CHAPTER XVII

GENERAL CONSIDERATIONS

Nitrogenous Materials. It was shown in Part III that under a system of animal husbandry it is possible to maintain the fertility of the soil by means of the barnyard manure used in connection with leguminous crops, provided the best methods of tillage, etc., are used and all the materials raised are fed on the farm. Where a part or all of the crops produced are sold from the farm it sooner or later becomes necessary to supply plant food derived from outside sources. This is especially true in truck farming, where the crops raised are such as remove large quantities of plant food. The needed fertility is supplied to some extent by the manure produced in the city stables, and is best so supplied when possible, but this source of fertilizing material is obviously inadequate to furnish the required amount of plant food. The constantly growing demand for something that will increase the crop production has given rise to the fertilizer industry which is rapidly assuming gigantic proportions. At the present time over $50,000,000 are spent annually in the purchase of fertilizers in the United States, and it is probably no exaggeration to say that fully half of this is money thrown away. This is no argument against the use of commercial fertilizers but simply means that they should be used with judgment, and not used at

all until actual investigation has shown them to be nec

essary.

Lack of Plant Food Not Sole Cause of Crop Failure.-"One must distinguish between lack of plant food in the soil and other conditions which prevent good crops, for lack of food is not the only cause that makes crops suffer. In some soils there is insufficient porosity, which causes the development of the roots to be checked. Lack of moisture, caking of soil, retention of stagnant water, deficiency of humus, lime, etc., unfavorable weather and other conditions may interfere with the healthy growth of plants and thus cause diminished crops, even when the plant has within reach all the food it needs. Under such circumstances the unfavorable conditions must be removed to secure good crops, which, according to the demands of special cases. may be done by irrigating, draining, harrowing, hoeing, marling, mucking, etc. It may often happen that the soil contains an abundance of plant food, most of which is still unavailable. Under such circumstances an effort should be made to bring this food into an available condition as rapidly as the plants can use it, and this may be done by an improved system of tillage, together with the application of such indirect fertilizers as have the power to make insoluble plant food available."-Van Slyke.

Fertilizers Should Not Take Place of Tillage.— Too frequently fertilizers are made to take the place of tillage when they should be used to supplement it. That is, fertilizers are most likely to produce profitable results when conjoined with superior physical conditions of the soil, and in general terms it may be said

that the man who would obtain the best yield without fertilizers of any kind is the one most likely to realize a profit from their use.

"The fact that fertilizers may now be easily secured,

Thorough preparation of the soil is of prime importance in the growth of crops. The upper picture shows buckwheat grown on a soil which was carefully prepared. The lower cut shows a part of the same field which was hastily and poorly prepared, no fertilizer being used in either case. Commercial fertilizers should not be expected to take the place of good tillage and cultivation of the soil

and the ease of application, have encouraged a careless use, rather than a thoughtful expenditure of an equivalent amount of money or energy in the proper prepara

tion of the soil. Of course it does not follow that no returns are secured from plant food applied under unfavorable conditions, though full returns cannot be secured under such circumstances. Good plant food is wasted, and the profit possible to be derived is largely reduced."-Voorhees.

What Are Commercial Fertilizers?-When it was first discovered that certain of the elements found in the soil are necessary to plant growth it naturally occurred to the agricultural investigators that it might be possible to renew the fertility of worn out soils by supplying these elements artificially. In the first experiments conducted along this line all the elements which the plant derives from the soil were supplied. As the investigations progressed it was discovered that increased production resulted in most instances from the addition of only three of these substances-i. e., nitrogen, phosphoric acid and potash. In other words, it was determined that except in rare cases all the other elements exist in the soil in quantities sufficient to supply the needs of the plant, even when the available nitrogen, phosphoric acid and potash are practically exhausted. For this reason it is generally considered unnecessary to supply any of the elements of plant food except the three named above, and these substances have come to be known as the "essential ingredients of a fertilizer," and the only ones that give the fertilizer a commercial value.

All Fertilizers Made From a Few Basic Materials. -From what has been said it will be seen that any material that supplies one or more of these "essential ingredients" may be used as a commercial fertilizer,

provided it could be purchased at a price that would make its use profitable. As a matter of fact, the number of substances that are available for this purpose is somewhat limited, owing to the prohibitive prices which the others bring on the market. Many persons seem to think that there is something mysterious about the manufacture of fertilizers and some of the makers encourage this belief by pretending that they have some secret process of manufacture that enables them to produce a better product than their competitors, and far better than the farmer can mix himself.

The truth is that there are a limited number of basic materials from which all the different brands of fertilizers are made, and these basic substances are articles of commerce and can be purchased by anyone. The so-called "complete fertilizers" consist of two or more of these substances mixed together in the proportion to give the required per cent of nitrogen, phosphoric acid, and potash in the finished product. Some of these materials are commonly purchased unmixed, while others are rarely seen by the farmer except as one of the ingredients of a complete fertilizer. Some of these basic materials contain only one of the essential ingredients of a fertilizer, while others contain two, but usually one is in such excess that the substance is used chiefly to furnish that one element. It is possible, therefore, to separate the basic fertilizers into three classes, viz.,

1. Materials used chiefly as sources of nitrogen.

2. Materials used chiefly as sources of phosphoric acid.

3. Materials used chiefly as sources of potash.