Role of N 2 fixation in the soybean N credit in maize production

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Many studies have shown that maize (Zea mays L.) requires less fertilizer N for optimum yield when grown in rotation with soybean [Glycine max (L.) Merr] than when grown in monoculture, which is referred to as the 'soybean N credit' in the maize growing areas of the United States. Because the specific source of this soybean N credit is unclear, our objective was to determine the role of nodules and N 2 fixation as a contributing source of the soybean N credit. Our research approach was designed to separate the effect of symbiotic N 2 fixation from other rotational effects, as the treatments included: maize grown after nodulated (N 2 fixing) soybean and maize grown after non-nodulated (non N 2 fixing) soybean. A separate experiment examined maize grown after maize. For each previous crop, maize was grown the following year with varying rates of fertilizer applied N. In both years, the yield differences between nodulated and non-nodulated soybean as the previous crop were much smaller than the apparent yield decrease associated with continuous maize. Although small in magnitude, maize following non-nodulated soybean accumulated less total N, was paler in leaf color, and yielded less than maize following nodulated soybean in the more favorable year of 1999, while most of these differences were not observed in 2000. These findings indicate that soybean nodules and N 2 fixation, while having a certain role, are not the major determinants of the soybean N credit.

Original languageEnglish (US)
Pages (from-to)383-394
Number of pages12
JournalPlant and Soil
Issue number1-2
StatePublished - May 1 2004


  • N use
  • Soybean N credit
  • maize production
  • yield components

ASJC Scopus subject areas

  • Soil Science
  • Plant Science

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