Productivity of Kentucky Bluegrass Pasture Grazed at Three Heights and Two Intensities

Abstract

Sward height before grazing and amount of forage harvested affect production, composition, and utilization of rotationally stocked pasture. In this 3‐yr field study, yearling steers (Bos taurus L.) grazed 400‐m2 plots of Kentucky bluegrass (Poa pratensis L.)–white clover (Trifolium repens L.) pastures every time sward height reached either 11.8 cm (short), 13.7 cm (medium), or 15.3 cm (tall). Plots were grazed with enough steers to remove either 50 or 60% (grazing intensity) of the herbage mass in 4 h. The experimental design was a 3 × 2 (height treatment × grazing intensity) factorial with four replications. Sward heights before and after grazing periods were measured. Herbage mass, apparent growth rate, herbage removed, rejected area, and percent utilization were calculated. Average herbage mass before grazing ranged from 1855 to 2350 kg dry matter (DM) ha−1. Average herbage mass after grazing varied from 855 to 1060 kg DM ha−1. Apparent herbage growth rate (54 kg DM ha−1 d−1) and herbage removed (7520 kg ha−1) were highest on the short height treatment with low grazing intensity (50% removal). Assuming a sigmoidal growth curve, maximum apparent growth rate occurred at 10.5‐cm sward height. More than twice as much herbage was removed in the wettest year compared with the driest. In the dry year, height and intensity of grazing had little effect on herbage production. Thus, the benefits farmers can expect from more intensive grazing management will be more evident in a year of good growth.

The Effects of Increasing Grazing Height on Establishment of Pasture Weeds in Management-Intensive Rotationally Grazed Pastures

“…In the summer (second to fourth simulated grazing events), no differences in forage yield were seen among treatments at either site. These data are consistent with results from Inyang et al (2010) and Bryan et al (2000) who demonstrated pasture grasses grazed or clipped to shorter heights had 21 and 18% higher yield throughout the season when managed for taller residual heights. While the highest overall yield would result from grazing to 5 cm, typical MiRG grazing heights recommended are 10 cm .…”

Effects of Native Grass Restoration Management on Above- and Belowground Pasture Production and Forage Quality

“…Many studies of temperate grazing systems reported significant year × treatment effects on pasture parameters, including canopy structure, production, NDF and crude protein (Popp et al, 1997b;Paine et al, 1999;Bryan et al, 2000;Brink et al, 2007). Some of the main conclusions from an extensive study of Wisconsin grazing farms were that 1) forage production and quality were very responsive to fluctuations in weather conditions and these fluctuations interacted with management, resulting in significant differences between years, and 2) while forage quality under rotational vs. continuous grazing was generally higher, it was less predictable (Paine et al, 1999).…”

Fructan accumulation and transcription of candidate genes during cold acclimation in three varieties of Poa pratensis

“…The contrasting modes of reproduction facilitate the high polyploidy levels and unusual chromosome numbers (x = 7, 2n = 28-147) observed in P. pratensis (Speckmann and van Dijk, 1972). P. pratensis shows persistence and resilience to cold and seasonal drought (Kanneganti and Kaffka, 1995) and good performance under frequent and close defoliation (Bryan et al, 2000;Durr et al, 2005). Contemporary fructan research is mainly focused on a few plant species including barley, wheat and ryegrass, and despite being a type species for the grass family (Poaceae), little is known about the fructan metabolism in P. pratensis.…”