坝上半干旱高寒区土壤水分运行规律与农田莜麦耗水特征

Laws of the Soil Water Movement and the Character of the Soil Moistrue Consumption in Naked Oats Field on the Semi-Arid Region with Cold and High Elevation in Bashang Plateau

于１９９２～１９９４年在坝上半干旱高寒区主要地貌单元坡梁地和旱滩地上研究了栗钙土周年土壤水分运行规律和雨养农田莜麦耗水特征．结果表明：土壤水分时空变化可以分为冬季水分冻结聚墒期（从１１月初至翌年２月底）、春季返浆强烈蒸发失墒期（３月初至５月底）、夏季雨水不淋水分恢复期（６月初至８月底）、秋季水分缓慢蒸发期（９月初至１０月底）４个时期和活跃层（０～４０ｃｍ土层）、次活跃层（４０～８０ｃｍ土层），相对稳定层（８０ｃｍ以下土层）３个层位，且存在２个水分高峰期即冬季水分冻结聚墒期和夏季雨水下淋水分恢复期，降水高峰期与土壤水分离峰期不相吻合．其中冬季水分冻结期包括不稳定冻结阶段（１０－２５～１１－０６）和稳定冻结阶段（１１－０７～翌年０３－０２），“冻后聚墒”明显，聚墒区呈类似“倒三角形”；春季返浆强烈蒸发失墒期包括不稳定融化阶段（坡梁地０３—０２～０３—１４，旱滩地０３—０２～０４－０８）和稳定融化阶段（坡梁地０３—１４～０３—２８旱滩地０４—０８～０４—３０），冻融深度曲线呈倾斜的‘凹形”．莜麦阶段耗水量分析表明：拔节－抽穗－开花－灌浆（５１ｄ）耗水量占全生育期（１２２ｄ）耗水量的６５％～６８％，是作物关键需水期?

This paper deals with the anaiversary laws of water movement in Chestnut soil and the water consuming character of naked oats in rainfield over the years 1992～1994 on the mail landforms units which are sloping ridge and arid shoaly lands in Bashang semi-arid region with cold and high elevation.The result shows that the variahon of soil moisimc in time and space can be divided into four stages; the freezing and accumulating of soil moisime in winter;the moisture lossing with strong evaporating in spring (from Mar.to may);the water resuming with rain drenching from June to Ag and the slow evaporation of soil moisture in autumn(form Sep.to Oct).Soil moisture changing in space can be divided intothree layers:the ctive layer(0～40cm),the secong active layer (40～80) and the relatively stable layer.There are two periods with good moisture:the water freezing and accumulating in winter and the resuming with rain drenching in summer.The precipitation peak is inconsistent with the soil moisture summt.The water freezing periol in winter includes the instable freezing stage(10-25～41-06)and the stable freeaing stage(11-7～next 03-02),The water lossing periol with strong evaporation in spring includes the instable melting stage(03-02～03-14)in sloping ridge land,03-02～04-08 in shouly land), and the stable melting stage (03-14～03-28 in sloping ridge land,04-08～04-30in shoaly land).The depth curve of freezing and melting is similar to incline '凹'shape the analysis of water consumption of naked oats shows that thd consumption at the'Jointing-Blooming-Being in the milk'stages is 65～68 percent of whole period of duration.To the crop the crucial period of needing water.