Foraoe Plants for ( Fltiyation on Alkali Soils

FORAOE PLANTS FOR ( FLTIYATION ON ALKALI SOILS. By JARED G. SMITH, Assistant Agrostologist. INTRODUCTION. When the excess of alkali in a soil rises to such a sum total that the cereals can not be grown, the best use to which the land can be put is the growth of forage. There is no crop, so far as known, which can be profitably grown on land that contains over 2 per cent of the combined alkalies within the first 2 inches of surface soil. Soils containing as much as 1 per cent of alkalies within the first 2 inches will not grow cereals, and the maximum for trees, vines, and root crops is much lower. There are extensive areas in the West which are thus excluded from the cate- gory of farming lands because of the excess of alkalies. Such lands are not necessarily barren, although they can not be profitably cultivated. They are often covered by a rank growth of vegetation, indi- cating that there is an abundance of plant food in the soil, if only the plants are so tolerant of alkali as to be able to secure it. Many of the alkaii plants have considerable value as forage, and of these some few show special adaptation to the changed conditions which cultivation brings. The crops which originated in humid regions will not grow on soils which are strongly impregnated with the alkalies, and so to meet the conditions one must either take the useful plants of the alkali regions of his own country or depend upon those which have been introduced from similar regions elsewhere. If it is not possible to grow a vine- yard or an orchard, a field of alfalfa or one of grain, there are a number of forage crops that can be successfully cultivated, because they originated in alkali regions and are tolerant of considerable amounts of alkali in the soil. As the amount of alkali in the soil increases the number of species of plants which will thrive decreases. Hilgard, Loughridge, and Davy have published many interesting observations as to the occur- rence of different plants an alkali soils, and as to the maximum quan- tities of alkali of which different native plants and cultivated crops are tolerant. Davy states that there are in the State of California, 197 species that grow only on alkali soils. Some of these occur in similar situations in many other parts of the West, while others are found only in California. The greasewood of the Pacific coast {Allen- rolfea occidentalis) will grow in a soil containing a maximum of 194,760 535 536 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. pounds of alkali salts pen* acre to the depth of 1 foot. The scrub saltbush {Atriplex polijcarpu) will grow where there are 78,240 pounds, while samphire {Salicorniu) Avas found gi'owing on land wiiich con- tained 306,000 pounds, or more than fourteen times as much as the greatest amount of Avhich wheat is tolerant. Wheat will grow on land w^liich contains a total of 20,520 pounds or less of the sulphates, carbonates, chlorides, and nitrates of soda and potash per acre to the depth of 1 foot. This amount of alkalies is less than one-half of 1 per cent by weight of the soil. In contrast, Kentucky blue grass Avill only withstand a total of 2,680 pounds, w^hile Australian salt bush will endure 30,020 pounds. EFFECT OF ALKALIES ON PLANT GROWTH. When wheat is sown on land containing as much as 1 per cent of the alkalies, the seeds are unable to germinate, or if germination takes place the young i)lants die of thirst, although the soil may contain wâter enough for the needs of the plants if the alkalies were eliminated. Alkalies in solution increase the density of the soil waters, and the young plants die of thirst, because the soil absorbs the Avater from their roots instead of the roots absorbing water from the soil. There is usually more alkali at the surface than at the depths where the roots feed, and it is often the case that a crop will live on land containing an amount of alkali which w-ould prevent Che germination of its seeds. Thus alfalfa is an excellent crop for mod- eratelj'^ alkaline soils, because the thick growth and abundant leafage shade the soil and prevent evaporation of water and accumulation of alkalies at the surface. The long taproots penetrate to the deeper levels, where there is comparatively little of the alkali present. When there is an excess of the injurious salts at the surface, the seeds are unable to absorb water and there is marked retardation of germination. Buffum^ has shown that while 82 per cent of alfalfa seeds germinated in five days on soil from wdiich the alkali liad been extracted and in four days on wet pads containing no alkali, it required fourteen days to