Modification of soil nitrogen and organic matter by Austrian winter peas
1931
Oveson, M.M.
The growth of Austrian winter peas as a green manure crop increased the nitrogen and the organic matter content of the soil. The good supply of calcium in soils used, as well as moisture control, contributed to the results. The total nitrogen of the soil remained unchanged when the crop was harvested and removed in all cases except where alfalfa tops were used as a fertilizer material. In this case there was a slight decrease in the nitrogen balance of the soil. The total nitrogen balance where peas were grown and harvested, including nitrogen in the crop, was higher than where peas were grown and turned under. The nitrogen content in the tops was highest in peas grown on the soil containing the higher nitrogen content. Changes in the organic carbon content of the soil tended to vary with those of the nitrogen content where the peas were either harvested or used as a green manure, crop. However, the turning under of the pea crop tended to narrow the nitrogen-carbon ratio of the soil. The addition of alfalfa tops to the soils decreased the amount of nitrogen fixed by the pea crop, but helped to maintain the nitrogen-carbon ratio more nearly like that of the initial soil. A saturated solution of copper sulfate added to the soil proved toxic to all soil organisms, except one type of fungus. This one persisted when in direct contact with crystals of copper sulfate. The fallow soils showed no increase in nitrogen content, although Azotobacter were present. The change in nitrogen content from that of the initial soil was practically the same in fallow and in copper sulfate treated soils.
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