INVESTIGATIONS AT ARDMORE, S. DAK. 5 



show the effect of hay crops in rotations and the results that may 

 be expected from the use of summer-fallow and green-manure crops. 

 Most of the rotations have been carried on continuously from 1912, 

 but some rotations were added as the need of studying particular 

 problems became evident. A few rotations were discontinued after 

 time had demonstrated their lack of adaptation to the locality. In 

 1932 there were in operation twelve 2-year, fifteen 3-year, nineteen 

 4-year, three 5-year, and three 6-year rotations. In addition there 

 were continuously cropped plots of spring wheat, winter wheat, oats, 

 barley, corn, and sorgo grown under widely different methods of 

 soil preparation. Alternately fallowed and cropped plots were also 

 devoted to these same crops. On one set of six plots the effect of 

 delayed seeding of wheat as a means of weed control was studied. 

 Eight plots were devoted to a study of the effects of different methods 

 of fallowing. Two plots, one each of spring wheat and winter 

 wheat, showed the results from continuous disking. 



AVERAGE YIELDS 



While the results from crop rotations are intended primarily to 

 show yields of given crops under given cultural methods, the aver- 

 age yields of all plots of each crop grown each year give useful 

 information on the adaptation of the several crops to the section. 

 Exact comparisons cannot be made with such averages, because the 

 relative numbers of good and poor methods of production that enter 

 into them are not the same with all crops. With crops like wheat, 

 oats, corn, and winter wheat the number of plots is large enough 

 so that the average yields are fairly accurate measures of the pro- 

 duction that may be expected. With crops occupying a smaller num- 

 ber of plots the measure is not so accurate, but in most cases they' 

 occupied a smaller number of plots because they were thought to 

 be relatively less important, at least in rotations. In some cases, 

 however, crops occupying a lesser number of plots are important. 



The number of plots of the different crops grown in 1932 was as 

 follows: Spring wheat, 50; delayed-seeding spring wheat, 5; winter 

 wheat, 17; oats, 40; barley, 10; flax, 4; corn, 44; sorgo, 8; alfalfa, 3; 

 bromegrass, 5; sweetclover, 4; winter rye, 6; peas, 4; potatoes, 2; 

 and beans, 2. Twenty-seven plots were fallowed. 



The 20-year average yields of the different crops are shown in 

 table 2. With most crops all the plots are included in the average. 

 Only one plot of winter rye was harvested for grain. The other 

 plots do not appear in the average. No peas were harvested. With 

 hay crops the yield does not include the first year. For example, 

 with alfalfa the yield given is for second-year and third-year plots, 

 and does not include the year in which the plot was planted. Only 

 one plot of sweetclover appears in the average yields, as there was 

 only one rotation in which a second-year hay crop of sweetclover 

 was harvested. 



