Summer Cover Cropping on the SIFT Farm

By John Wallace, SIFT Farm Manager

Year one cover crop
Year one cover crop. Photo: NCAT

In the past, I’ve written about fall cover crops to keep the soil protected during winter months. With mixed results from our previous trials, we have begun looking at types of cover crops we can fit into the summer months. We have had trouble with warm-season covers in Butte due to both the cold nightly temperatures and a very short growing season. This has limited the positive effects from “green manures” because they did not have enough time to develop full vegetation. In year one of the trial, our mixture of warm- and cool-season crops had mixed results. This following year, we are reverting to cold-tolerant covers that we can get established earlier in the year. This will give us a long enough growing season to increase the organic matter that will help build resilient soils.

One way we select the cover crops for our mix is by using a calculator tool developed by Green Cover Seed. This tool helps calculate the ratios needed of each seed to reach your management goals. The calculator helps save money on seed purchases by optimizing the benefits from a diverse mix of seed. For instance, if your goal is to suppress weeds, you would want a greater amount of broadleaves in the mix compared to grasses or legumes. Our primary goal is to increase nutrient cycling, so we have been using a range of legumes, grasses, and forbs.

DIY kulti-packer
DIY kulti-packer. Photo: NCAT

To initiate the first year of the cover crop trial, we had to break new ground that had not been utilized before. We rented a heavy-duty tiller to make the job easier. The majority of the seeds were small enough to be mixed together and broadcast at once; however, the peas needed to be drilled in order to keep the seeding ratios consistent. For our small scale, we were able to do this with a precision seeder. To pack the soil around the broadcast seed, we raked the plot and then used a kulti-packer that we built ourselves. We attached tires to an axle and rolled the soil to firmly pack the seeds in place.

The first year, we used the following mix:
• Austrian Peas
• Spring Oats
• Pearl Millet
• Teff Grass
• Purple Top Turnip
• White Mustard
• Chicory
• Phacelia

Year one cover crop stressed by drought
Year one cover crop stressed by drought. Photo: NCAT

This cocktail mix was seeded in mid-May while we were still experiencing cold weather often dropping below freezing. This slowed germination down significantly and consequently prevented two crops from emerging. The pearl millet and the chicory were never spotted in any of the plots. As summer progressed, the weather turned hot and dry. Our cold-season crops struggled through the drought and became stressed. In our year two trial, we will emphasize measuring soil moisture to ensure the crops are getting enough water.

We are making some adjustments in year two. Since some of the previous crops did not germinate in our May weather, we are replacing them with crops that are more commonly grown in colder climates. As well, we will be seeding a week or two later because of the longer-than-usual winter that we have been experiencing. The cover crop calculator tool gives us the proper ratios of each seed needed for the mix but the tool calculates the seeding density needed for an entire acre. We are only seeding an area that is 1/8 of an acre, and the minimum seed order is 25 pounds. Therefore, the tool is just a guide and the suggested amounts must be adjusted for our 25-pound order. This year, we have ordered mix shown in the table below.

Cover crop mix ordered for 2018
Cover crop mix ordered for 2018.

Our expectations are that with the adjustments made, all of the species will successfully germinate and thrive through the summer. We will be monitoring the soil moisture, as well as routinely performing water-infiltration tests. These tests, along with yearly soil testing, allow us to concretely measure the benefits of cover cropping over time. By increasing the organic matter in the soil, we are effectively trapping water within the micro-organisms. This water can then be tapped into when droughts such as last year re-occur.

Posted on: April 24th, 2018