Planting cover crops to build soil fertility will benefit any garden, big or small. Each season seeds are sowed and the plants are watered and taken care of with the eventual goal to harvest and eat. The soil is what gives the plants the necessary nutrients to grow strong, fight off pests and disease, and produce the best flavored, most nutrient-dense food possible and it requires those nutrients to be given back. Cover crops will give back to the soil.
Some cover crops are capable of adding nitrogen to the soil while others are intended to add a great deal of biomass to the soil; some do both and all of them will help prevent well-built and well-earned soil from eroding. Here we’ll go over the benefits some cover crops provide and give a brief explanation on how and when to plant them.
Cover crops are also referred to as ‘green manure’. At Mad Love Organix we do not have access to manure. We do compost but compost only goes so far. So we stretch out the compost and plant cover crops. The main goal in planting cover crops is to get massive growth in a minimal timeframe when or wherever land is not being used. Rather than having nutrients leach out, nutrients will be stored and preserved and healthy, strong soil will be built.
According to How to Grow Vegetables and Fruits by the Organic Methodwritten by J.I. Rodale, both the plant being grown to harvest and the cover crop should be grown in one season. The cover crops can be grown either before or after the harvest crop. This goes back to taking from the soil then giving back. Or as Rodale points out, giving to the soil then taking the harvest. Either way, the cycle will continue.
Nitrogen-Fixing Cover Crops
Legumes, alfalfa, and clover are known for their nitrogen-fixing capabilities. They’re also some of the cover crops I’m most familiar with seeing in Pennsylvania. They possess this magical ability to take nitrogen out of the air with their leaves and transfer it back into the soil with their roots. They also add organic matter to the soil.
According to the Encyclopedia of Gardening by the American Horticultural Society, the amount of organic matter these plants can add may add as much nitrogen as a regular feeding schedule. Due to its low carbon-to-nitrogen ratios, the organic matter breaks down fast making the nitrogen quickly available.
Planting Winter Rye to Add Biomass
Winter rye is a great cover crop to plant in order to add a lot of biomass to the soil the following season. It’s especially great here in the northeast because it protects the soil from eroding over the winter. To get the full benefit of rye it must be planted before September 15th, according to Rodale in his book. If planted after that it will result in too limited of growth to be of benefit.
Last winter our winter rye was less than 12-inches in height. After a few warm days in March and April it sprouted to more than double that. I used a hoe to chop the majority of the plant off the base of the stem, listening to and enjoying the sounds similar to popcorn popping on a stove top. There was so much biomass I had to carry most of it to the compost heap before turning the remaining – and much shorter – winter rye into the soil.
One other cover crop I enjoy growing is buckwheat. Last year a plot of blossoming buckwheat saved some potted golden berries from Colorado potato beetles. But that was just an added benefit. The main benefit of planting buckwheat as a cover crop is its good for “re-building poor soils or restoring acidic soils,” according to Rodale in his book. It also attracts a lot of bees.
How and When to Plant Cover Crops
Cover crops are thrown over the soil, lightly raked in, and watered, but the art of planting cover crops lies in the timing. Other than wanting cover crops to grow massively tall in a short amount of time, cover crops also need to be turned into the soil at the right time. This will maximize the nutrients availability to the plants being grown next.
According to Monty Don in his book The Complete Gardener, three to four weeks should be waited between turning the cover crops into the soil and planting the crops meant to harvest. This is how long the soil will be busy breaking down the cover crop into available nitrogen and other nutrients for the next crop. He also warns to not wait too long because after about a month “most of the benefits will no longer be available.”
They can also be planted during the growing season by planting them in-between the rows right before harvesting time. Or planted in early summer and allowed to grow then be turned into the soil just in time for a fall planting. Or if the garden is real big, half of it can have cover crops growing for a full season to build soil fertility while the other half is used for heavy vegetable production, and vice versa the following year.