1.0 INTRODUCTION
Florida ranks tenth among all states and second among states east of the Mississippi in beef production (Graetz and Nair, 1996). In 1995, Florida maintained 1.15 million beef cows, and total cash receipts from cattle and calves were $290 million (FDCAS, 1996). Florida's cattle production is dominated by cow-calf operations, so the industry has a significant impact on cattle production in other states.
The vast majority of Florida's cattle is located in south and central Florida, south of a line between Daytona Beach, Orlando and Tampa. Much of what was once native subtropical wet prairie ecosystem in this region is now managed for grazing. Land use changes within these ecosystems have resulted in dramatic changes in the wildlife habitat characteristics and the patterns of nutrient flow for upland, marsh and lake ecosystems. For example, total P concentration in Lake Okeechobee has almost doubled since 1970's and chlorophyll a level significantly increased between early 1970's and 1990 (James et al., 1995a,b). Coincidental with this general area of south Florida is one of the nation's fastest growing urban populations and one of the nation's most sensitive ecosystems. This region of Florida is home to many endangered plants and animals making it a "national hotspot" for endangered species (Cox et al., 1994). Also, water from this cattle production region feeds into Lake Okeechobee and the Florida Everglades. Preservation and restoration of this unique ecosystem ranks at the top of our national environmental priority list.
In an effort to restore the Everglades/Lake Okeechobee ecosystem, the South Florida Water Management District (SFWMD) developed a Surface Water Improvement and Management (SWIM) program for the Kissimmee River Basin and Lake Okeechobee watershed. The SWIM rule was intended to obtain phosphorus load reductions beyond what had already been realized from the Rural Clean Water Protection Program (1980 1990), the dairy buy-out program and the other related programs. Despite reduction in phosphorus loads from Lake Okeechobee watershed, the SWIM mandated targets have not been met, and in-lake total phosphorus concentrations have not begun to decline. Although the SWIM plan is now fully operational, additional phosphorus load reduction due to its implementation has not occurred. Nondairy sources of P in the Lake Okeechobee drainage basin are primarily from beef cattle pasture (improved pasture and native range). Although animal densities and runoff phosphorus concentrations associated with beef cattle pastures are relatively low, the vast acreage (approximately 470,000 acres) of this land use makes them a major contributor of phosphorus. In order to achieve the phosphorus load target and to hasten Lake Okeechobee's recovery, it is necessary to find ways to reduce phosphorus in runoff from beef cattle pastures. This optimization project seeks to do so proactively, not through the regulatory framework, but through a collaborative program that seeks and includes input from the stakeholder community. A guiding principle is to protect and enhance Lake Okeechobee, while minimizing negative economic impacts on the agricultural industry.
While a variety of potential BMPs can be implemented (fencing, drainage, rotational grazing, feed/water location, and fertilization), stocking rate is a relatively easy management variable for the rancher to manipulate. Thus, the strategy pursued at phase 1 by the project team is to focus the first field experiment on grazing density by manipulating cattle stocking rate. Upon completion of this first experiment, the project team will examine other management variables and potential BMPs. The objectives of this project therefore are:
1) To optimize beef cattle density Best Management Practices (BMPs) that ensure both environmentally and economically sustainable beef cattle practices in Florida.
To achieve this objective, BMPs must result in reduced phosphorus runoff from pastures and not result in substantially increased net costs for the rancher.
2) To communicate these optimized BMPs to beef cattle ranchers through trade journal publications or other appropriate mechanisms (newsletters, field days, etc.).
Optimization project results must be communicated immediately and continuously to ranchers to increase the likelihood of further phosphorus load reductions to Lake Okeechobee.
2.0 BACKGROUND
This two-year Phase 1 optimization project is designed to achieve the above objectives, which are consistent with the SFWMD's Lake Okeechobee SWIM strategy. The infrastructure necessary for implementing the proposed optimization project is being constructed with FY95, FY96, and FY97 funding provided through a Memorandum of Understanding (MOU) between the South Florida Water Management District (SFWMD), the University of Florida, Institute of Food and Agricultural Sciences (IFAS), and Archbold Biological Station, MacArthur Agroecology Research Center (MAERC). Recently, the Florida Cattlemen's Association (FCA), and the Natural Resource Conservation Service (NRCS) have joined on as partners. MacArthur Agro-ecology Research Center, located on Buck Island Ranch, is the site for field projects. Related research is conducted at the UF main campus in Gainesville and its participating Research and Education Centers in Immokalee and Ona.
