Project Title: Agro-Ecosystems Indicators of Sustainability as Affected by Cattle Density in
Ranch Management Systems
Principal Investigators: K.L. Campbell, J.C. Capece, J.J. Mullahey, M.D. Fanning, D.A.
Graetz, J. Holt, R. McSorley, R.M. Muchovej, K.M. Portier, F.M. Roka, A.D. Steinman, and
G.W. Tanner
Grant Number: 97-35108-5125 Reporting Year: 1998
Specific Aims: The objectives of this multidisciplinary project are to:
1. investigate the effect of cattle stocking rate on the following indicators of cattle ranching system sustainability:
Results: Installation of water measurement flumes and hydrologic instrumentation was
completed and the remainder of the year served as an equilibration period to remove the effects
of construction disturbance and establish consistent measurement performance and procedures.
Stocking rate treatments were established for the winter and summer pastures. During the winter
season (November-April) cattle stocking rates are 0, 2.3, 4.0, and 5.3 acres per cow. In the
summer season (April-November) cattle stocking rates are 0, 1.4, 2.5, and 3.3 acres per cow.
One hundred forty Brahman-cross, pregnant cows (4-9 years of age) were stratified by age and
body condition (5-7; scale 1-9) and randomly allotted to the stocking density treatments in
preparation for placement in the winter pastures. Winter pastures will be burned in early
November and approximately 60 days after the burn, cattle will begin grazing. Summer pastures
were mowed (October) and are targeted for burning after the first frost event. Forage samples
were collected from each pasture to determine standing biomass and forage quality prior to
burning. Burning during the winter grazing period was unexpected and will interrupt the winter
grazing period.
This year was devoted to background data collection to determine the chemical and biological
status of the pastures before any treatments were imposed. Soil samples were taken from the
winter and summer pastures arrays prior to cattle placement to provide pre-treatment soil P
characterization. Analyses have been completed for the winter pasture array. Average water-soluble P concentrations were 19, 4.5, 1.0, and 0.3 mg kg-1 for the 0-5, 5-10, 10-20, and 20-30 cm
depth increments, respectively. Soil samples for nematode analysis were collected from the
pastures in February, May, and early October. Analyses of these samples and data are pending.
In addition to establishing background levels of nematodes in each of the pastures in the
experiment, these samples will be examined for seasonal trends in nematode populations and
analyzed for any differences in nematode populations and community structure between winter
pastures (which tend to be wetter overall) and summer pastures (which tend to be somewhat
drier). Typically, the soil nematode community contains a great variety of different kinds of
nematodes, many of which are involved in decomposition, others which feed directly on the roots
of growing plants, and some which feed as predators or omnivores. Previous work indicates that
population levels of different kinds of nematodes may respond to inputs of organic matter,
fertilizers, and other sources of nutrients. Therefore it is anticipated that cattle populations and
their associated inputs may have some impact on the soil nematode community as well. Bird
census data collected in spring and late summer provide background data to reflect the general
avian community associations that typically occur on south Florida pasture lands. These pastures
have ephemeral wetlands and some forest islands. These habitat features provide for a mixture
of wetland, upland forest and grassland associated bird species.
Work on the ranch economic simulation model during this first year of the project consisted of
refining the initial spreadsheet model. University faculty in the animal science and range science
departments were consulted about the overall structure of the model and specifically reviewed
default values describing animal nutritional requirements and forage production coefficients.
Several research papers were identified and work is ongoing to incorporate those findings into
the model. Preliminary results, using data from two commercial ranches, indicate the model's
ability to accurately track revenues and expenses and to estimate after-tax returns.
Plans for the Coming Year: Experimental treatments with cows placed on the pastures at
assigned stocking rates will be in progress throughout the coming year. Cow body condition,
herd health, calf weights, and cow pregnancy rate will be monitored for all stocking density
treatments. Forage production and quality will be measured during the remainder of the winter
grazing season and during the summer grazing period. Soil sampling will continue on a 4-6
month interval on all pastures. In addition, soils and standing water in localized areas will be
sampled periodically to determine if nutrients are being accumulated in swales and ditches. Soil
samples for nematode analysis will be collected in May and November from each of the 16
pastures. Bird censuses will continue on a quarterly time frame. These samples will allow for
censuses to be taken during migration periods and when resident bird species are nesting.
Vegetation structure also is monitored during bird census periods to test if any association exists
between bird usage and structural aspects of the vegetation. Priorities in continuing the
refinement of the economic simulation model will include: 1) loading financial information from
MacArthur Agro-ecology Research Center at Buck Island Ranch and analyzing
production/financial trends, 2) writing a user's guide for the simulation model, and 3) conducting
ranch interviews in conjunction with county extension faculty to identify and solicit cooperation
from commercial ranches in south Florida. The objective is to configure the simulation model for
each ranch. The specific data collected from ranches will be used to develop and refine model
relationships. Hydrologic/water quality data will be measured continuously throughout the year
from all 16 experimental pastures with support from a Florida Department of Environmental
Protection/EPA Section 319 grant.
Publications:
The following publication resulted from data obtained as background information on the site of
this study before this project was funded.
McSorley, R. 1997. Correlation of nematode densities and rainfall in a Florida pasture. Soil Crop
Sci. Soc. Florida Proc. 56:55-57.
Other Products: Additional information regarding this project and other related activities at this location are available for review on the project web pages at the following URL address:
http://www.imok.ufl.edu/buck/index.html
Information available at this location includes project status, summary data, progress reports,
work plans, meeting notes, experimental plot layouts, and other similar information.
Students Sponsored: None