Coastal Bermudagrass, Bahiagrass, and Native Range Simulation at Diverse Sites in Texas

Effective comparisons of natural grasslands and improved pasture require a robust model for plant growth, soil water balance, runoff, soil erosion, and climatic impacts. Our first objective was to develop plant parameters in the field that enabled the ALMANAC model to simulate growth of coastal bermudagrass [Cynodon dactylon (L.) Pers.]. Pensacola bahiagrass (Paspalum notatum Flugge var saurae Parodi), and some common native, warm-season grasses. Parameters included leaf area, light interception, biomass growth, and nitrogen concentration. The maximum leaf area index values of coastal bermudagrass and bahiagrass were near 2.2. Those for native grasses other than switchgrass (Panicum virgatum L.) were much less. Mean values for light extinction coefficient ranged from 0.7 to 2.1. Radiation use efficiency values for four of the five measured grass species were between 1.0 and 2.0 g MJ(-1). Grass [N] values showed similar patterns of seasonal change among species. Our second objective was to use these grass parameters to simulate biomass production of coastal bermudagrass, bahiagrass, and some native grasses on representative soils in several counties in a number of regions of Texas. Counties and soils that were simulated represented a diversity of sites in Texas where improved grasses and native grasses are grown. The ALMANAC model reasonably simulated biomass means and SDs for native grasses, coastal bermudagrass, and bahiagrass. The model is a realistic tool to simulate effects of soil type and weather on native and improved grass productivity on such diverse sites.