2.1 Stocking Rate Treatments
The cattle stocking rate optimization project infrastructure consists of multiple, field-scale experimental pastures that are realistic in size, yet are fenced and ditched separately from each other, and are instrumented, so that all surface water runoff can be captured and analyzed. The experimental design for the improved pasture study is a completely randomized block employing four (4) stocking rate treatments on eight pastures as described in Table 1. Stocking rate treatments on the improved pasture plots will be 0, 1.4, 2.5, and 3.3 acres/cowcalf unit. The design for the native rangeland evaluation is also a completely randomized design employing four (4) stocking rates on eight plots, with the stocking rates being different than those used on the improved pasture plots (Table 1). Native rangeland stocking rates will be 0, 2.3, 4.0, and 5.3 acres/cowcalf unit. The difference in animal densities in the summer and winter array is necessitated by differences in potential biomass production between these areas. Each study animal will be assigned to a stocking rate at the beginning of the study and remain at this same stocking rate for the life of the project.
Table 1. Phase 1 Project Design.
Pasture Array Replicates Stocking Rates, Total Acres per Unit* Units* Summer (50 acres) 2 0 0 2 1.4 35 2 2.5 20 2 3.3 15 Summer Total 8 140 Winter (80 acres) 2 0 0 2 2.3 35 2 4.0 20 2 5.3 15 Winter Total 8 140
*Unit = 1 cow with calf
These grazing areas reflect the two principal pasturing regimes of a typical central Florida ranch. One array site is located on a wetter range area containing a mixture of native grasses, along with some bahiagrass. This range area is used for winter and spring (dry season) grazing by cows immediately after calving and during breeding. The other array site is on welldrained and improved pasture with bahiagrass, which is used for summertime (wet season) grazing of cowcalf pairs. The two arrays will be similar in design and instrumentation. The winter range array consists of a 700acre area. Within this array eight 80acre range plots are delineated. The winter range plots are 30 acres larger than the summer pasture plots because, in general, cattle are kept on winter range in lower densities than on summer pastures. The 80acre plot size allows the number of cows within a grazing herd to be kept at a level that provides greater statistical significance when evaluating animal characteristics. The 500acre summer array consists of eight 50acre plots.
The project will be carried out in two stages in order to separate the effects due to site disturbances from those due to stocking rate treatments. The first stage of the project will be an equilibration period lasting up to one year. In stage two, the test herds will be introduced to the grazing plots at the specified treatment stocking densities. Water quality data will be collected continuously throughout both phases.
3.0 SCOPE OF WORK
The contractor, UF-IFAS, will conduct the cattle stocking rate evaluation and optimization project according to the design mentioned in section 2 of this document. The proposed project will be conducted at Buck Island Ranch. The contractor will develop electronic data bases, trade journal publications, and manuscripts ready for submission to peer-reviewed journals. The outcome of the project will also be communicated to the beef cattle ranching community, Florida Department of Environmental Protection, South Florida Water Management District, scientists and other stakeholders through a Beef Cattle BMP public workshop to be convened at the end of the project. Interim results will be communicated to stakeholders through trade journal articles, technical and scientific presentations. The tasks to be conducted in the project are as follows.
3.1 Surface Water Measurements
All of the pasture construction and instrumentation described below is underway through prior funding. Flumes for collection of surface water runoff from each pasture plot will be constructed at the downstream end of each pasture plot. The plots are hydrologically isolated from each other by the construction of ditches and berms along their margins, and livestock will be isolated within each plot by pasture fencing. Trapezoidal flumes will be located and constructed as to collect all surface drainage leaving each plot. These types of flumes are hydrologically unobtrusive and do not significantly alter water table levels or surface runoff. Peak capacity for the flumes will be seven cubic feet per second; a capacity dictated by funding limitations but consistent with prior research conducted on similar sites by IFAS. Stilling wells, floats and digital encoders will monitor flume upstream and downstream water depth, and thus flow. Digital encoders will be connected to data loggers/controllers which record data and activate automatic water samples based upon instantaneous flow conditions. In addition, automated meteorological stations will be located within each pasture array. Each pasture plot will also be equipped with water table wells to assess water table status.
