12 BULLETIN 991, U. S. DEPARTMENT OF AGRICULTURE. 



lowing oats 15.7 bushels per acre. In the other nine years the fallow 

 averaged 14.2 bushels, and the oat stubble 13.4 bushels. The 13-year 

 average is 17.8 bushels on fallow and 14.1 bushels following oats, a 

 difference of 3.7 bushels in favor of the fallow. 



The average yield of oats on fallow in rotation No. 8 has been 36 

 bushels, and on fall-plowed Avheat stubble in rotation No. 5, 35.2 

 bushels per acre. The higher yield has been on fallow seven years 

 and on the wheat land six years. 



Other opportunities for comparisons are offered in the continuous 

 cropping series. In this series each crop— wheat, oats, barley, and 

 corn — occupies four plats. Plat A bears the same crop continuously, 

 the preparation being shallow spring plowing. Plat B is continu- 

 ously cropped under a system of deep (8-inch) fall plowing. Plats 

 C and D are alternately cropped and fallowed, plat C being in crop in 

 the even years and plat D in the odd years. 



The wheat on fallow has averaged 1.4 bushels more than on spring 

 plowing and 3 bushels more than on fall plowing. In 9 of the 13 

 years under study the yield on fallow has been higher than on either 

 of the other plats. In the duplication of these plats on section 9 for 

 the three years 1917 to 1919, inclusive, the yield on fallow has been 

 6.1 bushels more than on spring plowing and 8.1 bushels more than on 

 fall plowing. 



Oats in this series show a stronger response to fallow than wheat, 

 or than oats did in rotation No. 8 as compared with rotation No. 5. 

 Not only is the yield on fallow a little higher, but the yields of oats 

 in continuous cropping with which it is compared are much lower 

 than those in rotations. The yield on fallow in this series is 40.3 

 bushels; on spring-plowed oat stubble, 25.2 bushels; and on fall- 

 plowed oat stubble, 23.7 bushels. The increase in favor of fallow 

 in this case is 15.8 bushels over the average of the two other methods. 



In the same series barley on fallow has yielded 19.8 bushels; on 

 spring- plowed barley stubble, 17.8 bushels; and on fall-plowed 

 barley stubble, 15.4 bushels. The increase due to fallow is 2 bushels 

 over spring plowing, and 4.4 bushels over fall plowing, or 3.1 bushels 

 over the average of the two. 



With corn, there is practically no difference in the average yields 

 of the different plats in this series, although there have been some 

 years strongly in favor of and some as strongly against fallow. The 

 corn plats are duplicated on section 9, and there also no difference 

 in yield is observed. 



CORN GROUND COMPARED WITH FALLOW AS A PREPARATION 



FOR SMALL GRAINS. 



The experiments offer a number of direct comparisons of fallow 

 and corn ground as preparations for wheat and oats. Potation No. 5 

 is fallow, wheat, and oats, and rotation No. 3 is corn, wheat, and oats. 

 The heavier yield of wheat has been on the corn ground seven years, 

 and on the fallow six years. The fallow has had somewhat the 

 heavier yield of straw, but the grain has averaged only three-tenths 



