Interseeded clover during midsummer under the corn canopy
There is some concern about the impact of the cover crop on the corn. In most cases, though, we have observed that the corn is very competitive with the cover crop.
The concept is to seed the cover crop so that establishment occurs following the "weed free" period (6-7 weeks after planting) so that any impact on the corn is minimal, provide weed control treatments at interseeding and use cool season cover crops that are not as competitive as warm season weed species. We are currently conducting a multistate trial with interseeded cover crops in NY, PA, VT and MD to further assess yield impacts of interseeded crops in our region.
Figure 1. Impact of interseeding different species at V6 on corn grain yields at Rock Springs in 2013.
Our initial results are supporting the concept that yield impacts are minimal. In our 2013 trial at Rock Springs where we got good establishment early of several species, the impacts on corn yield were negligible (Figure 1). We are conducting these studies across a range of environments to better understand the relationship between interseeding and grain yield. Our hope is that any yield impacts in the year of interseeding would be offset by higher yields, better soil quality and less fertilizer use in subsequent years.
A number of published studies have evaluated interseeding in the literature and have generally found no impact on corn yield with plantings at the V4 to V7 stages of growth, or 4 to 7 fully exposed leaves. A Cornell study concluded that intercrops of red clover, ryegrass and other species had no impact on corn yields when the interseeding was done at the 6 to 12 inch tall corn stage (Scott et al, 1987). Michigan State study (Baributsa et al., 2008) found that interseeding red clover or chickling vetch in corn over four years had no impacts on corn yields and that the clover could provide N to a succeeding crop.
Canadian studies have found similar conclusions. In Ontario, a two year study concluded that intercropping corn with red clover could provide soil protection without impacting silage corn yields (Wall et al., 1991). In Quebec, Carruthers et al. (2000) also showed that intercropping with forages seeded 3 weeks after corn planting did not impact corn yields and concluded "The ability toproduce silage equal in yield to monocrop corn at a reduced cost and risk of environmental damage makes this an attractive intercropping system for eastern Canada". In British Columbia, relay cropping with ryegrass planted at the 3 to 6 leaf stage is an accepted practice described in an advanced production manual for corn silage (Bittman and Schmidt, 2004). They note that planting ryegrass before the 3 leaf stage may suppress corn growth. Relay cropping in that region has been shown to dramatically reduce runoff from manured silage corn fields (van Vliet, 2002).
South American studies are also evaluating intercropping and have found similar results. One recent example of the studies there is that Borghi et al. (2013) concluded that Intercropping systems with corn and guineagrass did not reduce the corn grain yield compared with sole corn crops.
This is not an exhaustive list of the literature on the topic of yield impacts of interseeded crops, but provides a sampling of the evidence that cover crops can be intereseeded in corn with minimal impacts on yield in the year of intereseeding.
However, as with the introduction of any new technology, there will likely be some new concepts learned about this system and continuing improvements in management. In the introduction of no-till corn for example, weed control, soil compaction and planting issues often reduced yields in initial work, but eventually these were overcome with improved management to reap the benefits of no-till crop production. Our goal is that we can achieve the same with the concept of interseeding cover crops.
Baributsa, D.N., E.F.F. Foster, K.D. Thelen, A.N. Kravchenko, D.R. Mutch, and M. Ngouajio. 2008. Corn and cover crop response to corn density in an interseeding system. Agron. J. 100:981-987. doi:10.2134/agronj2007.0110
Bittman, S. and O. Schmidt. 2004. A recipe for relay cropping. In Advanced Silage Corn Management: A production guide for coastal British Columbia and the Pacific Northwest. Bittman, S. and C.G. Kowalenko, ed. Pacific Field Corn Association, Agassiz, BC.
Borghi, E., C.A. C. Crusicol, G. P. Mateus, A.S. Nascente, and P.O. Martins. 2013. Intercropping time of corn and palisadegrass or guineagrass affecting grain yield and forage production. Crop Sci. 53:629-636.
Carruthers, K, B. Prithiviraj, Q. Fe, D. Cloutier, R.C. Martin, and D.L. Smith. 2000. Intercropping of corn with soybean, lupin, and forages: silage yield and quality. Journal of Agronomy and Crop Sci. 185:177-185.
Dickey, J.B.R. 1947. Efficient corn growing. Pennsylvania State College, Agriculture Extension Service, Circular 305.
Scott, T.W., J. Mt. Pleasant, R.F. Burt, and D.J. Otis. 1987. Contributions of ground cover, dry matter, and nitrogen from intercrops and cover crops in a corn polyculture system. Agron. J. 79:792-798.
van Vliet, L. J. P., B.J. Zebarth and G. Derksen. 2002. Effect of fall-applied manure practices on runoff, sediment, and nutrient surface transport from silage corn in south coastal British Columbia.Can. J. Soil Sci. 82: 445-456.
Wall, G.J., E.A. Pringle and R.W. Sheard. 1991. Intercropping red clover with silage corn for soil erosion control. Can. J. Soil Sci. 71: 137-145.
Drs. Roth and Curran have a financial interest in Interseeder Technologies, LLC, the company which licenses the Interseeder from The Pennsylvania State University. These relationships have been reviewed by the University's Individual Conflict of Interest Committee and are currently being managed by the University.
Prepared by Greg W. Roth, and William S. Curran Department of Plant Science, Penn State