Trampling effect on seedling production and soil strength under short-duration and continuous grazing
Graff, Paul Stephen
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Seeds of six grasses and four legumes were broadcast into low-density (IX) short-duration (SDG), high-density (2X) SDG, and continuously-grazed pastures in the Coastal Prairies of Texas to test the effect of different levels of trampling on seedling production. Seeding was also done on similar areas that had been sprayed with herbicide to reduce competition. Seeds of weeping lovegrass and Caucasian bluestem were broadcast in similar grazing treatments in the Rolling Plains of Texas, but competition reduction was not done. The Sinton loam soil on the coastal study area was monitored for changes in bulk density and crust strength using a bulk density core sampler and a proving-ring penetrometer. The penetrometer was also used to measure changes in surface strength of the Brownfield fine sand soil on the Rolling Plains area. Only seeds of Bell rhodesgrass, medio bluestem, Nueces buffelgrass, and meechie arrowleaf clover showed appreciable seedling production by broadcasting and trampling in the Coastal Prairies. Seedlings of medio bluestem and buffelgrass were increased by heavier trampling of SDG compared with the CONT, but only where competition was reduced. Medio bluestem produced many seedlings with or without reduced competition. Seedling production was extremely low on the Rolling Plains despite excellent rainfall conditions. Almost all seedlings were found within sand-shinnery oak canopies where little trampling occurred. Here, seedling production was not increased by trampling under SDG, apparently because competition was not reduced. Soil surface characteristic was not improved on the Sinton loam soil during 5 months of grazing under SDG, compared to CONT. Crust strength of the Brownfield fine sand soil was reduced by trampling under SDG compared to the CONT.