THE ASH CONSTITUENTS OF PLANTS. 



Atterberg's minima for oats. 



317 



Ripe ! Whole 

 kernels, j plant. 



Half-ripe 

 plant. 



Phosphoric acid . 



Potash 



Lime 



Magnesia 



Nitrogen 



Per cent. 

 0.37 



Per cent. 

 0.21 

 .37 

 .08 

 .10 

 .80 



Per cent. 



0.14 



.37 



.10 



.08 



It is seen from the above that in spite of much research and much 

 discussion the question of judg-ino- of the soil hy the results of ash 

 analysis of the plant grown therein is not settled. It might be help- 

 ful to a further clearing up of the question to grow plants like oats 

 or spring barley on a very poor soil and gradually increase the appli- 

 cations of potash, phosphoric acid, and nitrogen. With very little 

 plant food the plants would make insufficient growth; with somewhat 

 more the growth would be better, and gradually the amounts of ferti- 

 lizers would be determined with which the plants began to make satis- 

 factory growth. Then analysis of the resulting plants would show 

 certain percentages of potash, phosphoric acid, and nitrogen, and thus 

 the minimum for these elements in the plants would be found. If 

 similar plants grown on the soil to be tested should show a content of 

 potash, phosphoric acid, and nitrogen lower than this minimum the 

 indication would be clear that the soil was deficient in these elements 

 of plant food, and they should be supplied in the fertilizer. 



This method of determining the fertilizing elements deficient in the 

 soil by the analysis of the ash of the plants grown therein still requires 

 much investigation. The percentages of potash, phosphoric acid, etc., 

 in the plant ash, as well as the amounts in the dry matter, are, as 

 already descri))ed, infiuenced not only by the plant food contained in 

 the soil, but also b}" other conditions, as the water content of the soil 

 or the amount of rainfall. Many researches are yet reciuired to make 

 the method practicable and reliable. 



Although investigation on the subject of the ash constituents of 

 plants has l)een very extensive, much still remains to be done and the 

 subject presents an inviting field for thorough and exact research. In 

 the present status of our knowledge such researches are much to be 

 desired. 



