PLANT RESPONSES TO INSECTICIDES IN THE SOIL 9 



of soil in pots. Corn was nearly destroyed by the higher dosages, 

 but radish and cucumber were undamaged. McLeod (30) found 

 0.1 gram of technical BHC in 2 pounds of soil caused abnormal 

 germination, injury, and poor growth of onion. 



Wilson and Choudhri (46) found no significant effect of 300 

 p. p. m. of technical BHC on the micro-organisms of the soil. 

 Smith and Wenzel (40) showed, however, in a far more compre- 

 hensive study that 50 and 250 p. p. m. of BHC in soil were 

 strongly and persistently fungicidal ; also that the nitrifying bac- 

 teria were killed off for the 98-day duration of the study. 



A number of reports indicated no adverse effects of BHC in 

 the particular tests involved. Kulash (27) observed no effect of 

 1.6 or 3.2 pounds of technical BHC per acre on corn. Bourne (6) 

 reported that 8 pounds of technical BHC per acre applied in fer- 

 tilizer to open rows before dropping and covering seed pieces of 

 sugarcane hastened the emergence of shoots. Jameson and 

 others (22) stated that 8 to 15 pounds of technical BHC per 

 acre is harmless to grain crops. Pepper and others (35) found 

 80 pounds of technical BHC per acre to have no effect on growth 

 or yield of potatoes, although it did impart the BHC odor and 

 flavor to the tubers. Roberts (38) found that 4 grams of 4.5 per- 

 cent technical BHC powder per hill of muskmelons caused no 

 injury, although the same dosage per 8-inch of pot soil injured 

 germination of corn and cotton. Golds worthy (16) noted no 

 harmful effects of technical BHC on strawberries, up to 400 

 pounds per acre, but a possible stimulative effect from 12 to 300 

 pounds. 



OTHER SUBSTANCES 



Smith and Wenzel (40) found that chlordane at 100 and 500 

 pounds per acre was somewhat fungicidal in the soil but less 

 strongly or persistently than BHC. It temporarily suppressed 

 nitrite formers, then stimulated them, and temporarily suppressed 

 nitrate bacteria. It was less toxic than BHC to the soil bacteria. 

 Toxaphene at 100 and 500 pounds was easily attacked as a source 

 of food by the micro-organisms and therefore considered non- 

 persistent in the soil. Allen and others (3) detected no response 

 of tobacco, cotton, cowpeas, or rye to 20 pounds of toxaphene 

 per acre annually for 2 years. 



Bourne (6) reported that 4 pounds of chlordane per acre in 

 fertilizer applied in the open row before dropping and covering 

 sugarcane seed pieces stimulated shoot emergence. Morrison 

 and others (32) found that 28 pounds per acre of chlordane 

 stunted lima beans slightly. Fleming (13) stated that 20 to 25 

 pounds per acre of chlordane had no effect on a wide range of 

 grasses, although 40 to 80 pounds caused some temporary injury. 

 Doses of 10 and 20 pounds were harmless to rye, soybean, and 

 corn. Germination of about 20 vegetables was unaffected by 

 20 pounds per acre of chlordane, but subsequent growth of squash 

 was depressed by 5 pounds, celery by 10 or more, and many others 

 by 20 pounds per acre. Some varieties of strawberries were 

 retarded by 10 pounds, and some not by 20. Of 20 annual flowers 

 tested at 5 to 20 pounds all were unharmed but poppy and snap- 



