Agricultural BMPs ARE protecting water resources

By Stewart Swanson
Regional Sugarcane Extension Agent III
University of Florida, IFAS

Best Management Practices (BMP) programs, manuals and educational training have been developed for every aspect of agriculture in Florida: citrus, vegetables, agronomic crops, specialty fruit and nut crops, poultry, horse and cattle farms, nurseries, dairy and sod farms.

By definition, BMPs are a practice or combination of practices determined by the coordinating agencies, based on research, field-testing and expert review, to be the most effective and feasible on-location means, including economic and technological considerations, for protecting surface and groundwater resources.

Any BMP that reduces pollutants or the volume and rate of runoff from rainfall/irrigation events will lead to an increase in water quality. Reducing the amount of water used in agricultural operations not only saves water but reduces the risk of pollutants leaching into groundwater or draining into surface waters.

The University of Florida, Institute of Food and Agricultural Science (UF/IFAS) scientists, specialists and Extension agents have created educational programs to cover topics including irrigation efficiencies, nutrient application, soil testing, conservation techniques, runoff reduction, as well as other best management practices. Seminars, field days, workshops and demonstrations of BMPs have assisted 44,000 commercial farmers, who produce food, fiber and livestock on approximately 10 million acres in Florida, in adopting these practices. UF/IFAS researh has demonstrated that water and fertilizer management are inextricably linked. Changes in one will almost inevitably affect the efficiency of the other. The goal of proper water management is to keep both the irrigation water and the fertilizer in the root zone. Here are a few stories to illustrate the impact and successes of BMP implementation.

Potatoes grown in the Tri-County Agricultural Area near the St. Johns River have traditionally been fertilized by pre-plant incorporated broadcast applications. This practice tends to waste fertilizer because it invariably fertilizes the water furrows and other areas where potatoes are not grown. UF/IFAS on farm research has demonstrated the uniformity and value of banding fertilizer under each row of potatoes. Banding increases fertilizer use efficiency and allows growers to reduce the amount of fertilizer used by approximately 25 percent.

UF/IFAS researchers have done numerous nitrogen rate studies on vegetables in Southwest Florida. Many of these trials were large-scale plots on local farm fields. Recently, survey data from major vegetable producers who grow more than 80 percent of the vegetables in Southwest Florida, indicated a reduction in nitrogen usage from 300 pounds per acre to an average of 240 lbs. per acre. This represents a 20 percent reduction in the amount of nitrogen fertilizer applied and has resulted in a reduction of around 890,000 lbs. of nitrogen fertilizer applications per year. Without proper management of horse manure, excess nutrients such as nitrogen can leach into the groundwater or be washed into surface waters. A UF/IFAS Extension agent in Marion County consulted on the construction and management of impermeable compost bins that more carefully managed manure on six horse farms. These six farms represent about 1,700 acres and may stable as many as 315 horses. A 1,000-pound horse can produce around 8.5 tons of manure per year, which could contain 0.6 percent nitrogen. The nitrogen produced on these six farms per year would exceed 16 tons. The development of proper manure management facilities helps ensure that ground and surface water resources are protected.

Freezes in Florida can be very devastating to citrus crops. Orchards are protected from freeze events by running the irrigation system. Extension agents and university specialists have been providing educational programs from South Florida through Central Florida on the use of the Florida Agricultural Weather Network (FAWN) and locally acquired climatic data to precisely schedule irrigation for freeze protection.

Typically, irrigation would be turned on when the temperature approached a critical level that could result in tree damage. The irrigation would be left on until the grower felt that there was no potential threat of damage left. The use of the FAWN “Cold Protection Tool Kit” takes into account the critical temperature, wind speed, air temperature and the wet-bulb temperature. The use of these tools allows the producer to confidently end the irrigation when the wet-bulb temperature reaches the critical temperature of the crop being protected. The use of FAWN has become widely adopted by the citrus industry, with roughly 79 percent of growers surveyed using these tools for scheduling freeze protection. It is estimated that the tool kit can reduce irrigation by two hours per freeze event. At a pumping rate of 2,100 gallons/hour/acre over the 525,000-acre citrus crop in Florida, a savings of over 1 billion gallons of water per hour can be realized. On average, Florida winters produce five nights requiring freeze protection for an average saving of (2 hours x 5) 10 hours. So, the annual savings due to the adoption of the FAWN tools could save upwards of 11 billion gallons of water annually.

Many of the BMPs we have today were developed by UF/IFAS research in the 1980s that was done to reduce phosphorus (P) flow from the Everglades Agricultural Area (EAA) into Everglades National Park. One of the more surprising findings was that sugarcane grown in the EAA is a net sink for phosphorus. When you grow the crop, you might add 6 lbs./acre of total P, but when you harvest the sugarcane you remove 21.4 lbs./acre of total P. It was also found that more phosphorus is in the drainage water of a fallow field than one where sugarcane is being grown. “Sugarcane is one of the best crops that can be grown in the EAA in that it is a low-P-input, high-biomass-producing crop.” (Agricultural BMPs for Phosphorus Reduction in South Florida, F.T. Izuno,, 1995, American Society of Agricultural Engineers, 38(3):735-744). UF/IFAS researchers continue to evaluate fertilizer recommendations on many crops to ensure that the rates continue to be appropriate.

At the end of the introduction to the BMP manual for vegetable and row crops, the following statement is made: “This manual is a living document. Over time, BMPs will be modified and adjusted as additional research is conducted and/or as economic conditions change.” The development of new practices and technologies hold the potential to even further reduce the impacts of agriculture on both water quality and quantity.

University of Florida researchers in cooperation with agricultural producers continue to evaluate new technologies and management practices, which may in the future contribute to increased protection of the environment. An example is the work that has been done in Southwest Florida where the effect of several different bed designs on tomato production was tested. The grower standard is a 6” x 36” bed. The trial showed that changing the dimensions of the bed to 12” x 18” increased the efficiency of water and fertilizer use. The taller, narrower bed required half the irrigation water and less fertilizer than the conventional bed. Best Management Practices in Florida are an ever-evolving program that, with the continued involvement and dedication of farmers and scientists, developing new technologies and practices, will continue to protect Florida waters.

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