Soil Acidity and Liming

THE AUTHOR oj this article first shows that in general not nearly as much lime is used in the humid portions oj the United States as should he used for the good oj the soiL He tells what he considers to be the chiej obstacle to greater use and gives broad recommendations jor ^''balancing the lime budget'^ The rest oj the article considers scientific and technical aspects oj liming—the relation oj soil reaction to plant growth, the nature and use oj rapid chemical tests, and the nature and junctions oj the acids in the soil. Soil Acidity and Liming By EMIL TRUOG ^ LIME in the form of marl, chalk, or limestone is so widely and profusely distributed the world over, and the benefits derived À from its use on many soils are so favorable and striking, that liming of land was probably practiced, from time to time, long before present-day records make note of it. Records show definitely that liming of land was practiced before the Christian Era. It seems strange, then, that the practice should have lagged in this country, so that even in recent times it is not as widespread as would bo desirable. There is a good reason for this, however. Oidy within recent times have satisfactory methods ancl adequate scientific knowledge been available for determining the actual need for and proper use of lime in soil management, to say nothing of an adequate medium for inter- preting and extending the information to the farmer. In this country, the practice of liming land was tried in a few isolated cases in colonial times. During the nineteenth century the practice grew quite extensively for a time and in a few localities, but for the most part, except in Pennsylvania, never became a permanent general practice. Edmund Ruflln (1794-1865), a practical farmer of Virginia, was probably the first man to test soils in this country and to surmise or recognize the general prevalence of acidity in upland mineral soils. He conducted extensive field experiments with lime and wrote a com- prehensive treatise on calcareous manures {327a)? In the closing years of the century, Wheeler, at the Rhode Island Agricultural Experiment Station, made the positive demonstration that many upland mineral soils are distijictly acid and need lime {/jol^a)^ which was the beginning of a sustained appreciation in this country of the need and value of lime in agriculture. lEmil Truog is Professor of Soils at the University of Wisconsin, s Italic numbers in parentheses refer to Literature Cited, p. 1181. 563 564 4- Yearbook, 1938 Today liming of the land is accepted as a fundamental and neces- sary practice by all who are well informed in the matter. It is not too much to say that it must be the very backbone of profitable crop production, soil conservation, and permanent agriculture in the humid regions of this country. Wliile we still need to improve our chemical tests and methods for soil reaction, study further the function and action of lime in soils, and more accurately measure the rate of loss of lime under varying conditions, it is nevertheless safe to say that enough scientific and practical knowledge is now at hand to lend confidence and stabihty to the practice of liming land. Onlv one reason for the backward status of liming remains—the FIGURE 1.—Producing agricultural lime for local use with a portal)le grinder. This method has given farmers in many sections their basic soil-building material at a low figure. high cost of lime. Limestone and marl are among the most plentiful of materials in the earth's crust; machinery and cheap power are at hand for mining and grinding (fig. 1); transportation facilities are already good and are rapidly becoming better; it is known where lime is needed and how it should be used to insure satisfactory results; and finally, when lime has been made cheaply and easily obtainable through special agencies, farmers have used it in amounts approxi- mating those needed. Why did Kentucky, in 1936, use the equivalent of 124 pounds of lime o.xide per acre of cropland and Tennessee only 8% pounds, and similarly, in the same year, Wisconsin 64 pounds and Michigan only 14 pounds? The climate, need of lime, and natural supplies of lime in the pairs of States compared are quite similar. All of these States have extension services which for a long time have been offering infor- Soil i\cidit.y and Liming ^ 565 mation on the subject through demonstrations, publications, and