Evaluation of fertilizer yield response models
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Date
2006
Authors
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Publisher
CCSHAU
Abstract
Judicious use of fertilizer form one of the most important
means of stepping up agricultural production. For many cropping
situation, especially in developing countries some models do not fit the
responses of certain crops to fertilizer.
Performance of quadratic, square root, inverse quadratic and
modified quadratic response functions have been examined on major
food crops grown in Haryana. Based on R2 criterion, inverse quadratic
model gives better fit to Pearlmillet crop, where as quadratic function
describes the yield-fertilizer relationship in Rice crop. It has been
observed that a modified quadratic function is better suited when data
shows initial sharp rise at lower levels of fertilizer application.
Fertilizer yield data of wheat is often available of many
varieties and/or for a numbers of years. Dummy variables have used for
combining data for different varieties and over years and for testing
structural stability of quadratic response function for three varieties;
HD2329,WH542 and WH533 of wheat crop grown in Haryana. Models
for individuals varieties have also been deduced from the pooled
regression.
A comparative study of quadratic, square root, inverse
bilinear, and cobb-douglas response models used for the two nutrients
experiment. The canonical form is also performed for quadratic and
square root models. The characteristic roots of real symmetric matrix of
estimates are measured for the coefficients of quadratic and interaction
terms. Based on characteristic roots and R2, square root model give
better fit for wheat crop.
Description
Keywords
Quadratic, Square root, Inverse quadratic, Modified quadratic, Cobb-Douglas, Response surface, Dummy variable, Least square estimate, Economic optimum