112 FIRST PRINCIPLES OF AGRICULTURE. 



order to secure their complete distribution in the soil. 

 On soils of a heavy character a fall application is recom- 

 mended. 



In order to attain the best results from mixed fertili- 

 zers, great care should be given to the proper adjustment 

 of the various kinds and forms of the materials used. 



Kind of Soils. — Crops grown upon soils poor in 

 decaying vegetable matter are, as a rule, benefited by 

 nitrogen manuring, while those upon soils rich in this 

 substance are more benefited by phosphates and potash. 

 Upon heavy soils phosphates are likely to be more 

 beneficial than nitrogen, while the reverse is the case 

 on light, dry soils. All sandy soils are, as a rule, defi- 

 cient in potash, while clayey soils contain this element 

 in larger quantities. 



Different Methods of Growth. — The difference in 

 crops in reference to their capacity for acquiring food 

 must also guide in the application of manures. Crops 

 that have deep roots, and grow throughout a long sea- 

 son, are able to acquire their necessary food where those 

 of shallow roots and short seasons of growth would 

 suffer hunger. 



Crops of the same class, too, resemble each other to 

 some extent in their capacity for acquiring food. The 

 grasses, for example, do not possess a strong power of 

 assimilating nitrogen ; root crops possess a small capacity 

 for acquiring and utilizing phosphoric acid; while legu- 

 minous plants are unable to readily assimilate potash; 

 hence these crops are, in the order given, most benefited 

 by nitrogen, phosphoric acid, and potash. 



