Planting Cover Crops!

Green Manure

Planting a cover crop after harvest in your vegetable garden is a great way to replenish soil nutrients (especially nitrogen), loosen the soil, rebuild soil structure, reduce weeds, and control erosion over the winter months. It is also a great way to add some often much needed organic matter to the soil. This practice of planting a cover crop to revitalize your vegetable garden soil is one way to make your garden more sustainable.

Winter cover crops, often referred to as "green manure", are generally sown in the fall, allowed to grow all winter, and then are cut (if necessary) and tilled into the soil in the spring before the planting season. The nutrients that have been assimilated into the roots and foliage are then returned to the soil to be used by your vegetable plants during the growing season.

 

Different Types

There are a variety of different types of seed that can be used for cover crops. Probably the most common are some of the rye grasses, clovers, alfalfa, oats, buckwheat, and various brassicas. 

• Winter rye is a good cover crop for colder areas. It is hardy to -30°F, has a fast growth rate, and an extensive root system that helps with soil aeration. The seed is relatively inexpensive and it's easy to grow. It can be planted from August through October. To plant winter rye, first clear the garden of all the leftover summer vegetable crops and weeds. Rake the soil to loosen it and broadcast the seed evenly over the area according to the rate recommended on the package. Lightly rake the area again to work the seed into the soil. Water it periodically if necessary until the seed germinates and the seedlings are established. In the spring, mow or cut the winter rye and then till it, roots and all, into the soil. Soil organisms will soon break it down and the stored nutrients will become available to your vegetable crops when they are planted later in the spring or early summer.

• Crimson clover is another excellent winter cover crop. Clovers are legumes and have the added advantage of fixing nitrogen, converting it to a form that is available to plants growing in the soil. Crimson clover should be planted about 4 weeks prior to the average first hard frost for your region. The seed germinates a bit slower which is why it needs to be seeded earlier. In the spring, about four weeks before you will begin planting your summer crops, cut the clover down, rake it up and compost the foliage. Turn the clover under and let it decompose in the soil for 4 weeks before you plant.

• Brassicas are becoming more popular as a cover crop due to their rapid fall growth, quick decomposition, and potential pest management characteristics. Some brassicas have a large taproot that can penetrate to depths of 6 feet or more. These species can help breakup compacted soils - a process called "biodrilling". Brassicas also have been found to release biotoxic compounds that may reduce populations certain soil borne pests and diseases such as nematodes, fungi, insects, and bacteria. Brassicas should be established about 4 weeks before the average date of first freeze.