FERTILIZER NITROGEN DISTRIBUTION UNDER IRRIGATION BETWEEN SOIL, PLANT, AND AQUIFER

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 application on N uptake by irrigated corn and the movement of N into the aquifer 4. 5 m below the soild 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 NO//3 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 NO//3-N in the aquifer but one-time applications increased the concentration by 7 and 10 ppm. Nearly one-fourth of the applied N remained in the upper 45-cm soil layer at harvest regardless of treatment.; 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.