A METHOD OF CAPABILITY EVALUATION FOR UPLAND SOILS : III. Numerical Evaluation of Soil Tilth (2) Scaling of Soil Tilth and Its Evaluation with Field Characters

概要

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As a follow-up of the preceding study, in which "structure index" and "consistency index" were objectively defined, a method of attaining a numerical evaluation of soil tilth was worked out in this study, using the same 94 surface soils as samples. As the first step, numerical values of the "structure index" and "consistency index" were given to each sample as factor scores. Using these two numerical indices, tilth scores were computed as follows : Tilth score=(Structure index)-(Consistency index).^2 The scores thus computed were further standardized. Investigation of the standardized tilth scores of individual samples, as related to their laboratory data and field characteristics, revealed that this tilth scale was acceptable. Therefore, a trial was done to predict the tilth score from the field characters by means of HAYASHI's theory of quantification No.1. Of the field characters studied, a set of the following 5 variables, bulk density (BD), field humus rating (FOM), field texture (FTEXT), stickiness (STICK), and parent material (PM), was shown to be highly effective for prediction of the tilth score, resulting in a multiple correlation coefficient (R) as high as 0.90. Generally, volcanogenous soils from southern Hokkaido and Miyazaki had high tilth scores, whereas "junendo" from northern Hokkaido and residual soils from Okayama had moderate to low tilth scores.
社団法人日本土壌肥料学会の論文