requirements of different crops are not the same. Meadows require a water level near the surface; pastures are more profitable with a lower water table; cultivated farm and garden crops usually need a much greater depth to ground water. The position of the water level influences also to a marked degree the penetration of heat and the effect of frost. The fact is well known that crops on peat lands are more seriously damaged by frost than those on mineral soils. Although the frost hazard can be reduced by using fertilizers, by a thin surface coating of clay, sand, or loam, and by more hardy crops in the rotation, it can be further lessened by better control of the soil moisture. If the water table is properly lowered, peat land can be compacted and cultivated earlier in the spring. Moreover, deep drainage during winter favors a deeper aeration and disintegration. Unaerated, water-soaked layers, on the other hand, show a tendency toward leaching and corrosion. The extent of the injurious effects is often difficult to determine, particularly the corrosion of tile drains and cement foundations. In this connection, it should be kept in mind that the moisture content present in the profile section does not depend altogether upon the distance to the ground-water level but in part upon the character of the peat layers and the stage of disintegration. Hence methods of aeration and cultivation should be adapted to the structural profile features, in order to alter the respective water-holding capacity of the different types of peat land. EFFECTS OF THE MINERAL SUBSTRATUM The widely differing profile features of peat lands point to the fact that during the formation of a peat deposit the plant tissues and other organic remains in layers of peat are not greatly altered by chemical or bacterial action. It appears fairly clear, also, that the character and the number of different superimposed layers of peat overlying a land area are not determined by the nature of the mineral subsoil or its topography. The most tangible and readily recognized chemical change in undrained peat lands is seen in the marked deficiency of certain fertilizer constituents, in the progressive loss of oxygen from the plant tissues forming layers of peat, and in the reducing action of the water in various peat materials (6, p. 372). The conditions are quite different, however, when an area of peat has been drained, the surface layers are cleared and aerated, and decomposition of the organic matter sets in. Generally speaking, the solubility of mineral soils underneath peat areas is greater than that of the adjoining cropped and leached upland soils. The proportion in which the various mineral constituents are given up and accumulate in the rooting zone of crops is therefore highly important. Where these salts are dissolved in the soil moisture, the concentration of the solution may become excessively great in the course of time (pl. 2, B and C). The spots formed may prevent seeds from absorbing enough moisture to germinate, and they may injure the roots of plants growing at some distance from the place supplying the salts. It appears that the more disintegrated phases and finer textured types of peat are likely to show greater injury from dissolved salts and the adsorptive effects of organic colloids than the loose, fibrous layers of peat. Too much can not be said, therefore, about the desirability of studying carefully the mineral substratum as a limiting factor. Very few systematic observations of the influence of different mineral salts, including lime and fertilizers, upon cultivated peat lands have been made thus far. It is recognized to be a great drawback to the work that the analyses made are not comparable, because of the employment of widely different peat areas and methods of work. On this account opinions have been at considerable variance as to the effect of mineral salts in promoting the decomposition of peat materials, in accelerating the activity of beneficial microorganisms, or in modifying the availability of salts and organic compounds for the growth of crops. There is also the problem of alkali salts on certain peat lands, a solution of which can be reached, here as in other questions, only when a uniform method of analysis is employed. The outstanding feature of fertilizer analyses, reported by State experiment stations and other agencies, is the deficiency of potash and phosphates. Accordingly, the continued use of potash salts for crops such as potatoes, onions, or sugar beets, which show a response to this fertilizer, has become profitable on nearly all types of peat lands. Phosphates have the advantage that they stimulate the activities of certain microorganisms; thereby they lead to a more thorough utilization of the organic material of fibrous-peat areas and to the formation of larger quantities of available plant-food constit uents. Nitrogen, assimilable by crops, is most often deficient in coarsely fibrous peat layers. For this reason, frequent applications of soluble nitrate fertilizers are needed, in order to prevent injury to growing plants and to hasten the decomposition of the layers. The use of artificially prepared bacterial culture does