14 



THE rXDIAVA WEED BOOK. 



this robbery it has been shown by the Massachusetts Experiment 

 Station that "one ton of ox-eye daisy withdraws from the soil 25 

 pounds of potash, 8.7 pounds of phosphoric acid, 22 pounds of 

 nitrogen and 26 pounds of lime. To restore the stated amounts 

 of the first three constituents to the soil it would be necessary to 

 apply about 50 pounds of muriate of potash, 65 pounds of super- 

 phosphate and 140 pounds of nitrate of soda."* It will thus be 

 seen that this, as well as all other weeds, feed upon precisely the 

 same foods as do wheat, corn and other cereal crops. They de- 

 prive the crop with which they grow, or one which will come after 

 it, of exactly the same amount of plant food as they withdraw, 



7 * 



Fig. 2. Mixture of weed seeds commonly found in low-grade alsike clover seed: a, alsike clover; b, white 

 clover; c, red clover; d, yellow sweet-clover; e, Canada thistle; /, dock; g, field sorrel; h, backhorn; i, rat- 

 tail plantain; k, lamb's-quarters; /, shepherd's parse; m, dog-fennel; n, scentless camomile; o, white campion; 

 p, night-flowering catch-fly; q, ox-eye daisy; r, small-fruited false flax; s, cinquefoil; t, two kinds of pepper- 

 grass; w, catnip; v, timothy; x, chickweed; y, Canada blue-grass; z, clover dodder; /, mouse-ear chickweed; 

 2, knot-grass; S, tumbling pigweed; 4, rough pigweed; .5, heal-all; 6, lady's thumb. (After Hillman.) 



and if allowed to grow with other crops will take their due pro- 

 portion of any fertilizer that may be applied. 



b. They rob the soil of moisture which they waste by evapora- 

 tion, thus increasing the evil effects of droughts. 



c. They crowd out and shade cultivated plants, thus greatly 

 decreasing the yield of the latter. Most weeds have better devel- 

 oped roots which penetrate to a greater depth than those of the 

 plants with which they grow. They therefore gather food and 

 moisture more readily and usually soon out-top many crops, 

 shutting out the sunlight so necessary to perfect maturity of the 

 cultivated plants. 



♦Far. Bull. No. 103. 



