Sampling needs to establish effective management zones for plant nutrients in precision agriculture

The paper examines (1) how the number of samples and methods of interpolation affect mean nutrient values for each management zone (MZ), (2) if MZs based on sensed data are suitable for managing several nutrients simultaneously and (3) if dense standardized sensed data can be calibrated by the mean and standard deviation (SD) of a few soil samples to produce inexpensive contour maps. Results showed that when sampling interval is large, there is less difference in the means of properties between MZs, but interpolation reduces this effect. The MZs produced were most useful for phosphorus (P), pH and volumetric water content (VWC). For these properties, maps with small errors could be produced easily by calibrating standardized sensed data with the mean and SD of a few sample points.