not, however, assure a natural and normal inoculation of this type of peat land or of the seeds of nonleguminous plants. The best natural method for obtaining available nitrogen depends on the type of peat material, its proper preparation, and on the seasonal conditions. Moderately fibrous layers of peat, judiciously provided with lime, fertilizers, and an abundance of air and moisture, favor the fixation of free atmospheric nitrogen by bacteria. Suitable crop rotations are another means to this end. The liberal application of nitrogenous fertilizers is economically remunerative only with crops of high commercial value, grown under intensive cultivation. Before satisfactory results are obtained, it is often necessary to apply excessive and probably unprofitable quantities of potash and phosphate to restore a balance for plant growth. The conditions which favor losses of nitrogen are not well known, but fine-textured heavy peat soils show greater depletion of nitrogen than loose, light layers of peat. On the whole, a practical trial in the field from time to time affords the best method of determining the fertilizer requirements of individual peat areas or crops. It is a well-known fact that the fertilizer needs of peat soil can not be determined from their chemical analysis. Acidity in peat lands is of varying nature, the reaction being more or less influenced by the profile structure of the area and the differences in soluble salts. The high content of carbonaceous substances but slightly broken down in peat lands of the profile series with digit 2 in Plate 1 constitutes a reserve of potential acidity which is impos The following serial numbers refer to publications on fertilizer analyses in "Literature citied," at the nd of this bulletin: 1, 2, 3, 4, 17, 19, 20, 23, 24. sible of measurement. The actual presence of organic acid is, however, considered to be less important than the injury due to mineral acids and to lime deficiency. This condition may be remedied by the careful use of finely ground lime. Determinations of acidity and basicity have been included in systematic field work, partly because convenient and fairly accurate methods are available for this purpose. The results, however, are still inconclusive, because the different methods of determination give different indices of acidity. The Azotobacter test might be decidedly preferable as regards the lime requirement and the quantity of available salts, such as phosphates, needed to render a layer of peat productive. Further work on this subject is much to be desired. Not only do reclaimed peat lands vary widely among themselves in the fertilizer treatment required to make them profitable but also the chemical composition of layers of peat under cultivation changes continually. The methods of investigation are not yet sufficiently delicate to follow these changes from peat to muck and humus. Chemical and bacteriological tests should therefore be made over a long period of years on peat lands with a specific profile. Relative to the influence of the mineral substratum, the following conditions should be taken into account in the selection of peat lands for different uses. It is difficult to obtain satisfactory results on peat lands with unfavorable topography of the adjacent land, steep slopes, lack of outlet or fall, stony, gravelly, and quicksand subsoils, or hardpan underlying relatively shallow depths of peat. Excessive quantities of soluble salts, sulphur, and iron contaminations give rise to spotty areas, and even peat lands of considerable depth ave only a limited value under such conditions. Deep drainage and evaporation during periods of hot, dry weather must be fully reckoned with as the influences that bring salts from the mineral substratum to the surface. On the other hand, cool rainy seasons prevent a high concentration of soluble salts, both by stopping excessive evaporation and by leaching and distributing the mineral salts. Typical injury caused by iron salts is shown in Plate 8. The burned-over area of peat land (pl. 8, A) contains solid mounds of iron concretions in a locality where the ground waters and springs are ferruginous. Plate 8, B, gives a closer view of the newly excavated ditch, the drainage waters of which contain large quantities of iron in solution. Upon exposure to the air the iron becomes insoluble and precipitates. The cost of necessary labor and fertilizers and of transporting and marketing make unprofitable the utilization of peat lands with injurious subsoils. They should be recommended for suspension or exclusion until a thorough and systematic search. for the presence of harmful substances in the mineral substratum has been made. How extensively iron sulphide in the form of marcasite occurs in the underlying mineral soil of peat lands is not known. Nowhere, however, does it threaten any injury except after drainage. Because of oxidation by the air, marcasite forms ferrous sulphate and sulphuric acid, both of which are soluble in water and injurious to crops. In contact with calcareous waters or any form of lime these two substances are changed into calcium sulphate (pl. 3, C). Unproductiveness from this cause will not disappear until