Commercial Fertilizers. 163 



It is of value to those crops that are benefited by the use of 

 potash. For that reason it gives best returns when used on soils 

 rich in potential potash, as the clays, with practically no bene- 

 ficial results when applied to sandy soils. Its use as a source of 

 sulphur must not be overlooked, as it is possible that the bene- 

 ficial results obtained in many cases by its application will hava 

 to be traced back to the additional supply of this element. 



Salt has sometimes been used as a manure. It is certain that 

 in special cases it has given beneficial results, but in other in- 

 stances injury has resulted. It is well known' that salt checks 

 fermentations of all kinds so that it probably influences the rate 

 of nitrification going on in the soil. It is said that ^adding salt 

 will make the straw of wheat stiffer, but this effect is/probably 

 due to the fact that salt depresses the plant's growth, making 

 the straw shorter and consequently stiffer, due to reduced length. 



Mixed fertilizers. The tendency of the fertilizer trade in this 

 country has been toward the manufacture and sale of mixed 

 fertilizers. They have been sold in the form known as complete 

 fertilizers, which consist of a mixture of two or more of the 

 basal materials heretofore described. Where the basal material 

 alone is richer in the essential ingredient than is desired by the 

 manufacturer, sufficient gypsum, dry earth, peat or other inert 

 matter is added to bring the percentage of these ingredients down 

 to the desired point. Mixed fertilizers are indiscriminately 

 recommended for general use and all sorts of startling claims are 

 made for them by the manufacturers. They are offered as uni- 

 versal fertilizers, irrespective of the well known fact that soils 

 differ widely in their characteristics and that the crops vary in 

 their food requirements. So-called special fertilizers, designed 

 for special crops and supposed to be adapted to their particular 

 needs, are common on the market. Some manufacturers offer a 

 corn special, a potato special, a tobacco special, etc. Unfortu- 

 nately their chief claim lies in their attractive names. The 

 science of plant nutrition has not advanced to that stage where 

 one can define what the minimum of essential elements necessary 



