142 INFLUENCE OF SALTS ON THE SOIL 



The literature dealing with the influence of lime upon the nitrify- 

 ing organisms is so voluminous that no attempt is made here to 

 refer to all of it. In most cases the experiments were conducted on 

 soils which were acid and the lime supplied neutralized the acidity 

 of the soil, thus giving the necessary neutral medium for the action 

 of the nitrifying organisms. Such results give little if any idea of 

 the direct stimulating or toxic influence of calcium, Furthermore, 

 the work has recently been summarized by Brown who concludes 

 that the application of lime increased nitrate production from 

 ammonium sulphate and dried blood, the gain being almost propor- 

 tional to the quantity of lime applied. This, in turn, was found to 

 bear a close relationship to the number of organisms developing on 

 synthetic agar. 



Gypsum. Gypsum is a strong soil stimulant and in most cases it 

 greatly increases the crop yield. The beneficial effect may be due 

 to its liberating potassium or supplying sulphur for the direct nutri- 

 tion of the plant. At other times it may react with the ammonia 

 formed by the ammonifying organisms, the ammonium sulphates 

 formed being readily nitrified. There is also the possibility that 

 calcium sulphate acts as a direct stimulant to the microorganisms of 

 the soil. The literature is meager and inconclusive on this phase 

 of the subject. 



Severin concludes from his work that gypsum not only prevents 

 the loss of ammonia from manure, but it increases the speed of 

 decomposition from 10 to 20 per cent., while Paterson states that 

 gypsum slightly increases nitrification in soil, as determined by 

 laboratory experiments. Prior to this Pichard had shown that the 

 sulphates of calcium, potassium, and sodium promote nitrification. 



Opposite results are reported by Dezani who found that gypsum 

 in amounts varying from 0.5 to 2 per cent, had no appreciable 

 effect on nitrification. The results obtained by Lipman and others 

 varied and were inconclusive. 



Calcium Chlorid. According to Lipman calcium chlorid in solutions 

 accelerated the action of ammonifiers. It is interesting to note that 

 in a later work he failed to find antagonism between either calcium 

 and magnesium or calcium and sodium. The chlorid s of calcium, 

 magnesium, potassium, and sodium were found to be toxic in the 

 order named. Marked antagonism exists between calcium and 

 potassium magnesium and sodium, and potassium and sodium. 

 Sea water was found to be a physiologically balanced solution for 

 Bacillus subtilis. 



Iron Sulphate. Many writers have made great claims for iron 

 sulphate as a fertilizer. A goodly number of these have been made 

 by individuals who wished to profit by its sale, but even when these 

 cases are ignored there are still many cases in which it has produced 

 good results. The composition of the crop usually indicates Vthat 



