14 MISCELLANEOUS PUBLICATION 95 2, U.S. DEPT. OF AGRICULTURE 



Farm was located near Watertown 

 in Codington County. The soil 

 is Kranzburg silt loam. Annual 

 precipitation averaged 20.5 inches. 



At the two locations, experi- 

 ments were designed to compare 

 use of legumes and commercial 

 nitrogen as a means of increasing 

 crop yields. These experiments 

 were designed to run for 5 to 8 

 years. At this writing (1963), only 

 progress reports have been issued. 

 Definite conclusions cannot be 

 made until more data have been 

 collected. Results seem to indi- 

 cate that, in favorable years, legume 

 and inorganic nitrogen are about 

 equally effective in increasing crop 

 yields (42, 43, 72, 73, 74, 75). In 

 less favorable years, inorganic nitro- 

 gen is more effective. In dry years, 

 a preceding legume crop may reduce 

 yields of grain crops. 



Puhr and coworkers (68) reported 

 the results of 1957 soil-fertility ex- 

 periments conducted on representa- 

 tive soil types in the major crop 

 areas of the State. This study in- 

 cluded comparisons of legumes and 

 commercial nitrogen fertilizers as 

 sources of nitrogen at Brookings, 

 Plankinton, and Redfield. 



At Brookings, on Vienna loam, 

 sweetclover as the nitrogen source 

 produced significantly greater corn 

 yields than did 20, 40, or 60 pounds 



of nitrogen fertilizer per acre in 

 1957. Twenty pounds of nitrogen 

 was approximately equivalent to a 

 sweetclover crop in increasing oat 

 yields. 



At Plankinton, on Cavour silty 

 clay loam (solodized-Solonetz), ni- 

 trogen from manure or commercial 

 form was more effective for increas- 

 ing yields of spring wheat than ni- 

 trogen supplied by growing green- 

 manure crops in alternate years. 

 Ordinary fallow produced as good 

 yields of winter wheat as sweet- 

 clover fallow. Yields of corn after 

 alfalfa tended to be reduced as com- 

 pared with those after other treat- 

 ments, because alfalfa depleted sub- 

 soil moisture. 



At Redfield, experiments were 

 conducted on nonirrieated and irri- 

 gated land (21). Soils at Redfield 

 are Beotia loam and Harmony silty 

 clay loam (82) . Nitrogen was more 

 effective than alfalfa in increasing 

 wheat yields on nonirrigated land 

 (table 9). A combination of alfalfa 

 and nitrogen produced the greatest 

 wheat yields. 



Chemical and Physical Effects of 

 Legumes and Grasses on Soils 



Sod crops, in rotations at Newell, 

 had a beneficial physical effect on 

 Pierre clay for a temporary period 

 (65). Land in sod rotations was 



Table 9. — Yields of spring wheat in 2 rotations, with and without nitroge- 

 nous fertilizer, Redfield. S. Dak., 1949-53 l 



Rotation 



Yield, per acre, of spring 

 wheat with — 



Increase 

 with use of 





No nitrogen 



30 pounds of 

 nitrogen 



nitrogen 



Corn, wheat, alfalfa, alfalfa 



Bushels 

 20.4 

 14.9 



Bushels 

 25.6 

 22. 6 



Percent 



25.5 



Corn, wheat 



51. 6 







Increase with alfalfa, percent 



36. 9 



13.3 j 



1 



'Data from Fine and Campbell (f/). 



