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Soil Consistence and Structure as Predictors of Water Retention

USDA-ARS Animal Waste Pathogen Lab., Bldg. 173, Rm. 203, BARC-EAST, Beltsville, MD 20705

View larger version (30K): [in a new window]   Fig. 1. Distributions of structural and consistence parameters among the samples in the data set of this work.

View larger version (14K): [in a new window]   Fig. 2. Regression tree for the test data set in Table 1. The node number in brackets, the average value of the dependent variable for the group, the standard deviation of the dependent variable within groups in parentheses, and the number of samples in the group are shown beneath terminal nodes.

View larger version (20K): [in a new window]   Fig. 3. Effect of the size-complexity parameters on the accuracy, reliability, and number of terminal nodes NTN of the regression tree. RMSE, root mean squared error of the volumetric water content at -33 kPa.

View larger version (29K): [in a new window]   Fig. 4. Regression tree to estimate water retention at -33 kPa from structural and consistence parameters; y, yes and n, no answers to the parameter definition in the box above. The node number in brackets, the average value of the volumetric water content at -33 kPa for the group, the standard deviation of the water content within groups in parentheses, and the count of samples in the group are shown beneath terminal nodes.

View larger version (27K): [in a new window]   Fig. 5. Regression tree to estimate water retention at -1500 kPa from structural and consistence parameters; y, yes and n, no answers to the parameter definition in the box above. The node number in brackets, the average value of the volumetric water content at -1500 kPa for the group, the standard deviation of the water content within groups in parentheses, and the count of samples in the group are shown beneath terminal nodes.

View larger version (34K): [in a new window]   Fig. 6. Regression trees to estimate water retention from laboratory textural class and structural and textural parameters at (a) -33 kPa and (b) -1500 kPa. Left (right) branches lead to samples where the categorical variables have (have not) values shown in the box above splits; the average value of the volumetric water content at -33 kPa for the group is shown beneath terminal nodes.

View larger version (52K): [in a new window]   Fig. 7. Distribution of plasticity classes and stickiness classes among textural classes.