| Autor: |
Gast, R. G., Nelson, W. W., MacGregor, J. M. |
| Zdroj: |
Journal of Environmental Quality; July 1974, Vol. 3 Issue: 3 p209-213, 5p |
| Abstrakt: |
Results of long term continuous corn studies on tile drained Webster loam in southwest Minnesota show that annual N applications up to 70% greater than N removed in grain are required for maximum yields. The object of the reported study was to establish the relative role of N incorporation into the soil organic matter and/or losses through denitrification, downward leaching, or tile drainage in determining the fate of this fertilizer‐N added above that removed in corn grain. Nitrate and chloride accumulations and distributions were determined in a Webster loam and Waldorf silty clay loam profiles after long term fertilization for continuous corn. Concentrations in the profiles were determined at 0.3 m depth intervals and at increasing distances from tile lines. Maximum NO3−‐N accumulations accounted for less than half of the fertilizer‐N added but unrecovered in the corn grain. In contrast, Cl−accumulations in the soil profiles were approximately equal to that added, with little or no effect of distance from tile lines on either amounts present or on profile distribution: i.e. there was relatively little Cl−loss through tile drainage. Assuming Cl−and NO3−move with water at about the same rate, the results further suggest minimal loss of NO3−‐N in tile drainage. Since Cl−and NO3−concentration are small at depths greater than 3 m, downward leaching losses are apparently minimal leaving denitrification and/or incorporation into organic matter as the mechanisms largely responsible for disappearance of the unused fertilizer‐N. Denitrification is probably the main factor involved since similar experiments on well‐drained Minnesota soil showed little net incorporation of N into organic matter. |
| Databáze: |
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