194 Journal of Agricultural Research vo1.xvi,No. ? 



action upon the soil particles. A determination of total barium in the 

 soil of another field near by gave 0.08 per cent of barium sulphate, 

 obtained by decomposing the soil with hydrofluoric and sulphuric acids. 



CONCLUSIONS 



From the results obtained in the different series of experiments in 

 this investigation the following conclusions are drawn. 



(i) Barium compounds in the absence of calcium carbonate are 

 poisonous to plants; but barium carbonate in the presence of an excess 

 of calcium carbonate apparently exerts a distinct stimulating influence 

 on the growth of the plants studied. 



(2) There is no tendency for barium to replace calcium in the growth 

 of plants when calcium carbonate is omitted from a plant-food ration 

 under the conditions of these experiments. 



" (3) Strontium compounds have in most instances given larger 

 increased yields than barium compounds. 



(4) Strontium carbonate can not be substituted for calcium carbonate 

 in the growth of plants under the conditions studied, though strontium 

 carbonate is less toxic to plants in the absence of calcium carbonate 

 than barium carbonate. 



(5) Neither barium nor strontium compounds can be looked upon 

 as important plant foods, although the presence of small amounts of 

 the carbonate of each of these elements has given increased yields that 

 are noteworthy in most instances. 



(6) Barium and strontium carbonates accelerated the growth of the 

 roots of such plants as were examined. 



(7) Increasing the amount of strontium nitrate gave a corresponding 

 increase in the nitrogen content of wheat. 



(8) No barium compounds were found in the residue obtained upon 

 evaporating 25 liters of drainage water collected from the drain tiles 

 on the Station farm, which would indicate that the barium found in 

 plants is taken up in place by the plant roots. 