3.2 Water Quality Investigation
A comprehensive water quality monitoring plan will be conducted to evaluate the effectiveness of each stocking rate scenario. Surface drainage water leaving each pasture plot will be directed to a trapezoidal flume. These flumes are hydrologically unobtrusive because they do not significantly alter water table levels or surface runoff.
Each flume will be equipped with an automatic water sampler. Programmable data loggers will trigger the samplers based upon flow volume and hydrograph geometry. Water samples will be analyzed for total phosphorus, nitrate, ammonia and total nitrogen, according to DEP approved methods. Grab samples will also be taken at each site and tested for soluble reactive phosphorus. Chemical analysis of runoff water samples will be performed by Harbor Branch Environmental Laboratory in Ft. Pierce. Field parameters (dissolved oxygen, electrical conductivity, and pH) will also be measured at each flume by personnel supervised by the IFAS laboratory in Immokalee. Both the Harbor Branch and the IFAS Immokalee laboratories hold quality assurance quality control certification from the DEP.
Flow data from the flumes will be combined with nutrient concentration data to determine loading rates for total phosphorus, nitrate, ammonia and total nitrogen. Water budgets for each array element will be determined from flow, meteorological, and water table data. This will permit assessment of the water budget and its influence on nutrient runoff loads. To evaluate
the effect of stocking rates on nutrient concentration and loads, water level and nutrient concentration data collected at each flume over time will be subdivided into identifiable flow "events". Flow events will be defined after they occur and will usually be related to significant rainfall events.
Nutrient mass loadings will be computed for each experimental plot, for each event. Comparisons of nutrient loads from experimental treatments will be accomplished using the generalized linear mixed effects models, incorporating spatial (plottoplot associations), temporal blocks (events as stripplots in time modeled as random/repeated measures effects), and covariates (estimated event rainfall in the plot, previous event nutrient loads, past groundwater levels, etc.). Additional analyses will estimate annual water nutrient budgets for each plot, (flow weighted) averages of nutrient concentrations over time, and nutrient mass loadings.
3.3 Livestock and Pasture Management
The breeding females to be utilized for the experiment will be randomly chosen from one of the three breeding herds (570 head) on the Buck Island ranch. Animal selection will be based upon age [ability to fulfill experiment duration (2 yr)], pregnancy status at time of starting the experiment, health, conformation, and disposition. Animals selected will be identified with a number tagging system. One hundred forty breeding females will be selected and stratified by age, stage of pregnancy, and frame size then randomly assigned to a stocking rate (Table 1). Open females will be replaced with 4 year old pregnant cows from the replacement herd once a year at weaning time. This is the stage when a cow's offspring is separated from his mother and sold to other sectors of the industry.
Animals will be maintained on winter pastures from November through May and on summer pastures from June through October. Animals will continuous-graze while on pastures and nutritional supplementation will be provided throughout the year as standard management practices require. Each stocking rate herd will be maintained as a unit when moved between winter and summer pastures.
The following animal data will be collected: cow body weight, calf birth date, calf birth weight, calf weaning weight, calf average daily gain, and herd health schedule. Body condition score will be measured, according to methods described by Kunkle et. al. (1994) to assess if the nutritional needs of animals are being met. Animal dystocia (calving difficulty) will be measured since it represents a potential economic loss to the rancher. Calf weaning weight will also be measured. This is the weight of an offspring when the individual is separated from his mother and sold to other sectors of the industry. This is an important economic parameter because most producers sell their calves at weaning stage and receive the income for their operation at that time.
Table 2. Measurements associated with stocking rate experiment.
Category Parameter Frequency Water Flow Rate & Depth Continuous Water Table Elevation Weekly pH, EC, & DO Weekly Soluble Reactive Phosphorus Flow Based TKN, NOX, TP, NH3 Flow Based Soil pH, TP Annual Weather Rainfall Continuous Solar Radiation Continuous Wind Speed & Direction Continuous Temperature & Rel. Humidity Continuous Cattle Calf Birth Date, Weight & Birth Difficulty Calf Weaning Weight Weaning Body Condition Score Annual
4.0 WORK BREAKDOWN STRUCTURE
Task #1: Project Work Plan
A Project Orientation Meeting will be held within one month of the grant award. At this time, the Project Team, to include representatives from the MOU Advisory Committee (SFWMD, Archbold, and IFAS), and DEP and EPA, will discuss an overview of the project's objectives, project plans and methods, proposed project schedule, decision points, and deliverables. Following this meeting, the Team will prepare a Project Work Plan that describes the optimization project in detail, based on discussions at the Project Orientation Meeting. The Project Work Plan will include specific project and task objectives, and deliverables associated with each task. If agreed to by the Project Team, the Project Work Plan may be sent to outside reviewers for critical evaluation and to ensure it meets project objectives. Once revised (if needed) and approved by the Project Team, the Project Work Plan will guide the implementation of the optimization project.
