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Alvez, Juan Pablo

Plant and Soil Science

2005

M.S.

Vermont's 35,000 hectares of pastureland form an extremely valuable resource that could be used to a much greater advantage by farmers to cut production costs. Continuous grazing yields 2.2 ton or less forage dry matter DM/ha/year. This pastureland produces at least 5 ton DM/ha/year of high quality (6-month average: 23% crude protein, 1.6 Mcal net energy lactation/kg DM, 70% total digestible nutrients) forage, if Voisin management-intensive grazing is used. Further increase in pasture forage yield appears to be limited by soil moisture and nutrient deficiencies. Irrigating when needed could increase forage yield 50% or more. Irrigation of grassland will depend not only on the economic outlook or on improvements in irrigation technology, but on benefits of irrigation combined with proper fertilizer or organic amendment and grazing management. Perhaps the genuine benefit from irrigated pastures may come from stability of production. In forage production, variability is constant. The purpose of this study was to investigate N fertilizer and organic soil amendment effects on forage yield and quality of irrigated and nonirrigated pasture under Voisin management-intensive grazing. The data included in this thesis were collected from May to October 2003 and from May through September 2004, the first 2 years of this 3-year study. Irrigation increased forage DM yield 0.9 tons/ha in 2003, but was not needed in 2004. Compost produced on the farm was the only treatment that consistently improved forage yield and quality. Compost appeared to have an equal or greater positive effect on forage yield as irrigation water did, compared to the control. Even without irrigation, compost increased forage yield 1.4 to 2.2 ton DM/ha. In terms of current hay price, this increased yield would be worth at least $280 to $440/ha! The soil amendments of fish, fish/seaweed, and crab shell had no positive effect on forage yield or quality.