University of Vermont

Soil Nutrient and Manure Research at The University of Vermont Direct Incorporation of Liquid Dairy Manure for Fall and Spring Application of Corn

Bill Jokela, Sid Bosworth and Jeff

Duration: 1995 - 1997

Manure is commonly applied to corn land either in the fall after harvest or in the spring before planting. Spring application is generally recommended for greater efficiency of N use and less potential for leaching and runoff losses. However, for practical reasons (limited storage, time constraints in spring, field conditions, etc.) many farmers need to apply manure in the fall. If fall-applied manure is left on the surface until the following spring much of the ammonium-N in the manure is likely to be lost to volatilization and is also susceptible to runoff losses during the fall and early spring.

The objective was to determine the effect of manure application method and timing on corn silage yield, efficiency of manure N use, and nitrate leaching potential. This study was established on a field on the Steve and Richard Dodd farm in Sheldon. All manure treatments were applied with a commercial 1500 gallon slurry tank spreader with tandem axles. Treatments include the following: 1) fall manure, surface-applied; 2) fall manure, incorporated with shallow sweep injectors; 3) fall manure, incorporated with s-tine/field cultivator; 4) spring manure, incorporated with s-tine/field cultivator; and 5) fertilizer nitrogen, applied as ammonium nitrate at sidedress time at rates of 0, 40, 80, or 120 lb N/acre (in addition to 36 lb/acre in starter). The manure treatments were applied at a rate of approximately 8000 gal/acre.

In 1996, yield from fall, surface-applied manure was the lowest of the manure treatments and about the same as the control treatment that received no manure or fertilizer (except starter). This reflects the loss of ammonium-N from manure that is left on the surface. Incorporation of manure with either sweep injection or s-tine cultivators increased yields significantly by an average of over two tons per acre compared to leaving it on the surface. The highest yields were obtained from the N fertilizer treatments, averaging about two tons per acre higher than the incorporated manure treatments and more than five tons per acre higher than the control. The lower yields from manure may have been related to timing. Unusually high amounts of precipitation in the spring and early summer provided conditions conducive to losses of manure N via leaching and denitrification. The sidedressed N was applied on July 2 - after much of the wet period had passed and just before the largest N demand by the growing corn crop.

For a more detailed report go to Lower Missiquoi Factsheet 3.

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Last modified May 26 2004 12:55 PM

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