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From Garden to Watershed: How Compost Makes a Difference

Updated: Apr 14, 2023

World Water Day is an annual event that raises awareness about the importance of water conservation and water quality. As gardeners and compost enthusiasts, we can play a role in protecting our local watershed by using compost in our gardens and across our landscapes.

Compost not only helps with water conservation and water quality, making it a valuable tool for sustainable gardening, but it also just is a great way to grow a better, healthier garden! This is a win-win for our gardens and our local streams, rivers, ponds, and Chesapeake Bay!

Bridge over a clean stream in nature
Compost can help improve local water quality and reduce how much water we need in our gardens.

I like thinking about how compost impacts water in two ways. First, compost helps with water conservation—I water less frequently and use less water when I do need to water my plants. I love saving money on my water bill and have more time for other things in my garden. Second, compost can improve water quality by making it cleaner. I think this one is really fascinating.

I’m going to focus on the compost benefits specifically for water. However, there are a lot of reasons to use compost as described on our compost information page!

Compost reduces overall water usage, watering frequency, and erosion

Compost is a mixture of organic materials such as leaves, grass clippings, and food scraps that have been broken down by microorganisms—nature’s ways of recycling organics.

When compost is added to soil, it can help retain moisture by increasing the soil's water-holding capacity. Because compost is highly porous, it can absorb and retain water more effectively than bare soil. Some estimates are that compost can hold 20x its weight in water! It holds on to this moisture and then makes it available to my plants’ roots as the plant needs it. Thus, I don’t have to water as frequently.

Compost also helps improve the soil structure. For water, the organic matter in compost creates pore spaces in the soil that allow water to flow down through the soil. This makes it easier for water to enter my garden soil; less water runs along the surface of the soil and away from my plants. By entering my garden soil quickly, where compost grabs and holds on to the water, I spend less time watering and can use less water during each watering session.

Relatedly, compost can also help reduce erosion and runoff. Healthy garden soil will absorb the water that it needs and allow the rest of the water to go down. Unhealthy soil has the water run along the top, stripping away the top of the soil--an important layer of garden soil for nutrients, plant root growth, and root protection. When soil runs off our gardens, this can lead to sedimentation and other problems in our local water bodies.

There is a circular impact to this too. Using compost in my garden makes my plants healthier. Healthier plants are more resilient to drought conditions—like the high heat we get with our Northern Virginia summers! This further reduces the need for watering our gardens.

One study in the journal HortScience found that plants grown in soil amended with compost required up to 30% less irrigation water compared to plants grown in unamended soil! (Here is more information about what is a soil amendment or soil conditioner). Another study in the Journal of Soil and Water Conservation found that using compost as a soil amendment reduced water use by 30-50% and resulted in cost savings (of up to $6,000 per acre per year) in reduced water bills.

By reducing the amount of water needed for irrigation, compost helps me save time (less frequent watering) and money (less water = lower water bill!).

Compost improves water quality

Compost can also play a role in improving water quality by filtering out pollutants and contaminants.

Compost contains a diverse population of microorganisms, including bacteria, fungi, and other beneficial microbes that can help to break down and remove contaminants from water. When water is passed through a layer of compost, the microbes in the compost can help to remove pollutants through a process known as bioremediation.

Studies have shown that compost can be effective in removing a wide range of pollutants from water, including heavy metals, nutrients, organic compounds, and pathogens. For example, a study published in the Journal of Environmental Science and Health found that using compost as a filter media in a constructed wetland system was effective in removing up to 95% of contaminants from wastewater.

For example, excess nutrients such as nitrogen and phosphorus can lead to harmful algal blooms and other problems in water bodies. Compost can absorb and retain these nutrients in the soil, reducing their runoff into water bodies and making them available for plant roots. This can help prevent or mitigate water pollution and eutrophication and grow better, healthier plants!

Compost can also help break down and remove organic compounds such as pesticides and herbicides. These chemicals can be harmful to aquatic life and can persist in the environment for long periods of time. Compost can break down these chemicals into less harmful forms, reducing their impact on the environment.

In addition to removing pollutants from water, compost can also help to improve water quality by adding beneficial nutrients and organic matter to the water. When added to water bodies such as ponds or lakes, compost can help to stimulate the growth of beneficial microorganisms and aquatic plants, which can help to improve water quality and support healthy aquatic ecosystems.

Well-made compost is great for water conservation and quality, but not all compost is good for water—it must be a quality compost. If the compost is made from contaminated materials, it could contain harmful substances that leach into groundwater or surface water. It is important to use only high-quality, uncontaminated compost—here are some tips for finding a quality compost!

Indeed, compost can be an effective tool for water purification and can help to improve the quality of water resources.

Overall, compost is a powerful tool for water conservation and water quality in gardening and landscaping. By improving the soil's water-holding capacity and reducing the need for irrigation, compost can help conserve water resources and save money on water bills. By removing pollutants from water and wastewater, compost can help protect water resources and improve the health of aquatic ecosystems.

As gardeners and compost enthusiasts, we can play a role in protecting water resources and promoting sustainable gardening practices. By using bulk and bagged compost our gardens, we can help conserve water and protect the environment for future generations.


About Freestate Farms' Compost & Mulch Facility

Freestate Farms makes premium landscaping products—compost, topsoil, and mulch—by recycling food and yard waste in Manassas, VA. Our composts, topsoil, and mulches are specially designed to increase the health and productivity of local soils, and with our focus on sustainable practices, this lets the environment and your garden Grow Good, together. We sell bulk compost, bagged compost, bulk natural mulches, bulk dyed mulches, bagged dyed mulches, and bulk topsoil.


Compost for sale

Browse our landscaping products: compost, topsoil, and mulch.

Food waste for composting

Learn about composting food and yard waste at Freestate Farms.

Compostable items ->

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US Composting Council Member
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