Alfalfa Persistence and Regrowth Potential under Continuous Grazing
Alfalfa (Medicago saliva L.) generally does not persist well under continuous grazing. Experiments were conducted under continuous grazing to compare the persistence and regrowth potential of an alfalfa germplasm (Georgia—Grazed Collection, GA-GC), selected for continuous grazing, with two hay-type (Apollo and Florida 77) and two grazing-type (Travois and Spredor II) cultivars. The germplasm and cultivars were subjected to continuous, heavy grazing by beef cattle for 18 weeks in each of 3 yr to a height of 3 to 5 cm. Wire exclosures rotated at 28-d intervals on all plots were used to estimate the regrowth potential of each entry during the grazing period. Plant and stem counts were taken before and after grazing each year as estimates of stand persistence. Cultivars differed significantly for stand persistence after 3 yr of continuous grazing with 6 to 9 plants m−2 remaining for the hay-type cultivars and 40 to 48 plants m−2 remaining for grazing-type cultivars. The GA-GC maintained plant densities of 64 plants m−2 while producing the highest forage regrowth compared with all cultivars. Total nonstructural carbohydrates (TNC) in roots at the end of 1986 and 1987 grazing seasons ranged from 256 g kg−1 for Florida 77 to 429 g kg−1 for Travois, suggesting that grazing tolerance may be related to the TNC concentration in roots of alfalfa that had been heavily and continuously grazed. This study indicates that selection for plant persistence under continuous grazing from a broad-based population improved the grazing tolerance of the resulting germplasm (GA-GC) while maintaining the potential for good forage yields.
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