Deliverables: 1) Three hard copies and one electronic copy of the Draft Project Work Plan; 2) Three hard copies and one electronic copy of the Final Project Work Plan, incorporating revisions agreed upon by the project team (and based on outside review comments, if applicable); 3) Quarterly progress reports; 4) Quarterly meetings with DEP project manager to review progress on execution of the work plan.
Task #2: Soil and Water Quality Assessment During Pasture Equilibration
Pasture construction, including ditching and fencing, was completed in spring 1997. Water quantity and water quality instrument installation will be completed by July, 1997. It is expected that it may take as long as one year for soil and water chemistry to equilibrate back to steady-state conditions following construction-related soil disturbance. The pastures wll be stocked at the lowest stocking rate (0.3 cows-calves per acre).
During this time, pasture runoff volumes, water quality, and meteorological conditions will be measured continuously in a manner consistent with that used during the stocking rate optimization project as outlined in sections 3.1 and 3.2. These measurements will serve two important purposes. First, these data will provide critical background information on intra and inter-pasture variation in soil and water chemistry. This knowledge is important in the eventual design of BMPs for beef cattle ranching. Second, this data collection effort will permit the adjustment and optimization of data collection procedures to be employed during the stocking rate optimization stage.
At least 10 soil samples will be collected from 0-5 cm depth in each of the 16 plots of the winter and summer pasture arrays quarterly. Florida DEP approved standard operating procedures (SOPs) will be followed to collect soil samples. Soil samples will be analyzed for P by University of Florida Analytical Research Lab in Gainesville which is certified by DEP. This information will enhance a detailed pasture soil survey that is being conducted by the NRCS through a collaborative project (funded by NRCS).
Deliverables: 1) Trade journal publication describing variation of soil and water quality conditions within and between pastures, and possible implications for cattle denisty-related BMP development; 2) Manuscript on same topic ready for submission to peer-reviewed agricultural or soil science journal; 3) Electronic database containing all soil chemistry and water data. These and all subsequently described databases will be accessible through Internet and the World-Wide Web, or upon request from the Principal Investigators.
Task #3: Identification of Test Herd Animals and Initial Animal Data Collection
One hundred and forty breeding females will be selected for the optimization project during the pasture equilibration period. These females will be randomly assigned to the individual pastures, and tagging and initial animal health data will be collected during this time period. Data on animal health parameters are necessary for subsequent economic analyses. The data set will include information on: cow body weight, calf birth date, calf birth weight, calf weaning weight, calf average daily gain, herd health schedule, body condition score, calf weaning weight, and animal dystocia.
Deliverables: Electronic database containing all relevant animal identifications and health data.
Task #4: Stocking Rate Optimization Project
Following the equilibration period of the pasture arrays, the breeding females (and calves, depending on the exact season of project initiation) will be placed into the appropriate pasture arrays, and the optimization project will begin. Water quality, soil chemistry, meteorological, and animal data will be collected as previously described for at least one year. The pastures will be managed according to standard range practices as previously described to provide a range of animal management that falls within or close to commonly utilized beef cattle production standards in Florida. These practices, and the optimization project data collected, will be relevant to all beef cattle management in Florida, particularly on low topography landscapes having relatively low phosphorus retention capacities.
At the conclusion of one year of the Phase 1 optimization project, all data will be analyzed and submitted for publication, both in trade and scientific journal formats. The result of the first year of optimization will be the basis to decide to continue another year of the Phase 1 optimization project, or to proceed with the design and implementation of other projects that will examine the effect of various pasture fertilization practices on runoff water quality.
Deliverables: Extension publication describing the effects of various beef cattle stocking rates on pasture runoff water quality, including specific recommendations of interim BMPs based on these data; One or more manuscripts on same topic ready for submission to peer-reviewed agricultural or soil science journal; Electronic database containing all data.
