Relation of sorghum roots to certain biological processes
1928
Wilson, B.D. | Wilson, J.K.
Soil cultures containing the ground roots of corn or sorghum were compared with respect to their ability to cause nitrate nitrogen to disappear in soil. The roots were employed in equal quantities by weight and by soluble-organic-matter content. Sorghum roots were found to cause a more rapid disappearance of supplied nitrates than did corn roots. An organism, designated as "guttation," which is known to assimilate both nitrate nitrogen and carbohydrates, increased in numbers, as revealed by plate counts, less rapidly in soil cultures containing the roots of corn than in those containing the roots of sorghum. It is assumed that other organisms which oxidize organic substances will react toward these residues as did "guttation." The evolution of carbon dioxide from cultural flasks was more rapid from soil containing sorghum roots than from soil containing corn roots. This was interpreted as indicating that the organic matter of sorghum roots is more easily oxidized than is that of corn roots. The results of the investigation suggest that the injurious after-effects of sorghum may be associated with the comparative ease with which its roots are oxidized in soil. This process, which is accompanied with an increase in the number of soil organisms and an increase in the assimilation of nitrate nitrogen, would tend to deplete the soil of available nitrogen. The extent to which these processes are operative in soil when young plants are in need of nitrogen may determine the amount of injury which the sorghum crop exerts on those crops which follow.
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