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Environmental Management of Soil Phosphorus

Modeling Spatial Variability in Small Fields

^a Dep. of Agronomy, The Pennsylvania State Univ., 116 A.S.I. Bldg., Univ. Park, PA 16802
^b Pasture Systems & Watershed Management Research Unit, USDA–ARS, Curtin Rd., Univ. Park, PA 16802

View larger version (81K): [in a new window]   Fig. 1. Location of FD-36 watershed with land uses and soil sampling locations. Symbol size is proportional to Mehlich-3 phosphorus (M3P) concentration. Numbers near and within fields are field identification numbers.

View larger version (20K): [in a new window]   Fig. 2. Global and pooled within-stratum variogram for Mehlich-3 phosphorus (M3P) with spherical semivariance function fitted by weighted least squares. Nonwithin-field semivariance values are also presented. Numbers near points indicate the number of data pairs within the lag increment. Points without number labels are based on >100 data pairs.

View larger version (63K): [in a new window]   Fig. 3. Prediction surfaces of Mehlich-3 phosphorus (M3P) concentration in watershed FD-36. Classifications are based on agronomic and environmental critical levels.

View larger version (44K): [in a new window]   Fig. 4. Residuals from validation of prediction of Mehlich-3 phosphorus (M3P) concentration in watershed FD-36. Classifications are based on multiples of 71 mg kg-1, which was the average residual across all three models.