Nitrogen Movement Under Irrigated Corn as Influenced by Nitrogen Source and Rate

The purpose of this study was to determine nitrogen movements under a fall applied fertilizer as affected by rate of application of fertilizer, type of fertilizer carrier, and by crop grown. Two nitrogen fertilizers, calcium nitrate and ammonium sulfate, were applied in the fall of 1970. The soil profile was sampled in the spring of 1971 and again in the fall of 1971. Nitrate-nitrogen from both the calcium nitrate and the ammonium sulfate applications was found to have moved significantly from the time of application to the time of spring soil sampling. Two effects from the high rate of both calcium nitrate and ammonium sulfate which had influenced nitrate-nitrogen location in the profile were observed. The first effect was a promoting of deep movement of nitrate nitrogen by the high rate of calcium nitrate. The second effect was a delay of deep leaching of nitrate-nitrogen by the high rate of ammonium sulfate. The crop grown in the calcium nitrate plots was severely nitrogen deficient at all rates of fertilizer application. The corn grown in the ammonium sulfate plots at 150 pounds nitrogen per acre were nitrogen deficient to the same degree as the calcium nitrate plots. The crop in the high rate of ammonium sulfate plots looked quite good although some nitrogen deficiency symptoms did appear. Crop performance showed that severe leaching had taken place over the winter and through the growing season. This leaching was found to be affected by type of fertilizer carrier, application rate of fertilizer, and the crop grown. At the end of the growing season approximately half of the nitrate-nitrogen present in the soil profile in the spring was present in the fall after crop removal