| The study of the spatial variability of soil moisture provides a theoretical basis for the monitoring of soil moisture in the farmland,the design of sampling scheme,and the improvement of the precision of field tests and it also provides scientific guidance for the implementation of precision agriculture and the development of soil and water science.Therefore,it is necessary to study the spatial variability of farmland soil moisture in black soil area.For this purpose,this paper takes the farmland in black soil region as an example.Based on traditional statistics,geostatistics,multifractal and joint multifractal methods,this paper studies the spatial variability of soil water in different periods of maize,the spatial variability of soil water before and after rainfall,the spatial variability of soil water in different sampling intervals,and Spearman rank correlation coefficient and relative deviation were used to study temporal stability of soil moisture in black soil region.The main conclusions were as follows:(1)The variation of soil moisture in different soil layers shows different trends with the changes of growth period.The spatial variability of soil moisture at different growth period also shows different trends with the increase of soil depth.During the whole growth period of maize,the spatial correlation of soil moisture in 0-20 cm,40-60 cm and 60-80 cm soil layers showed a trend of increasing first and then decreasing,and the 20-40 cm soil layer tends to increase;The spatial correlation range of soil moisture in 0-20 cm and 60-80 cm soil layer showed a trend of weakening first and then increasing,the spatial correlation range of soil moisture in 40-60 cm soil layer showed an increasing trend,and the spatial correlation range of soil moisture in 20-40 cm soil layer is basically the same except for the mature period.The spatial variability of soil moisture in the 0-20 cm soil layer from the seedling period to the milk period is mainly caused by the low value information,and the spatial variability of soil moisture in the mature period is mainly caused by high value information.The spatial variability of soil moisture in the 20-40 cm soil layer during the grain-filling period and milk period was mainly caused by high value information,while other growth periods were mainly caused by low value information.The spatial variability of soil moisture in the 40-60 cm soil layer during the tasseling and spinning period was mainly caused by low value information,and other growth periods were mainly caused by high value information.The spatial variability of soil moisture in the 60-80 cm soil layer during mature period is mainly caused by low value information,and other growth periods are mainly caused by high value information.(2)The variation of soil moisture was moderately variable in different soil layers before and after rainfall;Mean value of soil moisture in different soil layers increased first and then decreased after rainfall,the changing trend of the range of spatial correlation and the extent of spatial correlation of soil moisture were differences in different soil layers after rainfall.The variation of soil moisture varies with the depth of soil depth before and after rainfall.The spatial variability of soil moisture in 0-20 cm soil layer is mainly caused by its low value information before and after rainfall and the spatial variability of soil moisture in other soil layers is mainly caused by its high value information.The multi-scale correlations of soil moisture in different soil layers between the day before rainfall and the day after rainfall was less than that between the day before rainfall and the secone day after rainfall.(3)The variation of soil moisture was moderately variable in different sampling intervals.With the increase of sampling interval,the mean value of soil moisture gradually increases,and the variation caused by the smaller sampling scale and experimental error and the extent of spatial correlation decrease first and then increase,and the range of spatial correlation increase first and then decrease.The spatial variability of soil moisture in 24 m×24 m sampling intervals is mainly caused by high value information,and the spatial variability of soil moisture in other sampling intervals is mainly caused by low-value information.With the increase of sampling interval,the spatial variability of soil moisture weakened,and the reasonable number of soil moisture was reduced.(4)Soil moisture in farmland scale in black soil region has good temporal stability.Temporal stability of soil moisture at different sites increased with the increase of soil depth.Mean value of soil moisture in different soil layers can be better predicted by the determined representative measurement points in the study area. |
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