Farm-Tuning Cover Crop Mixtures

What is the issue?

Here we used a long-term cover cropping experiment at Penn State to examine the soil and climate conditions that impact cover crop composition in mixtures. We evaluated how species composition and seed mix rates impact establishment of winter cover crops as well as their fall and spring growth. Cover crop responses to variation in environmental conditions were modeled to assist with prediction of mixture and monoculture performance. While cover crops are increasing in popularity, they are often planted in monocultures or 2-species mixtures. Our goal was to evaluate a variety of monocultures and multi-species mixtures to attempt to understand the effects of increasing species number and functional group on mixture growth. We also hope to demonstrate the differences between performance of monocultures and multi-species mixtures in providing a variety of ecosystem services.

What did we find and why does it matter? 

Farm Tuning? Changing species and rates in mixtures impacts cover crop stand composition, as well as fall and spring biomass.

• The seeding composition of mixtures matters, but mixture presentation is also impacted by variations in year-to-year growing conditions like temperature, precipitation, and available soil nitrogen (see below for an examination of environmental effects on cover crop growth).
• Mixtures can provide a variety of benefits, but realized benefits will depend on the actual composition of the mixture that grows at your farm. Fine-tuning a mixture’s species and seeding rates can shape its growth, even with significant variation year-to-year and field-to-field.

6 species mix with red clover and cereal rye

• Triticale
• Oat
• Canola
• Radish
• Pea
• Crimson Clover

6 species mix with crimson clover and triticale

• Cereal Rye
• Oat
• Pea
• Radish
• Red Clover
• Canola

A set of side-by-side panels showing the relative proportion of different species in a mixture treatment. The relative proportions are indicated by areas of different colors on the plots. In the lefthand panel, the Version 1 treatment shows that cereal rye eventually dominated the treatment, making it look more like a rye monoculture. In the righthand panel, the Version 2 and 3 treatments demonstrated a much more even distribution among the species included in the mixture. Credit: Hosler et al. (2024). Farm-Tuning Cover Crop Mixtures Via Species Replacement and Seed Adjustment

Variation in environmental conditions affects cover crop growth, often in tandem with mixture identity and composition

Key Research Insights

• Cover crop species demonstrated different responses to environmental conditions, such as precipitation, temperature, and soil nitrogen, during the long-term study. For example, most of our species preferred warmer growing conditions, while responses to precipitation were much more variable.
• Most cover crop responses to the environment depended on treatment, with many species apparently responding to competitive advantages/disadvantages of other species based environmental conditions.

  

  

Credit: Hosler et al. (in prep). A set of four plots showing some species’ responses to environment based on treatment. The top left plot shows the effect of soil nitrogen on canola biomass, which was generally positive but varied by treatment. The top right plot shows the effect of precipitation post-seeding on crimson clover, which was either positive or negative depending on the treatment. The bottom left plot shows the effect of minimum temperature on radish, which generally preferred warmer temperatures but grew the best in the six-species treatment. The bottom right plot shows the response of oat to Growing Degree Days, which was generally positive but grew the best in the six-species treatment.

What did we do?

For 10 years, different cover crop species and mixtures were planted at Penn State’s Russell E. Larson Agricultural Research Center in Centre County, Pennsylvania.

1. Single species monocultures: canola, crimson clover, oats, Austrian winter pea, radish, and triticale.
2. Multi-species polycultures: two, three, four, and six species mixtures of the species grown in monoculture.

Plant biomass, soil nitrogen, nitrogen leaching, corn yield, weed biomass, insects, and pathogens were measured to evaluate factors influencing cover crop mixture expression at the research site. Publicly available weather data were used to evaluate the impact of climate variables on mixture expression. Photos: Madeline Luthard

Publications completed for this work

Arrington, K. E., Ordóñez, R. A., Rivera-Ocasio, Z., Luthard, M., Tierney, S., Spargo, J., Finney, D., Kaye, J. P., & White, C. M. (2024). Improving a nitrogen mineralization model for predicting unfertilized corn yield. Soil Science Society of America Journal, 88(3), 905–920. https://doi.org/10.1002/saj2.20665

Hosler, S. C., Murrell, E. G., Arrington, K. E., Baraibar, B., Barbercheck, M. E., Bradley, B. A., Burgess, M., Finney, D. M., Hunter, M. C., LaChance, J. C., Mortensen, D. A., White, C. M., Lowry, C. J., & Kaye, J. P. (2025). Managing cover crop mixtures over a decade via species replacement and seeding rate adjustment. Agricultural & Environmental Letters, 10(2). https://doi.org/10.1002/ael2.70029