154 THE KITCHEN GARDEN, [chap. vi. 
of the unwholesome soil. This, however, is 
not the case with annuals, as the roots of the 
plants of one year are no longer than those 
were of the plants of the preceding year; and 
consequently as every year’s plants occupy 
exactly the same ground, when annuals are 
sown for several years in the same soil they 
must degenerate; or, in other words, become 
weak and small, from not having enough of 
wholesome food, or from being forced to 
take food unwholesome for them. Now it 
has been found, that excrementitious matter, 
though poisonous to the plant that exudes it, 
is extremely nourishing to other plants, com¬ 
pletely differing from the first in nature ; and 
what is meant by the rotation of crops, is the 
art of making plants of opposite natures 
succeed each other, till the ground shall be 
so completely cleared of the excrementitious 
matter exuded by the first crop, as to be 
ready to receive it again. It is true that the 
same ground may occasionally be made to 
bear the same crops for several successive 
years, by copious manuring, or by trenching; 
but in both cases the evil is overcome by 
supplying the plant with abundance of nour- 
