214 THE FIRST BOOK OF FARMING 



can use tough phosphoric acid and potash, but are 

 weak on nitrogen, and as they make the greater part 

 of their growth in the cool spring before nitrifica- 

 tion is rapid, they are benefitted by the application 

 of nitrogen, particularly in the form of nitrate, 

 which is quickly available. 



Clover, peas, beans, etc., have the power of draw- 

 ing nitrogen from the air, but draw from the soil 

 lime, phosphoric acid and potash. Hence the phos- 

 phates, potash manures and lime are desirable for 

 these crops. 



Root and tuber crops are unable to use the in- 

 soluble mineral elements in the soil, hence they re- 

 quire application of all the important plant foods in 

 readily available form. Nitrogen is especially bene- 

 ficial to beets. Turnips are benefitted by liberal ap- 

 plications of soluble phosphoric acid. White and 

 sweet potatoes require an abundance of potash. 



If we are growing tender, succulent market gar- 

 den crops, we need nitrogenous manures, which in- 

 crease the growth of stem and foliage. 



Fruit trees are slow growing plants and do not 

 need quick acting fertilizers. 



The small fruits, being more rapid in growth, re- 

 quire more of the soluble materials. 



A dark, healthy green foliage indicates a good 

 supply of nitrogen, while a pale yellowish green 

 may indicate a need of nitrogen. 



A well developed head of grain, seed pod or fruit 

 indicates liberal supplies of phosphoric acid and 

 potash. 



