1 84 



Journal of Agricultural Research 



Vol. XVI, No. 7 



COWPEAS 



In the first series of experiments twelve i -gallon earthenware jars 

 were filled with a clean quartz sand that contained very little plant 

 food. To each of the pots of sand was added the following basal plant- 

 food ration: lo gm. of calcium carbonate, lo gm. of tricalcium phos- 

 phate, 5 gm. of magnesium carbonate, 4 gm. of potassium nitrate, 2 

 gm. of potassium chlorid, and 2 gm. of sodium thiosulphate. In 

 addition to this plant food, varying amounts of barium carbonate were 

 added to all the pots except the first, which served as a check against 

 any other one pot in this series of experiments. Cowpeas ( Vigna sinensis) 

 were planted in the sand in the pots, and during the time the plants 

 were making their growth the sand was kept moist with clear hydrant 

 water. Previous to starting the experiment, 100 liters of hydrant water 

 were evaporated to dryness and the residue thus obtained examined 

 for barium, but none was found. In another experment 25 liters of 

 water flowing from the drain tiles on the Experiment Station fann 

 were collected and evaporated. The residue thus obtained was exam- 

 ined for barium compounds, but none were found. 



The cowpea plants were allowed to grow until they were about 10 

 to 12 inches tall. They were then taken up in such manner as to pre- 

 serve the roots intact, and the adhering sand was washed off as well 

 as possible. The photograph reproduced in Plate 24, A, was taken 

 two weeks after planting; that shown as figure B, after the plants were 

 removed from the sand in which they grew. 



Table I shows the amount of barium carbonate added to each pot 

 and also the weight of the air-dry plants that grew in each of the pots. 



Tabids I. — Effect of barium carbonate upon the growth of cowpeas — First series 



Pot. No. 



I (control) 

 2 



3 



4 



5 



6 



Pot No. 



7- 

 8. 



9- 

 10 



Quantity 

 of barium 

 carbon- 

 ate, 

 added to 

 soil. 



Gm. 



Weight 



of 10 



air-dried 



plants. 



Gm. 

 II. 40 



10. 90 



11. 15 

 10. 80 



11.65 



" This pat received no calcium carbonate, and all the plants died. 



From the results obtained in this experiment it is to be observed 

 that there were appreciable increases in the yields of all the plants 

 grown in the presence of barium carbonate and calcium carbonate 

 over that of the control pot. In the absence of calcium carbonate, 



