J 80 BOARD OF AGRICULTURE. 



acid, the proportions of which in 1000 lbs. of our ordinary crops 

 are given in the last column of this table. Sulphuric acid, in the 

 form of some sulphate, must be present in the soil. If we should 

 remove all the .sulphates from a given soil, it would be totally 

 impossible to grow any crop or any plant there unless the sul- 

 phates were replaced. That is one of the first principles of 

 agricultural science, which applies equally to all the ingredients 

 stated in the table, with the possible exception of soda, as has 

 been establish by such an amount of experimental evidence, that 

 there can remain no doubt of it whatever. Sulphuric acid, or the 

 sulphates, as they are found in nature, are very liable to be 

 removed from the soil. The sulphate of lime is the form in which 

 sulphuric acid chiefly occurs in land. This dissolves in about five 

 hundred times its weight of water ; and where the soil is so 

 situated that heavy rains fall upon it, leach through and go out of 

 it again, the sulphuric acid is rapidly washed away. Almost 

 everywhere, except in the poorest soil, you find the water a little 

 hard, when you use it with soap. This hardness is due to the 

 presence of lime, and in most cases you find the water contains a 

 little sulphate of lime, which is the same as plaster of Paris. This 

 continually dissolves from the soil and passes into the springs and 

 rivers. If the soil is not porous, but of such a nature that it can 

 hold the rain which falls upon it to a large extent, the case is 

 different, and the loss is not so rapid as from soil where the water 

 runs freely through ; but we have in this way a constant loss of 

 sulphuric acid from the soil. 



Unless there is an unfailing supply of sulphates in the soil itself, 

 furnished, for example, by the chemical alteration of some other 

 sulphur compound, as iron pyrites, there will in time come to be a 

 deficiency of sulphuric acid from this washing process alone, and 

 although this element of crops is the least prominent of them all 

 in respect to quantity it is likely t • Le soonest exhausted. The 

 moment when the available sulphates in the soil become less than 

 is required for a full crop, it will be impossible to realize such a 

 crop without making good the deficiency. 



The soil in a given case may be unfertile, may become ex- 

 hausted, simply because this one ingredient is removed by the 

 processes of washing and cropping. Lime and soda are also 

 washed out from the land, slowly to he sure, but continually, and 

 in quantities whose aggregate is very large. There are other ele- 

 ments, like phosphoric acid, which we do not lose by washing to any 



