alkali lands in Egypt, by T. H. Kearney and T. H. Means, Yearbook United States Department of Agriculture for 1902, p. 573; Agricultural explorations in Algeria, by T. H. Kearney and T. H. Means, Bulletin No. 80, Bureau of Plant Industry, United States Department of Agriculture, 1905; Alkali and alkali soils, by W. H. Heileman, Bulletin No. 49, Washington Agricultural Experiment Station; Origin, value and reclamation of alkali lands, by E. W. Hilgard, Yearbook United States Department of Agriculture for 1895, p. 103; Nature, value and utilization of alkali lands, by E. W. Hilgard, Bulletin No. 128, California Agricultural Experiment Station (1900); Annual Reports of the California Experiment Station for 1879, 1880, 1888-89, 1890, 1891-92, 1897-98; The distribution of the salts in alkali soils, by E. W. Hilgard and R. H. Loughridge, Bulletin No. 108, California Agricultural Experiment Station (1895), and Annual Report same station for 1894-95, p. 37; Investigations of alkali lands, by R. H. Loughridge, Report of California Agricultural Experiment Station for 1895-97, p. 37; Effect of alkali on citrus trees, by R. H. Loughridge, Report of the Director, California Agricultural Experiment Station, for 1897-8, p. 99; Tolerance of alkali by various cultures, by R. H. Loughridge, Bulletin No. 133, California Agricultural Experiment Station (1901); Reclamation of alkali lands in Egypt, by Thos. H. Means, Bulletin No. 21, Bureau of Soils, United States Department of Agriculture (1903); Division and Bureau of Soils, United States Department of Agriculture, Reports of Field Operations for 1899, 1900, 1901, 1902 and 1903; Effect of alkali on seed germination, by John Stewart, Ninth Annual Report Utah Agricultural Experiment Station, p. 26 (1898); Alkali, by J. D. Tinsley, Bulletin No. 42, New Mexico Agricultural Experiment Station (1902); The alkali soils. of Montana, by F. W. Traphagen, Bulletin 18, 54, Montana Agricultural Experiment Station (1904). Reclamation of alkali soils, by C. W. Dorsey, Bulletin No. 34, Bureau of Soils. Bulletin No. 35, Bureau of Soils, by Dorsey, discusses alkali resistence of plants and gives a bibliography of American writings. The preceding articles treat the subject of alkali soil mostly from the viewpoint of the arid regions, where such soil occurs in large and more or less continuous areas; but one of the characteristics of the soil of the semi-arid regions is the occasional occurrence of small "alkali spots." (Fig. 684, page 519.) They may vary in size from a few square yards to several acres. The handling of this soil is not so difficult as that of the larger and more strongly' impregnated tracts, found in irrigated regions. The alkali is usually white, being composed largely of sulfates of magnesium, sodium, potassium and calcium, chlorids of sodium and potassium, and some nitrates. These alkalis or soluble salts usually do not occur in sufficient quantities to prevent completely the growth of crops in times of good rainfall, but in periods of drought the concentration of the salts, and the compact condition of the soil which they help to produce, give rise to conditions so unfavorable to the crop that it is very likely to succumb, either because of the alkali alone, or because of the combined effect of alkali and drought. The effect of the salts is to make the soil more compact, and thus to dry more readily. Alkali spots may occur either on hillsides or on bottom-land. They are more common on heavy soil than on light. Land that has alkali spots is likely to be good, aside from that objection, and when the effect of the alkali has been sufficiently mitigated the land is usually very productive. There are a number of operations that may be applied with profit to these soils. Deep plowing is always desirable, but it should never be done when the soil is very wet. One of the simplest and most effective methods of treatment is plowing under fresh barnyard manure or other coarse and easily decomposable organic matter. This lessens the compactness, produces humus and promotes drainage. In a dry season it is possible that the fresh manure will dry the soil, as decomposition will be slow, but it is not advisable to delay treatment of alkali spots from fear of any such result. The manure should be added in heavy dressings and the applications continued for a number of seasons. As thorough drainage as possible should be secured by means either of tile drains or open ditches. Tile drains involve a considerable initial expense, and are likely to drain the water slowly at first, but they are a permanent cure for the difficulty, and improve greatly the mechanical condition of the soil. Open drains are not so effective as tile drains, but they are of service, and should be used in connection with the other methods of treatment. The alkalis are soluble and are readily carried off by water if it can be brought in contact with them. Certain plants are more tolerant of alkali than are others, and they absorb large quantities of salts which are removed from the soil when the crop is harvested. Sugar-beets are for these reasons one of the best crops for alkali land, and can be raised on most alkali spots. Alfalfa and bromegrass will be of service on such soils; of the cereals, oats is a good crop to raise. Constant cropping will improve the alkali spots, regardless of what the crop is. Moisture should evaporate through plants, not directly from the soil. Thorough stirring of the surface soil should be given hoed crops, and to the entire spot when no crops are on the land. Fall plowing is desirable, unless the soil drifts, because alkali soil has a tendency to compact and thus aërate inadequately. By plowing in the fall a better opportunity is given the soil to weather. Plowing for corn and surface planting is generally better practice than listing. By the use of the methods mentioned, especially when combined, any alkali spot as commonly found in semi-arid regions may be rendered very productive in a few years. CHAPTER XVI SOIL SURVEYS AND