Fertilizer Nitrogen Distribution Under Irrigation Between Soil, Plant, and Aquifer
1979
Gerwing, J. R. | Caldwell, A. C. | Goodroad, L. L.
A field experiment was established on a Sverdrup sandy loam in Central Minnesota to evaluate the effects of amounts and timing of nitrogen (N) fertilizer applications on N uptake by irrigated corn (Zea mays L.) and the movement of N into the aquifer 4.5 m below the soil surface. Nitrogen was applied as urea at rates of 179 and 269 kg N/ha in one application at planting or in split applications through the season. Soil solution analysis showed NO₃ moving below the rooting zone in all plots with much higher concentrations below the one-time fertilizer applications. Split applications of N had only minimal effect on the concentration of NO₃-N in the aquifer but one-time applications increased the concentration by 7 and 10 ppm. The use of ¹³N showed that splitting the 179-kg rate increased the N in the plant derived from fertilizer from 33.1 to 54.5%, and increased the recovery of fertilizer N by the plant from 30.4 to 52.1%, even though whole plant yields were not affected. Nearly one-fourth of the applied N remained in the upper 45-cm soil layer at harvest regardless of treatment. No accumulation of NO₃ was found in the soil profile or underlying material to a depth of 3.0 m.
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