206 CULTURE OF FARM CROPS. 



use the roller. The mode already described of breaking 

 up the land in autumn by a grubber or scarifier, and 

 ploughing the land immediately before sowing, appears to 

 Mr. Keary and other authorities to be preferable from 

 every point of view to that where only one ploughing is 

 done, and then putting in the seed. 



13. As to Mr. Frere's opinion that the barley takes less 

 out of the land than the wheat crop, seeing that it runs coun- 

 ter to the one frequently held, it will be well to note what 

 is said in support of it. The land selected for trial by Mr. 

 Frere was the very weakest portion of his heath land, 

 " black sand on chalk rubble." On this, which is too 

 light to carry any other " lay " than ryegrass, with an 

 admixture of trefoil and Dutch clover for sheep food, " the 

 worst part of the field has been left, at wheat-sowing time, 

 manured and ploughed at leisure during winter, and sown 

 with barley on the whole furrow in the spring, part of it 

 having been folded, the rest having received straw manure, 

 a ton or two less per acre than would have been applied 

 to wheat." Now those who rely upon the respective an- 

 alyses of the ashes of the wheat and of the barley crop 

 will, from their similarity, believe that they are equally 

 exhausting crops. But Mr. Frere, in advancing the con- 

 trary opinion, points out that our best chemists believe 

 that the cereals are parting with nitrogen to a considerable 

 amount, and that during the " whole course of their 

 growth." As a result of this, the waste of this valuable 

 manurial agent will depend upon the duration of the 

 growth of the plant ; so that more nitrogen will be parted 

 with by the winter wheat, the growth of which extends 

 over so much longer a period than the barley sown in 

 spring. Of course, the much - disputed question arises, 

 Granting that this parting of nitrogen by the cereals is 

 correct, does it follow that the soil is consequently weak- 

 ened 1 Those who believe in the large amount of ammonia 

 derived from the air will of course hold as favourable to 

 their views this same " nitrogenous exhalation " of the 

 cereals, rather than the reverse. But to these Mr. Frere 



