Interseeding cover crops into standing cash crops
Interseeding cover crops into a standing cash crop has several advantages over seeding after harvest, but management practices are critical to ensure successful establishment.
Michigan State University Extension research has shown that including cover crops into a rotation can provide several benefits for soil health, crop resiliency under weather stress and, ultimately, crop growth. However, to realize these potential benefits, the cover crop must be able to grow sufficiently in the fall to develop a vigorous root system and, depending on the species, to overwinter. When the cash crop is harvested later in the fall, species options become limited, and oftentimes it is difficult to get the cover crop to establish. The best way to ensure this fall growth is to interseed the cover crop into the current standing crop, says Jamie Scott, who farms 2,000 acres of corn, soybean and wheat in Indiana, and founded Scott’s Cover Crops to help other farmers incorporate cover crops into their rotations. Scott spoke about his experiences with various methods of interseeding cover crops at an integrated pest management (IPM) breakfast meeting in St. Joseph County, Michigan.
There are several different methods to seed cover crops and at least as many different types of equipment, according to “New technology expands options for cover crop establishment in northern climates” by MSU Extension. However, Scott says there are really only two ways: placing seed in the ground or on top of the ground. Whether seed is applied aerially (see photo) or with a modified highboy, the end result is that the seed will be lying on the surface. He prefers this method to waiting until the crop is harvested and then seeding with a drill or planter because it allows the cover crop to get established earlier.
According to Scott, “You lose 1.5 hours of sunlight and 12 degrees of heat [each day] when seeding cover crops after harvest versus interseeding a month earlier.” He also prefers aerial seeding to using a highboy because it can be done faster and is not limited by wet field conditions, although he acknowledges that each method has its pros and cons.
Research conducted by MSU Extension on aerial seeding has shown that cover crops can be successfully established into a standing corn crop, and Scott said success in soybean is similar, with one caveat – if the soybean variety is taller and produces more biomass, he found that the cover crop should be planted earlier rather than later so seedlings will not be smothered by the soybean residue after harvest.
Aside from adequate soil moisture, the success of cover crop establishment is impacted by various management factors. Scott believes the two most important factors are avoiding compaction and the proper selection of herbicides, if used, for the cash crop. Avoiding compaction ensures soil moisture is able to move upward and downward through the soil profile as needed and allows adequate pore space for roots to have access to air. Herbicide selection and timing is critical, as many options will restrict emergence and growth of different cover crop species for a few weeks to more than two years. Scott has seen a case where cover crop establishment failed due to the residual activity of a herbicide compared with an identical case where establishment was successful, with the only difference being that the herbicide was applied just three weeks later in the spring under the failed scenario. Pennsylvania State University Extension has published a good resource to estimate carryover potential for several herbicides and the impact on fall cover crops.
The St. Joseph County IPM Breakfast Series is organized by the MSU Extension field crops team in southwest Michigan. The meetings run mid-April through the end of June and are held on Tuesdays at the Royal Café in Centreville, Michigan, beginning at 7 a.m. Each meeting includes an update of the major field crops grown in the region, including a crop and pest report, followed by a presentation from a guest speaker on a topic important to crop production. Participants can order breakfast and eat during the meeting. Meetings are open to the public, and CEU and RUP credits will be available. For more information on this breakfast meeting series, contact Eric Anderson at the MSU Extension Centreville office at 269-467-5511.