12 



CIRCULAR 4 21, U. S. DEPARTMENT OE AGRICULTURE 



Table 4. — Average acre yields of crops grown continuously and under an 

 alternate fallow and crop system at the Ardmore station for the 20-year 

 period, 1913-32 



Crop 



Spring wheat. 

 Winter wheat 



Oats 



Barley 



Flax 2 



Aver- 

 age 



yield 



on 

 fallow i 



- Continuously 

 cropped 



In- 

 creased 

 yield on 

 fallow 



Plots 



Aver- 

 age 

 yield 



Bushels 

 17.2 

 17.4 

 38.3 

 31.7 

 5.3 



Num- 

 ber 

 4 

 4 

 4 

 4 

 4 



Bushels 

 11.1 



8.6 

 23.2 

 18.5 



3.7 



Percent- 

 55 

 102 

 65 

 71 

 43 



Crop 



Corn.. 



Sorgo ; 



Aver- 

 age 



yield 



on 

 fallow ' 



Continuously 

 cropped 



Plots 



Aver- 

 age 

 yield 



Bushels 

 20.2 



Pounds 

 4,502 



Num- 

 ber 

 5 



4 



Bushels 

 14.6 



Pounds 

 4,082 



In- 

 creased 

 yield on 

 fallow 



Percent 

 38 



1 1 plot in each case. 



2 Yields of flax are for the years 1916-27. 



3 Yields of sorgo are for the years 1916-32. 



The yields of spring wheat, oats, and barley averaged from 55 to 

 71 percent higher when grown on summer-fallowed land than Avhen 

 continuously cropped. Winter wheat showed a much higher per- 

 centage increase, but the actual yield on fallowed land was approxi- 

 mately the same as that of spring wheat. Under continuous -crop- 

 ping the yields of winter wheat were much lower than those of 

 spring wheat. The yields of flax were so low that the percentage 

 increase in yield has little significance. The actual increase was 

 less than 2 bushels per acre. Cultivated crops showed materially 

 lower response to fallow than grain crops. 



The response of small grains to fallow is as great at Ardmore as 

 in many sections where summer fallowing is a common practice. 

 The possibilities of fallow in the agriculture of the section have 

 been discussed in detail in an earlier publication. 2 



COMPAEISON OF YIELDS OF SMALL GRAINS IN DIFFERENT SEQUENCES 



It has been shown that with a few exceptions only minor differ 

 pnces in average yields were obtained through differences in cultiva- 

 tion, where the crop sequence was the same. The effect of crop 

 sequence in determining yields is shown in table 5. To reduce the 

 experimental error due to soil differences, as many plots as possible 

 were used in determining the averages. The yield of a grain crop 

 on fallow represents the average yield of all plots of that crop 

 grown on fallowed land, regardless of whether the fallow appeared 

 in 2-, 3-, or 4-year rotations. In like manner, the yields on corn 

 ground include all plots planted on corn ground, regardless of the 

 length of the rotation or the method of cultivation used. Yields 

 after small grains include all plots grown after oats, spring wheat; 

 winter wheat, barley, and flax. 



2 Mathews, O. R., and Clark, V. I. summer fallow at,. ardmore, s. dak. U. S. 

 Dept. Agr. Circ. 213, 15 p. 1932. For sale by the Superintendent of Documents, Wash- 

 ington, D. C Price 5 cents. 



