| Fluctuation of groundwater depth is closely related to soil salinzation and cropgrowth in Hetao Irrigaitgon District. Although researches about groundwater wereconducted a lot in the past both at home and abroad, qantitive study on proper groundwatercontrol depth and groundwater use of various crops during their growing period in HetaoIrrigationg District have not been reported. Moreover, since water application at Autumirrigatin in Hetao Irrigation District accounts for one third of its yearly total irrigationwater, improvement on Autum irrigation method is of importance to water saving in HetaoIrrigation District. The dissertation conducted a sysmetic study on the two respectsmentioned above and achived the follwing main results:1. The proper groundwater control depth and groundwater use of main crops growedin Hetao Irrigation District such as wheat,maize and sunflower were studed by anylizingwater application,groundwater recharge,soil salt&water dynamics during crop growingperiod and crop growth indexes,yield and water productivity obtained through aprecision groundwater depth control experiment using Lysimeter. Results showed that thegroundwater recharge for the3crops decreses as the increase of groundwater depth andbecomes the maximum at1.5-2.0m below ground surface. Considering the overall effectgroundwater depth on water saving,soil salt control and crop yield, it is recommended thatthe groundwater control depth be1.5-2.0m with a groundwatrer recharge of26-147m~3/muand the irrigation requiremen be220m~3/mu for wheat; that the groundwater control depthbe1.5-2.0m with a groundwatrer recharge of181-251m~3/mu and the irrigationrequiremen be240m~3/mu for maize; that the groundwater control depth be2.0-2.5m with agroundwatrer recharge of288-378m~3/mu and the irrigation requiremen be220m~3/mu forsunflower.2. Based on comprison field experiments of film-muched autum irrigation, themuching date, mulching pattern, irrigation pattern and irrigation requirement and theireffectc on water saving, heat keeping, soil moisture preservation and crop yield increasewere anylized anda improved Autum irrigation method-film-mulched Autum irrigation method, as a result, is put forward. The results show that mulched Autum irrigation methodcan greatly save irrigation water and increase crop yield and realize simutaniously watersaving, soil moisture preservation, yield increase and soil salt control. It also has theadvantages of low cost, quick effect, simple peration and easy farm acceptance. Theprospect of Its application is bright in Hetao Irrigation District and similar regions. |
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