Crops and Methods for Soil Improvement

by Alva Agee

Stone-lime.—Stone or lump-lime is composed of the 56 per cent of a pure limestone that gives value to the limestone. Forty-four pounds of waste material were driven off in the burning. Where railway or wagon hauls are costly, the purchase of stone-lime is indicated. There is advantage in getting this lime in pulverized form, provided it can be distributed in the soil before moisture from the air induces slaking and consequent bursting of the packages. The necessity of rapid handling has limited the popularity of pulverized unslaked lime, but no other form is equal to it when it is wholly unslaked. Some manufacturers grind the partially burned limestone often found in kilns, and furnish goods little better than pulverized limestone.

The slaking of stone-lime should be done in a large pile, and the distribution may be made with lime-spreaders. When the application is fairly heavy, a manure-spreader does satisfactory work. A good lime-spreader is to be desired, but care must be used to remove any stones or similar impurities in the slaked lime when filling it. Such spreaders are on the market.

The practice of slaking lime in small piles in the field is wasteful. It is difficult to reduce all the lime to a fine powder and to make even distribution over the surface. Any excess of water from rains puddles some of the lime, destroying practically all its immediate effectiveness. Distribution with shovels is necessarily imperfect.

The labor of slaking stone-lime and the difficulty in distribution are two factors to be considered when selecting the form of lime to be used. They may counter-balance in some instances the higher percentage of actual lime when comparison is made with the hydrate. That is a question to be decided by the buyer. He must be willing to use methods that will secure even distribution. The prevailing practice, however, of marketing the hydrate at a much higher price per ton than the stone-lime should prevent sales to farmers. The price paid for ease of handling is too great when purchase of the hydrate is made under such circumstances. It is better to do the slaking at home, furnishing the added weight of 32 per cent in water on the farm.

Ashes.—Hard-wood ashes have ceased to have much importance as a source of lime for land, but their use is held in high esteem even by those who regard fertilizers as mere stimulants and doubt the efficiency of lime. Hard-wood ashes, unleached, clean and dry, are valuable for acid soils. Their content of potash, which is variable and averages about 4 per cent, formerly was given all the credit for the soil improvement and increased clover growth that resulted from their use. Tests with other carriers of potash have shown that the potash probably produced only a small part of the effect noted, and the benefit is attributable to the lime in the ashes which exists in an effective form. The content of lime is variable, and largely so on account of the percentage of moisture and dirt that may be found in most ashes, and when no analysis has been made, the estimate of value should not be based on more than 30 to 40 per cent of carbonate of lime. The price of ashes runs so high, as a result of prejudice in favor of this well-known kind of soil amendment, that it rarely is advisable to buy them. Pure lime is a cheaper means of correcting the soil acidity, and the sulphate or the muriate of potash is by far the cheaper source of potash.

Marl.—Marls vary widely in composition. When quite pure, they contain 90 or more per cent of carbonate of lime, and have a value per ton about equal to finely pulverized limestone, and near half the value per ton of stone-lime. There are marls that are carriers of potash and phosphoric acid, and are to be valued accordingly as fertilizers.

Magnesian Lime.—Some limestone is a nearly pure calcium compound, and yields a pure lime, while much limestone contains a high percentage of magnesia. The latter is preferred by manufacturers who furnish pulverized lime because it does not slake readily, and is less liable to burst the packages before required for use. A pound of magnesian lime will correct a little more acid than a pound of pure lime, and no preference may be shown the latter on that score. There are soils in which the proportion of magnesia to pure lime is too great for best results with some plants, as plant biologists assure us, but there is too little definite information respecting these soils to justify one in paying more for a high calcium lime than for a magnesian lime when it is to be used on acid land. The day may come when more will be known, but the rational selection to-day is the material that will do the required work in the soil for the least money.

Amount per Acre.—The amount of lime that should be applied to an acre of land depends upon the degree of its acidity, the nature of the soil, the cheapness of the lime, and the character of the crops to be grown. The actual requirement for the moment could be determined by a chemical test, but the application should carry to the soil an amount in excess of immediate requirement. When clover has ceased to grow within recent years, it is a fair inference that the deficiency, if it exists, has not become great. When sorrel and plantain have gained a strong foothold, indicating that good grasses are unable to replace clover, the degree of acidity probably is higher. The results of tests at experiment stations and on farms show that 1000 pounds of pulverized lime, or one ton of pulverized limestone, evenly distributed throughout the surface soil, can restore clover to the crop-rotation on much land. This is an application so light that a state of alkalinity cannot be long retained. It is better to apply the equivalent of a ton of stone-lime in the case of all heavy soils that have shown any acidity. Where lime is low in price, 3000 pounds of stone-lime, or its equivalent in any other form of lime, is advised, the belief being that such an application will maintain good soil conditions through two crop-rotations, or eight to ten years. This amount can be applied quite successfully with a manure-spreader, and meets the convenience of the man who burns his own lime and does not want to screen it for use in a lime-spreader. The man who must buy his lime, and pay a freight charge upon it, will find it better to use only a ton per acre. This advice applies to heavy soils. A light, sandy soil should be given only a small application, as otherwise physical condition may be injured. The lime, used in excess, has an undue binding effect upon the sand. An application of 1000 pounds of stone-lime per acre can be made with safety.

Time of Application.—The use of lime on land should be associated in the land-owner's thoughts with the growing of clover. It does help soil conditions so that more grain can be produced, but if it is permitted to displace the use of fertilizers, and does not lead to the growth of organic matter, harm will result in the end. Lime should be applied to secure clover, and therefore it should be mixed with the soil before the clover is sown. The application may be made when fitting the seed-bed for the grain with which clover usually is seeded, or may be given a year or two years previous to that time. The important point is to have the soil friendly to plant life when a sod is to be made.

Lime should be put on ground always after the plowing, and it should be well mixed with the surface soil. Even distribution is just as important in its case as in that of fertilizers. A good practice is to break a sod for corn, harrowing and rolling once, and then to put on the lime. A cut-away or disk harrow should be used to mix the lime with the soil before any moisture causes it to cake. When large crumbs form, immediate efficiency is lost.