146 SOIL MANAGEMENT 



For larger crops, horse cultivators are necessary. These, 

 if drawn by two horses, are usually also riding cultivators. 

 Like "sulky" plows, these "riding cultivators" make the 

 work more rapid, easy, and interesting. 



97. The roller and the planker are compacting and smooth- 

 ing tools which are often used after plowing and harrow- 

 ing. Some soil moisture is sacrificed by their use; but 

 without them many clods in some soils can hardly be 

 broken up. Small seeds, too, germinate more quickly and 

 strongly in soil that is pressed tightly about them. 



98. Crop rotation is quite as important to the welfare of 

 the soil as is fertilizer or tillage. Crop rotation means 

 the growing of a series of different crops on the same field 

 in a definite order through a series of years. A field that 

 grows corn this year may perhaps grow wheat or oats next 

 year, clover the year following, and then begin with corn 

 again the next season. This is an example of a three- 

 year rotation. 



In a case like the above the farmer probably wants to 

 raise some of all three crops each year; so he divides his 

 tilled land into three nearly equal fields. Each of these 

 fields has one of the three crops; and just as the three 

 crops are rotated on each field through the years, so is 

 each crop "rotated" through the three fields. The im- 

 portant side of crop rotation, however, is the side men- 

 tioned first, the change from year to year in a given field. 

 Let us see why this change is necessary. 



99. The Need of Crop Rotation. A farmer and his teams 

 may work hard to prepare the soil for seeding ; the soil 

 may hold an abundance of plant food ; the seed may be 

 good, and the season favorable ; and yet the crop may be 

 poor because the same kind of crop has been grown on the 

 field for too many years in succession. 



Each kind of plant takes its particular kind of food 



