for the slightly greater amount of work in drawing and applying a given quantity of lime in the lower grade stone.

For a classification and description of the limestone formations of the State together with a map showing extent and location of same the reader is referred to Technical Bulletin No. 47 of this Station.

The usual method of limestone analysis determines total calcium and magnesium without regard to the form in which they exist in the stone, it being taken for granted that all is in the carbonate form. The methods used in obtaining the analyses in this bulletin. take account only of the carbonates in limestone, the part effective for neutralizing acidity, and we have found that the figures for calcium carbonate equivalent obtained in this way may run on different stones from 0 to 3 per ct. lower than would be shown by total analyses. But usually there is little or no difference.

FINENESS.

In referring to degrees of fineness of ground limestone reference is often made to the percentages passing different grades of sieves such as are shown in exact sizes on Plate IV. Sieves called 10-mesh, 20-mesh, 40-mesh, etc., have as many openings to the linear inch; 2, 1 and millimeter sieves have round holes of such diameters, as 2, 1, or millimeter, 25.3 millimeters being equal to one inch. The subject of fineness is more fully discussed in Bulletin No. 400 of this Station; here let us say only briefly:

1

Farmers who have had experience with the use of ground limestone are as a rule satisfied with only a reasonable degree of fineness, and are able to judge the material by inspection. When limestone is ground so the entire product will pass a 10-mesh, or 2 mm., sieve, the greater part of it will be finer than a 40-mesh, or mm., sieve, It is then as fine as the ordinary bone meal on the market sold as "fine ground bone." It is an established fact that the finer bone is ground the more readily "available" as a fertilizer, yet in the practical working out of the problem the above degree of fineness is accepted as satisfactory. In this condition it is a favorite form of phosphorus fertilizer, the only objection being the very limited quantity and consequently high price. Fineness in bone meal is more important than in limestone for it is used at 200 to 1000 pounds per acre and costs $20 to $40 a ton, while limestone is used at the rates of 2000 to 10,000 pounds per acre and the farmer pays $1.50

to $4.00 per ton. Moreover, calcium phosphate, bone meal, is less soluble under soil conditions than calcium and magnesium carbonates, limestone.

In the last few years limestone has almost entirely replaced all forms of burned lime for use in soil improvement and has done so on the basis of material of only medium fineness, such as described above. There are now in operation in this State more than a dozen small portable community grinders; they are doing much to help solve the ground limestone problem and their use is rapidly increasing. In the practical operation of these machines they grind only to medium fineness (2 mm.). To insist upon extreme fineness is to discourage their use.

For limestone ground as fine as cement the farmer must pay firty cents to $1.50 more per ton than for the medium ground, also it must be handled in sacks, which adds at least another dollar per ton. There is no good evidence that in practical use the proportionately smaller amount of such material his money buys will satisfy the farmer's lime-hungry soil as well as the larger ration of reasonably fine limestone. To meet the demands of eastern soils for lime at the present time we need an abundant and easy supply of that material and its production and use must not be delayed by academic considerations.

SOILS IN NEW YORK STATE IN NEED OF LIMING.

Three-fourths or more of the farm lands in New York State would be greatly benefited by a liberal application of lime in some form. They vary in the amount of limestone required to satisfy their acid conditions from 1 to 10 tons or more per acre. Just what are the corresponding amounts of limestone most profitable to use is another question. From such experimental evidence as is at hand it seems probable we should use two to four tons per acre as an initial application, the larger amount on the more acid soils or for crops responding most favorably to the use of lime.

The use of limestone on acid soils is fundamental to any systematic method for their improvement. And this is becoming to be so generally recognized and is a matter of such frequent discussion that it need not be advocated at length here.

The soils in this State not at present in need of liming are those which have been naturally well stocked with limestone by reason of their having been derived in large part from limestone formations,

although in regions where these occur there are now frequent areas in need of lime. However, in any community where alfalfa is commonly grown without difficulty it can safely be assumed that additional limestone is not much needed. Technical Bulletin No. 47 of this Station gives some indications as to where natural limestone soils are likely to be found. Sections of the State especially in need of liming compose nearly all of the southern half (excepting parts of Schoharie, Albany, Dutchess, Putnam, Westchester and Orange counties), the Lake Front lands bordering Lake Erie and Lake Ontario, nearly all of Long Island and a large portion of the rest of the State. These areas represent at least 10,000,000 acres of improved farm land and at lowest calculation should have one ton of limestone every four years, 2,500,000 tons annually. Since only about one-tenth of this amount has yet been used in this State in one year, it is plain that the practice of liming the land is now in its early stages.

