Anyone who follows CompostableLA knows that we love to emphasize how reducing food waste and regenerating soil are two of the best ways to help reverse climate change. As soil life plays a major role in many natural processes, water is a vital component of that system. Even though we often treat soil health and water security as separate conservation issues, they are actually interconnected.
The soil, particularly its surface zone, plays a fundamental role in the Earth’s hydrological cycle. The topsoil is where the interaction with rainfall, irrigation, or snow takes place, as well as where the processes of infiltration, runoff, evaporation, transpiration, and groundwater recharge are initiated and sustained. Taking care of our soils means taking care of our water, and for this reason, we want to point out two major benefits that soils high in organic matter have on source water protection:
Healthy soils capture and store much more water
Think of a rainfall that has just come through; water typically penetrates the surface and is absorbed into the deeper layers, making its way through the spaces between the particles in the ground. In healthy soils, earthworms create channels and large pores that are critical for water and air movement. On top of that, bacteria, fungi, and other microbes help build and stabilize the soil structure to further increase the land’s water storage capacity. Just like a sponge, soils with high organic matter and a stable system of pores have greater water entry at the surface, allowing it to easily infiltrate into the ground, and store as much as possible for future plant use - reducing runoff and erosion while increasing the drought resistance of crops.
Degraded soils, however, make it very hard for water to seep through, becoming almost impermeable. Unsustainable agricultural techniques, such as monocropping, the use of synthetic fertilizers, pesticides, and excessive plowing and tillage deplete the soil of microorganism diversity and structure integrity, causing significant compaction and erosion. Once that “sponge” is lost, so is the soil’s ability to capture and store water. When rains come, water will accumulating in puddles on top of the harden land, where it quickly evaporate back into the atmosphere, or it runs off the surface, leading to downstream flash flooding and erosion.
Though technically renewable, soil is considered a limited natural resource because it can take so many years to recover if it was severely eroded or contaminated. The good news is that we can speed up the healing process of degraded soils through regenerative practices, such as applying compost, reducing tillage, growing cover crops, and diversifying rotations. When farmers practice indigenous agricultural techniques that raise their soil’s organic matter content, they also improve their land’s water storage capacity. According to the Natural Resources Defense Council, “Each 1% increase in soil organic matter helps soil hold 20,000 gallons more water per acre.” When the soil’s biology is functioning smoothly, water use is reduced, while plant growth is increased.
Soil is the Earth's largest natural water filter
A clean water supply is a crucial part of any healthy community, and soil is a great purifier. Did you know that healthy soil, rich in carbon, greatly reduces sediment and nutrient pollution in our water?
When water enters the soil, it often contains a variety of elements that must be removed to minimize negative environmental impacts and to be reused by our society. Some of these common sources of water pollution are soil erosion and the runoff of fertilizers and pesticides. Luckily, healthy soils can be a match to some of these pollutants and are capable of filtering them out. This is achieved through a combination of physical, chemical, or biological processes that remove or degrade the various contaminants. As water seeps deeper into the ground, the soil acts as a multi-layer sieve, blocking particles that are too large to pass through and holding onto pollutants that can be broken down by the microorganisms. Reduced pollution, as well as erosion, and hence fewer sediment particles in suspension, lead to lower costs for water treatment and cleaner aquifers.
Since water and soil are increasingly becoming the most limited natural resources supporting our communities and agriculture, increasing soil organic matter content is key to improving soil health. By advocating for the use of compost, we are calling for the restoration of indigenous practices to restore our soil’s carbon and water carry capacity, both so fundamental to our ecosystem.
Written by: Andreea Botea