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CHAPTEE XI. 



CROPS. 



IN this chapter a brief account is given of the proximate 

 composition of some of the chief crops grown on a farm 

 managed according to the usual English methods. 



Crops may conveniently be divided into the following 

 classes : 



(1) Grain crops, in which the seed is the portion of the 



plant most valued. 



(2) Eoot crops, in which the root or tuber is the valu- 



able product. 



(3) Fodder crops, in which the stem and foliage are of 



most importance. 



(1) GRAIN CROPS. The most important of these are 



(a) Cereals maize, wheat, rye, barley, and oats. 



(b) Leguminous plants beans, peas. 



(a) The Cereals. These are characterised by containing 

 much less nitrogen than leguminous or root crops, and by the 

 richness of their seed in carbohydrates, particularly starch. 



They are also remarkable for the large amount of silica 

 which is usually present in the outer portions of the leaves 

 and straw. This silica, which is apparently not essential, is 

 absorbed as soluble silicates, the metals, probably chiefly 

 potassium, being used in the plant, the silica being thus 

 merely an excretion. Potash and lime are also present to a 

 less extent in cereals than in other farm crops. Owing to 

 their modest demands for potash, lime, and nitrogen, cereals 

 will grow for many seasons in succession upon soil which has 

 become so exhausted as to yield little or no return when 

 planted with leguminous or root crops. They, however, ap- 

 pear to depend for their nitrogen entirely upon nitrates in the 

 soil, and as their growth is practically over before the great 



