alone is applied, a full yield of potatoes is not produced unless the nitrogen is 

 dressed in conjunction with potash. 



From these statements it follows that the statistics and illustrations here given 

 indicate the needs of the various plants for the different plant-foods and of the 

 abilities of the individual crops to abstract the individual foods from the soil. These 

 experiments are therefore not necessarily to be taken as hard and fast examples of 

 how manuring should be conducted in actual farm practice. 



On ordinary farm land the results of manuring can scarcely be expected to be as 

 marked as on the E-field, where the different plots have each been treated in the 

 same way year after year for a considerable period. 



The failure of phosphoric acid in these experiments must be accounted for, solely 

 by the fact, that the soil is especially rich in phosphoric acid: the phosphoric acid 

 plot in comparison with the unmanured, and the nitrogen- phosphoric acid in 

 comparison with the bare nitrogen, having indeed as a rule shewn a slight 

 decrease in yield. The addition of a large store of phosphate where potash and 

 nitrogen are present in insufficient quantity will in this case naturally have a de- 

 trimental effect on plant growth, in as much as the balance of foods in the soil 

 will more than ever be disturbed. Under such circumstances the yield can be 

 expected to be maintained only where in addition to the phosphoric acid a pro- 

 portionate supply of potash and of nitrogen is also administered. 



46 



A. 



