CHAPTER IV Fertilizers By no method known to chemical science is it possible to determine the crop-producing capacity of a soil or to ascertain what should be applied in order to increase the yield. Analysis will show the total amounts of each of the elements necessary to plant growth present in a soil, but the plant alone can discriminate between the available and the non-available. Those that are available as plant foods are generally spoken of as soluble in water and those not available as insoluble. The insoluble ingredients act as a reserve and are slowly made available for the use of plants by the action. of carbonic acid. The determination of what is lacking in any soil must be made by the application of various kinds and quantities of fertilizers, and the results recorded by the growth of plants. Natural Fertility of Soils.-The natural fertility of most soils is sufficient for the production of from 20 to 200 crops if it be rendered available. Fertilizers are used on soils of this character to insure the production of a crop and also to aid in the transformation of the latent soil fertility. The liberation of the plant food locked up in the soil can generally be greatly promoted by drainage, the addition of humus, special tillage, or the application of some disintegrating material such as lime. In the culture of field crops where the net returns to the acre are small, heavy applications of fertilizers would not prove profitable. Where intensive cultivation is practiced, it is found profitable, owing to the greater returns to the acre, to supply large quantities of fertilizing materials. The celery plant. is a gross feeder, and there is perhaps no other crop that will give so large a return for the liberal use of fertilizers. Chemical Elements Required in Fertilizers.Many of the chemical elements of the soil required by plants are abundantly supplied by nature, but nitrogen, phosphorus, potassium, and calcium are often deficient or if present in sufficient quantities are not in an available form. The character and composition of soils are so variable it would be, impossible to give a formula for a celery fertilizer that would meet all requirements. Such being the case, all that can be given in a work of this kind is to describe the mixtures used by successful growers, and show wherein lies the fertilizing values of the ingredients of these mixtures. Sources of Nitrogen.-The celery plant, from its nature of growth, requires an abundance of nitrogen. The principal sources of nitrogen for use as fertilizers are barnyard or stable manure, nitrate of soda, sulphate of ammonia, dried blood, meat scrap or meat meal, tankage, dried fish, fish scrap, cottonseed meal, bone meal, and nitrogenous guanos. Nitrogen from different sources does not give equal results; for instance, that contained in nitrate of soda, fish scrap, and the nitrogenous guanos is in a very soluble state and is quickly available. The nitrogen in sulphate of ammonia, bone meal, and fresh stable manure acts more slowly and its influence extends over a longer period. Sources of Phosphorus.-This element is not found in nature except in combination; calcium phosphate is the usual form. The principal sources of this phosphate are the phosphate rocks of South Carolina, Florida and Tennessee, bones, guano, and stable manure. If bones are ground very finely they become soluble to a limited degree. Phosphate rock, however, as mined is very slowly available. It is therefore treated with sulphuric acid, which converts part of the phosphate into a more soluble form which for the most part is immediately available to plants. The untreated calcium. phosphate when ground very finely is sold under the name of floats, in which form its application to the soil gives a slow but lasting effect. For celery pure raw bone is perhaps the best form of calcium phosphate, but its availability depends largely upon how finely it is ground. Sources of Potassium.-This element is commonly found in the potash salts known as sulphate of potash, muriate of potash, and kainit. Large quantities of potash are also secured in the form of wood-ashes. Stable manure contains a considerable amount. Most of the heavier soils contain plenty of potash, but in a form that is slowly available for plants to feed upon. Humic, and light soils generally, are deficient in potash owing to their leaching qualities. Potash is one of the cheapest of fertilizing materials and is always safe to apply liberally. Care should be exercised, however, to have it well worked into the soil or injury to the plants may result. Sources of Calcium.-The principal sources of this element as employed for fertilizers are limestone, oyster shells, marl, and phosphate rock. Limestone and oyster shells are sometimes ground and applied as a fertilizer, but the usual method is to convert the calcium carbonate of the limestone or shells into calcium oxide or quicklime by burning. In the form of quicklime the calcium is more active in correcting the acidity of soils than in any other form. Lime has both a chemical and a physical effect upon soils. Heavy clay soils are loosened and made tillable by the application of lime, but light soils are rendered more adhesive and retentive of moisture by its addition. The chemical effect of lime upon any soil is to assist in the solution of potash and other plant foods, and prepare them for absorption by the roots. Lime also aids the bacteria to change the nitrogen in the soil from the nitrite or insoluble form to the nitrate or soluble form. Common Salt as a Fertilizer.-Many growers insist upon using salt on their celery land, but its value as a fertilizer is doubtful, though it is a fact that celery will assimilate a small amount of salt from the soil, thus gaining a decidedly saline flavor, quite pleasant to the taste. The salt, owing to its chemical composition, has a hygienic influence upon the soil and may assist in the prevention of con ditions favorable to the development of plant diseases. Salt has an affinity for water and its presence in a soil has a tendency to maintain the proper moisture content, which will be very beneficial during a dry season. A few hundred pounds of salt applied to each acre will not add greatly to the expense for fertilizers, and will at least assist in the control of any acid that may form in the soil. The salt should be applied at least a month before planting or injury to the plants may result. Barnyard or Stable Manure.-Barnyard manure may include that from all farm animals. Stable manure as a rule consists of the waste from work animals only, or at most that from work animals and cows. Manure from grain-fed animals is always to be preferred, but extreme care is necessary to avoid the introduction of weed seeds with the manure. Street sweepings and manure containing sawdust or shavings as bedding should never be used on land intended for planting to celery. The ultimate value of stable manure depends very much upon the handling; unless properly cared for and applied it will be almost worthless as a fertilizer. The fertilizing ingredients of a ton of stable manure are worth about $2.50 when calculated at the rate charged for them in the chemical form, but as they are not readily available in the manure their value is only about one-half as much, or $1.25 a ton. Aside from its chemical value, stable manure has a physical effect upon most soils which is very beneficial to crop production. When applied to |