FERTILIZERS AND PLANT FOOD. 217 



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

 examples of plant food. 



Plant food may be divided into two classes : 



First. Those substances, usuall}' abundant, which we will call 

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

 sulphur, water and carbonic acid. 



Second. Those that become exhausted by long cropping, which 

 we will call deficient plant food. This class includes potash, phos- 

 phoric 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 general it is true that 

 only the first three forms are deficient. 



Abundant plant food the farmer cares very little about, but defi- 

 cient 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 (7-10) 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. 



This 4,000 pounds of cured hay will be made up of the following : 



Lbs. 



Water 500 



Albuminoids , . 304 



Carbo-hydrates 2,960 



Fat 56 



Ash 180 



4,000 



The ash is made up of the following : 



Lbs. 



Phosphoric acid 17 



Potash 77 



Soda 2| 



Lime 20 



Silica. . . 53^ 



Magnesia 1 0| 



180 



