Abstract
Dung pats were artificially deposited in a bahiagrass pasture rotationally grazed by Holstein heifers in June (JD sward) and in August (AD sward). The dung-deposited and surrounding places of JD and AD swards gave different energy flow through the producer from the dung-free place (ND sward) as follows. (1) The dung-deposited places of both JD and AD swards took larger litter production (LP) than ND sward in the first periods after the dung deposition, which indicated some plant killing by the dung pat cover. However, bahiagrass was found to be considerably tolerant to the dung pat cover since the net primary production (NPP) in those places was not reduced. (2) The dung-deposited and surrounding places of AD sward in the first period after the dung deposition showed a tendency of higher NPP than ND sward mainly because of the higher storage in plant (ST). This was considered to be primarily caused by the increment in the leaf area index rather than the increment in the leaf nitrogen percentage. (3) Then, in the next year over winter, both JD and AD swards tended to be lower than ND sward in NPP chiefly because of the lower ST and LP. In case of AD sward, the reduction in photosynthesis due to the shading by large standing dead and the rise in respiration due to the large non-photosynthetic organs are regarded as the main reasons. However, in case of JD sward, no reason was found for the smaller NPP.
