1891.] PUBLIC DOCUMENT — No. 4. 15 



for plants and also for animals. In fact, every subject 

 appertaining to the business of the farmer has been the sub- 

 ject of study, and we have improved machinery, improved 

 tools, improved methods, and improved everything that 

 helps the farmer to succeed. Take, for example, the work of 

 those great experimenters who first applied science to the 

 art of agriculture, — Lawes and Gilbert of England. They 

 started their work in 1843. Their first investigations were 

 with manures, seeking to determine how the farmer could 

 use manure to the best advantage in the raising of crops. 

 Next they endeavored to find substitutes for barnyard 

 manure. They commenced with the use of bones and other 

 substances like the Spanish rock, coprolites, etc., which 

 contain a large proportion of phosphate of lime. In other 

 words, they were studying the question of plant food, and 

 seeking for materials which could be used as nutriment for 

 plants. When we turn back to the beginning of the use of 

 what are now called commercial fertilizers, we find that 

 bones were first used in the last part of the last century, 

 and then came the use of substitutes for bones, including the 

 " South Carolina rock," which has been largely used in this 

 country and exported to a great extent to foreign countries. 

 Then, came the German potash salts, nitrate of soda, sulphate 

 of ammonia, and other materials which are dug from the 

 earth or are waste products from other industries. The work 

 of these pioneer investigators was not confined to plant 

 nutrition ; they also considered the matter of rational stock 

 feeding; and. while the Germans, under the lead of Wolff 

 and Kuhn, have been leaders in the work of making stock 

 feeding a science, yet Lawes and Gilbert have contributed 

 much towards the accomplishment of this result. 



Having considered these three periods in the history of 

 agriculture, I want just to recapitulate. First we have 

 the so-called period of inexhaustible fertility, when it was 

 thought that the soil would continue to yield abundant crops 

 indefinitely, without the application of any fertilizer. Then 

 we have the period of exhaustion, when the soil has become 

 exhausted of plant food, and will no longer produce a good 

 crop. Then comes the third period, the period of renova- 

 tion, when we are asking how we can overcome the results 



