Carbon Management in Northwest Agriculture

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The Northwest United States is a mosaic of different climates, soils and conditions that support diverse agriculture. In cooler, wetter areas west of the Cascade Mountains, farmers grow specialty crops like strawberries, raspberries, blackberries, and hazelnuts. In warmer, drier areas east of the Cascades, farmers grow dryland crops like wheat and irrigated crops like wine grapes, apples, and potatoes. Alaskan farmers grow cold-tolerant crops like hay, potatoes, carrots, and kale. In all of these systems, farm management affects the balance of carbon, orthe amount of carbon stored in soils and plants versus the amount of carbon released into the atmosphere. Management activities that increase carbon storage in soils and plants improve soil function and crop quality. Activities that release carbon from soils and plants into the atmosphere reduce soil function and crop quality while also producing greenhouse gases that warm the global climate.

The Natural Resources Conservation Service (NRCS) grows cover crop mixes at the NRCS Plant Materials Center in Corvallis, Oregon. Cover crops like these increase carbon storage by providing living soil cover between growing seasons. Photo by Oregon NRCS.

Climate change and carbon

Changes in the climate itself can also affect the balance of carbon among soil, plants, and the atmosphere on Northwest farms. Climate models project that Northwest temperatures and precipitation regimes will change significantly during the coming century. Idaho, Oregon, and Washington are expected to experience higher temperatures and more extreme heat events. Models project slightly more winter precipitation, less summer precipitation, and more extreme precipitation events across Idaho, Oregon, and Washington. Alaska is projected to experience greater increases in temperature than the contiguous U.S. and increases in precipitation. 

Climate change has affected, and will continue to affect, carbon storage in Northwest farms. More winter precipitation may cause either carbon loss or carbon storage. Saturated soils release more carbon dioxide and methane during decomposition than dry soils. But soils that are moist and well-drained support more crop production, increasing carbon storage in plants. Increasing temperatures may reduce carbon storage in Northwest agriculture. Warmer air will allow atmospheric rivers to carry more moisture, causing intense periods of rain that will reduce carbon storage in plants by reducing crop productivity. During summer months, extreme heat and drought could decrease carbon storage through reduced crop growth and wildfire. Warmer soils release more carbon dioxide through decomposition, and dry conditions increase the risk of fire. 

Alaskan farms may also experience a net loss of soil carbon due to climate change. Though climate warming is expected to lengthen Alaska’s growing season, it will also thaw the permafrost soils that underlay a growing percentage of Alaskan farms and release a significant amount of carbon into the atmosphere. Producers are implementing management activities that will enhance crop resilience to projected extreme weather events and mitigate future climate change by reducing carbon loss.

Agricultural management practices to increase carbon storage

Many farm management activities promote carbon storage in the soil. Some activities increase carbon storage directly, such as adding organic material to soil or growing carbon-rich plants. Other activities maintain carbon storage by limiting carbon loss to the atmosphere (i.e., emissions). Here are some of the activities that can increase carbon storage on Northwest farms:  

Farmers Kenneth and Sheri Jensen use a variety of practices that enhance soil carbon storage on their farm in Jamieson, Oregon, including crop residues. Photo by Oregon NRCS.

• Cover crops – Plants sown between growing seasons or during fallow years increase soil carbon, increase soil nutrients, and reduce soil erosion.

• Soil amendments – Adding compost, biochar, fish waste, seaweed, or other organic material increases soil carbon. This practice can also reduce soil erosion, increase soil moisture, reduce soil temperature, and add nutrients.

• Crop residues – Plant materials left on the soil surface after harvest build soil carbon. Residues provide benefits similar to those of soil amendments.

• Agroforestry – Agroforestry is the incorporation of trees and shrubs on farms. Practices like silvopasture, alley cropping, and forest farming increase carbon in soil and plants, as woody plants contain a significant amount of carbon.

• Perennial plants – Adding perennial plants (trees, shrubs, grasses, or forbs) in crop fields or on field edges can increase carbon storage, as perennials sequester more carbon than annual plants.

• Reduced burning – Crop residue burning is often used to increase seed germination and reduce weeds. Yet, fire releases carbon into the atmosphere as carbon dioxide. Replacing burning with other weed control practices that add that material to the soil can build soil carbon.

• Reduced or no tillage – Tillage breaks apart soil and favors the decomposition of organic matter, releasing carbon dioxide into the atmosphere. Reducing or stopping tillage can increase soil carbon by keeping organic matter protected in soil aggregates. Reduced tillage can also increase soil water infiltration and soil nutrients.

• Increased biodiversity – In many cases, adding diverse plants and animals to the landscape can increase soil carbon, or make other practices more effective for carbon storage. For example, rotating grain or grass crops with non-grass crops reduces the effects of weeds and diseases under no-till, leading to increased carbon storage in plants.

Co-benefits of increased carbon storage

Many management activities that increase carbon storage in soils also advance other farm goals. Ecologically, carbon-building practices can increase crop resilience to extreme weather events, improve water quality, and/or increase biodiversity. These practices can also incur financial benefits for producers, like higher or more stable crop yields, and reduced equipment, energy, fertilizer, and pesticide costs. For example, soil amendments like compost increase carbon in soil. Compost also provides key nutrients for plants and keeps soils moist and cool. These combined effects can lead to greater crop yields and profitability. 

Agricultural management activities determine the fate of carbon at the multiple scales. At the local scale, management practices alter the amount of carbon assimilated into soils and growing crops. And at the global scale, management decisions determine the amount of carbon released into the atmosphere as greenhouse gases. There is no one-size-fits-all method for managing carbon in the diverse cropping systems of the Northwest. Each farm requires individualized management that considers the land’s unique opportunities, challenges, and projected climate change impacts. The management activities described here are a starting point, outlining strategies to keep Northwest farms productive and resilient in a changing climate. 

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