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Windbreaks have long been known to increase crop yields. However, published studies documenting effects of windbreaks on alfalfa yields are rare. To evaluate the effects of windbreaks on alfalfa production in Southwestern Utah, a study was conducted to compare yield differences in alfalfa protected by a windbreak to alfalfa in an adjacent unprotected area. Five subplots were harvested from each area. The first subplot was 100 feet from the windbreak and subsequent subplots were sampled every 50 feet out to 300 feet. This process was repeated in an adjacent area of the field not protected by a windbreak. First year results showed an average 10.7% increase in alfalfa yield behind the windbreak compared to the unprotected area. Second year data demonstrated a 10.9% increase in yield in the protected plots. Yield increases extended out to at least 250 feet from the windbreak. Windbreaks improve growing conditions of crops by allowing the temperature and humidity to increase during the day. Also, wind speed maybe reduced by 60% out to a distance of up to 10 times the height of the trees, thus reducing crop injury and evapotranspiration. In this study, measured wind reduction was 52% and 49% in year one and year two respectively between protected vs unprotected areas. source:abstract