Although the benefits of shelterbelts are generally well appreciated by vegetable crops growers, too many vegetable fields in Saskatchewan are still out on the bald prairie. Cost is the most common reason growers cite for not establishing a shelterbelt system – particularly the cost of devoting substantial amounts of valuable land to unproductive trees. However, in a recent paper, Hodges and associates out of Nebraska clearly showed that shelterbelts could more than paid their way on a typical vegetable operation. Using beans as a “typical” crop, they looked at the rate of growth, yields and quality of a crop protected by a shelterbelt systems versus one grown out in the open. The shelterbelt was a 30′ tall mix of mature ash and conifers planted perpendicular to the prevailing wind direction. The test plots were planted 30 to 60′ from the shelterbelt … but the shelterbelt effects were observed 200′ or more from the trees. As expected, proximity to the shelterbelt reduced the average wind speed to less than 40% of in the open. This completely protected the bean crop from damage by storm winds (winds stronger than 4 m/s-1). Air temperatures adjacent to the shelterbelt were warmer during the day but cooler at night than in the open. By contrast, soil temperatures in the sheltered area averaged 4C warmer than in the open – this resulted in better emergence and early growth. The relative humidity was also higher in the sheltered area than in the open – this would be advantageous in drought-prone areas, but could exacerbate problems with disease in more humid regions. Plants in the sheltered area were earlier, heavier and taller than in the open – culminating in a 50% increase in marketable yields. Factoring in price premiums paid for early product, the gross value of the crop grown with the shelter was approximately 60% more than the crop in the open. The shelterbelt system used in this study occupied about 8% of the area of the field – leaving an overall increase in gross crop value of 52% for the shelterbelt protected crop. Even greater benefits would be expected with more sensitive or higher value crops in more extreme locations.
Source : Hodges, Suratman, Brandle and Hubbard (2004). HortScience 39:996-1004.