Soybean Stover Nitrogen Affected by Dinitrogen Fixation and Cultivar
- V. Ravuri and
- D.J. Hume
Grain legumes often are credited with leaving residual N for crops that follow in the rotation. This study was conducted to determine if increasing N2 fixation in soybean [Glycine max (L.) Merr.] would result in higher amounts of stover N at harvest. Eleven early-maturing cultivars (Maturity group 00 and 0) in 1988 and 16 in 1989 were grown with five inoculant strain treatments and alone as uninoculated controls. There were slight cultivar-by-inoculant interactions but main effects were much larger. The order of N2 fixation with inoculant treatments, measured by the difference method, was 532C or three-strain mixture > USDA 110 > CB 1809 > HH303. Dinitrogen fixation ranged from 60 to 125 kg ha−1 in 1988 and from 31 to 84 in 1989. Higher N2 fixation caused related significant (P ≤ 0.05) increases in stover dry matter and stover N yields in both years, despite concomitant increases in the apparent harvest index (AHI) and apparent NHI. Stover N concentration was not affected by increased N2 fixation in either year. In 1988, cultivars differed only slightly in stover N content. In 1989, amounts of stover N in different cultivars depended on how completely N was translocated to seed. Over the 2 yr, amounts of N in harvestable stover of the early-maturing cultivars ranged from 9 to 24 kg ha−1, averaged across inoculant treatments. Although stover N increased with N2 fixation in both years, the amount of stover N available for return to the soil was quite low.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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