germinate 80 per cent when 1 per cent of combined alkalies was present. A similar retardation took place with turnips, barley, rye, oats, and wheat. The seeds appear to lie dormant for a short time, ready to start growth w^hen the alkaline solution becomes sufficiently diluted to enable them to take up the necessary water. Similar germination experiments were undertaken by Dr. Leather^ during his investigations of **usar" land in northwêst India in 1895 and 1896 to determine the effect of the soda salts on seeds of corn, wheat, barley, peas, gram, and cotton. The germination of the cereals was seriously affected by seven-tenths per cent of either sal soda or Glauber's salt in the soil. The germination of corn and barley was »Bui. 29, Wyo. Agr. Exp, Sta., 189G. 2 Agr. Ledg. Ko. 13,1897 (Calcutta). FORAGE PLANTS FOR ALKALI SOILS. 537 retarded by from two-tenths to four-tenths per cent of common salt, and cotton was similarly affected. Peas and chick-peas were affected by a much smaller per cent. Two-tenths per cent of the black alkali prevents the growth of most cultivated crops from the seed, corroding and destroying the plumule after it has emerged from the seed coats. But where the deeply rooted leguminous crops, such as alfalfa, once become established, or where rooted cuttings of other plants are set out so that the roots feed below the surface, they will withstand more alkali than the cereals or other annuals. The salts are concentrated at the surface, and thus prevent the germination of the seeds, while the alfalfa and the rooted cuttings feed at depths where a very much smaller amount is present. NATIVE PLANTS OF ALKALI SOILS. Among the plants which only grow on alkali soils, there ai'e many which are valuable for forage. The late Baron Von Mueller, the eminent Australian botanist, first drew attention to the importance of the cultivation of such plants. In the first edition of his work, * ' Select extratropical cultivated plants," published in 1872, he showed the possibility of utilizing the orache, a saltbush of the gardens, which is a native of southern Europe and Africa. In the 3876 edition he added two species of Australian saltbushes to his list. Later ext)lorations, conducted largely by Yon Mueller and associated botanists, developed the fact that the vegetation of extensive areas in the central portion of Australia, notably in western New South AYales, Queensland, and South Australia, consisted almost entirely of Atriplex. The fact was known that these Atriplex, or saltbush, areas would carry and main- tain in better condition a larger number of sheep and cattle than would be supposed, judging from the limited grass vegetation. Stock grazed on saltbush was also remarkably free from parasitic diseases, and it was assumed that the plants had tonic properties owing to some bitter principle, together with the large amount of salt, found in the leaves. Through Von Mueller's efforts, the cultivation of a number of saltbushes was undertaken in South Africa and Australia, northwest India, and later in California, and everywhere the plants showed remarkable adaptation to saline or alkali-impregnated soils. The success of these experiments led to similar ones with saltbushes native to the various alkali regions of the world, and a larger number of species have been shown to be adaptable to the various climatic zones. To show the small beginnings of one of these experiments, Mr. E. G.- Alston, the well-known experimental agriculturist of Cape Colony, planted in April, 1886, six seeds of Atriplex haJimoides^ which had been obtained by Professor MacOwan from Baron Von Mueller. Two of the seeds germinated, but one plant died before reaching maturity. The seeds from the single remaining plant were saved and tried the 538 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. following yoai*s on ¿i larger scale. This one plant lias been the mother of nearly all of the South African stock of a species now widely cultivated by sheep men in all of the colonies. The seed production of all of the saltbushes is enormous. Plants of Atriplex semÜKWcaia^ grown on the grounds of the Department of Agriculture, commenced to blossom and ripen seed w^hen only G inches high, and continued until their growth was cheeked by severe frosts, about the first of November, It is probable that many of the plants ripen thousands of seeds in a season's growth. A plat of Atriplex holocarpa, 6 feet square, ripened half a bushel of seed, gathered by frequent iîckings during the season of 1898. On the first of Novem- ber, when growth had entirely ceased, the ground was covered to the depth of 2 inches with the globular, spongy seeds.

Load more