The Effect of Long-Term Stocking Intensities and Fertility Regimen on Stand Purity in Bermudagrass Pastures.

Stocking rates and management can influence the long term persistence and stand maintenance of bermudagrass pastures. The objectives of this study were to assess genetic make-up of bermudagrass [Cynodon dactylon (L) Pers.] and species composition diversity in pastures stocked at different, controlled intensities for nearly 40 years. Pastures of common (COM) and Coastal (COS) bermudagrass were initially stocked in 1969, and continue to be stocked on average at about 2, 3.5, and 5 cow-calf (PAIR) ha^-1 (680 kg PAIR^-1) for COM, and 2.5, 4.5, and 7.5 PAIR ha^-1 for COS. From 1985 through 2008, fertility regimens of N + ryegrass vs no N + clover was superimposed on each stocking intensity x bermudagrass pasture. Forage mass ranged from about 500-1000 kg ha^-1 for high, 1250-2000 kg ha^-1 for moderate, and >2500 kg ha^-1 for low stocked pastures. All pastures were visually scored by two observers on 10-31-2005, mapped for percent composition of species diversity according to vegetative growth type and color and extent of seed head formation. Plant samples were taken from each species diversity site and were genetically analyzed with resultant species data plotted on a dendrogram and assessed with a coefficient of similarity matrix. Species diversity was detected in both COM and COS pastures with greatest impact from high stocked pastures. High stocked COS pastures were highly variable in species diversity with about 75% loss of COS and resultant invasion by other bermudagrass ecotypes. Low stocked COS pastures also had species invasion but had more than 80% COS remaining. The non N regimen COM pastures at both high and medium stocking intensities also had significant invasion of bahiagrass (Paspalum notatum Flugge).