FERTILIZERS. 73 



Dr. Sturtevant replied that we put back more than we have taken 

 from the soil. The onl}- plant food is the inorganic elements and 

 the nitrogen, and these are conserved from the soil b}' a green 

 crop, and we can consider green manuring somewhat in the light of 

 a fallow. 



Mr. Fuller said we do not admit that a grown plant has less 

 nutritious matter than a growing plant. 



Dr. Sturtevant said that straw contains a certain proportion of 

 ash element and nitrogen. 



Mr. Fuller asked if there is not more ash in a grown plant than 

 in an immature one. 



Dr. Sturtevant replied, 3'es and no. Much of the ash element 

 is not essential. Straw takes up much silica ; it can be taken up 

 in excess. Organic matter is not plant food. 



N. B. White, had known many failures of crops in' time of 

 drought from using dung. It was so in Minnesota last year. He 

 thought that the place for chemicals ; he had seen many instances 

 in the west where stable manure dried up, instead of decomposing, 

 and the crop was poorer than if no dung had been applied. 



James Cruickshanks said that he had made eighty bushels of 

 corn to the acre with barnjard manure. 



Dr. Sturtevant said that he could refer to a crop of one hundred 

 and twenty-three bushels raised with chemicals. He did not wish 

 to underrate barnyard manure, but simply said that the chemicals 

 in it can be supplied as well in fertilizers. He did not wish to draw 

 a comparison between barnyard manure and fertilizers. The 

 province of fertilizers, if a single element, like superphosphate or 

 potassa, is to supplement or add to the dung. The complete fertil- 

 izer is to be used when we are out of dung, and wish to till 

 additional land. In some cases the organic matter in dung will 

 give it an advantage, but this opens up other considerations than 

 those which we are discussing. 



]\Iarshall P. Wilder said that all would agree that manure does 

 contain the ingredients which have been spoken of as essential to 

 the food of plants, and he thought that Dr. Sturtevant had placed 

 the matter very fairly. The practical question is. What kind of 

 manure shall we use? He had always held to making a perfect and 

 thorough trial, for we have not practical knowledge enough. Mr. 

 Wilder related an instance where he directed a man to apply a 

 fertilizer to a plot of celery, and he put a whole bag on one row 

 10 



