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Publication Date
1981
Description
First-year results are presented on the photosynthesis of grass swards under intensive rotational or continuous grazing. In rotational grazing, crop photosynthesis was high in spring, declining during grazing but recovering rapidly during regrowth, possibly because of the high photosynthetic capacity of individual leaves and of the great area of active leaves left in the sward. In autumn, crop photosynthesis was rather high initially, declined rapidly during grazing, and recovered slowly during regrowth, possibly because photosynthetic capacity of the leaves was low, the decline with age was great, and the active leaf area in the stubble was small. Crop photosynthesis under continuous grazing was rather high in spring despite the low leaf-area index, most likely because photosynthetic capacity of the many small leaves was high. In late summer, crop photosynthesis was low, possibly because the remaining leaves were old and less active. Net photosynthesis of swards under continuous grazing, integrated over time at two radiant flux densities, was about the same in spring as for swards receiving rotational grazing. However, in autumn, photosynthesis was somewhat lower under continuous than under rotational grazing. This lower rate does not necessarily lead to a proportionally lower herbage production, as differences in respiration, translocation, and longevity may compensate for the differences. Research is being continued to compile an explanatory simulation model and to optimize grazing systems.
Citation
Deinum, B; 'T Hart, M L.; and Lantinga, E, "Photosynthesis of Grass Swards Under Rotational and Continuous Grazing" (1981). IGC Proceedings (1981-2023). 11.
(URL: https://uknowledge.uky.edu/igc/1981/section6/11)
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Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Photosynthesis of Grass Swards Under Rotational and Continuous Grazing
First-year results are presented on the photosynthesis of grass swards under intensive rotational or continuous grazing. In rotational grazing, crop photosynthesis was high in spring, declining during grazing but recovering rapidly during regrowth, possibly because of the high photosynthetic capacity of individual leaves and of the great area of active leaves left in the sward. In autumn, crop photosynthesis was rather high initially, declined rapidly during grazing, and recovered slowly during regrowth, possibly because photosynthetic capacity of the leaves was low, the decline with age was great, and the active leaf area in the stubble was small. Crop photosynthesis under continuous grazing was rather high in spring despite the low leaf-area index, most likely because photosynthetic capacity of the many small leaves was high. In late summer, crop photosynthesis was low, possibly because the remaining leaves were old and less active. Net photosynthesis of swards under continuous grazing, integrated over time at two radiant flux densities, was about the same in spring as for swards receiving rotational grazing. However, in autumn, photosynthesis was somewhat lower under continuous than under rotational grazing. This lower rate does not necessarily lead to a proportionally lower herbage production, as differences in respiration, translocation, and longevity may compensate for the differences. Research is being continued to compile an explanatory simulation model and to optimize grazing systems.
