LEGUMES AND GRASSES 



35 



Table 26. — Average yields of milo and winter wheat in various rotations, 



Colby, Kans., 1915-47 l 





Average yield, per acre, of — 



Rotation 



Milo 



Winter wheat 2 





Grain 



Stover 



Grain 



Straw 



Rye, 3 milo, fallow, winter wheat 



Bushels 

 20.3 

 20.6 

 25.4 

 24.9 

 12.0 



Pounds 

 3,330 

 3,310 

 3,860 



Bushels 

 20. 5 

 19.6 

 18.9 

 18.8 

 7.3 



Pounds 

 2, 410 



Field peas, 3 milo, fallow, winter wheat 



Fallow, milo, fallow, winter wheat 



Fallow, crop 



Continuous crop 



2,280 

 2,760 



i Data from. Kuska and Mathews (44). 



2 3 years after green manure. 



3 Green-manure fallow. 



the green-manure crop. The third 

 year after green-manure fallow, 

 winter wheat on fallow produced 

 slightly more grain, but less straw, 

 than in a similar non-green-manure 

 rotation. 



Fallow was substituted for the 

 green-manure crop in the same 

 rotations for 1948-50 (44) . During 

 this period grain yields of both milo 

 and wheat in the green-manure 

 rotations were almost exactly equal 

 to those in the fallowed rotations. 



The authors concluded that there 

 were no apparent differences be- 

 tween the effects of winter rye and 

 field peas as green-manure crops 

 and that there were no cumulative 

 beneficial effects from their use. 



The average yields of most crops 

 for the last 5 years of the experi- 

 ments compared favorably with 

 the average for the second 5 years, 

 when the precipitation was essen- 

 tially the same (44) • On some plots, 

 the highest yields were obtained in 

 1947, after 34 years of cropping to 

 the same crop. This indicated 

 soil productivity had not declined 

 appreciably with time. 



Metzger (55) studied residual 

 effects of several alfalfa cropping 

 periods on yield and protein con- 



tent of succeeding wheat crops at 

 Manhattan, Kans. Alfalfa crop- 

 ping for 2 years increased the 

 protein content of wheat for at 

 least 8 years. Yield increases per- 

 sisted for about 3 years. Longer 

 periods of alfalfa cropping produced 

 greater residual effects, but foot- 

 rot disease problems made it im- 

 possible to obtain reliable data on 

 longtime effects. 



In 1955, Hobbs (32) reported the 

 effect of different crop rotations on 

 crop yields at Manhattan. On 

 unfertilized plots, wheat yields de- 

 clined with time except in the 

 alfalfa rotation. Corn yields were 

 maintained or increased with the 

 alfalfa rotation by all fertilizer and 

 manure treatments. In the non- 

 alfalfa and continuous cropping 

 systems, corn yields declined regard- 

 less of fertilizer or manure treat- 

 ments. 



Alfalfa-yield trends were down- 

 ward. Hobbs believed that mois- 

 ture had become the main limiting 

 factor in the second and subsequent 

 times that this crop was seeded on 

 a plot of land. Another possible 

 explanation, not mentioned, is that 

 the nutrient supply in the deep 



