Perspectives

Practical insights and opinions from agriculture and natural resources experts—brought to you by the Center for Sustaining Agriculture and Natural Resources.

Cash Crops, and their Residues, Are the Best Cover Crops

June 2, 2025

By Andrew McGuire, CSANR Senior Extension Fellow

Think about this. If a cash crop provides all the benefits of a cover crop and generates a profit, should we consider it a cover crop? The National Association of Wheat Growers thinks so. They are petitioning the Natural Resources Conservation Service (NRCS) to issue a technical note recognizing winter wheat as a cover crop, even when harvested. Their argument is that winter wheat, when managed well, matches or exceeds the benefits of traditional cover crops in controlling erosion, scavenging nutrients, disrupting pest cycles, and improving soil health( Simão et al., 2024). The wheat growers have a point.

We distinguish between soil-building cover crops and profitable cash crops, but many cash crops, particularly high-residue grains like wheat (Figure 1), corn, and rice, outperform conventional cover crops in key services. They can exceed cover crops because they are grown under better conditions, with better seed, inputs, and management; all advantages of being a cash crop.

We emphasized that if you look at what the USDA classifies as a cover crop, winter wheat checks every single box.

Andy Juris

What Does a Cover Crop Do?

Cover crops are grown to:

• Protect the soil surface from raindrop impact and prevent associated surface sealing and crusting
• Reduce erosion
• Scavenge nutrients
• Suppress weeds
• Build soils by:
  • Feeding soil organisms
  • Adding organic matter
  • Creating root pores
  • Breaking up compacted layers
• Provide habitat for beneficial organisms
• Break up pest cycles

These benefits are largely linked to biomass production (Wagg et al., 2021). The more biomass a crop produces, the more services it can provide. And biomass is where cash crops excel.

Cash Crops Produce Big Biomass

Because farmers grow cash crops for profit, they are intensively managed: extensively bred varieties, high-quality seed, ideal planting dates, optimal fertility, and pest and weed control. This translates to more biomass production. Even when the crop is the same—say, winter wheat—the version grown for grain will outproduce the version planted as a cover crop. This applies in every season. Compared to summer cover crops, cash crop corn or rice yield more biomass above and below ground. More biomass means more potential for soil protection, nutrient cycling, and carbon inputs, both during growth and after harvest.

Crop Residues: Unrecognized Cover Crops

While living plants are important, residues from high-residue grain crops often exceed the biomass of many cover crops. Estimated aboveground residue biomass remaining after harvest of dryland and irrigated corn yields of 175 and 250 bu/ac are 4.2 and 6.2 tons/acre (9.4 and 13.9 Mg/ha). After dryland and irrigated wheat yields of 80 and 150 bu/ac, 2.1 and 3.9 tons/acre of residues remain (4.7-8.7 Mg/ha). Compare this to the typical winter cover crop biomass of 1-3 tons/acre, up to 4 tons/acre with early fall planting and late spring termination. As Smil (1999) observed, “Considering the biomass produced, crop residues are agriculture’s largest crop.” And because of this substantial biomass, crop residues from high residue crops provide many of the same benefits as cover crops, especially if managed well (Simao et al., 2024).

As with cover crops, the benefits from residues depend on biomass levels (Figure 2).

Even the fact that residues are dead has some advantages. In contrast to living cover crops, crop residues don’t use water, a crucial advantage in arid dryland systems where water conservation is often the top priority. And if there is enough residue cover, it actually conserves water by reducing evaporation (Ranaivoson et al., 2017).

Finally, like cover crops, dead crop residues are a source of material for building soil organic matter (Figure 3). Crop residues are thought to be a major source of the dissolved organic matter that feeds soil organisms in the soil (Chantigny, 2003; Haynes, 2005; Schomberg et al., 1994).

Dissolved organic matter represents a mobile source of energy in soils.

Haynes, 2005

All this means that residue management is very important.

Effective Residue Management Enhances the Positive Impacts of Crop Residues

Historically, the focus was on removing or disposing of “trash” to allow for planting or weed control. Today, however, crop residues should be seen as vital resources for sustaining productivity. Managed with intention, these materials are more valuable than many traditional cover crops. Conservation agriculture recognizes this shift in perspective, making “keep the soil covered” one of its three core principles. This goal is both practical and effective, especially in contrast to the regenerative agriculture slogan of “keep living roots in the soil,” which can be difficult to achieve in many situations.

Clearly, crop residues should be treated as a valuable renewable resource to be managed carefully to maintain soil quality and promote crop productivity

Smil (1999)

Management-Intensive Cropping Systems

Biomass production is the foundation of the benefits provided by both cash and cover crops. It represents the energy captured through photosynthesis that fuels not only the agroecosystem but, ultimately, us as well. Therefore, within the limits of climate, management, and market conditions, this means aiming to fill the growing season with productive cash crops. Techniques such as double cropping, relay cropping, and making cover crops into cash crops can extend the growing season, maintain continuous soil/residue cover, and support soil health while also generating income.

