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A Comparison of Two Nitrogen Credit Methods: Traditional vs. Difference
Author(s) -
Lory John A.,
Russelle Michael P.,
Peterson Todd A.
Publication year - 1995
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1995.00021962008700040007x
Subject(s) - fertilizer , crop rotation , rotation (mathematics) , significant difference , yield (engineering) , mathematics , legume , crop , nitrogen fertilizer , agronomy , agricultural engineering , nitrogen , statistics , engineering , chemistry , biology , materials science , geometry , organic chemistry , metallurgy
Cereals and other nonlegumes typically require less fertilizer N when grown following a legume. Nitrogen credits for a previous legume crop often are used to reduce fertilizer N recommendations in combination with other site‐specific information. Researchers continue to use two methods of determining N credits, the traditional and difference techniques, which often produce unequal estimates. Our objective was to clarify when each method provides accurate N credit estimates. The traditional method compares yield of a nonfertilized nonlegume crop grown in rotation to the fertilizer N response curve of the continuously cropped nonlegume. This approach assumes that fertilizer N compensates for all benefits of rotation. The difference method compares the economic N rate of the nonlegume crop grown in rotation with that of the continuously cropped nonlegume. We use examples from the literature to demonstrate that when non‐N rotation effects are present, N credit estimates from the two methods will differ. The difference method is more accurate and should be used unless it has been demonstrated that non‐N rotation effects are not present.