THEIR SIGNIFICANCE By MILTON WHITNEY and J. A. BONSTEEL HE early explorers and colonizers of the present domain of the United States were, almost without exception, in search of materials that would yield immediate financial returns to the companies of "gentlemen adventurers" by whom the expeditions were outfitted. Thus the early accounts of the new continent are taken up with relations, largely fabulous, of the precious minerals, furs and naval stores from which the associations and the governments at home might reap rich profits. With the coming of real colonization enterprises, information regarding the soil, the climate, and the natural vegetable products of the country, was eagerly desired, and many of the earlier explorers used their knowledge of the new continent for the enlightenment of their countrymen. Some of the accounts were written more with an idea of pleasing the reader than with a view of strict adherence to fact. Aside from the very general accounts of this period, which lasted until the end of the eighteenth century, nothing was written and little was known of the exact character of the soils of the new continent. About the close of the Revolutionary War, an agricultural revival was inaugurated in England, and the work of Sir Humphrey Davy, coupled with the interest of great landowners, brought agricul ture prominently to the front as a subject for investigation. An echo of this English movement soon followed in the newly established States, and agricultural societies began to be formed. They devoted themselves first to making known the resources of their respective loealities, to reforming the demoralized systems of cultivation of the time, and to publishing special papers on various technical subjects. The New York State Agricultural Society in 1798 and 1799 employed Dr. Mitchill to study the soils of that state, and his reports may be found in the Medical Repository, Vols. I, III and V. Dr. Mitchill first established beyond doubt the vegetable and organic origin of peat and muck deposits. Such material had previously been classed as one of the "earths," i. e., of unknown, probably inorganic, origin. Other societies, notably in Rhode Island, Vermont and Pennsylvania, made scattered observations on the soils of their localities. In 1821, Featherstonehaugh wrote an extremely able and scientific paper for the New York State Board of Agriculture, in which he developed the germ of the soil survey idea in the following words: "These soils also are various in their appearance and properties, and the forms of vegetables and their properties appear to depend on the particular nature of the soil they grow in, aided in some degree by climate and situation. We know that in sandy districts the pine tree universally prevails; we may therefore conclude that the pine is the natural production of that soil. We know also that the particular varieties of trees and plants, such as black ash and the spruce, are invariably found in swamps and low, marshy places; we therefore very justly conclude they are the natural productions of a rich vegetable mold continually saturated with water. It being then conceded that particular soils under the same circumstances will always produce the same results, the next step to learn is, how many varieties of soil there are and what are the properties of each variety, as they are connected with vegetation." (Featherstonehaugh, Memoirs of the Board of Agriculture of New York State, Vol. I, 1821, p. 54, et seq.) This attitude of mind in regard to soils was greatly affected by Liebig's work on the chemical analysis of the mineral matter of soils. Liebig's work seemed to reduce soil study and agriculture to a system of mathematical accuracy and certainty. It was believed, and the belief has not entirely passed away, that an analysis of any given plant would show its requirements from the soil; that an analysis of the soil would show its capabilities or deficiencies; that these being known, the material necessary to supply any soil deficiencies might be applied in the form of natural or artificial chemicals, and the process of producing crops would be made easy. The simplicity of such a proceeding rendered the Liebig hypothesis wonderfully popular, and the sweep of its popularity naturally obliterated the development of the physical, climatic and drainage studies of the soils. Thousands of chemical analyses were made, and as early as 1820 to 1830 various agricultural surveys were organized in Maine, Massachusetts, New York and North Carolina. One of the first official recognitions of the importance of soil study was in the establishment in 1847 by the legislature of Maryland of the official position of Agricultural Chemist for the state. The chemist was required to spend one year in each of the districts of the state and one month in each county, and he was also required to visit each election district for the purpose of studying soils and other agricultural conditions. His duties included the analyses of specimens of soils sent to his office, and of all the different varieties of soils which he himself might find within the state. In the year 1850, Dr. D. D. Owens, assisted by Dr. Robert Peters, began an extensive chemical examination of the soils of Kentucky, in connection with the Geological Survey of that state. About 1858, Dr. E. W. Hilgard began the study of the geology and the soils of Mississippi. He classified the soils of the state according to their geological origin, their physical and chemical characteristics, and the character of their natural vegetation. His report on the agriculture and geology of Mississippi was published in 1860. In it is to be found the first soil map published in the United States. The map covers one octavo page, and represents the generalized soil conditions of the entire state of Mississippi. The Civil War interrupted this work by Dr. Hilgard, and the scene of his activities was transferred to California in 1875. In 1880, he prepared a generalized soil map of the cotton-producing