460 INVESTIGATION BY CULTURE EXPERIMENTS 



With the 3-year rotation corn is grown for one year, followed 

 by oats with clover seeding the second year, and clover alone the 

 third year. During the first ten years under this system the yield 

 of corn has decreased from more than 70 bushels to 66, and during 

 the next 16 years the yield has further decreased to 58 bushels, the 

 average reduction being only one-half bushel a year. In this sys- 

 tem the most marked reduction in crop yields has not yet appeared, 

 although it must be expected in the future because the clover crop 

 is already beginning to fail on the oldest field, even in seasons when 

 clover succeeds well on newer land under the same crop rotation. 

 When clover fails, cowpeas are substituted for that year on that 

 field, which thus provides a legume crop and preserves the 3-year 

 rotation. 



In the lower part of Table 86 (third column) are recorded the 

 average yields of corn for the last three years in a system of grain 

 farming, in a 3-year rotation of corn, oats, and clover. This 

 system, when fully under way, provides that the corn shall be husked 

 and the stalks disked down in preparation for the seeding of oats 

 and clover the second year. In harvesting the oats, as much straw 

 as possible is left in the stubble, which may be mowed later in the 

 summer to prevent the seeding of the clover or weeds. In the 

 spring of the third year the clover is mowed once or twice before the 

 usual haying time and left lying on the land. The seed crop, if 

 successful, is harvested with a hay buncher attached to the mower, 

 or in any other way to avoid raking, and afterward the threshed 

 clover straw and oat straw (or at least as much as is practicable) 

 are returned to the land, all of this accumulated organic matter 

 to be plowed under for the following corn crop, which begins the 

 next rotation. In addition to this, catch crops of annual legumes, 

 such as cowpeas, may be seeded in the corn at the time of the last 

 cultivation and disked in the next spring with the corn stalks. 

 If biennial- or perennial legumes are used as catch crops, the corn 

 ground may be plowed for oats. (This is a practice of doubtful 

 advantage where the corn is rank.) 



The corn yields reported for this system in Table 86 were secured 

 where the system was not fully under way, the legume catch crops 

 being the only organic matter returned to the soil, aside from the 

 residues necessarily left from the corn-oats-clover rotation. By 



