unless they are able to combine with other substances that eliminate or render impotent this acid effect. We have a number of substances that can be used to correct this acidity, among which may be mentioned lime and wood ashes. Both of these substances are good, but lime is usually the cheapest, the most available and easiest to apply; hence, its use as a corrective for acidity is most often mentioned. Soils most likely to be found sour are: heavy clay soils, when poorly drained; soils abundantly supplied with organic matter; soils that have been poorly tilled, and consequently air-hungered; and soils deficient in humus but kept at work by mineral substances, like kainit, muriate of potash, and acid phosphate. When lime is applied to soils of such nature, its wholesome influence is manifest at once. In this connection the beneficial influence of lime on the availability of nitrogen is of interest. It has been shown by Wheeler at the Rhode Island Station that lime exerts a direct benefit to plant growth by overcoming soil acidity, and in doing so, increases the assimilability of the soil nitrogen. Hence, we have an improvement of the physical condition of the soil and also an increase in availability of plant nutrition.

How acidity may be detected.-Does your soil look sad and sickly? If so, it may need lime. Does your soil fail to produce vigorous growth and good color in the plants it grows? If so, it probably needs lime. Does your soil show acidity when tested? If so, it truly needs lime.

Suppose you try this method for detecting acidity: Get a penny's worth of blue litmus paper at the drug store. Dig from the field a handful of wet earth that looks suspicious; into this insert your knife blade, and in the opening put a strip of the blue litmus paper, and press the soil tightly about it. If sour, in a short time the paper, where in contact with the moist soil, will become reddish in

color and you may know that your soil is sour and that lime is needed as a corrective for the acidity, for the reason that most of our plants do but poorly in acid soils..

How lime may be applied.-A common way that is practicable and inexpensive is to place from 10 to 25 bushels of lime on an acre, in heaps of two or three

As soon as the lime is applied it should be harrowed into the soil

bushels, covering with soil or old sacks until the lime falls apart and becomes thoroughly slaked. This done, you should spread evenly over the soil and harrow in.

A more satisfactory method is to slake by means of water, and as soon as in a powdery state, apply to the land and at once incorporate with the soil, not by the plow, for that places it too deep in the soil, but by some surface-working harrow or cultivator.

The lime-spreading machine now does very excellent work, and has been so improved that it will very likely supersede all other methods of applying lime to the soil. It has this point in its favor: the work can be done quickly; it can be done while lime is still in a fresh state and before it loses its active properties. And here is another fact you should remember: incorporate lime into the soil by means of a harrow as soon as applied. You will make a mistake if you wait for a rain, for it may be long in coming. Unless a very heavy rain falls, so as to carry the lime applied into the soil, you will likely lose much of its value, since it readily returns to its carbonate nature-its state before it was burned when locked in store.

How much lime to use? How frequently?-Sand soils are influenced most favorably by rather small applications of lime; say, from 200 to 1,000 pounds per acre of slaked lime and twice the quantity if either ground limestone or ashes are used. It is believed that slaked lime long exposed to the air is best for sand soils. Larger applications of lime may be given clay soils-from 400 to 2,000 pounds. For such soils, burned limestone and water-slaked lime are preferred, usually, before either ashes or ground lime

stone.

Lime may be applied every five or six years, using it before the crop in the rotation that is most helped by the application.

Lime is helpful to bacteria.-You will recall the frequent allusions that have been made to the bacterial life of the soil; to the presence of immense quantities of those microscopic plants that always are working for the improvement of soils; that plant food may be rendered available; that air nitrogen may be gathered in and secured for on-coming years; that the entire body of the

soil may be bettered and improved. But do you know these useful kinds are active only when the soil is free of acid, or is neutral in its reaction? If this is true, then we cannot expect these good fairies of the soil to do their work, unless we do our part and get rid of this distasteful enemy. Our legumes-root tubercle plants— quickly disappear from any soil where an acid condition prevails.

Not many years ago we heard much about "clover sick" soils. We know more about these now: some were acid soils, and clover disliked them; root tubercles failed to develop because the bacteria were unable to thrive or even live in such soils; and, without bacteria, there could be no formation of the nodules, and without the nodules, there could be no vigorous growth of the clover plant. Just as soon as lime was used freely enough to correct the acid condition, bacteria returned to these lands and the clover plant prospered as it had done in former days, when the land was sweet and wholesome, and filled with an abundance of vegetable matter.

If it is your plan to employ leguminous crops in your system of farming, so that needed nitrogen may be secured fully and without cost to you, it will be to your profit and advantage to guard against an acid condition of your lands; for the tiny forms of plant life that multiply and grow and develop in the soil are the direct means of increasing the yields of the useful crops that grow out of it.

CHAPTER XII

THE QUEST OF NITROGEN

With the closing of each decade, some new discovery has been given the world, some new thought has been launched that has borne its fruit e'er Time went far on his journey again. It has been so in science and it is so in agriculture.

Men are ever seekers after truth. Their quest has been for it throughout all time, and in every direction. As a result of this quest, philosophy is the better, art is the better, government is the better, science is the better, law is the better, and all men are the better.

The quest of truth has gone on from the very beginning of time; it has led out in every imaginable direction. But the surprise of many is this: the postponement of the pursuit of the practical until recent periods in human progress. Especially has this been true of the practical arts, and of agriculture. And yet all the while the world has been dependent upon the soil for its bread, for its raiment, for its shelter; and back of these is the controlling influence of the nitrogen of the soil.

The quest of nitrogen is of comparatively recent times; but once its story learned and its truth established, the solution of its mystery becomes a most valuable contribution to crop production and to soil maintenance, as well as a most powerful force in a new agriculture.

Farming in a broad way, now, is being built upon the legumes: the tiller of the soil is becoming a legume farmer. This state of affairs has resulted in recent years, only; in fact, since the publication in 1886 of the