May 27, 1918 Boron 469 



borax and colemanite on the same crops at Arlington and Bethesda is 

 rather striking. The colemanite and borax showed no difference in 

 action on plants grown in the same soil the first season. More boron was 

 found in the lettuce, cabbage, spinach, and kale plants grown on the 40-ton 

 colemanite-treated plots than in the plants from the 40-ton borax- 

 manure plots at Arlington. Onions grown at Bethesda showed the 

 presence of boron only in the flowering tops of the plants grown on the 

 40- ton borax-treated plot. 



The second season 0.00176 per cent of boric acid as borax injured string 

 beans at both Arlington and Bethesda; 0.00232 per cent as colemanite at 

 Arlington injured string beans, while at Bethesda this percentage of 

 colemanite caused no injury ; but 0.00348 per cent of boric acid as cole- 

 manite injured string beans at Bethesda. At Arlington 0.00264 per cent 

 of boric acid as borax and 0.00348 per cent as colemanite reduced the 

 yield of com and turnips, but at Bethesda were apparently without 

 effect on the yield of com. At Bethesda 0.0044 P^r cent of boric acid as 

 borax and 0.0058 per cent as colemanite reduced the yield of potatoes 

 and com. 



The potatoes, com, beets, and string beans grown at Bethesda con- 

 tained but small amounts of boron. The tumips at Arlington con- 

 tained more boron than the plants at Bethesda. It is evident that the 

 vegetables took up more boron from the soil at Arlington than at 

 Bethesda. 



Rye was grown the third season at Bethesda following the third appli- 

 cation of boron manure. A reddish tinge was observed in the young 

 plants on the 40-ton boron-treated plots. This disappeared gradually, 

 and in the spring the rye looked normal The rye heads grow^n on the 

 boron plots were not as well filled out as the heads of the plants on the 

 control plots. The crops on the 24- and 40-ton control plots were 

 materially reduced by the large amounts of manure applied. The quan- 

 tity of manure added was of more importance in reducing the yield than 

 the added boron. 



There is a decided difference in soils in rendering the added boron 

 nontoxic to plants. This is seen in the divergent results as to plant 

 injury, etc., obtained on adding equal amounts of borax or colemanite 

 to different soils. In some cases boron is taken up by plants from soil 

 when no detectable quantities of boron are present in the soil samples. 



There is a complete disappearance of detectable amounts of soluble 

 boron from soils after the addition of borax and colemanite, although 

 small amounts of total boron are present. It is therefore evident that in- 

 soluble boron compounds are formed. In many soils there is a tendency 

 for plants to absorb boron in proportion to the quantities added. In 

 some soils the same amounts of boron were absorbed irrespective of the 

 quantities added. The calcium of the colemanite did not prevent the 



