A method of fertility evaluation for paddy soils

Open Access
Publisher Website
Google Scholar
Abstract
In the second paper of the series four constituents of soil fertility were evaluated by means of factor analysis. They are interpreted as representing, 1) skeletal organic matter status, 2) available phosphorus status, 3) inherent potentiality, and 4) available nitrogen status. In order to resynthesize such fragmented information for the overall soil fertility evaluation, the method of multiple regression analysis was adopted, using the four factor scores and the yield data for Malayan paddy soils as independent and dependent variables, respectively. A test of linear models with different combinations of independent variables revealed that the skeletal organic matter status has no relevance to the yield of paddy and that the phosphorus supply has by itself only an insignificant contribution to the yield. The best linear model with inherent potentiality and available nitrogen status explained about 40% of the variance of the yield. Introduction of quadratic terms to the linear model bettered the result. The best result with a coefficient of determination of 57% was obtained by a quadratic model with interaction terms among phosphorus status (F2), inherent potentiality (F3), and nitrogen status (F4). The final regression equation is where yield is in terms of tons of paddy/ha, and F2, F3, and F4 are the standardized factor scores. Assuming that the residuals were due to factors other than soil fertility, the predicted yield was computed by the above equation as the measure of soil fertility. Based on the predicted yield a grading of the Malayan paddy soils was established, which is the best approximation so far attained towards a soil fertility grading.

This publication has 2 references indexed in Scilit: