readily absorbed by plants, while in the case of phosphoric Food for 

 acid the soluble and immediately available forms contained Plants 

 in superphosphates may be obtained quite as cheaply as many 43 

 of the insoluble forms, as animal bone and tankage, which are 

 not so immediately useful; besides, these mineral elements, 

 however soluble when applied, are fixed by the soil, and are 

 thus not liable to rapid loss by leaching. When the farmer 

 applies the "minerals," or materials containing potash or 

 phosphoric acid in their best forms, his initial expenditure 

 is not so great as for an equal amount of Nitrogen; besides, 

 he can depend upon their presence there during the growing 

 season, and also that the plants can make use of the constitu- 

 ents; if the one season's growth of the plant does not use the 

 entire amount supplied, the residues will remain for future 

 crops, though they may be less readily acquired by them. 

 These conditions are quite different from those obtaining 

 when available nitrogenous materials are used, and are the 

 basis of the suggestions frequently made to furnish the soil 

 with an excess of the minerals, but adjust the Nitrogen to 

 the needs of the plant. 



A very important thing to remember in the application 

 of Nitrogen, however, is that, though it may appear very 

 efficient, it cannot fulfill all the conditions of a complete 

 fertilizer it is not a complete food in itself; it is only an 

 element of food, and its value as an element is measured 

 largely by the content of minerals in the 

 soil, with which it must associate and com- The Best Use of 

 bine, in order to fully meet the food needs Nitrogen Re- 

 of plants. Hence, where Nitrogen in any Quires an 

 form is recommended as a fertilizer, it Abundance of 

 should be understood that the phosphoric Phosphoric Acid 

 acid and potash necessary for the growth an " P tasn in 

 of the crop must either be supplied with it, tne ^"' 

 or have been previously applied, or should have existed 

 naturally in the soil. On poor soils, therefore, the applica- 

 tion of the minerals must be made with the Nitrogen, while 

 in cases where the soil is naturally rich in minerals, if Nitro- 

 gen only is added, the crops are largely increased, because, by 

 virtue of the presence of Nitrogen, they are able to gather the 

 phosphoric acid and potash needed from the natural supplies 

 in the soil, previously inaccessible to them, because of the de- 

 ficiency in Nitrogen. Under such circumstances, it is a com- 



