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Effects of Foliar Application of Urea on the Yield and Nutritive Value of Some Grass Hays¹

Cornell University, Ithaca, New York

Abstract

The effects of foliar application of urea on the yield, chemical composition, nutritive value and rate of uptake of urea by some grass hays were studied. The forages used for nutritional evaluation were second growth reed canarygrass and early- and late-cut timothy while those used for yield and rate of uptake studies were orchardgrass and bromegrass. Also included in the studies of nutritional value were timothy hays which had been fertilized by soil application of urea and early-cut timothy hay which was supplemented with urea at the time of feeding. The nutritive value of the hays was measured, (1) primarily by digestion trials with sheep and calves, (2) by an "in vivo" bag technique, and (3) by an in vitro rumen fermentation procedure.

In all cases, soil and foliar applications of urea increased the crude protein content of the hay and consequently increased the apparent digestibility of the protein but calcuated true digestibility was similar for all forages. Yields of forages were increased most by soil applications of nitrogen fertilizer made a month in advance of cutting. Foliar applications made 10 days prior to cutting had much less effect on yield, but did result in a greater increase in the nitrogen content of the forage.

When all the data were considered, there was no indication of any significant difference in the digestibility of any nutrient, except apparent digestibility of protein, among hays which were, (1) unfertilized or not supplemented with urea, (2) fertilized by foliar application of urea, (3) fertilized by soil application of urea, or (4) supplemented with urea at the time of feeding.

¹ This study was supported in part by a financial grant from the Grange League Federation, Ithaca, New York. Appreciation is expressed to Mr. Herbert Ley for help in caring for the animals and to Mrs. Alan Heegar and Mrs. James Roth for help with chemical analyses.

² Department of Animal Husbandry.

³ Department of Agronomy.

⁴ Present address: Agronomy Department, Iowa State University, Ames, Iowa.