Nitrogen is an element about which little is known. It is 

 pretty well understood that plants have the power of getting a 

 considerable portion of their nitrogen from the soil without ap- 

 plication from external sources, but this power seems to depend 

 upon the kind of plant to a considerable degree. It is also 

 known that application of manures containing nitrogen are ben- 

 eficial, but just how much of the nitrogen a crop can supply it- 

 self with, and how much may profita,bly be applied to the soil, is 

 an open question and likely to remain so for some time. 



We may now define the term 



PLANT FOOD. 



It is any substance that can contribute towards the growth of a 

 plant. 



Carbonic acid, water, ammonia, phosphoric acid, etc., etc., 

 are examples of plant food. 



Plant food may be divided into two classes : 



First. Those substances, usually abundant, which we will 

 call abundant plant food, including lime, iron, magnesia, silicia, 

 soda, sulphur, water and carbonic acid. 



Seconi. Those that become exhausted by long cropping, 

 which we will call deficient plant food. This class includes pot- 

 ash, phosphoric acid and nitrogen. In special cases soils may be 

 deficient in lime, or iron, or magnesia, and if so then these should 

 be included in the latter class for that particular soil, but in gen- 

 eral it is true that only the first three-forms are deficient. 



Abundant plant food the farmer cares very little about, but 

 deficient plant food must always be the chief factor to be regarded 

 in old agricultural regions. 



The deficient plant food required by the ensilage crop, above 

 mentioned, narrows down to forty four pounds of phosphoric acid, 

 one hundred and twenty pounds of potash, and one hundred and 

 thirteen pounds of nitrogen, in all two hundred and seventy- 

 seven pounds, or less than (^'(j) seven-tenths of one per cent, of 

 the entire crop. 



Let us take another case, that of the hay crop 12,000 

 pounds at time of cutting will make not far from 4,000 pounds, 

 or two tons, when fed out, after shrinking in curing and in the 

 barn. 



