1110 



Spraying of Cornfield Weeds. 



[Mar., 



very satisfactory. It has, however, two drawbacks, viz : — (a) copper 

 sulphate is poisonous and on this account requires to be used with 

 care, and (b) although it does not kill the cereal crop, it checks 

 it, as a rule, with the result that the crop may require stimulating 

 subsequently with a suitable nitrogenous manure. 



It would, however, be a great step forward if some material 

 could be found which would have the dual effect of killing the 

 charlock, etc., and at the same time stimulating the cereal crop. 

 Fortunately, there is reason to believe that a solution of sulphate 

 of ammonia possesses this dual effect, as will be gathered from 

 the experiments referred to below. 



Herefordshire Experiments. — When the writer was Agri- 

 sultural Organiser for Herefordshire, one of his Committee had 

 a crop of winter wheat which was being over-run with the Corn 

 Buttercup (Ranunculus arvensis), and he was particularly anxious 

 that some means of dealing with it effectively should be dis- 

 covered. Some French experiments showed that a solution of 

 sulphate of iron was slightly more effective than a solution of 

 copper sulphate. 



Sulphate of iron, however, was difficult to get at that time 

 (1920), and as a strong solution had been used (about 15 per 

 cent.) the cost would have been prohibitive. Bluestone (copper 

 sulphate) was therefore used. At the same time, seeing that 

 some of the highly soluble nitrogenous manures burn the leaves 

 of crops under certain conditions, it was decided to test the effect 

 of solutions of nitrate of soda and sulphate of ammonia. The 

 strengths of solutions used were as follows : — 



(a) Copper Sulphate 3 per cent, solution. 



(b) Nitrate of Soda — 1 cwt. dissolved in water and made up to 60 gal. 



(c) Sulphate of Ammonia- 1 cwt. dissolved in water and made up to 

 60 gall. 



('/) Sulphate of 'Ammonia — 2 cwt. dissolved in water and made up to 

 60 gall. 



Nitrate of soda was not easy to dissolve completely in water 

 owing to the large size of its crystals. It was, therefore, a little 

 troublesome in blocking up the spray nozzles, and further the 

 solution acted on the rubber tubing, causing it to collapse. Sul- 

 phate of ammonia, on the other hand, dissolved rapidly in water 

 and did not tend to block up the spray nozzles when previously 

 strained through an ordinary bag. 



The results of these trials were that the copper sulphate spray 

 had the usual burning effect on the Corn Buttercup 2 with a slight 

 burning effect on the leaves or " flag " of the wheat. Nitrate of 



