Publication Date


Advisor(s) - Committee Chair

David Stiles, Luther Hughes, James Worthington

Degree Program

Department of Agriculture

Degree Type

Master of Science


A comparison of the relationship of fermentation to chemical composition was made for forages which were wilted and ensiled at 35 to 45 percent dry matter. Trial I consisted of three forages ensiled in October, 1981: interseeded soybeans and grain sorghum. whole plant corn with added anhydrous ammonia, and whole plant corn with shelled corn added at a rate of 150 kg/t of fresh forage. Trial II consisted of two forages ensiled in 1982: interseeded soybeans and pearlmillet, and wheat. Temperatures of fermentation were collected, and chemical composition during the first 25 days of fermentation analyzed.

Production data were also collected in Trial I. The cash expenses and yields do not indicate a significant advantage to either crop in this study in terms of yields and return over variables. In terms of plant nutrient content there was an advantage for soybean/grain sorgum silage in protein yield of 854 kilograms per hectare as compared to whole plant corn silage.

Temperature data collected on the forages in Trial I covered 57 days from October 8 through December 4. The maximum recorded temperatures for soybean/grain sorghum, corn silage with added anhydrous ammonia and the corn silage control were 37, 37, and 24 degrees Celcius. achieved by day 11, 4, and 11 of ensilement respectively. The rapid temperature increase for material treated with anhydrous ammonia confirmed previous reports. Small fluctuations occurred in silage temperatures but these were not correlated to ambient temperature. Temperatures declined very slowly in all forages, with the lowest reading for silages by day 57 recorded at 19 C for soybean/grain sorghum silage. Ambient temperature was not reached in the ensiled mass during the 57 day period in which data were recorded.

The soybean/pearlmillet ensiled in Trial II quickly reached a high peak temperature of 44 C at 4 days of ensilement, gradually decreasing over a 57 day period to 35 degrees on October 19. The silage did not reach a desireable pH. Initial forage pH was high, 7.4, dropped rapidly to 5.1 on day 5, but did not decline further in succeeding samples. Samples were low in lactic acid and high in acetic acid content.

Initial buffering capacities for both of the soybean mixture forages were considerably higher than the other forage materials. Buffering capacities at day 0 for whole plant corn, whole plant corn treated with anhydrous ammonia, soybean/grain sorghum, soybean/pearlmillet and wheat forages IA ere 19.4, 20.0, 35.3, 35.3. 38.6 and 22.2 milliequivalents/100 g of dry matter respectively. Increases in buffering capacities during fermentation were smaller for soybean/grain sorgum and soybean/pearlmillet . Buffering capacity increases for the forages were 133.5, 290.5, 69.1, 64.2 and 87.4%.

High ammonia nitrogen levels were found in samples of whole plant corn silage with added anhydrous ammonia obtained on days 10 and 20 of ensilement. These contained .282 and .351% ammonia-nitrogen and tested 18.0 and 20.1% crude protein. The increase in buffering capacity which occurrs with addition of anhydrous ammonia was confirmed by the higher acetic acid and pH levels, with corresponding decreases in lactic acid from samples taken days 10 and 25. Crude protein levels were 17.9 and 17.4 percent while the other samples contained only 10-12% crude protein. It appeared that application of anhydrous ammonia was not uniform throughout the silage. Where high concentrations of ammonia occurred fermentation was prolonged as indicated by excessive amounts of lactic and acetic acids and a high pH in these samples. Values for L(+) lactic acid ranged from .2 to .523 in fresh forage to 5.66% of dry matter on day 25. Concentrations of ammonia-nitrogen in the other silages ranged from .061 to .131%.

The low buffering capacity of whole plant corn silage was reflected by normal concentrations of lactate and acetate but a more acidic pH when compared to the other forages. Lactic and acetic acid production for soybean/grain sorghum silage was similar to that of the corn silage control. Corn silage pH was lower, however, throughout fermentation and reached a stable pH by day 5 of fermentation. The wheat silage went through a gradual fermentation with low lactic acid production, and an intermediary ending pH of 4.0.

Fermentation was essentially complete by day 10 in all silages as indicated by pH, buffering capacity, and lactic acid production: however, there was a tendency for buffering capacity and acetic acid content to increase in all of the ensiled materials throughout the 25 day collection period.


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