Double Crops

Double cropping, the practice of growing two crops in a single year, is becoming increasingly viable because of climate change and lengthening growing seasons. No-till planting and crop residue management make possible a quicker turnaround between crops. These systems can take full advantage of extended windows for planting and harvest. Tools like climate analogs can help identify new opportunities where longer seasons and shifting weather patterns make additional cropping feasible.

To succeed, farmers may need to choose shorter-season crop varieties or change planting techniques, for example, strip-tilling into an alfalfa stand (Figure 4). Although each individual crop in a double-crop system may not reach its full yield potential, the combined output can exceed that of a single crop. This is beneficial in regions where rainfall exceeds the water demands of one crop alone. Effective examples being used here in Washington’s Columbia Basin include green pea-sweet corn sequences, Timothy hay followed by dry beans, or wheat followed by buckwheat. Continuous cropping reduces concerns about low residue as soil cover is regularly replenished by the next crop.

Relay Crops

Relay cropping is a system in which a second crop is planted into an existing crop before it is harvested. This intentional overlap extends the productive use of the growing season and maintains continuous ground cover, which contributes to improved soil health, reduced erosion, and more efficient use of rainfall and sunlight. Unlike intercropping, which requires crops to share space, relay cropping staggers crop demands over time, reducing direct competition for critical resources like light, water, and nutrients.

The success of a relay system hinges on two key factors: timing and crop compatibility. Planting and harvesting must be synchronized to minimize interference and maximize growth for both crops. Selecting crops that can tolerate each other’s presence without significant yield loss is essential. One notable example is the wheat-soybean system as developed by Jason Mauck (on X) and others. Soybeans are planted into standing wheat, a practice that captures more light and moisture while maintaining soil cover throughout the season. These systems only work where there is enough precipitation or irrigation for profitable yields of both crops.

Making Cover Crops Into Cash Crops

Finally, the most productive path forward may not be choosing between cash crops and cover crops, but rethinking how the two can be one and the same. The basic trade-off here is between cash crop yield and cover crop biomass, both depending on how much prime growing season each crop gets. When a crop turns a profit, it earns the management attention, inputs, and careful timing that cash crops receive. This shift—treating cover crops as cash crops—can enhance their value and effectiveness. Grazing a cover crop is one straightforward example. A more advanced case is pennycress, a once-overlooked species now being developed into a winter annual cash crop with market potential. With that transformation comes better management, better seed, and better outcomes for both soil and income.

Cash Crops for Profits and Stewardship

It appears that anything a cover crop can do, a cash crop and its residues can do better, and more profitably. Ultimately, the question is not just “Which cover crop should I plant?” but rather “How can I manage my cropping system, residues and all, to do more?” With the right approach, high-residue grain crops, diversified crop sequences, and managed residues can meet or exceed the ecological benefits of traditional cover crops while also sustaining the business of farming.

All Perspectives from Andrew McGuire

References

Chantigny, M.H. 2003. Dissolved and water-extractable organic matter in soils: a review on the influence of land use and management practices. Geoderma 113(3): 357–380. doi: 10.1016/S0016-7061(02)00370-1.

Haynes, R.J. 2005. Labile Organic Matter Fractions as Central Components of the Quality of Agricultural Soils: An Overview. Advances in Agronomy. Academic Press. p. 221–268.

Ranaivoson, L., K. Naudin, A. Ripoche, F. Affholder, L. Rabeharisoa, et al. 2017. Agro-ecological functions of crop residues under conservation agriculture. A review. Agron. Sustain. Dev. 37(4): 26. doi: 10.1007/s13593-017-0432-z.

Schomberg, H.H., J.L. Steiner, and P.W. Unger. 1994. Decomposition and Nitrogen Dynamics of Crop Residues: Residue Quality and Water Effects. Soil Science Society of America Journal 58(2): 372–381. doi: 10.2136/sssaj1994.03615995005800020019x.

Simão, L.M., G. Cruppe, J.P. Michaud, W.F. Schillinger, D.R. Diaz, et al. 2024. Beyond grain: Agronomic, ecological, and economic benefits of diversifying crop rotations with wheat. Advances in agronomy 186: 51–112.

Smil, V. 1999. Crop Residues: Agriculture’s Largest Harvest: Crop residues incorporate more than half of the world’s agricultural phytomass. BioScience 49(4): 299–308. doi: 10.2307/1313613.

Stella, T., I. Mouratiadou, T. Gaiser, M. Berg-Mohnicke, E. Wallor, et al. 2019. Estimating the contribution of crop residues to soil organic carbon conservation. Environ. Res. Lett. 14(9): 094008. doi: 10.1088/1748-9326/ab395c.

Wagg, C., A. van Erk, E. Fava, L.-P. Comeau, T.F. Mitterboeck, et al. 2021. Full-Season Cover Crops and Their Traits That Promote Agroecosystem Services. Agriculture 11(9): 830. doi: 10.3390/agriculture11090830.