|Kura Clover Companion Cropping
In this research program we are testing farming practices designed to maintain vegetative cover on the landscape on a year-round basis, to protect against erosional losses of sediment and nutrients. Our goal is to see if these systems can provide environmental benefits while preserving the productivity of row crops, particularly corn and soybeans.
Winter Cover Crops
There are two major challenges with winter cover crops in the Upper Midwest. First, there is a limited window for their establishment, in between corn or soybean harvest and the onset of winter. If the cover crop isn't seeded until the main crop has been removed, it often will not grow sufficiently in the fall to provide adequate soil cover. To address this, we have tried aerial seeding, where a helicopter is used to seed rye into standing corn or soybeans in late summer so the rye can germinate and begin growth earlier, prior to harvest. Results have been inconsistent, as described in Wilson et al (Agron. J. 2013), and other approaches are now being tried. The other challenge with winter cover crops is preventing yield reduction in the following grain crop. We are testing new methods for planting corn and soybeans into winter covers to determine optimal practices.
Living Mulch Systems
Perennial living mulches are low-growing, perennial species into which row crops like corn can be planted. Producers and researchers have experimented with various species, but our primary focus has been on kura clover. The primary goal is to provide year-round vegetative cover to reduce the exposure of the soil surface to the damaging effects of wind and water erosion. Secondarily, the living mulch can increase net primary productivity by photosynthesizing in the spring and fall when the companion row crop is absent. This aerial photo shows a green, growing clover field at our Rosemount, MN field site on March 30, 2012, a time when all of the surrounding cropped fields will be bare for another 6-8 weeks.
Aerial image of Clover field on April 3, 2012.
Kura clover is an unusual species - a legume that spreads by rhizomes. It is both drought tolerant and cold tolerant, making it well-suited to the Upper Midwest. Because it is rhizomatous it can spread to fill in thin areas, unlike most other legumes. Colleagues at the University of Wisconsin have taken advantage of this in developing a kura/corn companion cropping system for dairy operations. The kura provides a permanent living mulch in which strips can be created by tillage or herbicide for planting corn. As they decompose, the killed strips release nitrogen that can be used by the growing corn. By the time the corn has reached physiological maturity, the clover has spread back over the row, fixing nitrogen in the process.
Corn growing in kura clover living mulch
Soybeans growing in kura clover living mulch
In our research at Rosemount we use strip tillage rather than herbicide to establish rows in our kura clover living mulch. We have found that this system can produce excellent silage and grain yields with substantially lower nitrogen fertilizer inputs. However, in most years the yield is reduced relative to conventionally grown corn. We have been conducting research to isolate the factors affecting yield in these systems, and to develop management practices that will improve system performance. The most promising results have come from the use of a new form of tillage prior to planting. Instead of a conventional strip till unit, we use a rotary zone tillage unit that creates 30 cm wide rototilled rows. This reduces the competitive effects of the clover early in the growing season. Testing over the past two years has shown that both corn and soybean yields in this system are not significantly different from yields in conventionally farmed fields.
One additional problem with kura clover is that it is difficult to find seed. To alleviate this problem, we have tested field-scale methods for vegetative propagation, described in a short videoclip. While this method was effective, it is labor intensive, so expansion of kura clover use as a living mulch will depend on increasing the seed supply.