105 



CHAPTER VIII. 



MEANS ADOPTED FOR IMPROVING THE SOIL AND MAINTAINING ITS 

 FERTILITY BY THE APPLICATION OF MANURES. 



ANIMAL MANURES. 



149. To maintain the fertile condition of the soil, it is 

 necessary that the materials which are every year removed from 

 it should be restored. It contains, in mineral matters, and in 

 the decomposing remains of vegetables, an abundant, but not 

 always available supply of these materials ; so it is required 

 that certam artificial means should be adopted, to bring its 

 dormant powers into activity, to make the clay-slate and 

 granite give up their alkahes, and to convert the insoluble 

 silica contained in them into a state in which it can become 

 soluble in water, so as to be taken up by the roots of plants. 

 Analysis has taught us, that the different famihes of plants 

 which we cultivate, exhibit a partiality for certain ingredients 

 of the soil, and that the tendency of cultivation is to convert 

 vegetables which, in their natm*al state, abstract but a small 

 amount of phosphorus, and other elements, into powerful 

 exhausters of those substances: thus, the wheat and other seed 

 crops must find in the soil an abundant supply of the com- 

 pounds of phosphorus, (53) or they will not come to perfection ; 

 and, as these compounds are contained, in such minute quan- 

 tities, in even our most fertile soils, as to be discovered only 

 by refined investigation, it is evident, that their power of 

 producing full crops of such plants, without assistance, must 

 be extremely Umited. In the present state of the fields of 

 this country, neither fallow nor the rotation of crops is sufli- 

 cient to preserve them from exhaustion ; and the application 

 of certam matters to the soil, for the purpose of supplying 

 its deficient ingredients, has been found necessaiy. From 

 the earliest period, the use of manures in maintaining and 

 increasing the productiveness of soils has been known to 

 farmers, in various countries. 



150. In considering the prmciples of manuring, you must 

 bear in mind the effects which, as has already been explained, 

 plants produce upon the soiL You have seen, that our crops 

 appropriate certain matters, which become a part of their 



