We live in a part of Washington State where soils are lean and rocky. Our soils are only one step away from being the rocks that they were created from and lack the rich humus of organic matter that aids in water retention and allows plant roots to penetrate deeply into the earth. This can be a challenge when establishing a new garden. There are different techniques used for creating good soil but one of my favorites is the incorporation of green manure crops, also known as cover crops.
Green manure or cover crops are made up of a variety of plant species that, rather than being harvested for the fruits, are turned into to the soil to add nitrogen and organic matter and increase the water retention and overall structure of the soil. Cover crops can be incorporated into an already established garden rotation for a portion of the growing season or can be used to fallow a piece of garden for a year or more before being turned into the soil. Some of the advantages, other than adding organic matter to the soil, is the mining of nutrients from the deeper regions of the soil profile and bringing these nutrients to the surface, the increase of porosity through root penetration into harder soils and the stabilization of soils during the shoulder seasons and winter months when soil is prone to blowing away when left bare and un-planted which ultimately leads to nitrogen leaching.
Here is a quick list of cover crops that are suitable for a home garden:
· Triticale and Winter Rye can be planted anytime. Overwinters well if planted in September. Has an extensive root system to hold available nitrogen. Mow and till in 2-3 weeks before planting vegetable crop.
· Hairy Vetch and Winter Pea can be planted anytime. Will overwinter well if planted in September. Will fix nitrogen from the air if innoculated with rhizobial bacteria. Mow and till in 2-3 weeks before planting vegetable crop.
· Buckwheat can be planted from April until August. It grows quickly and can out-compete most weeds. The flowers attract a large diversity of beneficial insects. Mow and till under when seed heads are green, or it will re-seed.
· Annual Ryegrass can be planted anytime. It is useful in areas known to be weed prone as it tolerates mowing. Will hold available nitrogen and help to build soil structure. Mow and till in 2-3 weeks before planting vegetable crop.
· Clovers can be planted anytime. Will fix nitrogen from the air if innoculated with rhizobial bacteria. Taproots help open compacted soils and flowers attract a large diversity of beneficial insects. Most will overwinter. Can be very useful in underplanting an already established vegetable crop. Mow and till in 2-3 weeks before planting vegetable crop.