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Effect of Winter and Summer Windbreaks on Soil Water Gain and Spring Wheat Yield¹

ABSTRACT

Field windbreaks have been planted primarily for soil erosion control, but they also affect the growth and yield of nearby crops by modifying the crop's microclimate (summer effects) or by trapping snow for soil water gain (winter effects). The purpose of this study was to partition and determine the summer and winter effects of noncompetitive windbreaks using ‘Waldron’ spring wheat (Triticum aestivum L.) as a test crop.

We erected 2.3-m high by 32-m long slat-fence barriers in an eastwest direction during winter (W+S-), summer (W-S+), both winter and summer (W+S+), or not at all (W-S-). The top and bottom halves of each barrier were 42 and 21% dense, respectively. Three years of the 6-year study were classified as wet years and three were dry years based on total available water (available soil water at seeding plus seeding-to-harvest precipitation) for the crop. Snow depth, soil water gain over winter, crop water use, wheat yield, and plant height were measured at 2H (H = barrier height) units to 6H north and 10H south of the barriers. Snow trapped by the barriers ranged from 1.2 m deep 5H south of the barrier in 1975 to no measurable snow in 1973. Soil-water gain from snowmelt was greatest 5H south of the barrier and averaged 1.9 cm more over the test area for W+S+ and W+S- as compared with W-S+ and W-S- treatments. Average wheat yields for the 3 wet years were the same for all treatments, but for the 3 dry years the W+S+ and W+S- treatments increased yields by 3.2 and 2.1 quintal/ha, respectively, as compared with the W-S- treatment. The summer-only barrier (W-S+) had no measurable effect on wheat yields. Wheat yields during the dry years were maximum at 5H south of the barrier, which coincided with maximum snow depths and overwinter soil water gains.

Results of this study showed that grain yield increases obtained adjacent to noncompetitive barriers were mostly due to increased overwinter soil water accretion resulting from snow catch (winter effects) and not microclimate modification (summer effects).

¹ Contribution from Plant and Entomological Sciences and Soil, Water, and Air Sciences, Science & Education Administration, Federal Research, USDA.

² Plant Physiologist and Soil Scientist, respectively, USDA-SEA-FR, Northern Great Plains Research Center, P.O. Box 459, Mandan, ND, 58554 and Fort Collins, CO.

Received for publication April 24, 1978. Accepted for publication August 15, 1978.