The response of soybeans to sources of nitrogen in the field

The response of soybeans to sources of nitrogen was determined in the field with inoculated and uninoculated Biloxi soybeans on limed and unlimed soil. Yields and nitrogen determinations were made. The yields and nitrogen content data indicate that the production of carbohydrates was at a high level. The data may be summarized as follows: 1. Nitrate of soda and urea were superior to ammonium sulfate and cyanamid in the production of soybeans and increased the nitrogen content of the soybeans on unlimed soil. 2. On limed soil ammonium sulfate was almost equal to urea and nitrate of soda as a source of nitrogen for soybeans. 3. Cyanamid was decidedly inferior to nitrate of soda, urea, and ammonium sulfate as a source of nitrogen for soybeans on limed soil. 4. Lime increased the yield of soybeans where ammonium sulfate was applied and decreased it where urea, cyanamid, and nitrate of soda were used. 5. Inoculation produced significant increases in yield of soybeans where nitrate of soda and cyanamid were used but did not where ammonium sulfate and urea were used. 6. Inoculation did not increase the nitrogen content of soybeans significantly where any source of nitrogen was used. 7. The native strain of soybean root nodule bacteria was in greater need of lime on the unlimed soil than the strain which was added. 8. The strain of soybean root nodule bacteria added was better suited to the soil conditions as they existed than was the native strain. 9. Carbohydrate production was much higher in a year of good distribution of rainfall than in a dry year, and conversely, the nitrogen content was much higher in the dry year when the soybeans obtained their nitrogen primarily from the soil and the root nodules. 10. On unlimed soil nitrate and amid nitrogen were superior to cyanamid for soybeans, and the sulfate radical of ammonium sulfate reduced the yield. Where dolomite was added, nitrate, amid, and ammonium nitrogen were superior to cyanamid nitrogen for soybeans.