Your soil is like a buffet, full of nutrients for the plants that feed there. But just as a buffet line often runs short on the most popular foods, over time your soil can become depleted of some important ingredients. Using commercial fertilizer is an option, but it’s not the only way. Many of the same nutrients found in commercial fertilizers are also found naturally in cover crops, also known as green manure.
If plants' nutritional requirements are not met, they can't reach their full potential. In the worst case, they may die. As plants use nutrients in the soil, the nutrients need to be replenished. A green manure is a type of cover crop. It's planted specifically to be tilled under while still green and growing in order to add nutrients to the soil. Like its more famous cousin and namesake, green manure enhances organic matter in the garden and helps attract worms and beneficial microorganisms. And unlike its more fragrant cousin, a green manure cover crop also prevents weeds and erosion.
Cover crops, mostly consisting of legumes and grasses, have been used in commercial agriculture for years. Plants from the legume family (such as field peas, soybeans, alfalfa and clover) add nitrogen to the soil. Grasses and other plants (such as oats, buckwheat and rye) add organic matter. Depending on the growing season in your region, green manures are planted either before or after the food crop. Many green manures are winter hardy and should be planted in the fall and tilled under in spring prior to planting.
You don't have to be a commercial farmer to take advantage of green manure. Use green manure to rejuvenate your home garden during the active growing season or the off-season. For a new twist on crop rotation, divide your garden into two sections. During the growing season, plant one section with a food crop and another with a green manure. Till in the cover crop at the end of the season and reverse the sections the following year. If you don't have room to divide your garden during the growing season, plant a winter hardy green manure for off-season growth.