106 THE PRINCIPLES OF AGRICULTURE. 



priving the soil of the presence of living roots, which 

 would absorb and hold these elements, they are liable to 

 be lost as fast as formed, unless the soil from its nature 

 is able to retain them. 



In general, the answer to the question will depend 

 upon the nature of the soil, the climate, and the particu- 

 lar crop to be raised. 



A clayey or mucky soil would be free from the objec- 

 tion mentioned, while in the case of a sandy or gravelly 

 soil the loss by washing might be greater than the gain 

 by exposure to the atmosphere. 



In cold climates, where the ground remains frozen 

 through the winter, there can be no loss during this 

 season, and plowing in the fall gives land the benefit of 

 the crumbling and disintegrating effect of frost. 



In climates where the ground does not freeze, and 

 where rain is abundant during winter, there is a liability 

 of large loss both by washing out the soluble elements, 

 and by washing away the finest and richest parts of 

 the soil. 



For raising particular crops there may be special rea- 

 sons for plowing in the fall or in the spring, according 

 to the special wants of the crop. While ground plowed 

 in the fall has received certain changes from exposure to 

 the air and the action of frost, that plowed in the spring 

 will naturally be more loose and porous. 



Harrowing. Next to the plow, the harrow is the most 

 important implement of agriculture. The purpose of 

 harrowing is chiefly to pulverize and level the soil, and 

 a thorough performance of this work affords all the gen- 

 eral advantages of tillage. It prepares the soil for roots, 

 admits air, favors the formation of plant food, and 

 thoroughly mixes fertilizers with the soil. Experiments 