all the sulphide has been neutralized by lime and any remaining pyrite has oxidized and leached out. Sedge marshes with unfavorable mineral subsoils should be left as wiregrass meadows or drained moderately to permit the cutting of wild hay. If areas of peat land with a substratum of this nature are naturally wooded they should be kept, preferably as woodlot reserves. Areas of peat with excessive quantities of shell and Chara marl may become undesirable, on account of the deleterious effect of an excess of alkalinity on plant growth. Peat lands which accumulated over till, clay, or sandy-loam subsoils constitute, as a rule, the better grade for utilization. Neutral to slightly alkaline peat areas appear to fix larger quantities of fertilizers than the acid peat soils of the same type, but the degree of fixation and the compounds formed need further investigation. The presence as well as the character of thin layers of silt or marl and their location in the profile should not be ignored. In time they react favorably upon the surface layers, which are generally more or less acid, and they likewise influence the quality of crops. If the industrial use of a deep peat area is contemplated, only such deposits should be excavated of which the mineral substratum is in a condition suitable for future crop requirements or for the production of fishponds and aquatic crops. The latter is a field of work which so far has been little investigated. SUMMARY The problem of selecting peat lands for economic uses, like other problems of land utilization, demands reasonable forethought and planning. The chief hazards in the agriculture and industry of peat lands may be grouped into three classes: (1) Differences between peat lands in their distinctive structural framework; (2) lack of a proper method of controlling the supply of soil moisture; (3) the accumulation in the root zone of crops of excessive quantities of soluble salts from the mineral subsoil. These three difficulties may occur together, or any one of them may cause disastrous results. A clear understanding of the nature and effects of these three classes of trouble that may develop on peat lands makes it possible to have a better basis for operations and to anticipate financial and other difficulties before they have progressed to the point of serious injury to the community. There can be no doubt that a definite attempt to find and locate peat land with the most favorable structural framework and field conditions would benefit the regional development of peat-land utilization. It would reduce economic waste and encourage the conservation of peat areas that are important and feasible for water-storage purposes, for reforestation, and for wild-life reserves. Even a casual survey of noteworthy attempts made by several of the States collaborating with this department brings out the fact that the groundwork is already well laid for selecting desirable peat lands upon the basis of their stratigraphic framework. With proper attention to a related and continuously controlled water supply and like attention to the possible danger of an excess of active soluble salts from the mineral substratum, the prospect for effective advancement seems assured. The establishment of a well-considered program of selection will give to peat-land utilization the stability and permanence which it has not heretofore possessed. LITERATURE CITED (1) ABBOTT, J. B., CONNER, S. D., and SMALLEY, H. R. 1913. THE RECLAMATION OF AN UNPRODUCTIVE SOIL OF THE KANKAKEE MARSH REGION. Ind. Agr. Expt. Sta. Bul. 170: 329-374, illus. (2) ALWAY, F. J. 1920. AGRICULTURAL VALUE AND RECLAMATION OF MINNESOTA PEAT SOILS. Minn. Agr. Expt. Sta. Bul. 188, 136 p., illus. 1913. THE AGRICULTURAL UTILIZATION OF ACID LANDS BY MEANS OF ACIDTOLERANT CROPS. U. S. Dept. Agr. Bul. 6, 13 p. (6) DACHNOWSKI, A. P. 1912. PEAT DEPOSITS OF OHIO. Ohio Geol. Survey Bul. (4) 16, 424 p., illus. 1916. AGRICULTURAL POSSIBILITIES OF OHIO PEAT SOILS. Jour. Amer. Peat Soc. 9: 10-20. 1919. QUALITY AND VALUE OF IMPORTANT TYPES OF PEAT MATERIAL. U. S. Dept. Agr. Bul. 802, 40 p. 1921. PEAT DEPOSITS AND THEIR EVIDENCE OF CLIMATIC CHANGES. Bot. Gaz. 72: 57-89, illus. 1922. PREPARATION OF PEAT COMPOSTS. U. S. Dept. Agr. Circ. 252, 12 p. 1924. THE STRATIGRAPHIC STUDY OF PEAT DEPOSITS. Soil Sci. 17:107133, illus. (7) (8) (9) (10) (11) (12) 1925. THE (13) (14) (15) CHEMICAL EXAMINATION OF VARIOUS PEAT MATERIALS BY MEANS OF FOOD STUFF ANALYSES. Jour. Agr. Research (1924) 29:69-83. Amer. [1925] DIFFERENCES IN PEATLANDS FOR CROP PRODUCTION. Cranberry Growers' Assoc. Proc. Ann. Meeting 55:8-10. 1925. PROFILES OF PEATLANDS WITHIN LIMITS OF EXTINCT GLACIAL LAKES AGASSIZ AND WISCONSIN. Bot. Gaz. 80:345–366. 1926. PROFILES OF PEAT DEPOSITS IN NEW ENGLAND. Ecology 7: 120-135. (16) ELLIOTT, G. R. B., JONES, E. R., and ZEASMAN, O. R. 1921. PUMP DRAINAGE OF THE UNIVERSITY OF WISCONSIN MARSH. Wis. Agr. Expt. Sta. Research Bull. 50, 32 p., illus. (17) HOPKINS, C. G., READHIMER, J. E., and FISHER, O. S. 1912. PEATY SWAMP LANDS; SAND AND "ALKALI" SOILS. Ill. Agr. Expt. Sta. Bul. 157:94-131, illus. (18) JONES, E. R., and PACKER, B. G. 1923. DRAINAGE DISTRICT FARMS IN CENTRAL WISCONSIN. Wis. Agr. |