INVESTIGATIONS AT AEDMORE, S. DAK. 11 



No oats were grown on fall-plowed corn ground. The average 

 difference between oats grown on spring-plowed corn ground and 

 oats on disked corn ground was less than a bushel per acre. As with 

 wheat, the preceding crop and not the cultural treatment seemed to 

 determine the yield. 



No barley or winter wheat was grown on plowed corn ground. 



The average yield of flax was less than a bushel higher on spring- 

 plowed corn ground than on disked corn ground. This is not enough 

 to pay the cost of plowing. 



It appears that for all grain crops tested, where corn has been 

 kept clean, disking for grain is preferable to plowing. 



COMPARISON OF DISKING AND PLOWING GRAIN STUBBLE FOB SMALL GRAINS 



The expense of plowing the heavy soil at Ardmore makes it unde- 

 sirable to plow more frequently than is necessary. The practice of 

 disking in wheat on wheat stubble is common in the section. Three 

 rotations were started in 1927 to determine the effect of disking 

 stubble. Wheat was grown on all plots each year. The essential 

 difference between the rotations was that in one, plowing was done 

 every second year; in another, plowing was performed every third 

 year; and on one plot plowing was eliminated entirely, the wheat 

 being grown continuously on disked land. For 5 years the average 

 yield of wheat on continuously disked land was 7.1 bushels per acre. 

 Where plowing was done every second year, the yield was 8.3 bushels 

 per acre following plowing and 8.7 bushels on disked land. Where 

 plowing was done every third year, the yield was 8 bushels per acre 

 following plowing, 8.5 bushels on first-year disking, and 8.1 bushels 

 on second-year disking. 



The results show that where noxious weeds do not constitute a 

 problem, disking for at least 2 years may be practiced without mate- 

 rial loss of yield. On land continuously disked the yields were lower 

 in the fourth and fifth years than those on plowed land. The series 

 of years during which these rotations were conducted was much 

 below the average in precipitation and crop yields. 



A rotation in which corn took the place of the plowed plot in the 

 3 -year rotation was started in 1928 to determine whether one culti- 

 vated crop in 3 years is sufficient to control weeds. This rotation 

 was not used long enough for results to be conclusive, but it appears 

 likely that the method will control weeds fairly well and that the 

 aggregate yield of the three crops will be higher than in a 3-year 

 rotation of small grains only. 



COMPARISON OF CROPS GROWN UNDER ALTERNATE FALLOW AND CROP SYSTEMS WITH 

 SAME CROP GROWN CONTINUOUSLY 



Yields on fallowed land were obtained during the 20-year period. 

 With each crop two plots were used, one of which was fallowed 

 through the season and the other planted to crop. The yields of 

 grains grown continuously and the yields of the cropped plots in the 

 alternate fallow and crop series are given in table 4. 



