S64 HOW CROPS PEED. 



larger quantity depressed the yield. It is iirobable that less 

 than 71 lbs. would have ])roduced an equal effect, since 47 

 lbs. gave so nearly the same result. The ash composition 

 of barley, grain, and straw, in 100 parts, is as follows, 

 according to Zoeller, (H. C. G., pp. 150 to 151) : 



Tlie proportion of ash in the air-dry grain is 2^ per 

 cent, that in the straw is 5 per cent, {Ann. Ch. u. Ph. 

 CXII, p. 40). Assuming the average barley crop to be 

 33 bushels of grain at 53 lbs. per bushel = 1,750 lbs., and 

 one ton of straw,* we have in the barley crop of an acre 

 the following quantities of ash-ingredients : 



In the account of Ilellriegel's experiments, it is stated 

 that the maximum barley crop in some other of his trials, 

 corresponds to 8,160 lbs. of grain, or 154 bushels of 53 

 lbs. each per acre. This is more than 4^ times the yield 

 above assumed. 



The above figures show th:it no essential ash-ingredi- 

 ent of the oat crop is present in larger quantity than 

 potash. Phosphoric acid is quite the same in amount, 



* These figuree are employed by Anderson, and are based on Scotch statistics 



