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Nitrogen Distribution in Corn Silage Treated with Varying Levels of Ammonia¹

Michigan State University, East Lansing 48824and University of California, Davis 95616

Abstract

Whole corn plants (33% dry matter) were chopped and ensiled in laboratory silos of 9.1 kg each. Prior to ensiling, the material was mixed with 0, .51, 1.04, 1.44 and 1.99% ammonia (of dry matter) enriched with sufficient ^{1 5}N as (NH₄)₂S0₄ to increase the ^{1 5}N content of all treatments .1 atom percent (from .35 to .45% of the total nitrogen in silage). Samples from each treatment were immediately frozen as unfermented controls. After 126 days of fermentation, silos were opened and analyzed for nitrogen fraction and the ^{1 5}N content of the fractions. Silages ranged from 32 to 34% dry matter. The pH was directly related to ammonia additions. Lactic acid increased with added ammonia up to 1.04% (dry matter basis) and decreased with the higher percentages of ammonia. Recovery of nitrogen added to silage was 95%. Total nitrogen (of dry matter) for the respective treatments was 1.28, 1.66, 2.04, 2.44 and 2.92%. In freshly chopped corn plants, 40% of the added ammonia was recovered as ammonia in the water-insoluble nitrogen fraction, which accounted for all of the increase in insoluble nitrogen in unfermented silage. After fermentation, insoluble nitrogen of the respective treatments was .71, .98, 1.11, 1.26 and 1.26% of dry matter. The ^{1 5}N analyses showed that 28% of the added ammonia was recovered as insoluble nitrogen in fermented silage which accounted for only 59% of the total increase in insoluble nitrogen. The remainder of the increase in insoluble nitrogen (41%) could not be attributed to direct ammonia incorporation, and was presumably due to a decreased breakdown of plant protein caused by ammonia addition. Of the ammonia found in the insoluble nitrogen fraction, 80 to 90% remained as ammonia, and 10 to 20% was nonammonia nitrogen. Release of ^{1 5}N from the insoluble nitrogen fraction by papain digestion suggests some incorporation of ammonia by silage microorganisms.

¹ Published with the approval of the Director of the Agricultural Experiment Station as Journal Article No. 8689. Research was partically supported by Calor Agricultural, Inc., Okemos, MI 48864.

² National Institute of Animal Science, Department of Cattle and Sheep Experiments, Rolighedsvej 25, DK-1958 Copenhagen V, Denmark.

³ Grateful appreciation is expressed to Drs. Hugh Henderson and Fred Juengst for aid in preparation for silages; to Mr. John Bryant for aid in nitrogen fractionation procedures; and to Dr. F. E. Broadbent and Mr. T. Nakashima for ^{1 5} N analyses.

⁴ University of California, Davis 95616.