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Title: HERBAGE MASS, NUTRITIVE QUALITY, AND CANOPY SPECTRAL REFLECTANCE OF BERMUDAGRASS PASTURES.

Author
item Starks, Patrick
item Zhao, Duli
item Phillips, William
item Coleman, Samuel

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2006
Publication Date: 4/1/2006
Citation: Starks, P.J., Zhao, D., Phillips, W.A., Coleman, S.W. 2006. Herbage mass, nutritive quality, and canopy spectral reflectance of bermudagrass pastures. Grass and Forage Science. 61:101-111.

Interpretive Summary: Warm-season bermudagrass is a common forage crop used for pasture and hay in the Southern Great Plains of the USA. Remote sensing may provide a rapid assessment of forage biomass and quality during the grazing season which can help farmers and ranchers better manage livestock, grazing lands, and feed resources. The objective of this study was to determine seasonal variation of biomass, neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), and canopy spectral reflectance of bermudagrass pastures as a function of plant genotype. Three mono-cultured bermudagrass pastures of Midland, Ozarka and 74x12-12 were established in 1991 with the same field management and stocking rate. Forage quality and canopy reflectance data were collected throughout the 2002 and 2003 grazing seasons. Results indicated that year, genotype, and sampling date greatly affected pasture biomass production, NDF, ADF, CP concentrations, and canopy reflectance. Ozarka and Midland pastures were comparable in biomass, ADF, and CP concentration in 2002. In the drier and hotter 2003 growing season, however, Ozarka had higher biomass and lower ADF and CP concentrations compare to Midland. Genotype 74x12-12 had a slightly lower biomass, but higher ADF and CP than Ozarka. Canopy reflectance and reflectance indices in wide wavebands correlated well with most quality variables measured. Findings from this study suggest that selection of appropriate cultivars can mitigate detrimental effects of stress environments on pasture productivity. Furthermore, remotely sensed data may be useful in the management of pasture grasses, adjusting stocking rates based on nutritive value of the pasture, and in determining supplementation start dates for cattle grazing on warm season grasses.

Technical Abstract: Better understanding and more accurate prediction of changes in biomass and quality parameters during the grazing season can help farmers and ranchers better manage livestock, grazing lands, and feed resources. An experiment was conducted in 2002 and 2003 to determine seasonal variation of biomass, neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), and canopy spectral reflectance of bermudagrass pastures as a function of plant genotype. Three bermudagrass pastures of Midland, Ozarka and 74x12-12 were established in 1991 having the same soil type (Brewer silt loam clay), field management and stocking rate. Based on the long-term weather data, 2002 was a normal year, but 2003 was drier than the long-term average with high temperatures. Year, genotype, and sampling date significantly (P < 0.05~0.0001) affected pasture biomass production, NDF, ADF, CP, and canopy reflectance. Although CP concentration was the highest in the early growing season, the maximum CP availability matched the greatest pasture growth rate. Ozarka and Midland pastures were comparable in biomass, ADF, and CP concentration in 2002. In 2003, however, Ozarka had an 86% higher biomass, 7% lower ADF, and 15% lower CP concentration. Overall, 74x12-12 had a slightly lower biomass, but higher ADF and CP than Ozarka. Findings from this study suggest that selection of appropriate genotypes can mitigate detrimental effects of stress environments on pasture productivity. Furthermore, remotely sensed data may be useful in the management of pasture grasses, adjusting stocking rates based on nutritive value of the pasture, and in determining supplementation start dates for cattle grazing on warm season grasses.