Food for J supply my plants with Nitrogen, phosphoric acid and 



^_! potash, in the best forms and at the least expense? We 



6 will try to throw some light upon this question in the 



following pages. We will take first, Phosphoric Acid. 



„ , . . ., There are several sources of phos- 



Phosphonc Acid. , . i .-, , r • £ 



* phone acid, the principal 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 phos- 

 phoric acid, and it makes little or no difference 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 petri- 

 fied bones and excrements of extinct animals. When 

 this substance is ground and mixed with a sufficient 

 quantity of sulphuric acid, the larger part of the phos- 

 phoric 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 sul- 

 phuric acid, it becomes what is commercially known as 

 superphosphate, or acid phosphate. The same is true if 

 ground bone is treated in the same way. Good super- 

 phosphate, or acid phosphate, contains 14 per cent, of 

 soluble phosphoric acid. 



The best sources of potash are 

 sulphate of potash and unleached wood 

 ashes, which latter contain from 3 to 5 per cent, of 

 potash in the form of carbonate. They also contain from 

 1 to % l /2 P er cent - oi phosphoric 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 

 Nitrate. effective 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, 



