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Ecology and management of Sandhills rangeland: Fall grazing of uplands and ecosystem dynamics of subirrigated meadows

Eric M Mousel, University of Nebraska - Lincoln

Abstract

An experiment was conducted to determine the effects of 5 consecutive years of summer grazing date and fall stocking rate on vegetation and dietary crude protein content of cows grazing rangeland in the Nebraska Sandhills. Paddocks were grazed at a summer stocking rate of 0.5 AUM ha-1 in June or July, or deferred from summer grazing. The paddocks were then grazed in the fall at stocking rates of 0.0 AUM ha-1, 1.0 AUM ha-l, 2.0 AUM ha-1, or 3 AUM ha-l. Summer grazing date does not appear to consistently affect herbage production, fall standing crop, herbage disappearance, or fall diet quality. Fall stocking rate reduced cool-season graminoid production although this effect appears to require 3 to 5 consecutive years of fall grazing. Disappearance increased with increasing fall stocking rate by year 5 of the experiment. Crude protein content of fall diets declines with increasing fall grazing pressure but does not appear to be dictated by summer grazing date. Animal intake of fall herbage appeared to be restricted to some degree by low quality forage. ^ In the second experiment, botanical composition, root mass-density, and carbon/nitrogen budgets were compared between cool-season and warm-season subirrigated meadows in the Sandhills. Vegetation yields and composition were sampled at each of 5 cool-season and 5 warm-season meadows. The A and C horizons of one-half of the soil cores (n=150) extracted from each meadow were analyzed for total C and N content. Stable C isotope analysis was conducted on soil sub-samples from the A and C horizon to determine the origin of soil C. The remaining soil cores were segmented into 10-cm increments. Root material was extracted from each 10-cm increment to estimate root mass-density distribution. Cool-season meadows had 12% greater (P<0.1) herbage yields than warm-season meadows. Root-mass density was 30% greater (P<0.1) in warm-season meadows than in cool-season meadows. Total C and N content was 43% greater (P<0.1) in the A horizon of cool-season meadows, but was 40% greater (P<0.1) in the C horizon of warm-season meadows. Although cool-season meadows had more soil C, much of the C in cool-season meadows appeared to be recalcitrant C from historic warm-season vegetation. ^

Subject Area

Biology, Ecology|Agriculture, Range Management

Recommended Citation

Mousel, Eric M, "Ecology and management of Sandhills rangeland: Fall grazing of uplands and ecosystem dynamics of subirrigated meadows" (2005). ETD collection for University of Nebraska - Lincoln. AAI3190667.
http://digitalcommons.unl.edu/dissertations/AAI3190667

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