12 BULLETIN 486, U. S. DEPARTMENT OF AGRICULTURE. 



States usually ranges from 20 to 50 pounds per acre. In many of the 

 tropical countries, where much larger yields are produced, this 

 amount can be increased one or two fold with profit. 



To the application of phosphoric acid there is a good response 

 from the soils of nearly all sugar-cane localities both in this country 

 and in foreign countries, but the amount to be applied most advan- 

 tageously varies considerably. Most of the soils of Java are a nota- 

 ble exception to this rule, in that they do not respond to phosphate 

 applications. The amount of soluble phosphoric acid applied in 

 Louisiana is usually from 40 to 80 pounds per acre. To the lighter 

 soils of Georgia and Florida it is not unusual to add considerably 

 more, even up to 120 pounds per acre. 



To applications of potash there is little or no response in most of 

 the rich alluvial sugar-cane soils of the Mississippi Delta. In the 

 States east of Louisiana, however, potash is applied, usually at the 

 rate of 30 to 50 pounds per acre. 



In these States it is common practice to buy the fertilizers ready 

 mixed. However, many farmers do their own mixing in the interests 

 of economy. In trade the mixed fertilizers are commonly described 

 by three figures, referring in their order to the percentages of avail- 

 able phosphoric acid, ammonia, and potash which they contain. The 

 mixtures most popular in southern Georgia and northern Florida 

 for spring and early summer applications usually do not vary far 

 from the 8-2-3 formula, i. e., 8 per cent of soluble phosphoric acid, 

 1.65 per cent of nitrogen (equivalent to 2 per cent of ammonia) : 

 and 3 per cent of potash. This is supplied in one or two appli- 

 cations in quantities totaling from 800 to 1.600 pounds per acre, 

 often followed in late summer with a top-dressing of readily avail- 

 able nitrogen, such as nitrate of soda. These quantities are here 

 mentioned as an example of common practice in one locality and not 

 as a guide or recommendation for any wide range of soils or locali- 

 ties. It can not be too strongly urged that the farmer, in the absence 

 of trustworthy and conclusive experience with his particular type 

 of soil, should not blindly follow any special fertilizer formula that 

 may have been found suitable for some other type of soil, but rather 

 that he should experiment on his own farm on small plats with 

 several of the combinations that he has reason to suppose will most 

 probably fit his needs. 



The most common sources of nitrogen in the manurial mixtures are 

 cottonseed meal, tankage, and ammonium sulphate for early applica- 

 tions and sodium nitrate (Chile saltpeter) and ammonium sulphate 

 for late applications. Of these, cottonseed meal is most extensively 

 used in the Southern States, being near the source of its produc- 

 tion the cheapest commercial fertilizer. It contains about 7 per cent 



