Spring Seedbed Characteristics after Winter-Killed Cover Crops

Dr. Ray Weil and Natalie Lounsbury have been investigating the possibility of no-till planting early spring vegetables such as spinach and lettuce after a forage radish cover crop without the use of herbicides. They discuss soil moisture, temperature and nutrient status in early spring as well as seedling emergence and yield. Equipment limitations and new opportunities for small-scale farmers are addressed.

Watch the webinar now (recorded Feb. 4, 2013).

Related resources include:

• Forage Radish Fact Sheet - University of Maryland Extension. This fact sheet provides an in-depth assessment of the benefits, constraints, and management recommendations for using forage radish cover crops.
• Photo Gallery - Innovating with low-residue, winter-killed cover crops. Dr. Ray Weil and Natalie Lounsbury post photos of their research on low-residue, winter-killed cover crops in this photo gallery.

Webinar at a Glance

Prepared by Kristen Devlin

Winter cover crops offer farmers several benefits, including nutrient retention and soil conservation. However, growing winter cover crops can be a challenge for vegetable growers who have to terminate the cover crop in time to seed their early spring cash crops. While conventional growers can kill a cover crop with herbicides, organic farmers rely on mechanical means of cover crop termination. Since soils in spring are often too wet to allow for the use of heavy machinery, organic growers are faced with a dilemma.

This “kill-till dilemma” is the impetus behind a SARE-funded study conducted by Ray Weil, a professor of environmental science and technology at University of Maryland, and Natalie Lounsbury, a graduate student in his lab. Weil and Lounsbury are studying the suitability of forage radish as a winter-grown cover crop preceding early spring vegetables.

When grown as a cover crop, forage radish (Raphanus sativus var. longipinnatus) suppresses weeds, improves soil nutrient availability, breaks up compaction layers, and contributes significant quantities of nutrients and organic matter. Since it also winter kills, it may be a good winter cover crop option for organic no-till farmers.

In their trial, Weil and Lounsbury conducted spring-time comparisons of plots that had been planted to forage radish with plots that had been planted to oats. They found that forage radish plots had fewer weeds and almost no remaining cover crop residue, which resulted in warmer, drier soils. In their subsequent vegetable tests, the forage radish plots saw better emergence of early spring vegetables (kohlrabi, lettuce, peas, and spinach) than in the plots planted to oats or to no cover crop. Yields also were significantly higher in forage radish plots, especially for spinach. “I don’t usually think in terms of silver bullets,” said Weil, “but for planting early spinach I think we have one.”

Weil and Lounsbury shared some advice for growers to consider before planting forage radish as a winter cover crop. First, timing is very important. “In order for this to work really well, you need to plant your cover crop in mid to late August,” explained Lounsbury. Depending on winter temperatures, the cover crop should die by early March and a cash crop can be planted in mid-March.

Growers with less than 20-25 ppm nitrate N should plan on providing supplemental N before planting forage radish, to give it a good start. The crop will return plenty of N to the soil in spring, so growers won’t need to fertilize again before their spring vegetable planting.

No-till planting of spring vegetables after a forage radish cover crop may require some specialized seeding equipment. Weil and Lounsbury found that planting with an Earthway seeder was difficult, and that the seed bed required a seeder with a “more solid opener and pretty good press wheel.” They found that MaterMacc and Monosem seeders were more effective.

For more information, see the related SARE grant LNE11-312, No-till, No-herbicide Planting of Spring Vegetables Using Low Residue Winter Killed Cover Crops. For questions about the study, or for copies of the slides presented during the February 4th webinar, contact Natalie Lounsbury at nplounsbury@gmail.com.

About this Series

This webinar is part of the Cover Crop Innovations Webinar Series, hosted by Penn State Extension in winter 2013. Other webinars in the series can be found here.

The Cover Crop Innovations Webinar Series is a component of the training initiative sponsored by the Northeast SARE Pennsylvania State Program.  More information about the training initiative is available here.