Under Cover

April Garden Update:

Last fall, when the corn and squash had finished their harvest and the stalks were pulled out and the ground cleared, we planted fava beans and a hand-chosen mix of vetch, peas, and daikon radish in the row crop area of the garden. Cover crops keep the soil protected and have a beneficial effect by increasing the amount of organic matter in the soil. This in turn enhances water holding capacity, sequesters carbon, prevents weed growth and erosion, and continues microbial activity in the soil. Beneficial insect activity increases when the plants are in bloom—in short, it is an advantage all around!

Our cover crop of vetch, peas, and daikon right before it was cut down and mulched. The daikon has large roots that help break up the soil and leave space for water and air.

Plant groups such as brassicas—arugula and mustards, legumes—vetch, clover, fava beans and bell beans, and grasses—triticale and barley are all used for winter cover cropping. Buckwheat is a quick-growing cover crop that we use at the seed garden during the summer.

Buckwheat in flower as a beautiful summer cover crop.

We grow peas, beans and other legumes because they fix nitrogen into the soil. By working with a microorganism in the soil, they take the nitrogen out of the air and make nitrogen nodules on the roots of the legume plants. We turn under the plants while the nodules are fully developed and before seed production.

Many people grow fava beans as a cover crop, but at the seed garden, they are grown as a seed crop. We have been developing our seed for many years from a cross of several large seeded fava beans. We are selecting for plants that are both large seeded and are good food and seed producers with 4 or 5 seeds in each pod. Because we are growing our fava beans for seed, most of the beneficial nutrients in the plant have been used in developing the seed.

Fava bean plants in flower.

In the spring, there are several ways you can use the cover crop:

1. Cut off the tops and use them as a compost crop and leave the roots to break down in the soil.

2. Chop the cover crop up with a weed whacker, machete or scythe and turn the cover crop into the soil to break down and add organic matter to your soil. The chopped-up plant material, the so-called “green manure,” is left to decompose for another few weeks before planting.

3. Chop up the cover crop and leave it as a mulch on top of the soil. The roots will continue to break down in the soil. You can plant into this once it has broken down for a few weeks. This technique is best in order to plant larger plants like tomatoes, potatoes or squash.

Opinions vary as to when to cut down the cover crops and return the organic material to the soil. Based on the percentage of flowers in bloom it ranges from 15% to 75%. Whichever way we decide to work with our cover crops, we are improving the soil and in turn, helping our plants have a successful growing season.

For more information about cover crops, here is a link to a PowerPoint presentation about cover crops given by local gardener, Maile Arnold, in 2018. https://www.communityseedexchange.org/the-miracle-of-cover-crops