232 



BOARD OF AGRICULTURE. 



Nitrogen in either sulphate of ammonia or nitrate of soda is solu- 

 ble, and therefore more likelj' to be readily taken up b}^ the growing 

 crops. But in prepared fertilizers part, and often a large part of the 

 nitrogen is in organic matter and ma}' not be available. The potash 

 of the easily soluble muriate is ready for the plant at once. There 

 seems to be some reason for believing that the phosphoric acid of 

 bone-black is more effective than that in South Carolina Rock ; at 

 least we are sure of our materials if bought in separate form, while 

 we may not be so certain about the mixed goods. But the secret 

 of the increased efficiency of chemicals is to be looked for in the 

 ratio in which they are mixed. It is assumed by most fertilizer 

 manufacturers that a complete fertilizer should contain twelve per 

 cent of phosphoric acid, four per cent of potash and two per cent of 

 nitrogen, but if we look at the composition of the ash of plants we 

 find a different ratio. 



Ratio of phosphoric acid to potash in the ash of plants. 



Ensilage . 

 Hay. . . . 

 Corn . . 

 Oats 



Potatoes . 

 Clover . . . 

 Wheat.. . 

 Beans . . . 



In Manures. 



From neat cattle . . 



From horses 



From sheep 



From swine 



In prepared fertilizers,. . . 



Ashes 



It is seen at a glance that the plant requires on an average three 

 times as much potash as phosphoric acid, while the prepared ferti- 

 lizers as we buy them, give us three times as much phosphoric acid 

 as potash, just reversing the ratio. 



I am well aware that another factor comes in here, namely, the 

 capacity of the soil for providing plant food. 



