Table VIII gives the yields in pounds per acre secured for cach product and plat for the five years 1909 to 1913, inclusive. The alfalfa seeded in barley in 1910 was badly injured by freezing and thawing in its first winter. One cutting was made early in 1911 after which it was plowed up and reseeded in August. The results the following year were more satisfactory as indicated by the first cutting in 1912. The second cutting was so light that it was not removed from the field and the third cutting was also light as shown by the table. The 1913 crop was good, although extremely dry weather made the third crop so light that it was clipped and left on the field. From the last column of the table, it is evident that Plats 5 and 6 treated with ground raw limestone have given the largest total increase in crops. Plat 8, receiving 8000 pounds, gave a decrease in yield as compared with the check plats which receive 4000 pounds exposed lime per acre, and Plat II, receiving the extra heavy treatment, gave a very small in

crease.

Table IX, giving the increase (+) or decrease (—) in pounds per acre for each crop, plat, and year, will show more clearly just where and to what extent the growth of the crops has been increased or decreased by the different forms and amounts of lime. The method of comparison is the same as that used in the second field test.

Plat 2 with no lime shows an aggregate decrease of 593 pounds of products in five years as compared with check plats, Nos.I and 4, each receiving 4000 pounds per acre of exposed lime. Putting it in the reverse order this amount of lime has increased the yield of crops to the amount mentioned above. With corn at 50 cents a bushel, barley at 72 cents a bushel, corn stover and barley straw at $2.50 a ton, and alfalfa hay at $14.00 a ton, this increase is valued at only $3.20, a sum too small to pay for the amount of lime applied. Plat 8 with 8000 pounds of exposed lime per acre gave a reduction of 1057 pounds as compared with check plats 7 and 10, while Plat II with 24,969 pounds gave an aggregate increase of only 262 pounds over check plats 10 and 13. This is a poor showing for the exposed lime in this test.

The only plats showing consistent increases of fair magnitude are Nos. 5 and 6, receiving raw ground limestone in moderate

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cutting of alfalfa on No. 6 in 1913, that did not give an increase, the aggregate for the five years being 2549 and 2249 pounds, respectively. With values previously referred to in this article, the average value of increase in yields, on these two plats for the period of five years, is $14.30 and $13.44, respectively. This is more than sufficient to justify the expense of the raw ground limestone applied.

The applications of exposed lime seem to have been slightly depressing to the corn, the reduction in yield of ear corn being most marked for the largest application. The corn was planted 7 to 10 days after applying the lime and it is not improbable that depression of growth might have resulted from the caustic lime added in large amounts. The smaller increases in yield from exceptionally heavy applications of pulverized limestone are also significant and emphasize the uselessness of applying much more lime than is needed to correct the acidity in the soil. Comparing yields from the four rates of application we find that for 1980, 4000, and 8000 pounds of exposed lime the aggregate yield for five years is in favor of equivalent amounts of pulverized limestone to the extent of 2369, 2549, and 1518 pounds per acre, respectively. For the largest application the difference is negligible and the increase over the check plats is very small.

This field test, like both of those previously reported, is favorable to raw pulverized limestone as compared with burnt or caustic lime for application to soils of limestone formation.

SUMMARY OF THE THREE FIELD TESTS.

In the long-continued fertilizer test, the burnt lime alone gave no increase, and pulverized limestone alone gave an increase in crops valued at $1.20 for each ton of limestone used. The average lime requirement of the five plats in Tier 1, receiving no fertilzer for 30 years, given in Table III, is only 196 pounds of CaO per acre seven inches of soil while the average of all acidity determinations for all 20 check plats in the experiment was only 120 pounds. There is little reason to expect large returns from lime when the soil is no more acid than above indicated. From Table III, it will be seen that the lime requirement for all manured plats in Tier I was 751 pounds per acre. The requirement of all plats

receiving only 6 tons of manure was 200 pounds. It is possible that the somewhat higher degree of acidity in manure plats is responsible for the larger returns from the burnt lime on such plats. Determinations of humus and nitrogen show the soil of burnt lime plats to be lower in these constituents than either check plats or those treated with limestone.

It is commonly assumed that burnt or caustic lime would destroy some organic matter and result in a loss of soil nitrogen, but whether or not this takes place to an appreciable extent in usual farm practice of liming is open to some doubt.

