Although farmers have used manure to fertilize crops for 8,000 years, the widespread use of industrially produced synthetic fertilizer began in the 1960s, dramatically altering the natural nitrogen cycle by increasing the amount of bioavailable nitrogen in soils and water. Today, production and use of synthetic fertilizer fuels agricultural productivity that feeds almost half the people on earth (Erisman et al., 2008) and maintains ubiquitous urban turfgrass lawns and ornamental landscaping.
In the Sarasota County region, use of nitrogen fertilizer is dominated by synthetic mixes of inorganic nitrogen, phosphorus, and potassium (N-P-K) applied to turfgrass and lawns (80%) and farms (15%) (FDACS 2019).
Figure 4.1. Average annual distribution of all types of nitrogen-containing fertilizer to Sarasota County in FY 2016-2018. Source: FDACS
Inorganic slow-release formulas use a polymer coating to slow the rate of nutrient release, increasing efficiency of plant uptake and reducing runoff. Additionally, some fertilizer products are nitrogen- and phosphorus-free, and instead supply important plant micronutrients and/or soil enhancements like iron. Organic fertilizers—such as manure, compost, or animal byproducts—gradually release nutrients naturally, do not rely on fossil fuels for manufacture, and help build soil structure and health. Use of organic fertilizers promotes long-term soil productivity and carbon sequestration (see Chapter 4.6). Landscapes utilizing plants native to Florida are adapted to local soil and weather conditions. They require less fertilizer, pesticides, and irrigation and can be attractive alternatives to turfgrass and non-native ornamentals.
Nutrients from fertilizer can leach from soils or be washed off landscapes with stormwater runoff and transported to water bodies. This can occur when fertilizer is applied in excess of recommended rates or applied improperly, such as before a heavy rain or adjacent to a waterway. Excess nitrogen and phosphorus fertilizer can fuel algal blooms, degrade water quality, harm fish and wildlife, and threaten public health. In areas where new development provides reclaimed water for irrigation, fertilizer applications are compounded by irrigation with water already containing high nitrogen levels (see Chapter 1.2). Since Sarasota County soils are already naturally rich in phosphorus, primary productivity is more affected by increases in nitrogen.
Estimate nutrient loading from fertilizer
Understanding the relative contribution of fertilizer to nutrient loading can help prioritize management strategies. Loads may reasonably be estimated through an approach that calculates nutrient budget coefficients based on inputs, uptake, and outflows of nutrients for differing land uses.
Reinstate FDACS Public Reporting on Fertilizer Distribution
Publicly accessible data on the distribution and sale of fertilizer by category and by county is urgently needed to accurately estimate nutrient loading from fertilizer, assess compliance with fertilizer regulations, and track the success of educational efforts.
Strengthen Local Fertilizer Ordinances and Improve Compliance
Sarasota County was among the first in the state to enact local restrictions on fertilizer use to protect water quality. The ordinance could be substantially strengthened by additional provisions to require point-of-sale educational signage on proper fertilizer use to promote greater awareness and compliance.
Deliver Targeted Education and Resources to HOAs
Lawn care standards imposed in deed-restricted communities can conribute to excess fertilizer use and water pollution. Educating Homeowner Associations about Florida-friendly landscape practices is an efficient way to maximize environmental benefits with limited educational resources.
Deliver Targeted Education and Resources to Landscape Professionals and Golf Course Managers
Sarasota County has almost 6,000 acres of golf courses and athletic fields and a large number of professionally managed residential and commercial lawns and landscapes. Although training in Best Management Practices is required for golf course managers, athletic field managers, and lawn care professionals, compliance is not monitored. Improved outreach is needed to encourage fertilizer BMP adoption and assess nutrient reduction.
Deliver Targeted Education and Resources to Farmers and Ranchers
Sarasota County has a strong agricultural heritage founded on cattle ranching and now diversified into multiple commodities, including citrus, sod and ornamental plant nurseries. About 46% of Sarasota County’s registered and eligible farms voluntarily participate in agricultural Best Management Practices to reduce nutrient runoff and better manage water use. Additional incentives are needed to encourage more farms, including small crop, animal farms and hobbyists, to embrace sustainable practices.
Encourage and facilitate commercial composting and redistribution for rebuilding soils
State law mandates that Sarasota and other large counties recycle 75% of their waste stream. Composting of yard waste contributes to that goal, but food waste is not collected or composted at large-scale. Conflicting interpretations of food waste management within county codes should be resolved to facilitate recovery and recycling of organic waste as a source of clean energy, an alternative to synthetic fertilizers, and a small-business opportunity.