APPLICATION OF SCIENCE TO PLANT CULTURE. 75 



MEETING FOR DISCUSSION. 



Late Progress in the Application of Science to 

 Plant Culture. 



By Professor W. O. Atwater, Wesleyan University, Middletown, Conn. 



Ladies and Gentlemen : Ten j'ears ago it was my privilege to 

 give a short address here, on the chemistry of the feeding of 

 plants, as illustrated b}' some experiments with chemical fertili- 

 zers. In the correspondence with the chairman of your lecture 

 committee in regard to what I should sa}' to you today, it was 

 agreed that the subject should include a continuation of the former 

 address, and that something of the results of late investigations 

 should be added. 



Permit me then to recapitulate at the outset some of the funda- 

 mental principles of plant nutrition as applied to the ingredients 

 of the food of plants, their sources, and their artificial supply. 



1. Plants, like animals, require food for life and growth. A 

 part of the food of plants comes from the atmosphere ; the rest is 

 furnished by the soil. No ordinary cultivated plant can thrive 

 without a sufficient supply of each of a number of substances 

 needed for its food. With an abundance of all these, in forms in 

 which the plants can use them, and with other circumstances 

 favorable, the crop will flourish and the yield be large. But if the 

 available supply of any one of them be too small, a light yield is 

 inevitable. If all the other conditions for a profitable crop of 

 corn, potatoes, or other plants are fulfilled in the soil, except that 

 potash is deficient, the crop will surely fail. But if the potash be 

 supplied the yield will be abundant. 



2. The most important soil ingredients of plant food — the 

 ones which the atmosphere cannot supply' at all, or not in sufficient 

 quantity, and which the soil or fertilizers must supply, so that the 

 plant can absorb them through its roots — are potash, lime, mag- 

 nesia, iron, phosphoric acid, sulphuric acid, chlorine, and some 

 compound of nitrogen. Plants also take silica, soda, and some 

 other materials from the soil, but these are needed only in minute 

 quantities, or not at all. 



3. In removing crops from the soil we take away plant food. 

 This is the chief cause of soil exhaustion. Lack of fertility is 

 commonly due, in large part or entirely, to lack of plant food. 



