Fresh Burned Lime

An Old Practice. The beneficial effect of caustic lime on land is

mentioned in some ancient writings. Burning and slaking afforded the

only known method of reducing stone for use in sour soils. Lime in this

form not only is an effective agent for correcting soil acidity, but it

improves the physical condition of tough and intractable clays,

rendering them more friable and easy of tillage. Caustic lime also

renders the organic matter in the soil more quickly available, an

increase in yield quickly following an application. These three effects

of burned lime brought it into favor, and a rational use would have

continued it in favor.



Irrational Use. The ability of caustic lime to improve the physical

condition of land and to make inert plant food available has led many

farmers to treat it as a substitute for manure, sods and commercial

fertilizers. Immoderate use gave increased crop yields for a time, and

the inference was easy that lime could displace the old sources of

plant food supplies. It became the custom in some regions to apply 200

to 300 bushels per acre to stiff limestone soils that had no lime

deficiency, as a test for acidity would have shown. The lime not only

made some mineral plant available, but it attacked the organic matter of

the soil, making it ready for immediate use and leaving the land

deficient in humus. Wherever stable manure and clover sods were not

freely used, the heavy application of caustic lime was followed

ultimately by decline in productive power. Such practice has come under

the condemnation of people who have not seen that the ill results have

no relation to the rational use of lime.



What Lime Is. There is abundant evidence that pulverized limestone, or

lime marl, or oystershell, or any other form of carbonate of lime,

corrects soil acidity and helps to make a soil productive. It is good,

no matter whether nature mixed the lime carbonate with clay, etc., to

make a choice limestone soil, or man applied it. Fresh burned lime is

only the stone after some worthless matter has been driven off by use of

heat. The limestone, carbonate of lime, is represented by the formula

CaCO3. When heat is applied under right conditions the carbon dioxide,

CO2, is driven off, and there remains CaO, which is calcium oxide,

called fresh burned lime.



If there were 100 pounds of the stone, and it was absolutely pure, 44

pounds would escape in form of the carbon dioxide, which had no value,

and 56 pounds would remain. The 56 pounds calcium oxide, or fresh burned

lime, have the same power to correct acidity as this same material had

when it was bound up in the 100 pounds of limestone. The 44 pounds were

driven off by heat, while if the limestone had not been burned the 44

would have separated from the 56 pounds in an acid soil, leaving the

actual lime to do the needed work of correcting acidity.



Affecting Physical Condition. While burning the stone does not affect

the ability to correct acidity, it does increase the power to make a

stiff soil friable and to bind a sandy soil. No one may say how much

this power to influence soil texture is increased, but it is marked, and

when improved physical condition is the chief reason for applying lime,

there is no question that fresh burned material is to be preferred to

pulverized stone or marl, or any other carbonate form. A light

application is not markedly effective in this respect, and the chief use

for this purpose has been in limestone areas that may not have had any

lime deficiency, but did have a stiff soil. The presence of the stone in

great quantity for burning on the farm made heavy applications possible.



Using Up Organic Matter. The presence of carbonate of lime in the form

of pulverized limestone or marl favors the disintegration of any organic

matter, but the action is so slow that it may not be observed. While the

use of limestone in manure piles is inadvisable for this reason, the

loss is not comparable to that resulting from mixing caustic lime with

manure. The caustic lime in a soil hastens decay of vegetable matter in

a degree impossible to the limestone or marl. Irrational use of the

former has produced such destructive action in many instances that the

failure to add manure or heavy sods for a long term of years has led to

heavy decline in producing power.



We are naturally so lacking in judicial temper that opinion has swung

violently from favor to disfavor. As most soils need organic matter, we

seize upon the thought that anything evidently inclined to use it up is

an evil. The purpose of tillage is in no small degree to bring about

disintegration and resulting exhaustion of vegetable matter. The latter

is a storehouse of plant food, and some of it is needed to feed the crop

desired. Tillage is no more to be commended for this purpose than a

quantity of lime equivalent in power to do the needed work. Excepting

the case of raw soils rich in the remains of plants, most land hardly

needs lime for this purpose, it may be, the tillage required for making

a seed bed retentive of moisture and for control of weeds being

effective, but the point is emphasized that the disintegration of

organic matter into available plant food is one of the chief aims of a

good farmer. It is only the excessive use of caustic lime that causes

loss.



The use of caustic lime in sufficient amount to correct all acidity, and

the use of such material to free plant food in humus sufficiently to

produce heavy sods, are just as good farm practices as drainage and the

application of manure.