Soil water regimes of rotationally grazed perennial and annual forages
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Authors: D. A. Twerdoff, D. S. Chanasyk, M. A. Naeth, V. S. Baron, and E. Mapfumo
Date: 1999
Journal: Canadian Journal of Soil Science
Volume: 79
Number: 4
Pages: 627-637
Summary of Methods: The soil water regime of perennial and annual forages under three grazing intensities (heavy, medium and light) and four plant communities (meadow brome, barely/triticale, triticale and smooth brome) was characterized at the Lacombe Research Station (52° 28’ N; 113° 45’ W) in Alberta. Volumetric soil water content was measured biweekly from April to October during two summers. Aboveground net productivity, surface soil water, accumulated soil water, evapotranspiration, water-use efficiency, wilting point and field capacity were also measured once in April and again in October of both years.
Article Summary / Main Points: During the growing season both surface soil water and accumulated soil water generally fluctuated between field capacity and wilting point for all grazing treatments and forages. Heavy grazing generally resulted in the highest surface soil water. Over the majority of both summers, especially late summer, accumulated soil water was lower under perennial than annual forages. Soil water was the highest in the spring and declined throughout the summer. Evaporation rates were different among forages, but similar between grazing intensities. Pastures seeded with perennial species had greater evapotranspiration rates, water use efficiency and plant production than pastures seeded with annual species. Annual forages had the greatest accumulated soil water. In the spring, perennial forages had high evaporation rates, whereas evaporation rates from annuals was higher from late June to early August. Increasing grazing intensity tended to decrease water use efficiency, and sites with heavy grazing had greater soil surface water and accumulated soil water, possibly due to decreased interception by vegetative cover. Plant species and grazing intensity affect different aspects of soil water dynamics and influence the amount of water available for plant growth in pastures.
Vegetation Types: All Vegetation Types
MLRA Ecoregions: Not Applicable
Agrovoc Control Words: Rangelands Grazing Soil water
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: evapotranspiration, forages, grazing intensity, water-use efficiency
Annotation: This was a replicated study over two years and its findings can generally be applied to most grazing situations. It should be noted that the only loamy soils, cool season grasses and mid-summer grazing were examined and the effects of grazing may be different for other soil textures, or warm season forages, or if grazing occurred in a different season. These results are most applicable to sites of similar landscapes, season of use, livestock type and climatic conditions.
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