May s7, 1918 



Boron 



457 



absorbed by the plants grown on the 40-ton colemanite-treated plot 

 when the boron was added as the insoluble calcium colemanite than when 

 grown on the 40-ton borax plot where the boron was added in a readily 

 soluble form. The control samples tested were remarkedly free from 

 boron, only the tops of the kale showing any traces. The flowering tops 

 of the kale contained about the same amount of boron as the rest of the 

 tops of the plant. Nakamura (7) found that o.oooi per cent of boric 

 acid in culture solutions stimulated spinach, but had a slightly injurious 

 action on peas. 



Five samples of soil, two from each of the light and the heavy boron- 

 treated plots and a control sample, were analyzed for nitrates, ammonia, 

 and soluble boron. 



Table VI. — Percentage of the total boron as boric acid in lettuce, spinach, cabbage, and 

 kale, dry basis, Arlington, Va., 1^14-1^ 



Boric acid added to upper 

 6 inches of soil. 



Parts of plants 

 analyzed. 



Boric acid found. 



Lettuce. Spinach. Cabbage 



Per cent. 



0.00176 as borax (16-ton 

 plot). 



0.00264 as borax (24-ton 

 plot). 



0.0044 ^s borax (40-ton 

 plot). 



0.00232 as colemanite (16- 

 ton plot). 



0.00348 as colemanite (24- 

 ton plot). 



0.0058 as colemanite (40- 

 ton plot). 



40-ton control 



I Tops 

 Roots 

 Flowering tops . 

 {Tops 

 Roots 

 Flowering tops . 

 [Tops 



i Roots 



[Flowering tops. 



I Tops 

 Roots 

 Flowering tops . 



[Tops 



•^ Roots 



[Flowering tops. 



[Tops 



JRoots 



[Flowering tops. 



[Tops 



j Roots 



[Flowering tops. 



Per cent. 



Per cent. 



Per cent. 



Trace . . 



Trace . 



Faint 

 trace. 



004 



00006 



. 00225 



00475 



Per cent. 



00025 



0014 



. 00625 



• 00365 

 . 0001 



Table VII. — Percentage of nitrate and ammonia nitrogen and soluble boron in soil 

 samples, Arlington, Va., 191 j 



Boric acid added to upper 6 inches of soil. 



Per cent. 



0.00176 as borax (i6-ton plot) 



0.0044 as borax (40-ton plot) 



0.00232 as colemanite (16-ton plot) 

 0.0058 as colemanite (40-ton plot). 

 40-ton control 



Soluble 

 boron as 

 boric acid 



foimd. 



1 Folin method. 



