r plants with Nitrogen, phosphoric acid and potash, in the best 

 forms and at the least expense? We will try to throw some 

 light upon this question in the following pages. We will 

 take first, Phosphoric Acid. 



There are several sources of phosphoric 

 Phosphoric Acid. add) the p rincipal being bones and rock 



phosphate. Of these, the rock phosphate is the cheapest 

 source. A prevailing impression exists that superphosphate 

 made from rock phosphate is not as good as that made from 

 bones. It has been shown by many experiments that this 

 idea is entirely without foundation. What the plants want 

 is available phosphoric acid, and it makes little or no differ- 

 ence from what source it is derived. 



The largest deposits of rock phosphates exist in South 

 Carolina, Florida and Tennessee. These beds of phosphate 

 are supposed to be composed of the petrified bones and excre- 

 ments of extinct animals. When this substance is ground 

 and mixed with a sufficient quantity of sulphuric acid, the 

 larger part of the phosphoric acid which it contains becomes 

 soluble in water, and hence available as plant food. This 

 fact was one of the greatest agricultural discoveries of the 

 age. 



When the rock phosphate is thus treated with sulphuric 

 acid, it becomes what is commercially known as superphos- 

 phate, or acid phosphate. The same is true if ground bone 

 is treated in the same way. Good superphosphate, or acid 

 phosphate, contains 14 per cent, of soluble phosphoric acid. 



The best sources of potash are sulphate 

 Potashes. O f p 0tas h and unleached wood ashes, which 



latter contain from 3 to 5 per cent, of potash in the form of 

 carbonate. They also contain from i to 2 1 / 2 per cent, of phos- 

 phoric acid. They are worth, usually, as plant food, from 

 $7.00 to $11.00 per ton, not to mention the valuable lime 

 they contain. 



Nitrate is the most important and effective 

 Nitrate. element of plant food, and at the same 



time, as stated, is the one that is generally deficient in the soil. 

 Lands must have meals, that is, food cooked for them 

 in advance. The sun will help do this cooking, as its heat and 

 light promote nitration which is really a process of cooking 

 and also pre-digestion. When the plant food is cooked and 



