124 BOARD OF AGRICULTURE. [Pub. Doc. 



agree with this, that the commercial fertilizer trade origi- 

 nated in, and has been nourished b}', this one-time attitude 

 of the scientific world toward the maintenance of fertility. 

 What a magnitude this trade has reached ! The farmers of 

 the countr}^ are now pajdng annually more than fiftj^ millions 

 of dollars for commercial fertilizers. In 1899 the averaofe 

 cost per farm in Massachusetts for commercial fertilizers 

 was $35 per farm, or $1,320,600 for the whole State. The 

 manufacture of fertilizers is one of our greatest industries. 

 We have searched up and down the earth and have entered 

 its very bowels, and we have carefully scrutinized every 

 waste product of our great manufactures, in order to provide 

 raw materials for this constantly increasing traffic. The 

 search has been for the compounds of nitrogen, phosphoric 

 acid and potash, and the prices of the manufactured mixtures 

 are based upon what they contain of these three ingredients ; 

 thus placing tremendous emphasis upon the point of view 

 that the chief requirement for the maintenance of soil fer- 

 tility is to supply to the soil, artificially or otherwise, three 

 of the ten or more required constituents of plant growth. 

 It is indisputably true, I would reiterate, that at one time 

 our attention in commerce and in practice was so fixed upon 

 this general conception of soil exhaustion and fertility that all 

 other considerations were almost entirely ignored, at least 

 in popular discussions. 



It must be confessed that just now there is going on a re- 

 adjustment of the definitions of fertility, and, as is generally 

 the case in such periods of progress in knowledge, it is ac- 

 companied by more or less confusion of thought. It must 

 be confessed that fertility and its maintenance are not so 

 simple in their relations as they would appear to be on the 

 basis of keeping books with the soil. 



In order to understand some of the changes which are now 

 taking place in our point of view, we must refer to a division 

 of knowledge which to quite an extent stands apart from the 

 chemistry of plant nutrition, viz., soil physics. This field 

 of agricultural science relates to soil conditions rather than 

 to soil composition. It deals with soil texture, soil aeration, 

 soil temperatures and the sui)})lv and movements of soil 



