50 MISCELLANEOUS PUBLICATION 9 5 2, U.S. DEPT. OF AGRICULTURE 



Table 34. — Losses of organic carbon in surface avd subsurface soils compared 

 with virgin sod in rotations with and without green manure at 7 locations 

 in the northern and central Great Plains, 1908-47 l 2 





Loss of organic carbon at — 



Location 



0- to 6-inch depth 



6- to 12-inch depth 





No 



green 

 manure 



Rye 



green 

 manure 



Legume 



green 



manure 



No 



green 



manure 



Rye 



green 



manure 



Legume 



green 



manure 



Mandan, N. Dak 



Percent 

 33 

 50 

 24 

 41 

 37 

 30 

 32 



Percent 

 36 

 51 

 22 

 40 

 34 

 29 

 35 



Percent 

 33 



~~26~ 

 40 

 43 

 29 



Percent 



11 



16 



3 9 



6 



Percent 

 14 

 12 



3 7 

 8 



Percent 

 10 



Havre, Mont 





Sheridan, Wvo 



3 9 



Archer, Wyo 





Colby, Kans_ 





Hays, Kans _ _ 









Garden Citv, Kans 



















Mean __ _ 



35 



35 



34 



10 



10 



9 







i Data from Haas and coworkers (27) . 



2 Periods of cropping varied from 30 to 34 years. 



3 Sampling depth was 6 to 20 inches. 



Legumes used were sweetclover, 

 cowpeas, and field peas. These 

 were plowed in spring or early 

 summer aDd the land fallowed the 

 rest of the season. Data indicate 

 that neither rye nor legume green 

 manures were effective in reducing 

 nitrogen and carbon losses. 



At Sheridan, Wyo., one plot was 

 planted to peas continuously for 30 

 years (27). The crop was plowed 

 under for green manure each year. 

 Soil from this plot lost 28 percent 

 of its nitrogen, which was as high 

 as from row-crop and small-grain 

 rotations, where the crops were 

 removed. Wind and water erosion 

 was a problem on this plot, which 



f)robably accounted for some of the 

 oss. 



The results obtained in this study 

 (27) indicated that green manures 

 have been of little or no value in 

 reducing the loss of nitrogen under 

 dryland conditions in the northern 

 and central Great Plains. 



Nitrogen and carbon changes of 



surface and subsurface soils of ro- 

 tations with and without grass and 

 alfalfa were tabulated (table 35). 

 Grass and alfalfa rotations con- 

 sisted of six plots each. Three of 

 these plots were in grass or alfalfa 

 and three were in a rotation of corn, 

 wheat, and oats. 



Data indicate that grass and 

 alfalfa rotations reduced nitrogen 

 and carbon losses at Mandan and 

 Sheridan but had little effect at 

 Dickinson and Archer. It appeared 

 that alfalfa was adding nitrogen to 

 the soil at Mandan but not in 

 sufficient quantities to maintain 

 the soil at its original level. The 

 losses from these rotations were 

 substantially the same as from plots 

 continually cropped to small grains. 



As a part of this same study, Haas 

 and coworkers (27) determined the 

 nitrate-production capacity of 

 northern and central Great Plains 

 soils. High-nitrogen soils at most 

 locations maintained a higher level 

 of nitrate production than did the 



