304 CITRUS FRUITS AND THEIR CULTURE. 



ing the trees stronger and more sturdy. Citrus trees planted 

 on soils fairly well supplied with lime have a tendency 

 to mature their fruit somewhat earlier and the fruit 

 is bright and clean. 



Sources of Plant Food. The most noteworthy sources 

 from which the required fertilizing elements may be se- 

 cured are barnyard manure and commercial fertilizers. 

 k A good quality of the former, when well rotted, will con- 

 f"~~tain about .C^ per cent, of phosphoric acid^ .Qfi per cent. o 

 I potash and .Qj6 per cent, of nitrogen, while the latter may^ 

 be of almost any conceivable composition. 



The use of stable manure as a fertilizer for citrus 

 trees in California has been followed by satisfactory re- 

 sults, but in Florida, its use has too frequently been fol- 

 lowed by attacks of die-back and by other troubles. 

 Whether this be true in all cases or not, in the vast ma- 

 jority of instances the benefits to be derived from the use 

 of stable manure are doubtful. It is essentially a nitro- 

 genous fertilizer, and,_whenever used, should be accom- 

 panied byheavy applications of potash, unless thp soil . 

 is already rich in this substance. Potash is notoriously 

 deficient in Florida soils. An additional supply of phos- 

 phoric acid may also be needed. The greatest difficulty 

 encountered in the use of stable manure is that people 

 generally fail to realize that it is, at best, a one-sided 

 fertilizer. 



Sources of Pfeogjifonffo Aftf ( fl,. , The principal sources 

 of phosphoric acid are bone and phosphatic rock. The 

 bone is sold either as ground bone, steamed bone or dis- 

 solved bone. The other as super-phosphate (acid phos- 

 phate) and double super-phosphate. Ground bone contains 

 about 22 to 26 per cent, phosphoric acid. Steamed bone 

 about the same; dissolved bone, 16 to 19 per cent.; 



