CHAPTER XV
WHAT SHALL ONE BUY?
Relative Values. The relative strengths of the various materials containing lime may be known and yet doubt continue respecting the choice to be made. The conflicting claims of dealers, and inaccurate deductions from a single test made by some individual, aid the confusion. If there were always the single purpose of correcting soil acidity, and if there were the same ease of application in case of all the materials, the choice would present much less difficulty. Notwithstanding this, most land now has a lime requirement, or will have one as leaching, crop removal and chemical change within the soil continue, and the puzzle is no worse than a score of others that present themselves continuously in farming.
Destroying Acids. The cost of liming to improve the physical condition of land is prohibitive for most farms remote from supplies of stone that can be burned and put upon the land at a low price per ton. Where stone is at hand, and soils are intractable, lime burned on the farm should be used. Some slight benefit to a stiff soil may be obtained from the light application that is deemed practicable where all forms are costly, but this benefit is not usually marked in case of an application of a ton or less of burned lime. It is a safe statement that most buyers of lime in some form or other will profit chiefly through the correction of soil acidity and promotion of bacterial life. This renders the situation more simple as any carbonate, hydrate or oxide of lime will accomplish these purposes.
Composition. The first consideration is the actual content of calcium and magnesium. A guaranteed analysis is the only safe basis of purchase. The unstable nature of fresh burned and hydrated forms makes an exact statement of percentages impossible for goods not wholly fresh, but at least the purity of the original limestone can be judged.
Equivalents. One ton of fresh burned lime, made from pure stone, is equivalent to 2640 pounds of the hydrate, and to 3570 pounds of pulverized limestone or of air-slaked lime. It is easy to carry in mind the proportions expressed by 1, 1⅓ and 1¾. If there were no other considerations, such as convenience in handling, evenness of distribution, etc., to take into account, one ton of fresh burned lime, one and a third tons hydrated and one and three-quarters tons finely pulverized limestone would have the same value when delivered in the field. Lime fully air-slaked, high-grade marl, and finely pulverized limestone would have the same value, ton for ton.
Even Distribution. The value of even distribution is not easily overestimated. If lime in proper amount does not go into each square foot of an acid soil, some of the soil will remain sour unless mixing is done by implements of tillage. Lime is diffused laterally through the soil in a very slight degree. If a strip of sour land is protected by canvas, so that no dust from lime applied to uncovered land can blow upon it, a seeding to clover will show that plants a few inches from the edge of the limed area will fail to start thriftily and may die before their roots reach the lime. Full effectiveness of an application is possible only through even distribution.
Using Lump Lime. Lump lime, slaked on the farm, is difficult to apply satisfactorily. Spreading with a shovel from small heaps is bad practice, and when the lime is slaked in a large heap, it cannot be handled as well as pulverized stone or commercial hydrated lime. The latter two are in condition for application by means of a lime distributor, or even a fertilizer attachment of a grain drill. The farm-slaked lime contains impurities that interfere with distribution.
An Estimate. It is always hazardous to attempt an estimate of cost of labor without knowing the particular farm conditions, but the expense and discomfort attending the slaking and use of lime bought in lump state justify a willingness to pay as much for a ton of hydrated lime as lump lime would cost, although the former has only three-fourths as much strength as the latter. Some farmers pay nearly twice as much for the hydrated, partly to escape the inconvenience and partly because they hope that the extraordinary claims for superiority made by some dealers may prove true. They should know that it is only fresh burned lime slaked, but incline to credit a claim that special treatment enhances value in some mysterious way.