In the second field test the returns per ton of lime are larger than on the fertilizer plats. There are two reasons for this: First, the soil is more acid, the lime requirement being 1092 pounds of CaO per acre seven inches; second, the initial application of lime was not repeated and the returns are measured over a period of six years. Here the returns per ton of lime applied in case of both burnt lime and limestone have been the largest when used in amounts just sufficient to meet the lime requirement. The returns per ton for burnt lime were $4.25 and $2.12 when the rate of application was 1676 and 2544 pounds, respectively. For limestone it was $9.56 and $5.34 per ton when used at the rate of 1921 and 2976 pounds, respectively. In this test, the returns, excepting for the smallest amount of burnt lime, are quite profitable and are very decidedly in favor of the limestone.

In the third test, the soil is even more acid than in the second, being equivalent to 1312 pounds CaO per acre. The returns from the initial application in this test are for 5 years instead of 6 as in the preceding one, and the failure of the alfalfa in 1911 virtually reduces the time to four years of returns. The returns per ton of material in case of limestone are $11.47 and $6.04 for applications of 2343 and 4735 pounds per acre, respectively. This is slightly larger than in the preceding test. Excessive applications of 9470 and 29,556 pounds of limestone show no benefits from the additional amounts. In fact the returns are less than for the smaller applications. With burnt lime at the rate of 4000 and 1980 pounds per acre, the returns per ton were $1.69 and $1.45, respectively. In this instance not only are the returns very low but they are not consistent with the preceding, in that the smaller

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All of the field tests are more favorable to the finely crushed limestone than to equivalent amounts of burnt lime. They indicate no advantage in applying much more than sufficient to neutralize the acids present in the soil. Unusually large applications in the third test emphasize the wastefulness of such applications so far as the needs for five or six years are concerned. Large applications may last much longer, how long only long-continued observations on these plats can determine. While these tests are favorable to the finely pulverized limestone, they are not all sufficiently decisive to justify the use of ground limestone at a disproportionate price.

If two tons of ground limestone cost much more than one ton of burnt lime, one would ordinarily not be justified in using the former.

In cases where lime must be shipped some distance, the more concentrated forms are usually the cheaper.

Burnt lime appears to exhaust the humus in the soil more rapidly than ground limestone. Burnt lime with manure gave returns over manure alone. Burnt lime alone gave no increase. It is desirable that the use of lime or limestone lead to larger supplies of organic matter in the soil.

The value of lime in any form depends on its purity and mechanical condition. It should be in such mechanical condition that it can be thoroughly distributed in the soil. The more calcium a given weight of lime contains, the more valuable it is. When the impurities in limestone do not exceed 10 per cent, the limestone and lime may be rated as high grade.

While there may be soils in Pennsylvania that would profit in higher degree from an application of pure lime than from an application of magnesian lime, our present knowledge does not permit us to discriminate against the magnesian lime for use on our farms. It may be as good an investment as a pure calcium lime. Quantity per Acre.—The amount of lime to apply depends on the degree of acidity of the soil and also on the character of the soil. If a soil is a tenacious clay, and physical improvement is desired, an application of two or three tons of stone lime may be profitable. Ordinarily lime is applied to correct acidity and make a soil friendly to clover and other plants and the equivalent of one

to one and one-half tons of stone lime per acre, applied once in each crop rotation, is usually a maximum amount. In some instances 1000 pounds per acre will accomplish the desired result. The equivalent of 1000 pounds of stone lime is between 1300 and 1350 pounds of slaked (hydrated) lime, or a little less than one ton of raw limestone reduced to a powder.

Time of Application.—An application of lime should usually pave the way for clover. It is well to apply lime a year or more before the seeding of clover. If this has not been done, it may be put on the land when the seed-bed is being made for the wheat, oats, or other crop with which clover is to be seeded.

Method of Application.-Lime should be applied after the ground is plowed and thoroughly mixed with the soil by harrowing or disking. The more thoroughly it is mixed with the soil the better and quicker the results will be. It should never be plowed under, because its tendency is to work downward rather than upward in the soil. Apply lime with a spreader after the ground has been plowed. Do not drill lime in with seeds, nor mix it with commercial fertilizer, nor use it in place of fertilizer. Apply lime to meet the lime requirement of a soil, and when this has been done use manure and commercial fertilizers in the ways that have been found profitable for the crops which are to be grown, regardless of the fact that lime has been applied.

The grower of staple farm crops, who does not use a systematic rotation in which clover or some other legume enters, is slowly going into bankruptcy. Land on which clover generally fails, and which produces sorrel and red top instead, will be benefited by the use of lime.