CAUSE OF THE LOSS OF FERTILITY. 



PART SIXTH. 



CHAPTER XLI. 



THE CULTURE OF FARM CROPS. 



The previous chapters have been devoted to the explana- 

 tion of the principles upon which the culture of farm crops 

 depends. This knowledge is indispensable to successful 

 practice in farming, and thrown a flood of light upon the 

 otherwise mysterious operations of nature, as w r e meet with 

 them in farm work. The reader w T ho has followed us through 

 the previous chapters w r ill now be prepared for the discus- 

 sion of the practical questions w T hich arise in the daily labors 

 in the field; and we now take up the subject of the culture 

 of farm crops in its practical bearings, applying to it the 

 principles which have been heretofore explained. 



When a farmer has worked his land for a number of 

 years, he finds the richest soils to gradually decline in pro- 

 ductiveness; to become worn out and exhausted in fact; and 

 he will not be surprised by this, after having read and stud- 

 ied what has been said in regard to the nature of the soil 

 and of plant growth, and the relations of these to each other. 



Continuous cropping removes from the soil as has been 

 shown a very large quantity of its soluble fertile constit- 

 uents; and in time, takes from it the available plant food 

 which has accumulated during a very long period; we know 

 not how many centuries or ages, of graduaj storing up of 

 this available fertility; and brings it back again to its origi- 

 nal condition when the mineral elements of the soil and the 

 atmosphere, were the only sources from which plants could 

 derive materials of which to form their substance. The 

 continuous growth of such crops as wheat and corn, year 

 after year, very soon carries off the available plant food and 

 brings the land to this impoverished condition. But under 



