Disintegration of crop residues as influenced by subtillage and plowing
1943
McCalla, T.M. | Duley, F.L.
Measurements of plant residue fragments in the soil of macroscopic size showed approximately 1 ton of plant residue fragments in the upper 4 inches of normal cultivated soil at Lincoln, Nebr. More than one-half of this amount of plant residue fragments was found in the size group of less than 3 mm and greater than 0.4 mm. Since these soils contained about 40 tons of organic matter per acre, these organic matter fragments constitute only 2.5% of the total organic material of the soil. When alfalfa tops and wheat straw were left at the surface of soil in pot cultures, maintained under controlled moisture and temperature conditions, the alfalfa tops decayed far more rapidly than did the straw. When straw was used as a mulch for a period of 6 months, the 2-ton application had lost two thirds; the 4-ton, one half; and the 8-ton, one third of the added material. Where straw was left on the surface for 18 months, there was little residue left except from the 8-ton application. When 2 tons of cornstalks were applied to the surface, about two thirds of the material was left after 6 months. Some cornstalk residue was left after a period of 18 months. From these data it appears that cornstalks are more resistant to decay than straw. The weight of organic particles remaining in corn land where oats and wheat straw from the two previous crops had been returned was 2,227 pounds where left on the surface and only 308 pounds per acre where the residues were plowed under.
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