At Mære, we have been conducting practical trials over several years with sowing various cover crops in grain with a view to soil improvement and capturing surplus nutrients. The sowing has been done at different times and with different equipment (weed harrow with seeding unit and drone). The challenge has been to find the right sowing time with good moisture conditions and the right sowing depth. We think we have succeeded well, but we see that we are completely dependent on good soil contact and enough rain after sowing (especially when sowing with drones). We have tested ryegrass, white clover and several types of cover crop mixtures. The cover crops have not come into their own until the grain has been cut, just as it should be.
Crops that are sown before, at the same time as or after the main crop have the following tasks:
- Capture excess nutrients – and keep them at the surface
- Maintain organic matter in the soil
- Stimulate soil life for as long as possible through plant growth
- Protect against driving rain and erosion
- Help create and maintain good soil structure
Undercrops are crops that are sown in grains or vegetables. They are sown at the same time as the grains in the spring, or a few weeks after. The term catch crop is most often used if the primary purpose is to collect and retain nutrients from one year to the next.
Plant cover in autumn, winter and spring can also slow down water velocity and increase infiltration. The cover crop can reduce leaching of nutrients from the soil, and prevent soil erosion by stabilizing the soil.
An undercrop will compete with the cereal plants for light, water and nutrients. Oats tolerate competition from undercrops best, while spring wheat and two-row barley may experience some yield reduction. Ryegrass, often in combination with clover, is widely used as an undercrop. Of the ryegrasses, biennial (Italian) or perennial ryegrass is recommended. Perennial ryegrass needs longer to establish, and does not compete as strongly with the cereal plants from spring onwards. The undercrop is sown at the same time as, or slightly after, the cereal. If one chooses to sow the undercrop slightly after the cereal, sowing can be done at the same time as an early weed harrowing. It is important that clover seeds are sown shallowly, 0.5-1 cm. To get the best effect from the undercrop, spring ploughing is recommended.