lectures. Evidently that method alone will not do tlie job. Until the extension services are able to form some connection with a large- scale organization, either private or governmental, that can be depended upon to^ furnish the farmer this basic and fundamental soil-buildhig material—lime—at a reasonably low price, or some other equally effective method is found and adopted, permanent soil improvement and soil conservation w'ill remain, to a large degree, ''a pot of gold at the end of the rainbow." BALANCING THE LIME BUDGET There is still a lack of definite informatio]i regardhig the rate of loss of lime brought about by cropping and leaclnng and the length of time that a dose of lime is amply effective. The rate of loss through leaching in the North Central States appears to be less than was form- erly believed. High evaporation and effective use of w^ater by cropping tend to cut dow;n this loss greatly. Alfalfa, in particular, having a high, water requirement, growling from early si)ring to late fall, and drawing both lime and water from a great depth, should, when it occupies the land, teiid to cut the loss by leaching to a minimum. In this case, unless the annual rainfall be considerably more than 30 inches, the loss is probably restricted almost entirely to what the alfalfa plants take, and in livestock farming this can be partly returned in the form of manure. For general farming in the North Central States, it may be conserva- tively estimated that the annual loss of lime (in terms of calcium carbonate) above wdiat is returned in manure and crop residues raaiges between 100 and 500 pounds per acre. Farther south, wehere the rainfall is heavier, and east, where evaporation is less, the loss may in many cases be greater. For the North Central States, wdiere the great bulk of the lime is now used, a 2-ton application of ground limestone per acre should in most cases talce care of the total net loss over a period of 10 to 20 years. Table 1, prepared by the National Lhne Association, gives a summary of the annual lime consumption, total and pounds per acre, on cropland in the United States by States and regions for the years 1029-36. The data disclose some interesting aiîd very important information. First of all, it is seen that the Midwestern States take about three-fourths of the total national consumption. If the data giving tlio amount used per acre of cropland are taken as a basis of comparison, a much better picture of the situation is obtained. These data show that only in recent years is the consumption, in the Mid- western States as a wdiolc approaching that of the New England States and Mid-Atlantic States. The amoimt used in Pennsylvania has been, very consistent over this period of years. This State was a pioneer in the use of lime in colonial times, and the practice has un- doubtedly become ingrained in the minds of the better farmers there. The lasting influence in Illinois of C. G. Hopkins (fig. 2), the foremost advocate of lime in the Midwestern States during the first quarter of the century, is show^n in the Illinois figures for the period. The amount of lime used in some of the Southern States is very small indeed. 566 ^ Yearbook, 1938 Table 1.—EighUyear summary of liming material^ consumption on United States Jarms, and resultant quantity of effective lime oxides applied per acre of cropland, by States and regions, 1929-36 1929 1930 1931 1932 state and region Oxides Liming Liming Oxides Liming Oxides Liming Oxides materials i:er materials per per per acre 2 acre 2 materials acre 2 materials acre 2 Tons Pounds Tons Pounds Tons Pounds Tons Pounds Maine 8,343 5.1 8, 704 6.6 8, 289 7. 1 4,808 4.1 New Hampshire 5,500 10.5 5,500 10.5 5,500 13.1 4,100 9.8 Vermont _ _ 8,601 8.0 7,268 7.0 4, 702 4.5 3,632 3 6 Massachusetts 56, 336 93.0 56, 336 93.0 60,000 138. 3 46, 009 95 8 Rhode Island 1, 276 21.1 1, 276 21.1 2,812 55.1 1, 350 24 4 C onnecticut 27, 500 53.4 27, r>()0 53. 4 22,000 53.0 35, 000 8,5.8 New Enjiland 1(Î7, 556 25. 6 lOf), 644 25. 6 109. 303 31.2 94, 899 26.6 New York ._- 185, 000 21.6 191, ()50 22. 5 1(56, 800 21.7 110,922 14.8 New Jersey _ _ 48, 336 56. 2 58, 293 68.4 52, 478 69. 6 35.151 45 0 Pennsylvania _. 255,178 36.2 242, 275 35.2 213, 480 32.8 18(5,881 28.8 Delaware.- 17,170 48.7 16, 562 46.4 10, 382 30. 5 5, 812 10.5 Maryland 28, 848 18.2 36, 049 23.2 40, 000 26.

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