Landscape
And
Nursery
Dialog
Mary Ann Rose
Commercial Landscape
& Nursery Specialist
The Ohio State UniversitySeptember, 1995
Selection and Establishment of Cover Crops for Nursery Row Plantings.
Keywords: best management practices, soils, nursery, field production
L ast month at the American Society for Horticultural Science meetings in Montreal, Dr. Larry Kuhns of Penn State University presented a summary of twelve years of research on low-maintenance cover crops for the nursery. For this month's LAND column I will give readers the highlights of this excellent presentation.
Use of a cover crop between nursery rows will help prevent erosion and facilitate the movement of heavy equipment and people in the field. Furthermore, recent studies have also demonstrated the value of vegetation buffer strips in preventing the runoff of pesticides and fertilizers from field plantings. While cover crops between rows are beneficial, they are also agressive and will dramatically reduce growth of the crop if allowed to grow unchecked in the nursery row. A cover crop system works well only if the grower intends to use herbicides to maintain a 30 to 36-inch wide weed-free zone in the nursery row.
A desirable cover crop will establish a dense sod rapidly, withstand traffic well, require infrequent mowing, tolerate low-fertility, and will not attract rodents. Legumes and cool-season grasses were evaluated as covers in the Penn State trials. Among the legumes tested, white clover was the most promising. However, in general, all of the legumes were unsatisfactory because they died out after several years, were slippery when wet, and worse, were very attractive to deer.
Among the grasses tested were Canada bluegrass ('Ruebens'), perennial rye ('Elka,' 'Manhattan,' 'Palmer,' and 'Pennfine'), redtop (common redtop and 'Streeker'), tall fescue ('Rebel' and 'Ky 31'), and fine fescue. The fine fescues are a large group that contain red fescue ('Ensylva,' 'Fortress,' and 'Pennlawn'), chewings fescue ('Jamestown,' and 'Shadow'), hard fescue ('Reliant' and 'Waldina'), and sheep fescue (common sheep fescue and 'Covar'). For very heavy traffic, 'Ky 31' tall fescue was the best choice, however this cover requires much more frequent mowing. Although they were somewhat slower to establish, the fine fescues made superior covers compared to other grasses. Once established, fine fescues formed a very dense, but slow-growing cover that required only a few mowings per year. The fine fescues also were reasonably tolerant of traffic. Of the fine fescues, hard fescue was the best because it was very dense and matted less than the other fine fescues. A mixture of two-thirds hard fescue and one-third red fescue also made a superior cover.
Covers can be established in spring or fall, before or after planting the nursery crop. Prepare the site by killing all weeds and cultivate prior to seeding. Rates of 20 to 80 pounds seed per acre are sufficient - the higher the rate the more rapid the establishment. Rolling can aid in germination by providing better contact of the seed with soil. When the grass is about an inch high, fertilize with 40 pounds N per acre. In the first year of establishment, limit weed competition with the turf by mowing weeds before they reach about 10 inches. Broadleaf turf herbicides also may be used. After the cover fills in weed competition should not be a problem.
Using a drop seeder, the grass seed can be sown between the rows only. However, if a broadcast seeder is used, the grass that germinates in the row will have to be killed off. Dr. Kuhns described a strategy where the grass seed was broadcast in either August or October prior to a spring planting of Christmas trees. Herbicide (Aatrex, labeled for Christmas trees only) was applied after tree planting to kill the grass in the rows. Where the cover had been sown in August, the cover was too far established in the row and the roots of the cover crop actually prevented the planting furrow from closing. This was not a problem for an October cover crop planting. Because of the furrow-closing problem, Dr. Kuhns did not recommend the August sowing. However, an August sowing would be fine if a drop seeder was used, or if an appropriate herbicide was used in the fall or winter after broadcast seeding. Preemergence herbicides could be used in the row right after seeding. Kerb could also be used in fall or winter, and provides the best control of the fine fescues, with both pre and post-emergence activity.
Once the nursery crop is in, directed sprays of Roundup are somewhat effective in preventing covers from encroaching in the row, but require several applications. Grass herbicides such as Vantage or Fusilade will not touch the fine fescues, although they effectively kill tall fescue and perennial rye. Where Kerb can be used in existing plantings, it provides the best control of fine fescues, but is recommended only for cool-season application.
