IS CIRCULAR 421, U. S. DEPARTMENT OF AGRICULTURE 



Eesults from the 20-year test show that the average yield of ear 

 corn where corn followed a small grain crop was only a little lower 

 than where corn followed corn, and the yield of stover was materially 

 higher. The fact that corn stover has some value as a feed makes 

 it apparent that corn following small grain is at least as valuable 

 as corn after corn. 



Corn on fallowed land produced 42 percent more grain than corn 

 following small grains. The yield of stover was not increased 

 through fallowing. It is apparent that fallowing has no place in the 

 production of corn. 



The average yield of sorgo on fallowed land for 17 years was only 

 a little higher than that of sorgo grown continuously. Sorgo was 

 grown following small grains for only 5 years. During this period 

 the average yield exceeded that of sorgo after sorgo. Sorgo should 

 be grown on land where small grains have been grown, and sorgo 

 ground should be planted to small grains rather than to grow each 

 continuously. 



The value of long-time records in determining the response to 

 cultural methods is again demonstrated in table 7. During the last 

 5 years of the experiment both corn and sorgo showed a response to 

 fallow much higher than for the entire period. Experiments con- 

 ducted during only the last 5 years would be very misleading. - 



EFFECT OF SOD CROPS ON YIELDS OF SUCCEEDING CROPS 



Only two grain crops, oats and flax, were grown on sod land in 

 the rotations. For the 20-year period oats following alfalfa produced 

 a yield of 20.3 bushels, oats after bromegrass 23 bushels, and oats 

 after clover or sweetclover 27.1 bushels per acre. The average yield 

 of oats following any sod crop was less than the yield of oats follow- 

 ing small grain, the reduction m yield being especially sharp following 

 alfalfa and bromegrass. These two crops leave the soil so extremely 

 dry that the succeeding crop is likely to suffer from drought. Sweet- 

 clover, a biennial, usually makes little or no growth following cutting 

 in its second year, and consequently does not dry the soil so com- 

 pletely. Yields of oats after sweetclover were substantially the same 

 as after small grains. 



A depressing effect on crops following sod sometimes extends into 

 the second and even the third year. In the sod rotations the oats 

 were followed by corn. Volunteer alfalfa and bromegrass sometimes 

 persisted in the corn crop and increased the cultivation necessary to 

 keep the corn clean. In some cases the volunteer growth was suffi- 

 cient to reduce the yield of corn. In all rotations containing sod 

 crops the yield of corn was lower than the average yield in rotations 

 not containing sod crops. 



Flax after sod was nearly as productive as in other sequences, but 

 flax as a sod crop in a regular rotation was not a success. Good yields 

 were occasionally obtained, but many years of failure or nearly com- | 

 plete failure were recorded. Flax on sod was a complete failure in I 

 the 4 years, 1929-32. 



Low yields of crops following sod crops, and the fact that a year | 

 is lost in securing a productive stand of the sod crop, make it ap= 

 parent that these crops have no place in short rotations. 



