Can I plant a cover crop with my asparagus for weed control?
Answer: The ATTRA publication Organic Asparagus Production addresses some of the research that has been done in this area. From the following information excerpted from that publication, however, doing so appears to be quite management-intensive.Cover cropsCover crops are another useful tool in asparagus weed management. Two cover crop systems that have potential in asparagus are “dying mulches” and “living mulches.” Dying MulchesA dying mulch is a cover crop planted out of season. While growing it suppresses weeds; then it dies back out on its own without requiring the use of herbicides, mowing, or tillage. Winter rye?planted in the spring?has been used successfully in this manner in several agronomic and horticultural crops.In asparagus here’s how this might work. Following post-harvest tillage of the asparagus field, the field is over-seeded with winter rye at 120 pounds per acre to establish the living mulch. Since the winter rye is planted in late spring and consequently does not receive normal winter vernalization (cold treatment), it never tillers (i.e., it stays short) and eventually “cooks out” by mid-summer. By this time, the asparagus ferns form a thick canopy that shades out most underlying weeds.The success of this system is dependent on proper timing and good luck. Timing is critical to get the rye established early enough to promote germination when the soil temperatures are still relatively cool, but at the same time, late enough that a cold spell is avoided. Vernalization can occur when the rye is exposed to only 10 days of 45? F nighttime temperatures.Dr. Astrid Newenhouse, formerly with the University of Wisconsin, conducted cover crop research in horticultural crops and provided some preliminary insights into dying mulch and living mulch systems for asparagus. Dr. Newenhouse tried the non-vernalized rye system described above. She agreed that timing was critical with respect to a cool spell. As a result of a cold snap one year, her rye headed out and created additional management problems. Living MulchesLiving mulches are cover crops grown in association with annual or perennial crops, primarily for weed suppression and as a soil management practice. The goal is to plant a low-growing cover that suppresses weeds without competing too much with the main crop.In Wisconsin, Dr. Newenhouse’s living-mulch work in asparagus focused on two cover crops: perennial ryegrass and ‘Dwarf White’ Dutch white clover. Both cover crops were fall-established and managed the following growing season with one to three mowings using a walk-behind sickle-bar mower. Preliminary results indicated that perennial ryegrass performed better than the Dutch white clover the first growing season. However, in the second growing season these results were reversed, with the Dutch white clover performing better. This research found that living mulches could be highly effective in weed suppression but also quite competitive with the crop, reducing asparagus growth 50 to 75% in some instances. Clearly, more research is required to find living mulch systems that are more viable.”The living mulch system, while it controls weeds, appears to compromise the asparagus yields too much to be economical. Organic Asparagus Production is available at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=377.