Spatial Variability of Soil Nutrient in Wheat Field

Ninety eight observing points by a square of 10m×10m were made in a wheat field approximate 1 hm². Soil samplers were obtained from each point under two layers of 0～20 cm and 80～100cm with different soil moisture and different time. Ammonia、NO₃-N、Olsen-P in the soils of 0～20 cm and 80～100 cm, organic matter and total-N in surface soil (0～20 cm) were measured. The geostatistics theory was applied to analyze the data, the results indicated that both NH_４-N in bottom soil and organic matter in surface soil showed a normal distribution, others with a lognormal distribution. The rational sample number was determined within a given precision at a known confidence level. Semivariance analysis gave that those nutrients were correlated in a given spatial range. The Kriging method was applied to calculate the unobserved points and generate the contour map. Preliminary analysis was made for the spatial dynamic variability of those nutrients in different time. These results shows some merit in increasing nitrogen use efficient and precision agriculture.