ii6 The Great World's Farm 



Corn crops, for instance, take up much flint, which 

 goes chiefly to give the hard, glossy coating to their stems; 

 and they want from a fifth to a tenth part as much potash. 

 Turnips and beet, on the other hand, take in httle flint, 

 but more hme and potash; and turnips and carrots will 

 use up the suphuric acid; while clovers want little sul- 

 phuric acid, but much potash, lime, and soda. 



All plants need more or less of several mineral sub- 

 stances, and even when it is "less," they cannot do with- 

 out this lesser quantity, be it never so small. When, 

 therefore, we. say that corn crops take up much silica, or 

 flint, it is not at all meant that they do not take some 

 proportion of lime, potash, soda, sulphur, iron, and phos- 

 phoric acid as well; for they use them all, in larger or 

 smafler quantities. 



The amount of each mineral taken up varies in diff"erent 

 kinds of corn; wheat, oats, barley, etc., have all their special 

 needs, and so, as stated, have different varieties of the 

 same kind of corn. More than this, different plants of the 

 same variety differ slightly in this respect, as if they had 

 their own individual preferences; but the difference is 

 very slight, and in plants of the same species the propor- 

 tion always remains nearly the same. 



And this is true, no matter where the plant may grow. 

 If it grows at all, its ash, that is, the mineral substances 

 which it has taken from the soil, will always be found to 

 be pretty nearly the same; the proportion will be the 

 same, that is to say, for of course, in unfavorable soil, 

 the plant may be a dwarf. Grasses, for instance, which 

 are like corn in taking in considerable quantities of silica, 

 will take up just as much of this when they grow on the 

 chalk soil of the downs as when they grow in a soil con- 



