Study On Water Saving And Salt Reduction Effect And Comprehensive Benefit Of The Farmland Shelterbelt In Hetao Irrigation Area

With P. Popularis'〔Populus simonii×(Populus pyramidalis+Salix matsudana) cv.'Poplaris'〕Farmland Shelterbelt in Hetao Irrigation Area as test material , The study focuses on the water consumption characteristics, salt ions absorption characteristics, renewal age of Farmland Shelterbelt, and made a cpmprehensive assessment on comprehensive benefit. The main results were as following:(1)〔P. simonii×(Populus pyramidalis+Salix matsudana) cv.'Poplaris'〕has a strong absorption selectivity on K+,Ca 2+,Na +,Mg2+, through absorbing K+ to prevent other Nutrient Elements, inhibiting excessive Na + enter root. However, the inhibition effect was limit, the root salt concentration was higher than CK when in high salt concentration envioronment. The excessive Na +also existed in stem, so that Na+/ Nutrient Elements keep a low level.(2) One year after Farmland Shelterbelt was mature , the salt decreacing effect account to accumulative salt amount from early stage to mature stage, equal to the total precipition of mid-May,August and September. The 90% of salt ion was accumulated in the soil ground water system, planting〔P. simonii×(P. pyramidalis+Salix matsudana) cv.'Poplaris'〕on large scale has the tendency to increace the salt content of local area soil-ground water system.(3) In irrigation area site condition, P. Popularis'protective manturity,numerical maturity,economic maturity,techniques and regeneration age were 8a,13a,15a,15a,15a.(4) The order of affecting factors to evaporation degree was: air temperature>air humidity > wind speed,radiation trimmed and soil temperature gradient. The main forest belt should be intermediate cut to increase spacing from 100m to 200m, as a result, the wind controlling, hydrology and thermal benefit had changed seldomly, so as to implement water conservation-salt reduction purpose. The amount of water conservation and annual salt reduction were 146m~3/hm~2. a and 170 kg/ hm~2. a。In present Farmland Shelterbelt construction theory and comprehensive assement, water balance affect factor is shelterbelts water consumption, water conservation amount owing to reducing soil evaporation . The salt balance affect factor is field tillage salt reduction amount, understory accumulative salt amount, forest belt cutting salt reduction amount, P. Popularis'Farmland Shelterbelt can decrease salt accumulativetion effectively, and reduce soil ineffective evaporation, the water conservation effect of which play an important role in agriculture production.