Fertilizers containing nitrogen and phosphorous may not be applied on turfgrass or landscape plants from June 1-Sept. 30 in Hillsborough County

From June 1 through Sept. 30, it is against the law to use fertilizer that contains nitrogen and/or phosphorus. Hillsborough County's rules on the use of fertilizers containing these nutrients are intended to protect and preserve the cleanliness of local streams, rivers, lakes, and bays. Protecting the county's water reduces the chances of severe algae blooms, such as red tide, from forming. This, in turn, benefits the health of the area's wildlife and residents.

Nitrogen and phosphorous-based fertilizer and red tide

The issues caused by nitrogen and phosphorus-based fertilizers may worsen during summer months when West-Central Florida receives much of its rainfall. It's during this season that deluges of fertilizer-rich water can enter the county's waterways through stormwater and irrigation runoff. This is especially problematic where there are no shoreline plants to consume nutrients.

Excessive algae growth, sometimes in the form of red tide, can occur when certain types of fertilizer mixes with bodies of water. The resulting algae blooms in the water can block sunlight needed for seagrass and other desirable aquatic plants to grow. When aquatic plant growth is reduced, oxygen levels decrease. Lower oxygen levels as well as toxins contained in some algae can cause fish kills.

Large and out-of-control algae blooms can also be harmful to other aquatic animals, including manatees and dolphins. For instance, the neurotoxin produced by red tide can cause manatees to have seizure-like symptoms when inhaled. In severe cases, the animals drown as a result. Furthermore, red tide can induce coughing and sneezing in dolphins, which is similar to the irritation it causes in humans.