The home-mixer may substitute tankage of guaranteed analysis for part of the nitrogen and phosphoric acid. Let us assume that the tankage runs 9 per cent nitrogen and 20 per cent phosphoric acid. If half the required nitrogen per acre, or 4½ pounds, is wanted in tankage, 50 pounds of the tankage will supply it. At the same time the 50 pounds of tankage supplies 10 pounds of phosphoric acid, replacing one third of the 214 pounds of acid phosphate. We thus have for the acre 30 pounds of nitrate of soda, 50 pounds of tankage, 143 pounds of acid phosphate, and 36 pounds of potash, or 259 pounds. The content of plant-food remains the same, but one half of the nitrogen is only slowly available. The farmer who buys unmixed materials will incline to use only a few kinds, and at first he will confine himself chiefly to materials whose composition varies little. In this way he quickly sees in a ton of the material, not the whole bulk, but the definite number of pounds of nitrogen and other constituents of plant-food contained in it, and the calculations in home-mixing become simple.
Materials that should not be Combined.—The advocate of factory-mixed goods warns the farmer against the danger of making combinations of materials that will cause loss by chemical action. The danger is wholly imaginary if no form of lime, wood-ashes, or basic slag is used in the home-mixtures. As has been said, some materials will harden, if permitted to absorb moisture, and if the mixture must stand, a few hundred pounds of muck or dry road dust should be added to each ton as a drier, and a correspondingly larger amount per acre should be applied.
Making a Good Mixture.—The process of mixing is simple, and careful station tests have shown that it is fully as effective as factory-mixing. The unmixed materials should be kept in a dry place until the mixing is done. If there are any coarse lumps, a wooden tamper can crush them on the barn floor, and the material should be passed through a sand-screen. The material of largest bulk should be spread on the floor, and the other materials should be put on in layers. Three careful turnings with a shovel will secure good mixing. Scales should be used to secure accuracy in desired amounts of the materials.
Buying Unmixed Materials.—Acid phosphate, animal bone, and tankage can be bought of any fertilizer agent, but when one pays cash, he does well to get quotations from various leading manufacturers. The names of dealers in nitrate of soda can be secured from the New York agency which keeps its address before the public in agricultural papers. This is likewise true in the case of the syndicate controlling all the potash. When the addresses of leading distributors of all needed materials have been secured, quotations should be obtained on a cash basis. The best terms are obtained by groups of men combining their orders.
CHAPTER XX
MIXTURES FOR CROPS
Composition of Plant not a Guide.—It has been pointed out that a chemical analysis of a soil is not a dependable guide in the selection of a fertilizer. Years ago the theory was advanced that the analysis of the crops desired should be a guide, but it has proved nearly worthless. This theory does not take into account the soil's supply of plant-food. Moreover, a certain crop may demand a large supply of an element at a time of the year when the soil's supply is inactive. The need of nitrogen for grass in the early spring, before nitrification in the soil is active, is an illustration. Let the causes be what they may, the fertilizer formulas that call for plant-food in a fertilizer in the same proportions that it is found in plants are disappointing in their results. The analysis of the plant is not a dependable index.
The Multiplication of Formulas.—Fertilizer manufacturers have made all possible combinations of fertilizer materials, using them in various quantities. Each manufacturer has given a mixture a brand of his own, and confusion reigns. There is no formula for a soil or crop that will remain absolutely the best, even for one particular field. It represents one's judgment of the present need, and is employed subject to change, just as is the prescription of a physician. It is usually only an approach toward the most profitable amount and kind of plant-food that may be supplied. The one important consideration is that no manufacturer can know the need nearly so well as the intelligent farmer who knows the history of his field and constantly tests its ability.
