How do select the right cover crop mix?
Over the last few weeks I have shared with you the benefits of cover crops and the importance of good planning. Now that you have decided that a cover crops may be an important tool to help your farmland, the next step will be to determine what to plant. There are many options when it comes to the different cover crop species on the market today. I don’t want to overwhelm you with too many options, so I will cover a few of the more common species.
To get started, let’s divide the species list into three categories: grasses, legumes and brassicas. Each of these serves a totally different purpose, so I will break down the differences of each.
Select a grass cover crop
Grasses are a very important piece of the cover crop mix. Grasses are known for their deep rooting, even the ability to break through a compaction layer in the soil. This vigor is beneficial to help with water infiltration, even helping that cash crop to put down deeper roots. They do an excellent job of scavenging nitrogen that is in the soil and tying it up in the plant for future use. Grasses are a staple to every cover crop mix. Some of the species include annual ryegrass, cereal rye, barley, triticale, oats and buckwheat.
Do I need a legume in this field?
Legumes, on the other hand, instead of scavenge nitrogen, they fix nitrogen. How does this work? With legumes, there are symbiotic bacteria in the soil that attach to the root, feeding off the sugars that the roots exude. These bacteria will fix nitrogen from the air and attach it to the plant roots. This allows the plant to use the nitrogen the bacteria is fixing. This nitrogen fixing process help to provide nitrogen to crops like corn and wheat. Legume cover crops include various clover species like crimson, red, and white. Austrian winter peas and many vetch variety like hairy vetch are all great nitrogen-fixing cover crops.
A brassica is always good.
The final category of cover crops are the brassicas. These species of cover crops are also great for scavenging nitrogen and breaking up compaction layers. They are typically a root crop which help to aerate the soil and many of them produce a bulb or a tuber. These brassica species improve earthworm activity in the soil. Some of the more common brassica species include the daikon oilseed radish, purple top turnip and dwarf essex rape (canola).
Each one of these cover crop species plays a different role and impacts the soil and the soil biology in different ways. The best way to approach your cover crop selection is to create a mix that will impact many biological populations. There is much being learned in the field of soil microbiology, but the importance to your farmland is unquestionable. I also like to conclude a mix will give you a combination of species that will grow through the winter. Some will die due to winter kill if your field is in a colder climate, allowing the nutrients of that crop to be taken up by the remaining cover crop. This give you a scenario of growth, death and decay all going on at the same time. This resembles more what would happen in nature and allow you to reap these benefits.
It you are considering cover crops on your field and want to talk to someone about it, there are many knowledgeable people you can speak with. I would be glad to help answer any questions you may have too. Just give me a call.