122 CHYMISTRY APPLIED TO AGRlCULTtJllEr 



exhaust the soil, without sensibly repairing the loss, either 

 by their stalks, which are cut to be applied to a particular 

 use, or by their roots, which are all that remain in the 

 ground, and which are dried and exhausted in completing 

 the process of fructification. 



Those planta, on the contrary, that are provided with 

 large, fleshy, porous, green leaves, imbibe from the atmo- 

 sphere carbonic acid and water, and receive from the earth 

 the other substances by which they are nourished. If 

 these are cut green, the loss of juices which the soil has 

 sustained by their growth, is less sensibly felt, as a part 

 of it is compensated for by their roots. Nearly all the 

 plants that are cultivated for fodder are of this kind. 



There are some plants, which, though generally raised 

 for the sake of their seed, exhaust the soil less than the 

 grains ; these are of the numerous family of leguminous 

 plants, and which sustain a middle rank between the two 

 of which I have just spoken. Their perpendicular roots 

 divide the soil, and their large leaves, and thick, loose, 

 porous stalks readily absorb- air and water. These parts 

 preserve for a long time the juices with which they are 

 impregnated, and yield them to the soil, if the plant be 

 buried in it before arriving at maturity ; when this is 

 done, the field is still capable of receiving and nourish- 

 ing a good crop of corn. Beans produce this eflfect in a 

 remarkable degree ; peas to a less extent. 



Generally speaking, those plants that are cut green, or 

 whilst in flower, exhaust the soil but little ; till this period 

 they have derived their support almost exclusively from the 

 air, earth, and water ; their stalks and roots are charged 

 with juices, and those parts that are left in the earth after 

 mowing, will restore to it all that had been received from 

 it by the plant. 



From the time when the seed begins to be formed, the 

 whole system of nourishment is changed ; the plant con- 

 tinues to receive nourishment for the perfecting of its 

 seed, from the atmosphere and the earth, and also yields 

 to the grain all the juices it had secreted in its own stalks 

 and roots : by this means the stalks and roots are dried 

 and exhausted. When the fruits have arrived at maturity 

 the skeleton remains of the plant, if abandoned to the 

 earth, restore to it only a small portion of what had been 

 taken from it. 



The oleaginous seeds exhaust the soil more than the fa- 



