SECRETARY'S REPORT. 61 



return to his land in kind or quantity, and that the atmosphere 

 and soil cannot furnish in sufficient amount to grow satisfactory 

 crops, then purchase of foreign substances containing them in 

 available form is necessary to keep up the productiveness of 

 the soil. 



Manures may be practically divided into three great classes, 

 known as carbonaceous, ammoniacal, and inorganic. The first 

 is made up almost exclusively of woody fibre. Its great source 

 is the manure from our farm animals. Deposits of peat and 

 muck are referable to this class. They all form, in their 

 progress toward ultimate decay, under favorable circumstances, 

 what we denominate humus. Ammoniacal manures are those 

 which contain nitrogen in their composition, and which by its 

 union with hydrogen forms ammonia during progress toward 

 decay. The principal available source of this substance is the 

 liquid evacuations of stock. It is contained in the solid manure 

 to some extent when fresh, and also in most other animal 

 products except fat, such as hair, wool, horns, hide, flesh, 

 blood, (fee. The inorganic matters are all derived originally. 

 from the inorganic substances composing the soil. The more 

 important ones are lime, potash, and phosphoric acid. These 

 substances exist in nearly every soil, but in such combinations 

 that they are only very slowly available to vegetation, but they 

 are nevertheless, just as absolutely necessary to plants as humus 

 or ammonia. Tlieir ordinary source is in ashes and bones. It 

 is evident that an ox, wliose bones are made up in large propor- 

 tion of lime and phosphoric acid, in combination as phosphate 

 of lime, could never have attained his growth had not his food 

 contained tliose substances. If that food, which is hay and 

 grain, possessed them, they must have derived them from the 

 soil. If these elements had not existed in the soil, then the 

 hay and grain could not have been developed from it. 



These considerations teach us that we must be sure that the 

 soil is furnished with all the substances needed to grow crops, if 

 we would get maximum results. A soil filled to repletion with 

 humus, but having no available phosphate of lime, or potash, 

 cannot hy any possibility grow a crop in the composition of 

 which they are indispensable. Neither can a soil holding large 

 amounts of inorganic matters, produce a crop without some form 

 of carbonaceous material. Ammonia is found in the atmosphere 



