Cover Crops for Soil Health and Forage
The first mix we looked at was crimson clover and annual ryegrass. Annual ryegrass is a high quality forage with relatively inexpensive seed and an amazing root system that provides food for soil organisms and builds soil. Crimson clover in the mix fixes nitrogen and adds protein to the forage. Many folks are more familiar with red clover which is a little more winter hardy than crimson. Researchers chose crimson because it grows faster in the fall.
Crimson clover was also mixed with triticale. Forage quality has tested out in the moderate range. One farmer at the cover crop walk noted that he likes to use triticale for forage because, “It is later. This spreads [the harvest] out a bit compared to rye.” Like annual ryegrass and crimson, this mix will provide both nitrogen and carbon to the soil.
Crimson clover also mixes well with oats. The oats act like a nurse crop, competing with weeds, while the slow growing clover gets started. One disadvantage is after a hard frost oats will winter kill. Without living roots, the cover crop will not continue to take up any excess nutrients which may instead leach down below the root zone. Oats has advantages, though, as well. Farmers at the walk noted that oats, “sometimes give you a good fall harvest.” For example, in 2011, oats plus crimson clover yielded between 0.75 and 1.5 tons of dry matter in high nutrient sites. In this mix, crimson clover survived the winter and put on nearly two tons of dry matter in the spring, containing 120 pounds of nitrogen. After the clover is terminated in the spring and starts decomposing, the nitrogen in the clover rapidly becomes available to the next crop, reducing the need for fertilizer. Farmers at the field walk also observed that oats can also “leave the ground mellow compared to rye.”
Other interesting combinations included oats with annual ryegrass and oats with cereal rye. The oat annual ryegrass combination gives farmers the potential to double cut in the fall and spring. Cereal rye with oats can yield very high for a fall cutting. In last year’s trial oats+rye averaged one ton dry matter per acre in the fall and 2.5 tons dry matter in the spring. The rye will then still be around to suck up nitrogen over the winter and keep the soil from eroding. You have to be careful though that the rye does not get too big in the spring to handle.
Penn State Extension Associate Charlie White explained that not only do some of these mixtures fix nitrogen, but they also capture nitrogen from manure applications in the roots and soil organic matter. This acts like a “long term investment that will slowly pay back dividends. Over time farmers won’t have to apply as much nitrogen.” I am excited to see the final results of this three year trial.