SOUTH PORTLAND — The South Portland City Council approved a new ban on synthetic fertilizers citywide last week, mirroring similar language already spelled out regarding use of pesticides.

Sustainability Director Julie Rosenbach said this week that the new ban, effective Dec. 7, will “move the city toward organic land care practices.”

The City Council Nov. 17 approved the ban as a new section of the city’s pesticide ordinance. The new changes, Rosenbach said, limit the application of any fertilizer to no more than twice a year, and even then the fertilizer must be “organic,” or free from synthetic chemicals. The changes apply to residential and commercial use, but users can apply for a waiver if they are putting in a new lawn or using performance turf, such as on athletic fields, she said.

Rosenbach said most commercial organic fertilizers are labeled as such on the bag, making it easy for residents to know which kind of fertilizer they are using.

Violators, after a first warning, will be punished with fines up to $1,000.

Rosenbach acknowledged that enforcement might be difficult in some cases, but for new construction, and residents going through the planning and permitting process, the new ordinance will be easier to apply.

“Honestly, we don’t know what enforcement would look like because this is a brand-new ordinance,” she said.

But, she added, the ordinance is still useful as an educational tool to help drive awareness of the need for more environmentally-friendly lawn care.

“Education that’s backed up by an ordinance really has an impact,” she said.

Fred Dillon, the city’s stormwater program coordinator, said this week that he recommended the ban based on data nationwide suggesting a growing problem with non-organic chemical pesticides and fertilizers.

According to a study published in August by the National Science Foundation in the journal Nature Geoscience, pesticides and fertilizers are now the leading contributors of sulfur to the environment. The study indicates the last time sulfur levels this high were recorded was in the second half of the 20th century, when sulfur was linked to acid rain.

“Sulfur is a naturally occurring element and an important plant nutrient, helping with the uptake of nitrogen,” the foundation wrote on its website. “But sulfur is also highly reactive, meaning it will quickly undergo chemical transformations once its stable form surfaces — affecting the health of ecosystems, and reacting to form heavy metals that pose a danger to wildlife and people.”

Dillon noted there is very little data analyzing the relationship between fertilizer and water quality in South Portland, saying, “We don’t have that much of it, because it’s expensive to collect.”

Nevertheless, Rosenbach said studies dating back to the 1990s from other parts of the country, including Massachusetts, New Hampshire, Connecticut, Vermont, Rhode Island and New York, indicated pesticides and lawn care chemicals were found in enough water samples to suggest similar contamination was happening locally, which could lead to chemicals and elements such as nitrogen leaking into Casco Bay.

“We used the precautionary principle to move forward,” she said.

The ban also mandates users test their soil first before applying fertilizer. Test kits are available at City Hall for free, though there is a $25 fee for processing from the University of Maine’s Cooperative Extension.

Kenny Roberts, a manager at CKC Landscaping in South Portland, said the new ban might make it harder on some companies like his. Organic fertilizer, he said, is more expensive, and is not as effective as synthetics.

“Basically you have to put down three times as much,” he said.

Roberts said he doesn’t use a lot of fertilizer in his day-to-day work, but the ordinance could have an impact on other companies that specialize in new lawns, which require heavier fertilization. Even with the waiver clause, Roberts said, the process is sure to take time.

“It’s going to slow the process up huge,” he said.