Spatio-temporal Variability Of Soil Water And Water Balance Analysis In Field

Ninety-eight observing points by a square of 10m×10m were arranged in a wheat field approximately 1 hm2 at QuZhou Experimental Station of China Agricultural University in HeBei Province. Spatio-temporal variability of soil water properties was analyzed by geostatistical approach during different time. Through the observation of the soil water in 3 plot, the dynamic distributing regulation of soil profile water and characteristics of drainage and actual evapotranspiration in 2m soil profile were studied Relationships among actual evapotranspiration, potential evapotranspiration and water coefficient were established. Regulation that crop requires water was analyzed in different years. The reasonable irrigation scheduling was recommended. The main results were as follows.The correlation distance of bottom soil water content was larger than that of soil surface at different times. By comparing the performance of Co-Kriging (COK), Ordinary Kriging (OK) and Inverse Distance Weight Interpolation (IDW) , the results showed that COK attainted the best results, the IDW was similar with the OK.The soil profiles in three plots of field could be divided into three changes layer, there were quickly changing layer (0-30cm), slow changing layer(30-140cm) and stable changing layer(140-200cm).Under the condition of sufficient water supply, ETa can be calculated with ETp; While, under the condition of the soil wilting point was smaller than 0.37, ETa equals to 0; when under the condition ofinsufficient water supply, the equation could be expressed as ETa = Sw×ETp.The amount of drainage in 1998-1999 was caudated by the equation, the average was 149.4mm, the maximum value was 197.5mm and the minimum was 93.1mm, coefficient variability (CV) was 2.9%. The average amount of drainage in 1999-2000 was 286.4 mm, the maximum value was 391.9 mm and the minimum was 193.9 mm, the maximum value was two times than minimum value, and CV was 6.4%.Based on the rainfall data (1981-2001), the optimal irrigation schedule for winter wheat and summer maize were established in this study area. It was concluded that the optimal amount of irrigation was 60-70 mm.