126 



Table IX. Effect of a combination of toxic compounds 

 on crop yields on College Farm soil. Crops 

 grown in l-gallon pots in the greenhouse, 

 1914-1915. 



SPECIAL TRKA TMEN r 



^ 



£ 



u 



Check — no treatment 



CaJ. carbonate, 36 grams 



CaJ. carbonate, 36 grams; pyridine, 18 c.C; 

 quinoline. 18 c.c; vanillin, 9 grams; 

 coumarin, 9 grams; dihydroxystearic 

 acid, 9 grams -^ 



100 



126 



1086- 



* "K" means 1.5 grams of kainit; "P" means 4.5 grams of 

 acid phosphate. 



It is generally known that most of the poor sandy 

 soils of the Southern states will produce very vigorous 

 crops of cowpeas, even though they be so poor that thej* 

 do not produce profitable crops of corn or cotton. 

 Now% if the poor yields of corn or cotton obtained from 

 such soils are due to the presence of toxic bodies in 

 the soil, rather than to deficiencies of plant food, it 

 would seem that cowpeas are not injured by the same 

 compounds which do reduce the yields of the non- 

 leguminous crops. It was decided to try to determine 

 the effect on cowpea yields of certain of the compounds 

 which had been used in the experiments already given. 

 In the last column of Table X is shown the yields of 

 cowpeas obtained when this crop was grown five 

 months after the various .toxic compounds had been 

 added to the soil. Oats were grown immediately after 

 the application of the special treatments had been 

 given, and the oat yields arc reproduced here for ease 

 of comparison. The oats were harvested in the early 

 spring before the plants were headed out; the pots 

 were fertihzed as shown in the fourth column, and 

 peas planted. The weights given are for the stems 

 and vines, excluding leaves and leaf stems. It was 

 impossible to prevent leaf shedding in the greenhouse 

 after the beginning of the hot weather of May and early 

 June; and since some of the plants lost leaves more 

 freely than did others, all leaves and leaf stems were 



