Mulching (NRCS #484)

Applicable Systems

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About

Mulching¹ is the practice of applying plant residues or other natural or synthetic materials to bare, exposed soil surfaces. In most cases, mulch consists of grain straw residue, but common natural mulch materials also include wood chips, leaves, straw residue, compost, and wool. Mulching is considered a best management practice (BMP) for soil and water quality protection.

Key aspects and considerations:

Apply mulch material evenly at a minimum of 70% ground cover.
Use adequate methods for anchoring mulch, especially in steep areas.
Use irrigation to help bind mulch and establish vegetative cover before fall rains.
Avoid excessively thick, tightly packed, and low permeable mulches.
In concentrated flow areas, apply mulch with higher C:N ratio to avoid negative water quality impacts.
Use organic mulch (6-8 Mg ha⁻¹) to regulate soil and water loss².

Benefits and Limitations

ACRE Category	Benefits	Limitations
Soil Health	Protects soil surface and reduces soil loss by water and wind erosion. Improves soil structure by reducing compaction due to impact of traffic and increased soil organic matter. Moderates soil temperature. Conserves soil moisture by reducing evaporation. Improves soil quality and health.	Excessive mulch can delay soil warming in spring.
Water Management	Reduces runoff and increases infiltration. Promotes more available water to plants. Improves water use efficiency. Decreases irrigation water needs.	May increase concentrated flow and erosion on the non-mulched areas when low-permeable material is used.
Nutrient Management	Reduces nutrient losses associated with soil erosion. Organic mulches gradually release nutrients during decomposition. Improves nutrient cycling.	High-carbon mulches temporarily immobilize nitrogen during decomposition.
Agricultural Production	Protects crops from extreme temperatures. Improves seedling establishment and survival. Can improve crop productivity and health, especially in dry regions. Improves weed suppression.	Thick mulch layers may interfere with plant emergence. Some mulch materials may introduce weed seeds or contaminants, as well as provide habitat for rodents, slugs or other pests. Diseases and pest problems to the main culture may happen when low-permeable material is used.
Biodiversity and Wildlife	Mulch buffers soil habitat from temperature changes. Supports biodiversity by creating microhabitats and providing food and cover for wildlife and soil organisms.	Synthetic mulches provide fewer ecological benefits than organic mulches. May favor pest populations.
GHG Emission	Reduces CO₂ emissions by lowering soil disturbance, microbial respiration and organic matter oxidation. Maintains or increases soil organic matter, increases C sequestration and improves long-term soil carbon stocks. Reduces energy use by reducing the need for irrigation and improving water use efficiency.	Mulch production, transport and application generate GHG emissions. Organic mulches rich in N can increase N₂O emissions, especially in wet soils. In flooded systems, mulching can increase CH₄ emissions by promoting anaerobic decomposition. Plastic mulches are agronomically efficient, but have environmental trade-offs.
Economics	May qualify for conservation cost-share programs. Costs can be offset by benefits such as weed management and associated labor costs, reduced irrigation costs, along with cleaner marketable production. Can reduce long-term costs associated with erosion damage.	Mulch can be expensive and hard to obtain in large amounts. Significant costs associated with labor for seedbed preparation and mulch application. Installation and monitoring are time-consuming.

Impact on Agricultural Resilience

By regulating soil temperature, mulching protects roots from extreme temperature fluctuations and enhances plant resilience.
Reduces evapotranspiration and increases plant resilience during dry periods.

Regional Applicability

Mulching can be applied to a range of cropping systems, including those in the Midwest, including small farms and gardens.
Mulch can be especially important in the central Midwest, where soil and crops are prone to freeze-thaw cycles. Additionally, mulch can help protect crops from cold stress, which is especially important for Christmas tree farms and other perennial crops grown in the Upper Midwest, which must survive winter temperatures.

Case Studies

Get to know Janaki and his wife Annie Dugan, who operate a certified organic fruits and vegetables farm in Wrenshall, MN. They work in a winter rye cut-and-carry mulch system for several crops. "The better we can treat the soil, the healthier it is, the better crops do, the more resilient they are. Whatever I can do to reduce tillage operations, especially when it's too wet or too cold here, that's a good thing. It makes our lives easier," Janaki said.
Tom Rogers and his brother from Rogers Farm, an almond farm near Madera, CA, began applying compost and mulching his orchard prunings in 2009. Since then, he has seen a 10% increase in yield annually. Tom reflects on the decision to implement soil health practices: "Take care of the soil and it will take care of the trees."

Resources

Video. USDA-NRCS: Mulching
Video. University of Nebraska Extension, Backyard Farmer: Mulch Types & Usage
Washington State University, Small Fruit Horticulture Research and Extension Program: Mulch Matters Podcast
Sustainable Agriculture Research and Education (SARE): Towards Resilient and Sustainable Grape Production in the North Central Region with Renewable Mulching Systems
University of Wisconsin-Madison, Wisconsin Horticulture Division and Extension: Mulches for Home Gardens and Plantings
Iowa State University Extension, Sustainable Urban Landscapes: Using Mulches in Managed Landscapes
Iowa State University Extension and Outreach: Organic Mulches
Michigan State University, MSU Extension: Organic Mulching for Weed Control and Mitigating Cold Stress in Christmas Tree Production

References

USDA-NRCS (2017). Conservation Practice Standard Document, Mulching, Code 484. https://www.nrcs.usda.gov/sites/default/files/2022-09/Mulching_CPS_484_Oct_2017.pdf
Li, R., Li, Q., & Pan, L. (2020). Review of organic mulching effects on soil and water loss. Archives of Agronomy and Soil Science, 67(1), 136-151. https://doi.org/10.1080/03650340.2020.1718111
Kohnke, H., & Werkhoven, C. H. (1963). Soil temperature and soil freezing as affected by an organic mulch. Soil Science Society of America Journal, 27(1), 13-17. https://doi.org/10.2136/sssaj1963.03615995002700010010x
USDA-NRCS (2017). Conservation Practice Standard Overview, Mulching (Code 484). https://www.nrcs.usda.gov/sites/default/files/2022-09/Mulching_484_Overview_Oct_2017.pdf

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Mulching photo 1 — Photo 1: Mulch is applied to avocado trees in Somis, CA to reduce weeds and save water.

USDA photo by Lance Cheung.

Mulching photo 2 — Photo 2: Aerial view of lemon and avocado trees after applying mulch in Somis, CA.

USDA photo by Lance Cheung.