Buckwheat, when used as a cover crop, can reduce both the emergence and growth of weeds, thereby presenting an easy and economical alternative to herbicides. Buckwheat is a short-duration broadleaved annual species which provides very effective weed suppression due to its rapid early growth that establishes a canopy faster than many weeds.
Phacelia is a plant that is native to the United States, but was adopted and improved by Europeans for us as a cover crop. Phacelia is quick to establish and will winterkill at 18 degrees Fahrenheit. Phacelia is an excellent source of high quality nectar and pollen, which increases the population and diversity of beneficial insects. Phacelia will begin to slower 6-8 weeks after emergence and will continue to flower for 4-6 weeks. Phacelia is comparable to Buckwheat in many ways, but is more resistant to cold and drought. Phacelia can also be used for forage, as a green manure crop, nematode control, and a nitrogen trap crop.
Sunn Hemp is a tropical legume that acts like a summer annual in the United States and is an excellent choice for increasing organic matter, nitrogen fixation, nematode suppression, and weed control. Sunn Hemp (seed inoculation required) can product over 5,000 pounds of biomass and 100 pounds of nitrogen per acre in 8-12 weeks of frost-free growth conditions. It is recommended that Sunn Hemp be mowed back to 12-18 inches high when it reaches 6 feet tall to allow the residue to break down faster. A killing frost will eliminate Sunn Hemp.
Summer annuals such as sorghum, pearl millet, and sorhum/sudangrass can provide high quality forage and silage as well as an excellent cover crop in a short period of time during the summer months. Most varieties work well in cover crop situations after wheat or small grain harvest, or when cool season grasses are less productive. Heat, moisture, and fertility will make them very productive and when moisture is short, the plants will wait for the rain.