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Retention of Organic Matter and Nitrogen by the Silt and Clay Fractions and by the Whole Soil as Affected by Lime and Organic Residues¹

ABSTRACT

The experiment was conducted in glazed 3-gallon pots in the greenhouse, using Kirvin clay soil, limed and not limed, treated with red clover, wheat straw, and Juniper wood residues. An application of 59.5 mg. of nitrogen per 100 g. of soil was made at the beginning, and again after 15 months. Soil samples were taken from each treatment before planting the first crop, after 15 months, and again after 48 months. Ten crops were grown during the 4-year period.

There was a marked loss of nitrogen from all soils during the experiment, but loss from limed soil was greater than from unlimed soil. The highly carbonaceous materials retarded nitrogen loss. There was a tendency for nitrogen to accumulate in the silt fraction, especially in unlimed soil.

The amount of organic matter retained by the soil was not affected by lime content and there was no difference in organic matter and total nitrogen contents of the wheat straw and red clover treatments after 48 months, although the organic matter/nitrogen ratio was 21.0 for the red clover treatment and 34.4 for the wheat straw treatment when the experiment started.

Only the Juniper wood had a significant effect on aggregate stability after 48 months.

¹ Paper No. 8, Karl Hoblitzelle Agricultural Laboratory of Texas Research Foundation, Renner, Texas. Presented before Div. I, Soil Science Society of America, Cincinnati, Ohio, Nov. 13, 1956.

² Chairman, Soil Science Department, and Senior Soil Scientist.

Received for publication November 16, 1956. Accepted for publication October 18, 1957.