A comparison of two nitrogen credit methods: traditional vs. difference

• Published in: Agronomy journal Vol. 87; no. 4
• Main Authors: Lory, J.A. (USDA-ARS, Univ. of Nebraska-Lincoln, Lincoln, NE.), Russelle, M.P, Peterson, T.A
• Format: Journal Article
• Language: English
• Published: 01.07.1995
• Subjects: ABONOS; ABONOS NITROGENADOS; CULTIVO CONTINUO; CULTIVOS; CULTURE CONTINUE; DOSE D'APPLICATION; DOSIS DE APLICACION; ENGRAIS; ENGRAIS AZOTE; EXIGENCE DES PLANTES; GLYCINE MAX; GRAIN; GRANOS; LEGUMINEUSE; LEGUMINOSAS; NECESIDADES DE LAS PLANTAS; PLANTAS DE COBERTURA; PLANTE DE COUVERTURE; PLANTE DE CULTURE; RENDEMENT DES CULTURES; RENDIMIENTO DE CULTIVOS; ROTACION DE CULTIVOS; ROTATION CULTURALE; TRIFOLIUM INCARNATUM; ZEA MAYS
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj1995.00021962008700040007x

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