Soils of healthy pastures contain a pore system that provides soil structure and allows for the exchange of gases and water. These characteristics are key to supporting soil life and, in turn, plant growth. Animal traffic can compact the soil and limit water infiltration. Researchers aimed to compare the effects of continuous and rotational grazing on the rates of water infiltration of soil.
The grazing trials were conducted in News Brunswick, New Jersey from August 1, 2014 to November 22, 2016. Four fields of similar size (3.7 to 4.0 acres) were established in 2013 and contained tall fescue, Kentucky bluegrass, and orchardgrass. The researchers divided the two fields designated for rotational grazing into four smaller pastures. All the horses had access to shelter, water, and a hay feeder, but these resources were set up in a stress lot (dry lot) for rotationally-grazed horses. Twelve mature (14 ± 2 yrs.), Standardbred mares were assigned to either rotational or continuous grazing with a stocking rate of 1.3 acres per horse. For rotational grazing, horses were grazed when forage heights were over 6 inches and moved to the next pasture when forage was eaten down to 3 inches. Prior to rest, the pastures were dragged and mowed. Pastures under continuous grazing were dragged and mowed twice a season. Water infiltration measurements of the soil were taken multiple times during the study.
Overall, rotationally-grazed fields had taller forage, greater aboveground biomass, and more cover than continuously-grazed fields. Rates of water infiltration through large soil pores (macropores) tended to be greater for fields under rotational compared to continuous grazing during dry periods. During wet periods, infiltration of smaller soil pores was comparable or lower in rotationally-grazed fields than continuously-grazed fields. Growth of pasture grass roots likely increased during wet periods in rotationally-grazed fields and caused a decline in infiltration.
The results of this study suggest that rotational grazing better supports macropore networks in soil and greater water infiltration rates compared to continuous grazing. Macropores can increase soil water content, decrease soil temperature, and promote plant recovery from animal traffic. These functions are key to healthy soil and productive pastures. However, many factors can influence soil properties within pasture systems such as soil type, weather, or frequency of animal traffic. Therefore, further research is needed to investigate the role and interplay of additional factors.
For more information on this research, read the abstract published in Soil and Tillage Research.
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