5^6 Journal of Agricultural Research voi. x.No. u 



Agulhon (i) grew wheat in pot cultures with sand and nutrient media 

 to which he added varying amounts of boric acid. He found that 0.005 

 per cent of boric acid killed the wheat plants, while o.ooi per cent had 

 no toxic effect. 



Voelcker (6) in experiments with pots holding 40 pounds of soil, deter- 

 mined that 0.005 to o.i per cent of boric acid (H3BO3) and borax (Naj 

 B4O7) prevented the germination of wheat. He found that o.ooi per 

 cent of either compound was harmful, but amounts from 0.0005 to o.ooi 

 per cent were beneficial, the effectiveness increasing v;ith the decreased 

 percentage of boron. 



In the field tests conducted by the writers at Arlington, Va., the pres- 

 ence of 0.0088 per cent of boric acid (added as borax) in the upper 6 

 inches of soil was toxic to wheat, while 0.0022 per cent added as borax, 

 or 0.0029 per cent as colemanite was nontoxic to wheat. 



It is interesting to recall that the soil sample taken nine months after 

 the addition of the 0.0088 per cent of boric acid as borax in 1914 con- 

 tained soluble boron. The other soil samples for three years and samples 

 from this plot the next two years showed no detectable amounts of sol- 

 uble boron and no injury to the wheat. The results of the analyses for 

 soluble boron in soils from Orlando, Fla., New Orleans, La., and Dallas, 

 Tex., to which borax had been added showed the presence of consider- 

 able amounts of soluble boron in the soils from Orlando and New Orleans 

 where the crops had been decidedly injured by the borax. The crops at 

 Dallas showed no injury, and no soluble boron was detected in the soil. 



In brief, there appears to be a direct connection between the presence 

 of soluble boron in soil and injury to plant growth. There is apparently 

 a gradual combination of the soluble boron added to soil either as a 

 silicate or calcium borate. The rapidity with which soluble boron be- 

 comes insoluble varies with each individual soil or soil type and with 

 climatic and other factors. 



SUMMARY 



In field tests at Arlington, Va., based on the yield of the manured 

 control plot, borax reduced the yield of wheat (grain) 10 per cent in 

 1914 and 1915, while colemanite had little, if any, effect. The manured 

 control gave the largest yields of grain in 1914 and 191 5, and the 

 unmanured controls the lowest yields. 



In 1 91 6 the yields from all four plots were low, and the proportion 

 of straw to grain was higher than during the two previous years. In 

 1 91 6 the borax plot gave the best yield. 



During the three years there were seasonal variations involving a 

 gradual decrease of fat and an increase of nitrogen in the grain and 

 Straw from all plots. During this period the moisture in the straw 

 increased and that of the grain decreased. 



