Sodium nitrate as a fertilizer for corn on Iowa soils

A series of eight plats was established on each of 16 different fields in various parts of the state for the purpose of testing the action of sodium nitrate applied at the rate of 100 pounds per acre to corn in early, divided, and late applications, with and without superphosphate. These 16 fields included nine different soil types, mainly on the less productive soils of the state. Due to damaged plats and other circumstances only 11 of the fields were harvested. Without superphosphate the divided application gave slightly the highest yield, 6.2 bushels per acre increase over the checks as an average for all fields. The early application of nitrate made an average increase of 4 bushels per acre and the late application an average increase of 5 bushels per acre over the checks. When superphosphate was used in addition to the nitrate, the increase in yield was somewhat less. On some of the fields, superphosphate tended to depress the yield due to dry weather conditions. Clinton silt loam was most responsive to nitrate fertilizer. The average increased yield for the three fields of this soil type was about 10 bushels per acre from the nitrate fertilizer with very little difference as to the time of application. The fertilizer applications did not materially influence the nitrogen content of the grain. One field of Carrington loam was selected for some special studies regarding the effect of sodium nitrate on corn. Sodium nitrate was used on this field in amounts of 100 and 200 pounds per acre in early, late, and divided applications. On some of the plats superphosphate was used at the rate of 120 pounds per acre. On other plats the nitrate was used in connection with different artificial manures and some undecomposed plant residues. There was no evidence that the nitrate fertilizer was of any value on Carrington loam which had been kept in a relatively good state of fertility.