BEHAVIOUR IN THE SOIL 17 



found that sulphate of ammonia gave a very inferior result to 

 nitrate of soda on soils containing 10 per cent., or more, of 

 carbonate of lime. While top-dressings of ammonia salts on 

 such soils gave unsatisfactory results, good results were 

 obtained when the salt was applied to crops which allowed of 

 the salt being buried by the harrow or the plough. The 

 odour of ammonia did not appear when the salt was covered 

 with one inch of earth. 



There can be little doubt that a profitable return from 

 sulphate of ammonia is greatly favoured by covering the salt 

 with the soil as soon as possible after it has been spread upon 

 the surface. Mixing the salt with kainite, or especially with 

 superphosphate, will also greatly aid in preventing loss from 

 volatilisation. 



If sulphate of ammonia is added to a pure quartz sand it 

 undergoes no change ; it will in this case remain in solution in 

 the water which the sand holds, and be easily washed out if 

 rain falls on the surface. If the salt is mixed with pure peat 

 the same results will follow. It is doubtful whether under 

 these circumstances sulphate of ammonia is capable of acting 

 as a plant food, its effect at least will be very limited. 

 For the salt to become effective as a manure it must undergo 

 change in the soil. For this change to commence it is neces- 

 sary that the soil should contain some basic matter capable of 

 decomposing the sulphate ; the only basic matter occurring 

 in soils in considerable quantity is carbonate of lime. Thus 

 while the presence of an abundance of carbonate of lime in 

 the soil is unfavourable to a profitable use of sulphate of 

 ammonia, it may be laid down as a general principle that 

 sulphate of ammonia cannot be employed regularly with 

 success except on soils containing a distinct amount of car- 

 bonate of lime. Soils very poor in lime may be successfully 

 cultivated with farmyard manure, or they may receive nitrate 

 of soda, but they do not belong to the class of soil that will 

 give profitable results with sulphate of ammonia. 



The reaction which takes place between the carbonate of 

 lime in the soil, and the sulphate of ammonia added to it, 

 results in the formation of a little carbonate of ammonia, and a 



