新疆农田作物覆膜地温极值的时空变化

土壤温度的上限和下限值极大地影响农田作物的生长发育．根据对新疆农田2年度不同观测时刻、不同覆膜条件及不同作物的最高和最低地温的分析，可知2年度全生育期地温极值均发生在0cm位置．地温极值依观测时刻的不同而变动．覆膜最低温度始终高于裸地，说明覆膜对提高低温段土壤温度有明显作用．最低温度的日变化可用二次函数表达；14：00和20：00时最高地温可分别用深度的椭圆曲线和线性关系表达．不同条件下的地温极值和气温具有线性关系，其中裸地最低温度与气温的相关性高于覆膜；玉米最低温度与气温的相关性高于棉花；最高温度与气温的相关性比最低温度与气温的相关性差．

Spatial and temporal variation of soil temperature extremum under plastic mulch in Xinjiang

The upper and lower limit values of soil temperature affect crop growth and development greatly.Observations on the soil maximal and minimal temperatures under different mulching and cropping conditions in Xinjiang showed that during crop growth period in 1998 and 1999,soil temperature extremums were both at 0 cm,and varied with different observation time.The soil minimal temperature under plastic mulch was higher than that without mulch,indicating that plastic mulch could remarkably increase soil temperature.The diurnal variation of soil minimal temperature could be expressed by quadratic function,while the maximal temperature at 14:00 and 20:00 could be expressed by ellipse function and linear function of soil depth,respectively.Soil temperature extremums correlated linearly with air temperature under different conditions.The correlation between soil minimal temperature and air temperature was higher for bare soil than for mulched soil,and higher for maize field than for cotton field,while the correlation between soil maximal temperature and air temperature was lower than that between soil minimal temperature and air temperature.