states, and also special maps of each of these states, for publication in connection with his report on cotton, included in the Tenth Census. In this work he employed the same basis of geological origin, chemical and physical properties, and the character of the natural timber growth for the classification of soils. The report is accompanied by a large number of chemical analyses. In 1861, and at other more recent dates, Johnson pointed out the doubtful utility of the ordinary chemical analysis of soils, as an indication of the relation of the soil to plant growth, except in special and rather rare cases. He showed that the ordinary amounts of fertilizer can not be detected in the soil by the usual methods of chemical analysis, and also that nearly all the analyses by the methods then used indicated an amount of plant-food even in the poorest soils sufficient for the production of many average crops. In 1891, the Maryland Experiment Station made an investigation of the physical properties of Maryland soils in coöperation with the United States Department of Agriculture. This work was published in 1892 as a Weather Bureau bulletin entitled, "The Physical Properties of Soils in their Relation to Crop Production." In this bulletin it was shown that there was a direct relationship existing between the texture of the soils, the crops to which they were adapted, and the agricultural methods best suited to the land. This had already been recognized to a certain extent by the farmers themselves in the specialization of truck-farming on the light, sandy soils of the coastal plain. This investigation showed further that nearly all soil types that differ in agricultural value and in adaptation to crops, differ also in texture and in their other physical properties, to an extent sufficient to account for the differences in crop adaptation as observed in the field. In 1893, a generalized map of the state of Maryland was prepared for distribution at the Columbian Exposition. On this map were shown the relationships of the soils to the geology of the state; the relationships of the soils to actual crop production; and the distribution of both soils and dominant crops throughout the state. This map, although published on a small scale, contained all of the fundamental principles on which the more detailed mapping of the Bureau of Soils of the United States Department of Agriculture has since been based. In 1899, the Division of Soils of the United States Department of Agriculture began actual field mapping of the soils of the United States. The soils of the New England tobacco district along the Connecticut river were mapped, and the adaptation of the different kinds of soils to the different varieties of tobacco was pointed out. At the same time, maps were made of various areas located in the arid West and Southwest, and an additional study of alkali and irrigation conditions undertaken. This work has been continued to the present time, and the Bureau of Soils now maintains about twenty parties continually in the field for the mapping of the soils of the United States. Soil-mapping. The field classification of soils is based on those features which control the kind of crop that should be raised on the different kinds of soils. The fundamental principle of the classification involves the water-holding capacity of the soil, its surface topography and its climatic surroundings. The features causing variation in these respects are found to be the texture of the soil, or the absolute size of the soil grains; the structure of the soil, or the state of aggregation of the soil grains; the amount, condition and distribution of partially decayed organic matter within the soil; the altitude, surface topography and the character of the materials underlying the soil, i. e., the physiography of the soil body. In making a soil map of any given region, it is first necessary to secure an accurate base map on which the conditions actually found may be plotted. For this purpose, the United States topographic sheets on the scale of one inch to the mile are considered as standard. In areas for which such maps have not been made, the best available county maps, or maps made by private parties, are secured, and their scale changed when necessary, by photographic process, to the standard of one inch to one mile. If the map is imperfect either because of age or because it represents only a few of the necessary features to be considered, it is revised by the field party, who use a plane-table for plotting on the map any additional features that may be required. Each field party is equipped with an ordinary one and one-halfinch auger having a three-foot stem (Fig. 690); by means of this auger a sample of the surface soil is bored out, and its texture, struc Fig. 690. The soil auger used by field parties of the Bureau of Soils, for securing samples. ture and other characteristics are determined by the operator. The boring is continued to a depth of three feet, and the record of the boring taken in the note-book. When several of these borings distributed over a field have been taken, the field man is in a position to classify the soils that he has examined into their respective groups, as clay, sandy loam, gravelly loam, and so on. He then proceeds to plot the extent and the boundaries of these various types of soil on his map, using colored pencils to indicate the different types. Two men work together in the party. As they proceed along the road one is engaged in making borings while the other is recording distances, sketching boundaries, or doing any necessary plane-table work. Under ordinary circumstances the party can Fig. 691. Outfit for sampling, shipping and storing soil samples. take a sufficient number of borings each day to enable them to map four to six square miles of territory. Unusual complexity of soil conditions reduces this rate, as unusual uniformity increases it. When a sufficient amount of territory has been covered to warrant general conclusions, a study of the crop