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.

THE AUTHOR

Roland McKee, a senior agronomist, has been with the Department since 1905. As director of investigations on miscellaneous legumes, he has seen the now well-known cover crops like Austrian Winter peas, Willamette vetch, purple vetch, Hungarian vetch, monantha vetch, blue lupine, Crotalaria spectabilis, C. intermedia, C. straita, and alyceclover come into use. He has also instigated the development of nonpoisonous strains of lupines in both the blue- and yellow-flowered species, and the development of high-yielding late strains of annual lespedezas, particularly the variety Climax. Mr. McKee's latest major interest has been the establishment of lupines as a crop. The work was begun in 1931, and in 1946 more than 17 million pounds of seed were produced.