only the traditional district in which alfalfa is planted, but also the intensive district. With the carry out of returning farmland on hill to forest and pasture and strategy adjustment of industry in rural district, Alfalfa became the new increase point of income in many district of Loess Plateau, and the area increased by and by. But the water consumption of alfalfa is very large, if alfalfa was planted perennially, which would lead to the dry layer of deep soil layer, then the function of regulation of soil reserior lost. So whether the alfalfa can better the economic benefit and ecological benefit, and how to slower or avoid the formation of dry layer, has become the emergent demand of development of alfalfa in this district. On the hill-gully region of Loess Plateau, we study the relation between the economic property and water environment under four establishments, which includes the halve sowing establishment, the intercrop establishment, the plastic film mulching establishment and the check establishment.The main results showed:The height, branch number and stem and leave ratio of the four establishments changed. Although there is difference among every establishment, the formation of yield is formed with the same regulation. Based on the yield of the whole year, four establishments has the remarkable increasing effect, and the plastic film mulching establishment has the largest yield, which is 1.84 larger than that of check. Based on the path analysis of the individual plant, there is a very significant linear dependence between the height, branch and stem and leave ratio and yield. There is also a very significant linear dependence between every two of the three treatments. The height affected the yield greatly, but the other three properties have different effect on yield with different order. The soil water is analyzed by margin model, and the seasonal change of soil water is devided into four stage: from March to May, when the soil water-storage lost very slowly; from June to July, when the soil water-storage lost heavily; from August to October, when the soil water-storage increased greatly; in November, the soil water-storage lost very slowly. Based on the analysis of SD and CV, the vertical profile is divided into two parts. The plastic film mulching and intercrop have the same active layer and stable layer, while the halve sowing norm and check have deeper active layer and stable layer.The water-storage capacity of 0-180 cm of the four establishment presents the trend as: the plastic film mulching>the intercrop>the halve sowig norm>the check, and the compensation of rainfall has the same order .The plastic film mulching has the most significant effect. The trend of the water consumption in whole growth stage presents as: the intercrop>the check>the plastic film mulching>the halve sowing norm. The water-use efficiency presents the order as: the plastic film mulching>the intercrop>the halve sowing norm >the check. The precipitation productivity presents the same trend,and the plastic film mulching has the biggest precipitation productivity, while the check has the smallest one. The order of precipitation productivity presents as: the plastic film mulching>the intercrop>the halve sowing norm >the check.