Marin IJ Articles

The miracle of cover crops

• Alice Cason

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  Mustard is a cover crop planted in vineyards to prevent soil erosion, recharge nitrogen, and suppress harmful soil-dwelling nematodes.

  For an Earth-Friendly Garden, keep a succession of plants in the soil by planting cover crops. These are plants grown to improve the soil rather than for harvest. I prepare the soil for the next year when my tomatoes are finished for the season. I reuse my raised beds over again since there is no extra room for crop rotation or time for winter crops. We use the ‘no-till’ method and disturb the soil as little as possible to support plant health and growth. Winter rain takes care of the irrigation.

  Cover crops have many benefits. Their roots create soil structure for the aeration of water and nutrient flow. Improved soil structure also promotes the development of beneficial soil microorganisms, which are essential for nutrient cycling and overall soil health.

  

  Bell bean crops are harvested and chopped up, then they decompose for 5- 6 weeks before planting starts.

  Cover crops help reduce soil erosion by providing ground cover. Fast-growing crops like buckwheat and rye establish quickly and create a dense canopy that suppresses weed germination. Cover crops also conserve water by improving the soil’s ability to retain water.

  Certain cover crops can help control pests, such as the mustard plant, which controls harmful nematodes.

  Below the soil, legumes (plants in the Fabaceae family) fix nitrogen. Sugar (in the roots, mucilage) feeds the soil fungi, which help maintain soil structure. Cover crops improve soil health and mitigate climate change through carbon sequestration. By capturing atmospheric carbon dioxide (CO2) through photosynthesis and storing it in the soil, cover crops store or “sequester” carbon, reducing greenhouse gas concentrations in the atmosphere.

  

  Crimson clover is a cover crop that adds organic matter, fixes nitrogen, attracts beneficial insects, and provides nectar for bees and butterflies.

  The nodules on the roots of legumes (clover, vetch, peas, and beans) contain Rhizobium bacteria, which are responsible for fixing nitrogen for the plant. Applying an inoculant to the seed can ensure that the correct type of bacteria specific to that legume are available to the plant once it germinates. Some seeds come already inoculated; you can purchase an inoculant and apply it yourself when planting.

  Cover crops can provide biodiversity and offer habitat for beneficial insects and earthworms -- plant borage, mustard and radish, fava beans, buckwheat, and other plants that bloom. Crimson clover is an example of a cover crop that adds organic matter, fixes nitrogen, attracts beneficial insects, and provides nectar for bees and butterflies. Cover crops potentially reduce the need for chemical fertilizers and pesticides.

  Tips for Planting Cover Crops:

  • Plant cover crops whenever the soil is bare.
  • In the winter: brassicas:( mustard, daikon radish, rape), legumes:( bell and fava beans, vetch, peas, clover), and grasses: (annual rye, barley)
  • In the summer: buckwheat, Phacelia tanacetifolia, Queen Anne’s lace (Daucus carota)
  • For a complete list of cover crops, pictures, and specific benefits, use the California Cover Crop Chart.

  

  Bell beans are excellent cover crops. The flowers attract pollinators and the leaves and blossoms are edible.

  To plant your cover crops, rake the soil until smooth, removing any significant debris from the previous crop. Broadcast the seed at the recommended rate and depth. Cover your seeds to the recommended depth. Water, if necessary, until the rains begin.

  Timing is important when harvesting your cover crop. If you sow your crops in September or October, they can be harvested in February or early March. When they are 25- 50% in flower, chop them up and dig the material into the soil. If I plant Fava beans or Bell beans (a variety of Fava beans), I harvest them when they are in flower and before the beans are set. You can always save a few to eat. The leaves and flowers are edible, too.

  After the harvest, pile the shredded material and wait 3-6 weeks for the plants to decompose. This material has been called “Green Manure,” adding significant nitrogen to the soil. Now, the soil is ready for you to plant your next crops. Shredded cover crops may also be added to your compost pile.
  
  Restore the soil using cover crops, and garden miracles can happen.

  Photo credit: Alice Cason