conditions on each soil is conducted simultaneously with the field mapping. The farmers of the region are interviewed with regard to the agricultural methods employed, the crops raised on each soil type and the yields secured; on the use of fertilizers, both regarding amount and kinds, and the results secured on the various soil types for the different crops. Any special industry, such as trucking, fruit-growing, berry-raising or sugarbeet production, is thoroughly studied. The transportation facilities and the markets to which Fig. 692. Electrical instrument for determination of amount of alkali in a soil. produce is shipped are ascertained. The history of the agricultural development of the region is secured, either from pioneer settlers or from local histories, and these are supplemented by more general information furnished from the central office. The local climatic conditions are learned, and these, in connection with the records of the United States Weather Bureau, furnish the material for a report on the climate of the district being surveyed. On the completion of the field work within any given area, the completed field map is sent to the office to be prepared for engraving and for publication. Submitted with the map is a report on the different soil types, their origin, properties and crop adaptation; the agricultural history and development of the given region; the transportation facilities, the markets and existing condition of agriculture; and the climate and the physiography of the region. These constitute the map and report published on each area by the Bureau of Soils. Special problems in soil-mapping. Under arid conditions it becomes necessary, in addition to the usual work, to study water-supply and irrigation problems. It is also necessary in many of the arid region areas to make a special study of the occurrences of excessive amounts of soluble salts, commonly known as "alkali." For this purpose, each party is supplied with an electrical instrument (Fig. 692) by means of which a sample of soil can be tested rapidly and the percentage of soluble salt present in it can be determined. By the use of this machine, the percentage of alkali present in each foot of soil from the surface to a depth of six feet or more is ascertained. The party also carries apparatus for the determination of the character of the alkali salts, since the dreaded "black alkali" (sodium carbonate) is fatal to plant growth when present in small quantities, while various other salts known as "white alkali" may be tolerated by plants when present even in considerable amounts. Thus, not only the amount but the kind of alkali is determined in the field, and a special alkali map is prepared on which is shown the amount and kind of alkali present to a depth of six feet or more. (Fig. 693.) As the alkali conditions are frequently controlled by the depth from the surface of the soil to the point of saturation, a ground-water map is also constructed. This shows the depth at which the soil contains stagnant water. Soil provinces and types. The work of the soil survey since 1899 has developed the fact that the United States may be divided into soil provinces. In each of these provinces the soils are formed by similar geological processes from materials of similar character. Thus, in the coastal plain province the soils are sediments, eroded from older rocks, transported, sorted and deposited as marine or river deposits. In the piedmont province, however, the soils are directly formed through the weathering of underlying rocks, chiefly crystallines. Thus these two provinces are units, with material distinctions between all of their respective soils. Within each province are groups of soils known as series. These groups are essentially similar in In this nomenclature the method of all scientific naming is followed, and the geographical name corresponds to the genus as the class or texture name does to the species. The series name is usually adopted from a locality where the series relationship of the soils is first recognized. The texture name is descriptive of the individual. [For further information on soil provinces, series and types, see Soil Survey Field Book of 1906, Bureau of Soils.] The practical value of the soil survey. The reports and maps published regarding single areas are chiefly valuable within the areas concerned, but the collections of maps and reports on areas scattered over nearly every state and territory within the country form the basis for many important generalizations in regard to the relationships existing between crops and soils, and between crops and climate. Again, the study of a single Fig. 693. Making an alkali determination in the field. all characteristics except texture, but a complete series grades continuously from coarse gravelly and sandy soil types to fine-grained silt or clay types. Each series is given a geographical name to express its province location and its uniformity of characteristics aside from texture. It is divided into individuals or types by the addition of a texture name or class name. A single example will illustrate the classification. area may show that within this area some desirable crop is being produced with special success on a given kind of soil, and that its production is not particularly successful on other kinds of soil. The map of such an area has fully as high a value in other sections of the United States as within the area itself, since, wherever the given type is found under the same climatic conditions, the experiences on the first area may be taken as conclusive proof that the same crop may be raised to advantage. Similarly, when experiments have been conducted concerning crop varieties, cultural methods, fertilization, systems of rotation, forced production and various forms of intensive farming, on any given soil type, the results of these experiments may or may not be applicable at a distance from the point where the experiment was conducted. However, if a soil map of the experiment plot has |