Can Slow-Release Fertilizer Save Our Seagrass?
Quick-release fertilizers have devastating long-term effects on terrestrial and marine environments. We know community members of Fishers Island want to limit their environmental impact, so today, we are looking into slow-release fertilizers and what makes them preferable to their fast-acting counterparts.
Quick-release fertilizers are water-soluble and are usually applied as a liquid to your lawn and garden. They give plants nitrogen in the chemical form required to immediately uptake and use the nutrient. However, these fertilizers are easy to over-apply, and this can lead to some long-term consequences [1].
Nitrous Oxide - specialized bacteria in the soil convert excess nitrogen into nitrous oxide and release the gas into the atmosphere. This has serious consequences for climate change as nitrous oxide has 300x the warming potential of carbon dioxide.
Soil Compaction - water-soluble fertilizers leave behind mineral salts that form compaction layers. Over the years, these compact layers will reduce root growth, create poor soil aeration and drainage, and leads to erosion and soil deterioration.
Soil Acidification - over-application of fertilizers will also contribute to a shift in the pH of your soil. Acidified soils will reduce the plant’s ability to uptake phosphate and inhibit growth. Sandy soils, such as the soil found on Fishers Island, are particularly susceptible to soil acidification.
Shift in the soil microbiome - the bacteria in the soil plays a key role in the fertility of the soil. As fertilizers add compaction layers and acidify the soil, the composition of the bacterial population in the soil will change. This will result in lower fertility as the soil environment becomes less hospitable to the natural soil microbiome.
Eutrophication - Fertilizer contains nutrients that leach into water bodies, fresh and marine. This leaching enriches the water bodies with nutrients, particularly nitrogen and phosphorous. While phosphorous content in fertilizers is strictly regulated in New York because of its consequences on freshwater systems, the law does not contain similar restrictions to protect marine systems from the nitrogen content in fertilizers. When nitrogen enriches marine ecosystems, it fuels phytoplankton activity that can create harmful algal blooms, fish kills, and low oxygen zones.
Slow-release fertilizers contain nutrients for plants just like the fast-acting kind but with one major difference: the nutrients in slow-release fertilizers are not available for immediate use. It takes time for the environment to make the nutrients available to the plants. There are two ways that slow-release fertilizers accomplish this:
Synthetic, sparingly water-soluble - This is a type of chemical, manufactured fertilizer that slowly dissolves and disperses its nutrients over many weeks [2].
Natural, organic - This fertilizer is plant/ animal manure and compost [3]. They contain plant nutrients but in forms that require microbial breakdowns and conversions before the plants can uptake and use them.
In both cases, the rate at which nutrients are released is based on temperature and moisture conditions in the soil. Higher temperatures can release nutrients much faster and could risk overfeeding the plants. This could lead to the same issues created by quick-release fertilizers listed above. Still, because these fertilizers are solid, they are good at maintaining their positions in the soil, so rain is less likely to leach them into water sources as fast-acting alternatives.
So are slow-acting fertilizers going to Save Our Seagrass?
They are certainly a step in the right direction.
Synthetic slow-release fertilizers can be useful in preventing nitrogen leaching and runoff, but we caution that these fertilizers can still be quite high in nitrogen content. Be sure to use care not to apply more than necessary, especially when seasonal conditions might make them release their nutrients faster than usual.
We recommend organic alternatives like composting to Fishers Island community members who are considering making the switch - they restore the natural microbiome and fertility of the soil and reduce the negative effects caused by soil compaction and acidification. Finally, they provide the lowest dose of nutrients to the plants while still positively impacting the lawns and gardens they are applied to.
Reducing nitrogen runoff from fertilizer use is an excellent first step to protecting our terrestrial and marine environments. Slow-release fertilizers, when applied sparingly, can help the Fishers Island community to Save Our Seagrass!
