4 The Bulletin. 



stances in contact with it, and to become somewhat less soluble. This 

 latter is known as reverted or gone-back phosphoric acid. This is 

 thought to contain two parts of lime in combination with the phos- 

 phoric acid, and is thus an intermediate product between water- 

 soluble and the original rock. 



Water-soluble phosphoric acid is considered somewhat more valu- 

 able than reverted, because it becomes better distributed in the soil 

 as a consequence of its solubility in water. 



Available Phosphoric Acid is made up of the water-soluble and 

 reverted ; it is the sum of these two. 



Water-soluble Ammonia. — The main materials furnishing am- 

 monia in fertilizers are nitrate of soda, sulphate of ammonia, cotton- 

 ■seed meal, dried blood, tankage, and fish scrap. The first two of 

 these (nitrate of soda and sulphate of ammonia) are easily soluble in 

 water and become well distributed in the soil where plant roots can 

 get at them. They are, especially the nitrate of soda, ready to be 

 taken up by the plants, and are therefore quick-acting forms of am- 

 monia. It is mainly the ammonia from nitrate of soda and sulphate 

 of ammonia that will be designated under the head of water-soluble 

 ammonia. 



Organic Ammonia. — The ammonia in cotton-seed meal, dried 

 blood, tankage, fish scrap, and so on, is included under this heading. 

 These materials are insoluble in water, and before they can feed 

 plants they must decay and have their ammonia changed, by the aid 

 of the bacteria of the soil, to nitrates, similar to nitrate of soda. 



They are valuable then as plant food in proportion to their content 

 of ammonia, and the rapidity with Avhich they decay in the soil, or 

 rather the rate of decay, will determine the quickness of their action 

 as fertilizers. With short season, quick-groAving crops, quickness of 

 action is an important consideration; but with crops occupying the 

 land during the greater portion, or all, of the growing season, it is 

 bettei' to have a fertilizer that will become available more slowly, so 

 as to feed the plant till maturity. Cotton-seed meal and dried blood 

 decompose fairly rapidly, but will last the greater portion, if not all, 

 of the growing season in this State. While cotton seed and tankage 

 will last longer than meal and blood, none of these act so quickly, or 

 give out so soon, as nitrate of soda and sulphate of ammonia. 



Total Ammonia is made up of the water-soluble and organic ; it is 

 the sum of these two. 



The farmer should suit, as far as possible, the kind of ammonia to 

 his different crops, and. a study of the forms of ammonia as given in 

 the tables of analyses will help him to do this. 



