46 CONTROL SERIES No. 74 



The word lime when applied to Hming materials means either calcium oxide 

 or calcium and magnesium oxides. 



Mono-ammonium phosphate (fertilizer grade) is a commercial salt made 

 by combining phosphoric acid with ammonia. It shall contain not less than ten 

 per cent (10%) of nitrogen and not less than forty-six per cent (46%) of available 

 phosphoric acid. 



The term phosphoric acid designates P2O6. 



The term potash designates potassium oxide (K2O). 



As the terms phosphoric acid and potash are used universally in guaranteeing 

 and in reporting the analyses of fertilizers it is recommended that the same terms 

 also be used in reporting and discussing the results of analyses of related materials. 



Acid and Basic Fertilizers. 



Although acid forming and non-acid forming fertilizers have not been officially 

 defined by the appropriate Committee of the Association of Official Agricultural 

 Chemists of North America, yet at the 1934 meeting of the Association the ten- 

 tative definitions which follow were submitted by the Committee: 



Acid forming fertilizer is one which increases the permanent acidity of the 

 soil immediately or when used over a period of years. 



Non-acid forming fertilizer is one which does not increase the permanent 

 acidity of the soil when used over a period of years. 



Although a basic fertilizer was not defined by the Committee, yet there seems 

 justification for the following definition: 



A basic fertilizer is one which decreases the acidity of the soil upon which it 

 is used. 



During the past year considerable interest has developed, particularly in the 

 Southern and Middle-Southern States and in New England, with reference to 

 acid and basic fertilizers. That the question should be of greater interest in 

 those sections of the country where good grades of limestone are not plentiful 

 is but natural. In mixed commercial fertilizers, with the exception of some of 

 the high-analysis mixtures, some form of conditioner or filler is usually necessary, 

 in which case it would seem to be a better practice to use finely ground dolomite 

 where this product can be secured at a low cost than to use some inert material 

 for this purpose. The advantage of dolomite over a high-calcium product for 

 this purpose is that it supplies the element magnesium in available form, and as 

 certain sections of the country show unmistakable evidences of magnesium 

 deficiency this is of considerable importance. Dolomite also has a higher acid- 

 neutralizing value than high-calcium limestone and it does not revert the soluble 

 and available phosphoric acid present in the mixed fertilizer. 



In certain parts of the country where desirable lime products are available at a 

 low cost and are therefore freely used for liming soils when needed, some other 

 material of low cost, yet possessing some fertilizing value, might be preferable 

 to ground limestone as a conditioner in fertilizers. Finely ground garbage 

 tankage, finely ground rock phosphate, etc., are examples of such products. 

 The fact should not be ignored that in many instances an acid-forming fertilizer 

 is preferable to a basic mixture, and in general it may be said that an acid-forming 

 fertilizer is not such a great problem to the farmer who has become accustomed 

 to making direct lime applications to his soil when needed. 



The subject has seemed of sufficient interest to Massachusetts agriculture to 

 warrant a general survey of the reaction of fertilizers sold in the State during 

 the seasons of 1933 and 1934. The tests of the fertilizers sold in 1933 were not 

 made until early in 1934 after the 1933 fertilizer bulletin had been issued; the 

 results are therefore given in the table which follows and furnish an interesting 