Task #5: Beef Cattle BMP Public Workshop
A public workshop will be held to convey the results of the Phase 1 optimization project to the beef cattle ranching community, agency and governmental personnel, and any other interested parties. This workshop will consist of presenting the results of the project that were published in the extension publication described previously, and describing specific BMPs that have the potential to improve water quality in beef cattle pasture runoff. The workshop will include a panel discussion format, with breakout groups, to ensure feedback from attendees. This feedback will be considered in the design of future projects, and will increase the chances for project acceptance by the affected stakeholders, and the chances for long-term project relevance and success.
The workshop will be held as an independent event, located to maximize participation by the beef cattle ranching community, or held in conjunction with the annual FCA meeting. The optimum timing and location of the workshop will be determined collectively by the FCA, SFWMD, IFAS, and Archbold.
Deliverable: Public workshop and field day, including an extension report summarizing the workshop results and feedback; Final report plus video documentation of project.
Table 3. Work tasks, deliverables, and schedule.
Work Task Deliverable Months after Execution 1. Work Plan Draft Work Plan 1 Progress Reports 3,9,12,15,18,21,24 Project Meetings 1,3,9,12,15,18,21,24 Final Work Plan 2 2. Equilibration Extension Publication 12 Peer-reviewed Manuscript 14 Electronic Database 14 3. Animal Data Electronic Database 24 4. Stocking Rate Trial Extension Publication 20 Peer-reviewed Manuscript 23 Electronic Database 24 5. Results Public Workshop 18 Dissemination Field Day 20 Extension Report 21 Project Video 23 Final Report 24
LITERATURE CITED
Cox, J., R. Kautz, M. MacLaughlin and T. Gilbert. 1994. Closing the gaps in Florida's wildlife habitat conservation system. Florida Game and Fresh Water Fish Commission, Tallahassee, Fl. 239 p.
FDACS. 1996. Florida Agricultural Statistics. 1995 Livestock, Poultry, Dairy Summary. Florida Department of Agriculture and Consumer Service.
Graetz, D.A. and V.D. Nair. 1996. Water quality impact of grazed rangelands and pastures: Literature review. Department of Soil and Water Sciences. University of Florida, Gainesville. Technical Report Submitted to South Florida Water Management District, West Palm Beach, FL.
James, R.T., B.L. Jones and V.H. Smith. 1995a. Historical trends in the Lake Okeechobee ecosystem. II. Water quality. Arch. Hydrobiol. Suppl. 107:25-47.
James, R.T., V. H. Smith and B.L. Jones. 1995b. Historical trends in the Lake Okeechobee ecosystem III. Water Quality. Arch. Hydrobiol. Suppl. 107:49-69.
Kunkle, W.E., R.S. Sands and D.O. Rae. 1994. Body Condition Scoring Of Beef Cattle. Cooperative Extension Service . University of Florida Institute of Food and Agricultural Sciences. Gainesville, FL.
Littell, R. C., G. A. Milliken, W.W. Stroup, and R. D. Wolfinger. 1996. SAS System for Mixed Models. Cary, NC.: SAS Institute Inc.
SAS. 1988. SAS User's Guide: Statistics. (6th Ed.) SAS Inst. Cary, NC.
SAS, Institute Inc. SAS/STAT Software: Changes and Enhancements through Release 6.11,
Chapter 18, Cary N.C.:SAS Institute Inc., 1996.
PROJECT TEAM
Table 3. Members of the project team.
Organizatio Project Member Title Unit n UF-IFAS Dr. John C. Assistant Southwest Florida Research and Capece Professor Education Center UF-IFAS Dr. Michael Assistant Southwest Florida Research and Fanning Professor Education Center UF-IFAS Dr. Kenneth Professor Agricultural and Biological Campbell Engineering UF-IFAS Dr. Donald Professor Soil and Water Science Graetz UF-IFAS Dr. Kenneth Professor Agricultural Statistics Portier SFWMD Dr. Alan Director Okeechobee Systems Research Steinman Division ABS Dr. Hilary Swain Director MacArthur Agro-ecology Research Center
Table 4. Additional Project Cooperators.
Florida Cattlemen's Association Mr. Edgar Stokes Florida Cattlemen's Association Mr. Marty Smith USDA Natural Resources Conservation Mr. Pete Deal Center