8Fisher E,Thornton B, Hudson Getal. The variability in total and extract able soil phosphorus under a grazed pasture [J].Plant and Soil, 1998,203: 249 ~ 255.
9Meirvenne M V,Hofman G. Spatial variability of soil nitrate nitrogen after potatoes and its change during winter [J]. Plant and Soil, 1989,120:103~ 110.
10Cahn M D, Hummel J W, Brouer B H. Spatial analysis of soil fertility for site-specific crop management [J]. Soil Sci Soc Am J,1994,58:1 240~1 248.