Green Manures & Cover Crops

Lyle T. Stoltman
King Conservation District

Organic farming has made a comeback during the last decade. Consumers and landowners are willing to reduce the amount of chemical applications on behalf of the environment.

Many of the "organic" farming techniques aren't new ideas. They are old methods that have been forgotten as technology develops alternatives, or haven't been passed down from one generation to the next. One explanation is hat over the last 50 years people have moved into urbanized areas. Now their children are lured back to the country without the benefit of hands-on farming experience.

The use of green manures and cover crops to add organics and prevent soil erosion by wind and rain are two of these practices.

The organic matter content in soils is one of the most important components of a fertile soil. Some benefits of organic matter are seen as:

1. Increased nutrient availability and holding capacity.
2. Improved tilth, i.e. workability of the soil.
3. Increased water holding capacities.
4. Reduction of soil erosion on bare soils.
5. Decreased weed infestations due to competition.
6. Improved water quality.

A green manure crop is usually seeded early in the fall when temperatures are favorable and adequate moisture allows germination. The crops are then plowed in before they go to seed at least 7-1O days before planting. It a good idea to be sure there is adequate moisture in the soil when you turn the crop over to insure proper rotting 0f the vegetation. If possible, disc lightly before plowing the stand under to aid in decomposition.

Legumes are well suited for being planted Examples include lupines, vetch, lentils, chick peas, clover and alfalfa. Perennial clovers are not recommended as green manure crops.

Annual grasses such as cereal grains may also be used. A mix combining grasses an legumes makes an excellent green manure or protective cover crop.

An acre of legumes tilled under can provide 100-200 lbs. of nitrogen Because the nutrients are contained within the plants, minerals are actually stored over the winter. This is in contrast to the quick release characteristics of most synthetic fertilizers.

Soils with textures high in clays and sands can be improved by the addition of organics. Clays are less likely to become compacted and sandy soils won't be as draughty during the summer.

Agriculturally speaking, crop production can be increased and fertilizer costs can be reduced. On bare soils green manure crops can compete with weeds and suppress their growth, reducing the costs or need for herbicides. It's a farming practice that is beneficial in urban areas, too, especially for lawns and gardens.

Green manures and cover crops are relatively inexpensive to grow and are a good practice for protecting the environment. Call your local Conservation District, Soil Conservation Service, or Cooperative Extension office for more details.

Seeding rates

• Cereal grains planted at 100 lbs./ac. (wheat, oats, etc.)
• Cereal grains at 80 lbs./ac. and hairy vetch at 20 lbs./ac.
• Cereal grains at 80 lbs./ac. and sickleweed lupine at 30 lbs./ac.
• Crimson clover at 120 lbs./ac. (Can be 2 ft. tall by April. Crimson clover is an annual and is very attractive.)
• Austrian field pea is a good one for Western Wa. because it survives our winter very well. plant at 80 lbs./ac.
• Faba bean is good because its very high in Nitrogen. Plant at 1O lbs./ac.
• Winter wheat at 200 lbs./ac. (Don't let it get too tall or tillage can be very difficult.)
• Annual rye grass, 15 lbs./ac. (Establishes quickly, strongly competitive and retards establishment of perennial grasses and legumes if seeded heavily in a mixture.)
• Field brome planted at 15 lbs./ac.

NOTES:

• One acre equals 43,560 ft. sq. (Divide lbs./ac. by 43 to get lbs./1000 ft. sq.)
• Small seeded varieties such as annual rye and field brome have many more seeds per pound than larger types, e.g. cereal grains, which is why it takes fewer lbs./ac. to obtain the same coverage.

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