A SECOND CKOP DEPENDS ON THE rRECEDING ONE. 179 



to bear crops, because tlie subsoil is exhausted, and its 

 fertility is not easil}^ restored. 



It" a farmer grows upon three fields, potatoes, corn, and 

 vetches or clover, alternately, or if he cultivates one field 

 with potatoes, com, and vetches successively, selling the 

 crops, and going on in the same way for many years, 

 without manuring, any one can foresee the end of such 

 husbandry, because such a system cannot possibly last. 

 No matter what plants may be selected, what variety of 

 cereals, tuberous or other plants, or in what rotation, the 

 field vrHl at length be reduced to such a state that tlie 

 cereals will yield no more than the seed sown, tlie 

 potatoes will give no tubers, and the vetches or clover 

 will die away after barely appearing above ground. 



From these facts it follows indisputably, that there is no 

 plant which spares the ground, and none which enriches 

 it. The practical farmer is taught by innumerable instances 

 that the success of a second crop depends upon the pre- 

 vious one, and that it is by no means a matter of indiffer- 

 ence, in what order he cultivates his plants ; by previously 

 cultivatmg some plant with extensive ramification of roots, 

 the soil is made fitter for the growth of a succeeding cereal, 

 which will now thrive better, even without the application 

 of manure (with sparing appHcation), and yield a riclier 

 crop. But this is not a saving of manure for future crops, 

 nor has the field been enriched in the conditions of its 

 fertility. There has been an increase, not in the sum of 

 the nutriment, but in the available particles of that sum, 

 and their operation has been hastened in point of time. 



The physical and chemical condition of the field was 

 improved ; but the store of chemical elements Avas 

 reduced. All plants, witliout exception, drain tlie soil, 

 each in its own way, and exhaust the conditions for tlieir 

 reproduction. 



N 2 



