By Tyler A. Groh
What does soil health have to do with water quality?
Cover crops and perennial vegetation help protect soil from erosion, increase soil water infiltration, and decrease sediment and nutrient contributions to surface water bodies.
Soil, we all walk on it, but what is it? Commonly, soil is defined as a living (always changing) mixture of organic and mineral solid material, gases, and water. The ideal soil composition is 50% solids (organic and mineral) and 50% pore space that is filled with both gases and water. Soil is a medium in which life is sustained through plant growth, the recycling of matter and nutrients, and the purification and cycling of water. Soil can act as a sponge to purify water, and thus plays a role in water quality. However, soil is fragile and improper management can throw the ideal soil composition out of balance. This may happen over time in some agricultural fields, leading to a loss of nutrients and sediment. Thankfully, farmers are natural stewards of the land, and can implement conservation practices that shift soil composition back into an ideal proportion, making the soil healthy.
Soil health is difficult to measure and describe, but attributes of a healthy soil include increased organic matter addition and accumulation, enhanced nutrient cycling with fewer nutrient losses from soil, increased soil microbial community function, formation of soil aggregates (larger pieces of soil) and large soil pores, and a decrease in compaction. These attributes are enhanced by some agricultural conservation practices including conservation tillage (reduced tillage or no-till), reducing soil compaction by minimizing passes over a field, extending rotations by growing a variety of crops, planting cover crops between growing seasons, and growing perennial vegetation. While sometimes difficult to implement, a combination of these conservation practices can help increase a soil’s health.
So, what does soil health have to do with water quality? Well, when a soil is healthy, it is better able to act as a sponge, and absorb more water from precipitation events. Roots from cover crops and perennial plants, the absence of turning over topsoil with annual tillage, and the reduction of compaction all increases water infiltration into a soil by creating and protecting a network of soil pores. The greater the amount of water infiltrating into the soil, the less water available to run off a field. This translates to less sediment and nutrient export to stream(s). Infiltrated water can instead be used by plants in the field to grow or to recharge shallow groundwater. In larger precipitation events where soils cannot infiltrate all available water, cover crop roots anchor soil particles in place, preventing erosion when excess water runs off the field. Additionally, cover crops and perennial vegetation can take up nutrients in the field while they grow, reducing the total amount of nutrients exported to surface water bodies and increasing the amount of carbon (organic material) in a soil. Greater soil carbon then enhances nutrient cycling and removal within the soil by microbial processes and increases a soil’s fertility. One example of the use of perennials in fields is through the installation of riparian buffers, which remove sediment and nutrients from agricultural water before entering a stream. Riparian buffers, in combination with the other conservation practices discussed here, show great promise for increasing water quality by protecting soil health.
Soil, we all walk on it, but let us not treat it like dirt. A healthy soil is what we need to help keep our water clean and our tables full of food. Whether you live on a city lot or farm hundreds of acres, helping keep soil covered by growing vegetation all year long can make a soil healthier. Soil is one of our most precious resources, and it has a vital role in our water cycle. We all have a part to play in enhancing soil health and water quality.
Source : psu.edu