376 



Journal of Agricultural Research 



Vol. XIX, No. 8 



seed germination, may render the seed unusually susceptible to the sub- 

 sequent copper-sulphate treatment and thus defeat its purpose. 



A marked increase in the percentage of germination was observed in 

 the presoak-treated seeds over the controls. This was probably due 

 not only to the lack of injury in the former but to the residual effect of 

 the copper sulphate and lime, which, by preventing seed infection 

 through soil organisms, enabled more seeds to germinate. There was 

 also a marked stimulating effect on the growth of the seedlings. 



The use of the presoak method of treatment also reduces copper- 

 sulphate injury in barley, as shown in Plate 76, figure 3. The fact that the 

 presoak method can reduce seed injury from formalin and copper sul- 

 phate, two disinfectants of widely different chemical nature, suggests 

 the possibility of its use in conjunction with mercuric chlorid also, 

 another commonly used seed disinfectant. 



FIELD EXPERIMENTS WITH FORMALIN AND COPPER SULPHATE 



EPPECT OF 6 hours' PRESOAKING FOLLOWED BY FORMALIN I TO 320 TREATMENT ON 

 GERMINATION OP WHEAT SEED UNDER FIELD CONDITIONS 



That formalin injury to germination can be greatly decreased under 

 field conditions when the presoak method is used is shown by the follow- 

 ing experiment. Using seven wheat varieties, 16,800 seeds were planted 

 on a uniform level plot at the Arlington Experimental Farm. For each 

 variety 1 2 rows of 200 seeds each were distributed as follows : four rows 

 of controls, four rows of seeds treated with formalin i to 320 for 6 hours, 

 and four rows of seeds similarly treated but presoaked 6 hours. The 

 results were striking. In each variety the central four rows, which 

 received the usual treatment recommended for smut, showed a marked 

 decrease in germination (27 to 53 per cent, averaging 38 per cent for 

 the seven plots) while in each case the four rows receiving the presoak 

 formalin treatment scarcely differed in appearance from the controls 

 (PI. 78). Table VII and figure 5 give the data obtained. 



Table VII. — Effect of 6 hours' presoaking followed by formalin 1:320 treatment on 

 germination of wheat seed under field conditions 



