748 



irrigation purposes the whole of the fertilizing matter is received 

 into the land. If some of the precipitation methods are used to 

 purify the sewage, the sludges obtained contain almost all the 

 phosphoric acid, very little of the ammonia, and almost none of the 

 potash. The late Prof. Way gives the following analyses of sewage 

 before and after treating it with lime. 



Phosphoric acid 



Potash 



Ammonia 



Grains per gallon. 

 Before. Afterwards. 



2*63 

 3-66 



'45 

 3-80 



It is evident very little can be expected from sewage-sludges, 

 except from the phosphoric acid. Sewage irrigation farms have 

 been most successful in growing grass and green fodders for feed- 

 ing milch-cows, but both the milk and butter are liable to be 

 tainted. Vegetables have also been grown successfully with 

 sewage. 



In the buying of manures too much must not be taken for 

 granted. It does not follow that because so-and-so used a particu- 

 lar manure last year or the year before, and had a good crop by 

 using so much of it per acre, that the same results will be secured 

 on the land in another season. The farmer may have seen his 

 neighbor's good crop which was obtained by using so many 

 hundred pounds per acre of a particular manure, and he comes to 

 the conclusion this is just what he wants to give him a good crop 

 on his land. But he arrives at this conclusion without a proper 

 knowledge of the constituents of the manure, as well as without 

 knowing what is required by his soil for a particular crop. His 

 neighbour's soil may contain a sufficiency of potash. The manure 

 may contain little or none, but lit- gets a good crop, because the 

 soil already contains all the potash required, and the manure con- 

 tains all the other elements of food for that crop, while his neigh- 

 bour's soil contained sufficient potash his might be deficient in this 

 constituent, and no matter how much nitrogen and phosphoric acid 

 he gives to the crop which requires a liberal supply of potash, the 

 result will, in most cases, be little better than if he applied no 

 manure. What he wants to know, when lie lias decided what he 

 intends to grow, is, what is his land deficient in that the crop 

 requires. This knowledge can be obtained by chemical analysis 

 and also by the use of experimental plots. This latter method 

 should be undertaken by all tanners so that they may know in what 

 respects their soils are deficient, and thus be able to maintain them 

 always in a fertile- state. Km! her reference will be made to ihe>e 

 experimental plots. The farmer is now supposed to know what his 

 crop will require, and also the constituents of fertility his soil is 

 deficient in. He must then see that the manure he proposes to buy 



