Date of Award

2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Plant and Soil Science

First Advisor

Sidney C. Bosworth

Second Advisor

Sabrina L. Greenwood

Abstract

Legume-grass mixtures are commonly grown on livestock farms in northern New England that feed high forage diets. Such farms typically ferment stored feed into silage that can be fed throughout the year. Many legumes and grass species are available for use in temperate climates and information on the yield, forage quality, and fermentation characteristics of various legume-grass combinations would help farmers make informed decisions about species selection and optimum management for their forage programs.

One obstacle to evaluating numerous forage treatments in agronomic research is the high variability in silage dry matter content. We hypothesized that a method of artificial wilting could reduce dry matter variability and improve the feasibility of fermented forage experiments without altering fermented forage quality parameters. In two experiments, we evaluated the use of forced air drying at 55°C for this purpose and found that this method reduced dry matter variability while maintaining fermented forage quality similar to field wilting.

A small plot study was conducted on a well-drained loamy sand soil in South Burlington, VT to evaluate binary legume-grass mixtures including combinations of alfalfa, red clover, or birdsfoot trefoil with timothy, tall fescue, meadow fescue, or perennial ryegrass managed at two harvest intensities. Two years of results suggest that alfalfa-grass mixtures had the highest yield potential, and were intermediate in quality but had the highest protein degradation during fermentation. Mixtures containing birdsfoot trefoil were highest in quality and fermented well, but they were limited in yield potential in this study. Red clover-grass mixtures were consistently lower in fiber digestibility, but they had the least protein degradation during ensiling. Of the grass treatments, legume-tall fescue mixtures often showed greater protein degradation than mixtures with other grasses. Legume-timothy mixtures were consistently the highest yielding, but they tended to be slightly lower in quality. Conversely, legume-perennial ryegrass mixtures yielded poorly, but they were often high in quality. Modeling potential milk production per unit land suggests that the yield differences observed in this study generally outweighed quality differences between mixtures. Intensive cutting management was shown to be an effective way to maximize the quality of legume-grass mixtures and did not negatively impact yields. The greatest benefit of intensive harvest was found in legume-meadow fescue mixtures while the least benefit was observed in legume-timothy mixtures.

Language

en

Number of Pages

178 p.

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