22 Diseases of Truck Crops 



effect of fertilizers. A chemical analysis of the soil 

 win enable the trucker to make a more economical 

 use of his fertilizer. If a land, for instance, contains 

 too much iron and aluminium, applied phosphate 

 fertilizers may be modified into ferric and aluminium 

 phosphate, which become slowly available to plants. 

 Cta the other hand when phosphate fertilizers are 

 changed in the soil into tricalcium phosphate it 

 becomes available more readily. Sandy soils are 

 generally quick to respond to fertilization ; they can 

 therefore stand heavier application than the cold clay 

 soils which respond more slowly. In the latter, the 

 fertilizers are Hkely to be converted into forms un- 

 available to plants. The trucker should therefore 

 avoid depending altogether on the use of chemical 

 fertilizers. The best results are always obtained and 

 the fertility of the soil best preserved when the use of 

 chemical fertilizer is supplemented with flTiimal or 

 green maniires. 



