Stuty On Water-salt Transport Law Under Drip Irrigation With Film Mulch Of Cotton

Drip irrigation technology has being wildly applied in arid region of northwest China due to its water saving and water retention advantages. In order to exploiting saline-alkali soil and preventing the soil from secondary salinizations, the analysis of salt and water movement under drip irrigation conditions and characteristics was conducted. This paper aimed to reveal the characteristic of the salt and water movement and salt accumulation under mulch drip irrigation conditions in the cotton fields that was used for the prevention of method of secondary salinization cotton soil and water resources in arid areas to provide a scientific basis for sustainable use.This paper summarizes characteristics of salt and water movement at home and abroad and the irrigation system on the basis of research, laboratory and field experiments using a combination of methods, arid region of Xinjiang, salt and water movement under drip irrigation conditions and the current irrigation systematic study system, the following conclusions: 1 (1) Through the two-point source infiltration intersection of the laboratory experiments. Before the intersection of two-point source, single point source infiltration wetting front and time has the power function with a significant relationship; After point source intersection, the intersection of moist front horizontal transport distance and time showed infiltration polynomial. The larger emitter discharge occured intersection ahead of a small emitter discharge. Under the same emitter flow, the longer infiltration, the greater of the intersection width. At dripper irrigation and the same distance, the intersection wetting front migration of small emitter discharge moved deeper and vertical transport width of the narrow, large emitter flow just for the opposite.(2) Interface center owed higher moisture content. Far away the intersection with the center, the moisture content decreased gradually. At same distance of point source moist central location, the intersection area soil moisture content is higher than single point source. The large emitters increased water content in the intersection area is greater than the small emitter discharge, and improve the uniformity of soil wetting.(3)Under the same irrigation, small emitter discharge rate has salt leaching effect in single point source and the intersection area at the vertical direction. The horizontal direction is very significant leaching effect under bigger emitter discharge. With the increase in irrigation, soil salinity confluence of the upper section gradually reduced, desalination depth increased, the width and the intersection in the soil wetting front ends of the bottom accumulated, became higher than the initial soil salinity value. The moderate wetting emitter discharge has leaching salt better in the horizontal and vertical. 2 (1) Through the optimization of cotton irrigation system test, in 3900～4500m3/hm2 irrigation quota,5 to 7 days of irrigation interval, can maintain a higher soil water content. With same irrigation quota, soil moisture increased by shorting irrigation cycle time. To meet the water requirements of cotton under conditions of (the whole growth period irrigation 390mm), Drip Irrigation of Cotton in Northern, water consumption 63mm in the seedling stage, bud stage is 110mm, during the blooming period reached 315mm, accounting for the whole growth period 60% of water consumption, boll opening period of 37mm, the whole growth period consume water 525mm.(2) The higher irrigation frequency effectively reduced the salinity, the treatment of long day cycle introduced fluctuations of salinity in soil and resulted in salt accumulation at growth period. Considering water conservation, yield enhancement and soil salt reduction, the irrigation quota of 3900m3/hm2 is desirable for agriculture industry in north of Xinjiang. The irrigation scheduling are:at the seedling stage, the irrigation quota is 250～300m3/hm2 one time; From bud stage to flowering, the frequency is 11 and 300～350 m3/hm2; The last time, the quota is 300 m3/hm2 at the boll stage.The frequency is 13 in the whole stage.3 (1) Different of drip Irrigation years in the 121 groups, monitored soil water and salt, It showed that after statistical analysis, the non-irrigation period, it was no significant difference between the land of water. The same plots with soil moisture differences in the different layers, surface water is minus,0-60cm increases with depth, but 60-100cm gradually decreases; soil moisture content is low in seedling and boll opening period, the peak blooming period. This cotton irrigation systems and growth characteristics are closely related. Soil water distribution in the horizontal direction significantly different distribution in the order:emitter>line>film room.(2) In the absence of winter irrigation purposes, only for drip irrigation in cotton growth period in the way of the land on which irrigation, drip irrigation, the longer the duration, the more severe salt accumulation, soil salinity levels in irrigation gathered in front of the gradual move to the surface, different depth of soil salinity has increased significantly, the level of highly significant differences between the levels (P<0.01). Age difference of 6～7a drip irrigation of cotton fields is between 0-100cm salt was significant (P<0.05). According to the degree of soil salinization and growing experience that the local cotton field in the implementation of drip irrigation 5a, the need for flood leaching of salt or restore the previous winter and spring irrigation, but water and good drainage to control for prevent water level rise.