488 NATURE AND PROPERTIES OF SOILS 



dry place until needed. Each sack should be labeled, especi- 

 ally if different mixtures are made. 



A word of caution should be inserted here regarding the 

 concentration of the mixture. Some farmers, in order to les- 

 sen the work of mixing and application in the field, raise the 

 percentage of the elements exceedingly high — a condition very 

 likely to occur when high-grade materials are used. This 

 sometimes is bad practice, in that it may interfere with ger- 

 mination after the fertilizer is applied and may also injure 

 the young plants. Also, it is likely to result in a poor physi- 

 cal condition, which may clog the drill, and in uneven distribu- 

 tion, which will bring about a lowered efficiency of the fertil- 

 izer. The use of sufficient dry finely divided filler will obviate 

 such dangers. 1 



275. The choice of a fertilizer.^ -Two primary considera- 

 tions must be observed in the actual utilization of fertilizers. 

 The first of these has to do with the composition of the fer- 

 tilizer and its suitability to soil and to crop. A careful study 

 should be made not only of the percentages of ammonia, phos- 

 phoric acid, and potash but also the availability of these con- 

 stituents. The second consideration in the rational use of 

 fertilizing materials is in regard to the amounts to be applied. 

 As much care and good judgment are necessary in handling 

 a single carrier as a complete ready-mixed material, especially 

 if the rotation as a whole is considered. 



It is evident, due to many factors that cannot be controlled, 

 that fertilizer formulae for different crops on particular soils 

 are difficult to determine. In fact, such data can never be 

 more than merely suggestive. Further, the best quantity of a 

 mixture to apply, even though it is perfectly balanced, is a 

 figure that can only be approximated. Probably the largest 

 percentage of the fertilizer waste that occurs annually can 



1 Sand, dry soil, saw dust, dry muck, and even ground limestone, if in 

 small amounts, may be used as fillers. 



