12/09/1999 

0177999 

2. CRGO 3. FLA 4. 

FLA-AGE-03689 

Progress

AGRO-ECOSYSTEMS INDICATORS OF SUSTAINABILITY AS AFFECTED BY CATTLE DENSITY IN RANCH MANAGEMENT SYSTEM 

Campbell, K. L. 

Cows grazed the winter pastures (Feb-Apr 1999) and the summer pastures (Apr-Nov 1999) with a 100% calf crop at weaning for each treatment. Body condition score in June was highest for the medium stocking density (20 cows) with a score of 7 followed by the low (6) and high (5) stocking densities. Calf weights at weaning were similar for low (407 lb) and medium (417 lb) stocking densities and lower for the high density (387 lb). Total beef produced per acre increased with stocking density (122, 166, and 270 lb/ac, respectively). A higher return on investment would be expected with a higher stocking density. Pregnancy rate in June was 90% for the low stocking density, 92% for medium and 96% for high density. In April, available forage was highest in the control (816 kg/ha) followed by the low (764), medium (744) and high (425) stocking density. Forage utilization was 51.4% for the low treatment, 52.8% for medium, and 61.7% for high. In June, available forage was highest in the control (3495 kg/ha) and declined with increasing stocking density (1055, 597, and 247 kg/ha, respectively). Forage utilization increased with increasing stocking density (46, 74, and 86%). In September, utilization was near zero for all treatments indicating that forage production was higher than consumption. Soil phosphorus (P) in seasonal wetlands in the pastures was measured. Soil analyses included water soluble P (WSP), total P (TP) and P fractions. TP was higher (240-660 mg P/kg) in the detrital than in the mineral layer (16-180 mg P/kg). WSP comprised 1-9% of the TP and was higher in the wetland interior than on the edge of the wetland. TP and WSP were greater in the summer pastures than in the winter pastures, and were significantly related. Much of the TP was in the residual P fraction that is considered to be recalcitrant. Soil samples for nematode analysis were collected from winter and summer pastures. Preliminary examination and analysis shows a great variety of nematodes, especially bacterivores and fungivores, were present, even during the dry conditions in April. Birds were sampled using strip counts within each pasture. During winter, mean avian species richness was 14.0-23.5 in the summer pastures and 9.0-14.5 in the winter pastures. During spring, these means were 8.5-11.5 and 6.5-9.0, respectively. During fall, these means were 12.0-16.0 and 11.5-14.0, respectively. There was no pattern of species richness with stocking density during any of the seasons. Presence of small isolated wetlands and scattered trees seemed to have the strongest association with species composition. Balance sheets and cash flow reports were added to the economic simulation model to more completely represent financial implications of management changes on a cow-calf ranch. Faculty in animal and range sciences were consulted further about the overall structure of the model. The model was distributed to county extension faculty. It was introduced to the ranching community through a county agent meeting, a presentation to the Florida Cattlemen's Association, and a ranchers' workshop. 

Use of wetland prairies for cattle grazing is critical to beef cattle production in Florida. The wetland prairies are grazed during the winter months when forage productivity is low on upland improved pastures. Results will help determine if grazing degrades habitat function and if there is a problem, how ranch management practices can be modified to minimize such effects while maintaining ranch profitability. 

Earman, J. and F. Roka. 1999. What if I changed my ranching operation? The Florida Cattleman and Livestock Journal 63(11):65-67.

Graetz, D. A. and P. J. Bohlen. 1999. Phosphorus status of wetland soils in subtropical rangelands. Agronomy Abstracts. p. 327, American Society of Agronomy 1999 Annual Meeting.

Graetz, D. A., K. L. Campbell and P. J. Bohlen. 1999. Agro-ecosystem indicators of sustainability as affected by cattle density in ranch management systems. Agronomy Abstracts. p. 367, USDA-NRI Poster Session, American Society of Agronomy 1999 Annual Meeting.

Campbell, K. L. and J. C. Capece. 1998. Agro-ecosystems indicators of sustainability as affected by cattle density in ranch management systems. In: Current Research at Archbold Biological Station, 1998 Fall Symposium. Archbold Biological Station. Lake Placid, Florida. p. 3.