FIELD TESTS FOR THE NEED OF LIME.

Speaking for New York State: Soils derived from siliceous rocks are in need of liming. Such rocks include sandstones, sandy shales, clay shales, granites, trap, gneiss, schists and others. Soils derived mainly from limestone are little or not at all in need of liming. Where the growing of red clover has become difficult the soil is probably in need of liming. The prevalence of sorrel or paintbrush usually indicates a distinctly acid soil. Soils with a light color, gray, grayish brown, or yellowish shade, are usually in need of liming. Soils which turn blue litmus paper pink are nearly always in need of liming.

The litmus-paper test for soil acidity may be made as follows: Form a ball of wet soil about the size of the fist, break it open and insert a double thickness of blue litmus-paper (obtainable at drug store). Press the ball firmly together and allow to stand as much as a half hour. If at the end of this time the sides of the paper in contact with each other have changed to a distinctly pink color there is positive evidence of acidity and it may safely be assumed that benefit will follow liming.

It is now nearly always possible to tell in advance whether or not a soil is in need of liming without waiting for the slow and expensive method of trying out an application of limestone in the field. Besides, one year's trial may often fail to give conclusive results.

COMPARATIVE RESPONSE OF CROPS TO LIMING. Plants vary greatly in regard to their sensitiveness to an acid condition of the soil, but with only a few exceptions all agricultural crops are distinctly benefited by the use of limestone when grown on such lands. There are a rather large number of crops that can scarcely be grown with success on lands only moderately acid. Without doubt the best evidence on record showing the comparative effect of liming on a large number of crops grown on the same land is that published by the Rhode Island Station in Bulletin No. 160. The following table sums up this data for those crops of greater agricultural interest. The soil was distinctly in need of lime and both the limed and unlimed land was liberally fertilized with nitrogen, phosphorus and potassium. The figures given represent the yield with fertilizer and limestone as compared with a yield of 100 for fertilizer alone. Thus 104 shows a 4 per ct. increase and 200 shows a 100 per ct. increase. Where 300 + is given it indicates that there was at least 200 per ct. increase but in such cases the difference may often be due to a practical failure on the unlimed land and so the exact figures for comparisons might be misleading.

TABLE III. COMPARATIVE RESPONSE OF DIFFERENT CROPS TO LIMING ON A BASIS OF 100 FOR THE YIELD OF UNLIMED Land.

Summarized from data in Bulletin No. 160 of Rhode Island Experiment Station.

The test on a crop was each year made in duplicate, limed and unlimed with nitrogen applied as sulphate of ammonia and limed and unlimed with nitrogen as nitrate of soda. The yield on the unlimed land with sulphate of ammonia was usually much lower than with nitrate of soda, but in preparing this summary the results in connection with nitrate of soda only were used, since sulphate of ammonia has been a rather uncommon fertilizer in New York State. The figures nearly all represent the average of two or more seasons' tests, usually four or more, and often include more than one variety of the crop. Since these tests were made only upon soil having a rather limited range of physical and chemical characteristics it is not assumed that the relative effect of liming for these crops will within narrow limits always be the same as in this case; but the figures do represent the best comparative data on record at present.

NATURE OF SOIL ACIDITY.

In natural soil processes acids are constantly being formed incidental to the decay of organic matter. These acids consist of carbonic acid, various organic acids and the stronger nitric acid (HNO3). All have ability to combine with and remove from action the bases present in the soil. The formation of organic acids is familiar to everyone in the souring of milk, in the production of sauerkraut, in the fermenting of silage, and in the manufacture of wine and vinegar from fruit juices. Nitric acid is formed from the nitrogen of organic matter by the process of nitrification. In the production of almost any ordinary crop as much as 100 pounds of nitrogen per acre is converted into nitric acid. Under favorable conditions 200 pounds or more of nitrogen per acre are commonly transformed into nitric acid. One hundred pounds of nitrogen forms 450 pounds of nitric acid which is capable of using up 357 pounds of calcium carbonate. The carbonic acid and organic acids produced at the same time would be capable of using up a much larger quantity of limestone than this. If carbonates are not present to combine with these acids they attack the silicate compounds of the soil and extract from them their basic constituents, such as calcium, magnesium, sodium and potassium. Acids are added to the soil to some extent by the use of many commercial fertilizers. When 500 pounds of acid phosphate are applied to the soil enough acid is introduced to