Winter cover crops as cash crops?
Its peak produce season and the last thing you’re probably thinking of is winter. I don’t blame you! That word is normally stricken from my vocabulary until after the first frost. However, now is a great time to begin thinking about winter cover crops and soil health. Cover cropping has been researched, recommended, and adopted as a practice, because of issues with nitrogen depletion, reduced organic matter, decreased soil microbial health, increased incidence of soilborne disease…the list goes on. Aren’t many of these issues similar to what high tunnel growers are dealing with? Why isn’t cover cropping as common a practice in high tunnel settings?
Let’s focus in on high tunnel tomato production, as more than 80% of our NYS producers that grow in “protected settings” grow tomatoes. These growers have limited options when it comes to implementing a cover crop into their crop rotation. In order to reap the benefits of cover crops, they require cold hardy species that germinate quickly in the fall, produce biomass throughout the winter, and are easy to terminate and incorporate in the spring. Even if suitable species are identified, is winter cover cropping a good fit for high tunnel tomato systems? In the Fall of 2018, Judson Reid and I began a multi-year trial to answer just that.
More specifically, some of the questions we’re hoping to answer include:
Which cover crop species or combination of species works best in a high tunnel setting?
Can we grow our own nitrogen over the Winter, and in turn, reduce the amount of fertility we have to add during the tomato season?
Do we see a positive effect from cover cropping on tomato yield and quality?
In turn, can winter cover crops put more cash in your pocket?
In our current work, we’re trialing two species: Austrian field peas and Triticale. Austrian field peas provide the benefit of nitrogen fixation through their relationship with Rhizobacteria, and Triticale may produce more biomass than winter wheat or barley and is less likely to produce volunteer plants. Establishing a winter cover crop after the tomato season has ended requires a quick turnaround. An additional question we’re seeking to answer is how does planting date influence cover crop biomass production? Our trials are planted in the month of October into two tunnels, two weeks apart. Finally, although the cover crop is being grown in a protected setting, N.Y.S. winters are cold and skies typically overcast. Can the simple addition of row-cover create a warmer microclimate and in turn, increase biomass production?
Preliminary data shows that there is a significant benefit to adding row cover. In both years, nearly every treatment produced more above-ground biomass under row cover. The benefit is even more pronounced in the later planting where biomass was 2 to 3X higher under row cover than without. While this may suggest that a late-planted cover crop can survive, and even thrive, biomass production is higher across most treatments when planted early. The benefit of an earlier planted cover crop is more easily seen when comparing estimated nitrogen contributions. Throughout the winter, nitrogen is either scavenged (by the winter grain) or fixed (by the legume). This nitrogen is then returned to the soil when the crop is mowed and incorporated. In both 2019 and 2020, estimated nitrogen contributions were 1.5 to 3.5X higher in the earlier planted cover crop. While biomass and nitrogen data may support the practice of cover cropping in high tunnels, we don’t quite have a full picture. Tomato yield, foliar, and soil nitrogen data is still being collected. This data will help us to fully understand if the cover crop biomass, and in turn, nitrogen contribution is benefiting the tomato harvest in terms of increased yield or benefiting the grower, in terms of fertilizer reductions.
For more information, visit the Cornell Vegetable Program’s YouTube page for our April 2020 update: https://www.youtube.com/watch?v=Hr1K0qX-F7g&t=28s
This work is supported by Federal Capacity Funds, The Sustainability Foundation at Cornell University, and a Specialty Crops Block Grant from the New York Farm Viability Institute.