New Legumes for the South

IT IS JUST as big an accomplishment to introduce a new and suitable legume into any area as it is to build a highway or perfect a new kind of airplane. The same degree, if not type, of knowledge and skill is needed—basic information about weather and soil, the uses to which the project is to be put, fundamental natural and physical laws and sciences, and adaptation. Adaptation means suitability; in the case of plants, it means suitability to the usual farm operations of a locality, its rainfall, fertility, length of season, temperatures, incidence of diseases, topography, and market requirements. It would not do to plant a crimson clover adapted to Carroll County, Iowa, in Carroll County, Ga., and expect it to do equally well in both places.  [My emphasis: "Modern" plant breeders need to re-learn this truism. -ASC]

In recent years several new legumes have been added to southern agriculture. They fit into places and uses for which other legumes were not available. Some of them are new varieties of familiar crops—lespedeza, field peas, crimson clover, vetch, crotalaria, and lupines. Others, hairy indigo and big trefoil, are new to southern farmers. Lespedeza is perhaps the most important.

Korean lespedeza now covers millions of acres in the United States, but it was unknown to agriculture only 25 years ago. But despite its newness, selection of improved strains has been possible, and two varieties of special value have been perfected. One, known as Early Korean, is recognized as superior for northern parts of the lespedeza area, and has extended the use of the crop farther north. It was first selected 15 years ago, but its increase and extension of use are a current development. The other, even more recent, is a high-yielding, late-maturing strain that has been named Climax. Climax was released in 1946 after experimental tests so the amount of seed could be increased. It is adapted to southern sections and will help extend the use of Korean lespedeza in the South. Furthermore, the habit Climax has of maturing late will extend the grazing season and give larger hay yields.

Both strains have outyielded unselected commercial lespedeza in the region of their adaptation. The Early Korean variety not only yields well, but can be grown farther north than commercial Korean. It also makes earlier growth and thus affords earlier grazing. Climax, on the other hand, produces heavy hay yields, makes late growth, and affords later pasturing than other Korean varieties.

Austrian Winter fieldpeas are used extensively for soil improvement, but diseases have greatly reduced their value. After several years of breeding work and study of these diseases, investigators have evolved varieties with partial resistance to disease. Seed of them is now being increased for more general use. Unfortunately, fieldpeas do not develop seed well in the South, and it is necessary to depend on other regions for seed.  In developing discase-resistant strains, hybrid seed selected in the South is sent to other areas for increase and commercial production.

With any legume, old or new, it is desirable or essential that seed be available at low cost. If a crop must be seeded every year, the cost of seed and preparation of land must be given consideration. If a crop can be volunteeted from seed produced on the land by a preceding crop, the cost of seeding is cut way down—an especially desirable factor in the case of soil-improving crops. Spotted bur-clover, crotalaria, and roughpea are three such crops that can be handled in this way. Spotted bur-clover has been grown a number of years, but the use of crotalaria and roughpea is recent. Of interest in this connection is a variety of crimson clover that has recently been developed, Dixie crimson clover.

Another winter legume that produces seed well in the South and can be readily volunteered is big-flower vetch. It has proved its worth in experimental tests, and growers have made commercial plantings of it.  When once established, it persists without further cost for seed, and because it makes good winter growth it is a promising winter cover crop for soil improvement. Like most commercial vetches, it is of European origin. When the plant is ripe the seed shatters easily—a deterrent to seed increase. High cost of seed, however, is of minor importance when one considers that when vetch is once established it will last 5 years or more.

Although crotalaria has been grown widely since 1930, it is a comparatively new crop. It is of special interest for soil improvement because it makes good growth on poor, sandy soils and does not harbor nematodes.

For that reason, crotalaria helps rid the land of this pest, and can be used to advantage in rotation with crops susceptible to nematode damage. Crotalaria also keeps down weed plants that are hosts to nematodes. In orchards, susceptible trees can be protected from infection by keeping a covering of crotalaria on the land during the season when weeds or other susceptible plants might be growing. The full value of crotalaria for use in reducing nematode damage has not been fully appreciated, but with extended use its value for the purpose will be further demonstrated.

