Concerns about long-term effects of beef cattle browsing more than 11 million acres of Florida grazinglands led Agricultural Research Service (ARS) scientists to examine soil fertility changes in bahiagrass-based beef cattle pastures from 1988 to 2002. Analysis of data from that research shows that cattle can be managed in an environmentally safe way, despite the large quantities of waste the animals generate.
Forage-based livestock systems have been cited as a major cause of deteriorating water quality in Florida and other cattle-producing states. Phosphorus runoff from manure and fertilizers applied to enhance forage production can pollute rivers and lakes. However, very limited data have been available to quantify nutrient losses to adjacent bodies of water from pastures managed for grazing and hay production.
For this long-term monitoring study, the pastures were managed for spring grazing and late- summer haying. Soil scientist Gilbert C. Sigua and colleagues in the ARS Beef Cattle Research Unit in Brooksville, Fla., monitored changes in soil nutrients. The data they generated enabled them to predict soil chemical and physical changes likely under continuous forage-livestock cultivation, and to devise measures to manage them.
Testing was done in three large pasture units with a combined area of about 3,800 acres, of which about 3,200 acres were in permanent pasture. The herd used in the study—about 1,000 cows, bulls and calves—is maintained for nutritional, reproductive and genetic research at Brooksville.
Overall, there was no buildup of soil phosphorus or other crop nutrients, despite the annual application of fertilizers and daily in-field loading of animal waste. Periodic soil analysis showed declining nutrient levels, especially of phosphorus.
Next, Sigua and other collaborators will integrate environmental, plant and animal genetic resources into a sustainable beef cattle-agroecosystem suitable for the subtropical United States. The goal is to optimize forage-based cow-calf operations to improve pasture sustainability and protect water quality.
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