Green Manure Crops

What is a green manure crop? A cover crop? The term “green manure crop” refers to any crop that may be turned into the soil in an undecomposed, green tissue stage. In contrast, a cover crop refers to a more or less permanent crop used for the purpose of preventing erosion.

How are green manure crops planted? For small areas, seeds of the green manure crops can be broadcast. For large areas a drill is used. Seeds should not be covered too deeply – approximately twice their diameter is sufficient.

What are several good summer green manure crops? The crops most commonly used for summer green manure are alfalfa, cowpeas, crimson clover, red clover, sweet clover, crotalaria, lespedeza, soybeans, and Sudan grass.

What green manure crop can be left growing in the ground over winter to be turned under in spring? The most common winter green manure crops are rye, perennial rye grass, and oats.

What quantity of seed should be sown, per 1,000 sq. ft., of green manure crops? Alfalfa, 1/2 lb.; cowpeas, 2-1/2 to 3 lbs.; crimson clover and red clover, 1/2 lb.; sweet clover, 1/2 to 3/4 lb; crotalaria, 1/2 to 3/4 lb.; lespedeza, 1/2 lb.; soybeans, 2 – 3 lbs.; Sudan grass, 1/2 to 3/4 lb.; rye, 2 to 3 lbs.; rye grass, 1 to 2 lbs.; buckwheat, 1-1/2 lbs. These are approximate amounts. For thick and quick coverage, on small areas, they can be increased up to double these quantities.

I cannot obtain cow manure. What do you suggest as a substitute? Old, partly rotted straw, or alfalfa hay, together with a complete fertilizer, can be used as substitutes. Plow in early in the fall and add fertilizer at time of plowing. Or use a green manure crop.

How tall should a green manure crop be before it is turned under? In general, it is best to turn under green crops when their succulence is near the maximum, yet at a time when abundant tops have been produced. This stage occurs when they are about, or a little beyond, half mature. Always allow at least three weeks to elapse between plowing under a green manure crop and planting.

Are clover and buckwheat good for soil? Clover and buckwheat are good green manure crops, but soybeans and rye are better and quicker. Sow soybeans in the spring and plow under in early fall. Sow rye in September and plow under in the spring. Use 2 lbs. per 1,000 sq. ft.

Where a green manure crop is plowed under in fall, is it advisable to follow with a winter crop? Only where there is possibility of soil erosion.

What winter green manure crops can be used following the turning under of red clover? Rye, rye grass, or oats.

How soon after the summer green manure crop is turned under can the fall crop be sown? It is advisable to delay the sowing of the second crop three weeks, if possible; but follow the specific planting dates recommended for the winter crop used.

When should winter green manure crops be sown? Late August or early September. Rye can be sown as late as first week of October. If soil areas are available, sow at any time if space is not needed for planting the same season.

If soil is respaded in spring, following turning under of green manure (clover) in fall, will the crop come to the top? If the green manure crop is turned under at the proper time, it will be sufficiently decomposed by spring so that respading can be done.

When land is cleared, and winter rye is sown, what should be done in spring to prepare for vegetables? Plow the rye under in April. Apply a fertilizer recommended for vegetables at twice the recommended rate.

How can organics and nitrogen be supplied in city gardens without compost or chemical fertilizer? Peat moss and dried manures may be used. Soybean meal and cottonseed meal will add nitrogen.

Should turf and large roots be removed from virgin soil or turned under to make humus? It is advisable to turn under as much organic matter as possible in preparing soil for planting. Turf and roots of annual and herbaceous plants should be turned under. Remove the large roots of woody plants.

Can a green manure crop be planted which will raise the pH and sweeten the soil? No, green manure crops in themselves exert very little influence on the degree of acidity of the soil.

When there is a shortage of animal fertilizer, what kind and proportion of other fertilizer are suggested for garden use? Incorporate green manures. Apply fertilizers made for vegetable gardens at twice the recommended rate.

Do any plants, other than legumes and green manure crops, supply any nutrients to soil? Any plant which is turned under supplies a certain amount of nutrients. The proportions vary with the type of plant.

Does planting rye in fall and plowing under in spring keep up fertility of the soil? The use of rye as a green manure crop will do little toward increasing the nitrogen content of the soil; in fact, it may even decrease it temporarily. It does, however, add humus, and thus helps to increase crop production.

Should green manure crops such as rye be used every year? In gardens devoted to the production of vegetables or annual flowers, it is advisable to sow a winter green manure crop each autumn.

At what stage should rye be turned under? As late as possible to produce more green growth, and up to within 3 weeks of planting time.

Should rye be completely covered when it is turned under? Yes, but the green manure crop should be incorporated with the upper 8 to 12 ins. of soil instead of being plowed or dug under in a layer. If a few of the stems are not covered, it is all right.

What is a legume? All leguminous plants belong to the pea family, recognizable by the formation of their flowers. Peas, beans, and clovers are legumes. They all attract bacteria which collect nitrogen and store it on the roots. The small nodules on the roots, when they decay, add nitrogen to the soil.

What is the special advantage of using a leguminous green manure crop? The advantage of a legume (as compared to a non-legume) is that the nitrogen content of the soil will be increased by the root-nodule organisms. However, the legume crops take longer to grow. For a small garden, rye or perennial rye grass is usually more practical.

Are inoculant powders for use on legumes really helpful? Yes. These inoculant powders are listed under various trade names (such as Nitragen, Legume Aid) and are obtainable in local garden stores. They are used to assist in the development of nitrogen-fixing bacteria on the roots of leguminous plants. They are applied when seeds are planted. The mixtures vary with the crop to be planted, so the crop should always be mentioned when buying these products.

Is it advisable to try to grow alfalfa for soil improvement in southern parts of Maine? Yes. But plant early (mid-August) to avoid heaving out and winter killing. Sow 12 to 15 lbs. per acre.

How is the land prepared for growing alfalfa? Same as for any other crop. It may be necessary to add lime.

When is it best to plant crimson clover and expect results from it in improving the soil for a garden? Crimson clover is usually seeded in July or August, or at least 6 weeks before normal date of the first killing frost in fall. It may be turned under the following spring or early summer.

Do you plow crimson clover under when it is in bloom? It is best to turn it under when in bloom, or shortly after this stage. It can, however, be turned under at any stage; but the less growth has been made, the less humus will be produced.

Are Austrian peas good to use as a green manure crop? Yes, they are a good winter crop. Use soybeans as a summer crop. Plow both under to add organic matter to the soil.

At what rate should soybeans be sown for a green manure crop? Three lbs. per 1,000 sq. ft.