The most widely used species is Crotalaria spectabilis. It has been favored for improving soil, but it is poisonous to livestock. The seed particularly contain a deadly poison and cause death even when taken in comparatively small amounts. Plant breeders, therefore, have worked to develop species that are not poisonous and that are just as good for soil improvement. Newer species that have shown their value in experimental plantings are C. intermedia, C. juncea, and C. lanceolata. They are on the way to displacing C. spectabilis. Most used for that purpose is C. intermedia, a variety that is a good soil improver and can be used for forage. Another species, which surpasses C. intermedia in some ways, has been used in experimental plantings for some time and deserves attention for general use. It is C. lanceolata. It does not grow quite so tall as C. intermedia, but yields about the same tonnage of forage and produces a good crop of seed. In experimental plantings it has volunteered more consistently than others.

Of the recently introduced southern crops, none has developed more rapidly than blue lupine. Its introduction is the result of an experimental program started in 1931 by the Department in cooperation with several Southern States. By 1935, results were sufficiently encouraging to justify small demonstrations and plantings to get more seed. In subsequent years, plantings were further increased, and by 1941 large plantings were being made by commercial growers.

Blue lupine is used primarily as a winter green-manure or cover crop.  In the sections to which it is adapted, it is superior for this purpose.  Because blue lupine produces an abundance of easily harvested seed, local seed supplies are assured, an important factor because home-grown seed reduces the cost of seeding and assures seed in season. Seed of the common blue lupine cannot be used for feed, nor can the crop be used as forage because of poisonous alkaloids contained in both the seed and plant. Nonpoisonous strains, however, have been developed recently and give promise of producing a late spring feed crop; if these nonalkaloid strains give satisfactory returns, a local seed feed crop also will be had.

Another species of lupine, known as yellow lupine, has given good results in experimental plantings. In some places it has been superior to the blue type. It seems to be more resistant to some of the diseases that have attacked the blue lupine and in very sandy soils it has made better growth. Nonalkaloid or nonpoisonous strains have been developed in this species, as in the blue lupine, that have possibilities of making yellow lupines a forage crop as well as a soil improving crop. Both lupines make large winter growth, and, therefore, supply greater amounts of organic matter for soil improvement than other winter cover crops. Besides being the largest growing winter cover crops, lupines are the only winter legumes adapted to the South that give promise of producing a seed crop that can be used for livestock feed.

Hairy indigo, a native of Asia, Australia, and Africa, is proving adapted to the lower South for forage and soil improvement. It will grow on moderately poor sandy soil and needs comparatively little lime.  The plants are coarse when grown singly, but in thick stands they make good forage. Tests showed it to be a long-season plant. Its seed matures late, however, so that harvesting of seed is difficult. Recently, an earlier strain was obtained that matured early enough to produce seed without difficulty. The Florida Agricultural Experiment Station, in cooperation with the Department, has taken the lead in developing this plant, which, according to information we now have, can best be used in Florida and other areas touching the Gulf of Mexico. Commercial plantings were made in 1945 and seed was harvested in considerable quantity.

Big trefoil, a legume that has been in experimental plantings in the South for several years, gives promise of being adapted to wet, low-land pastures. It is a perennial, leafy, fine-stemmed plant somewhat similar to alfalfa. It is a native of Europe, but it is grown in many parts of the world. In the United States, commercial plantings are confined to the coastal area of western Oregon and Washington. Since wet areas are especially suited to big trefoil, it is under such conditions that it may have a place in the South. It has survived and made good growth for a number of years in low, wet pasture land at the Georgia Coastal Plain Experiment Station at Tifton, Ga., and more recent plantings have survived and done well under somewhat similar conditions in Florida and North Carolina. A good legume for such situations in the South is needed, and big trefoil may serve this purpose. Where big trefoil is being grown commercially it is recognized as having good forage quality.  It can be cut for hay and used for pasturage. The plants have underground rootstocks, by means of which it spreads. It is not in any way a weed. The seed habits of big trefoil are poor for commercial harvesting.  The seed is extremely small and the pods burst open and scatter the seed when it is ripe.