Weighing the crop on the fertilizer test plots. The yield must be carefully measured if accurate information regarding the relative value of the fertilizers is desired 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 necessary. 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 |