138 



Dry Spraying of Charlock. 



[May, 



The same substances were used as in the previous year, with 

 the difference that a new supply of ground nitrolim was obtained, 

 and the sulphate of copper was supplied by a local firm of manu- 

 facturing chemists in a much more finely ground state than 

 that used in the 1919 trials. It was decided to test the respective 

 substances in the following quantities : — 



Sulphate of Copper ... ... 30 11). per acre. 



20 „ 



10 „ „ „ 



Nitrolim ... ... ... 100 „ „ „ 



50 „ „ „ 



Sulphate of Iron * ... ... 100 „ „ „ 



„ „ „ ... ... 50 „ „ 



At the Kipling Cotes centre 10 plots each l/20th acre were 

 marked out in a field carrying Barley, and an abundant growth 

 of Charlock. When, however, the actual amounts of the spray 

 powders to be used per plot were calculated, they were found 

 to range from 8 oz. to 5 lb., and it was feared that any quantity 

 less than 5 lb. could not be easily distributed over the plots 

 with the knapsack spraying machines at our disposal. It was 

 therefore, decided to make up the bulk in each case to 5 lb. 

 with some inert substance, and Silica was chosen for this pur- 

 pose. In order to ascertain whether this diluent might in any 

 way, either by absorption or mechanical obstruction of the spray 

 powder, tend to weaken its chemical action, it was decided to 

 put in a control plot to the plot of sulphate of copper at 30 <b. 

 to the acre, in which only 1 lb. instead of 3| lb. of Silica was 

 added. 



The final treatment of the plots was as follows : — 













Total wt. 











lb. of Silica 



(lb) 







lb. per 



lb. per 



added per 



Spraying 







acre. 



plot. 



plot. 



Powder. 



1. 



Sulphate of Copper 



30 





3± 



5 



2. 



V V J5 



20 



1 



4 



5 



3. 



5? 5? ?? 



10 



_1 



4* 



5 



4. 





30 



H 



1 



2i 





(Control for Silica). 











5. 



Untreated 











6. 



Nitrolim 



100 



5 







5 



7. 





50 



2i 



2A 



5 



8. 



Untreated 











9. 



Sulphate of Iron 



100 



5 







5 



10. 





50 



2h 



H 



5 



Arrangements had been made for spraying the crop much 

 earlier in 1920, when the Charlock was about 3 in. high, but 



