REPORT OF THE SOCIETY 97 



one. In some cases the weeds will themselves decide the nature of the crops 

 used, but all good alterations in crop help. If they contain both hoed crops 

 and pasture the best opportunity is had to kill those weeds such as pig^vveed, 

 mustards, or purslane, which thrive in cultivated fields, or in hay, such as 

 daisy, Canada thistle and buttercup. Small grains and hay, then, should 

 alternate with tilled crops. 



Annual and Biennial Weeds. 



Annual weeds germinate, fruit, and wither in the same season, and 

 when sown with grain and other annual crops, such as roots, peas and 

 flax may cause hea\->' losses. To sow clean seed, to seed heavily rather than 

 lightly, and to cultivate the growing crop before the weeds gain headway, 

 are some of the most important steps to be taken in dealing with annual 

 weeds. Another vital point in eradication of these weeds is to prevent 

 their setting and ripening seed, and, where possible, cultivation must be 

 kept up as long as possible. The practice of killing weeds by chemical 

 sprays has spread chiefly from the great wheat-growing districts of the 

 U.S.A., those of the prairie states. The spray, usually sulphate of iron (cop- 

 peras), or sulphate of copper (bluestone), is applied with a power machine 

 of the row-sprayer type used for potatoes. For small patches a practical 

 hand sprayer will be useful; It should be of brass or wood, and of three or 

 four gallons capacity. For grain fields, the traction sprayer or power 

 sprayer is useful, throwing a misty spray. About 75-100 lbs. iron sulphate 

 to the barrel of water costs nearly S1.00-S1.25, and sprays one acre. Chemi- 

 cal sprays, while they do not seriously affect grasses, kill the leaves and stalks 

 of many weeds. Such crops as clover, buckwheat, and flax should not be 

 sprayed. The spray kills back the tops and keeps the weeds from seed- 

 ing. Mustard may be sprayed when the most advanced plants are in bud, 



A great many chemical sprays have been used with success, such as 

 common salt, using 125 lbs. to the barrel of 50 gallons, or copper sulphate 

 12 pounds, calcium cyanamide 80 lbs. per acre; sulphuric acid 6, 8 or 10% 

 strength, 107 gallons per acre; or the poisonous sodium arsenite at the rate 

 of iH lbs. per acre; The spray of sodium arsenite must not be inhaled. 

 The question is still an open one whether dandelions in lawns can be control- 

 led by spraying (13), (22), (20, 289). Spraying every three to five weeks 

 kills the dandelion tops, but is very hard on the grass too. Spraying may be 

 used successfully on paths, roadways and public squares. It should be noted 

 that iron sulphate stains concrete sidewalks. When the harvest is completed 

 the ground should be plowed and harrowed as soon as possible. This will 



