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This article in AJ

  1. Vol. 62 No. 3, p. 381-384
     
    Received: Oct 16, 1969
    Published: May, 1970


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doi:10.2134/agronj1970.00021962006200030022x

Prediction of the Nitrogen Requirements of Field Crops Part I. Theoretical Models of Nitrogen Release1

  1. J. O. Reuss and
  2. J. M. Geist2

Abstract

Abstract

Theoretical models for the prediction of the total supply of mineral nitrogen available for crop production have been developed. These models are based on the assumption that the supply of available N is determined by fertilizer N, native soil mineral N, and N released from organic matter. Model No. [1] is of the form Y = b0 + blXl + b11X12 + b2X2 + b22X22 + b12X1X2, where: Y = yield or other parameter dependent on N supply, Xl = fertilizer N plus available soil mineral N, X2 = any index of organic N release, and bl, b2, b . . . are coefficients determined by regression techniques. Model No. [2] is of the form Y = B0 + B1(X1 + aX2) + B2(X1 + aX2)2, where: a represents a release coefficient appropriate to a given X2; B0, B1, B2 are regression coefficients; and Y, X1, and X2 are the same as in Model [I]. The release coefficient a can be evaluated by ratios of coefficients from Model [1], ratios of slopes from Model [1], or by a reiterative procedure. More sophisticated models based on Model [2], but assuming nonlinear release of organic N, have also been developed along with methods for evaluating the constants involved.

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