MOVEMENT OF NITRATE NITROGEN WITH DIFFERENT CROPPING SYSTEMS IN TWO SOILS

Abstract

In a field experiment with different crops on a loam and a sandy loam soil in a 3-yr period, N uptake by grasses accounted for 64–96% of the N fertilizer added at a rate of 112 kg N/ha annually. The recovery was 40–54% when the rate was 448 kg N/ha. The grass species were more effective than corn in removing N from the soils. Regardless of the rate of fertilizer used, however, the amounts of NO₃-N in the soil of corn, fallow and grass plots sampled to a depth of at least 90 cm in the fall were high enough in many instances to account for much of the excess of added N not used by the crop. Corresponding data for NO₃-N in the soils in the following spring showed that except for the moderately fertilized grass plots, the fertilized soils were susceptible to considerable loss of excess NO₃-N from early fall to the following spring. In several instances, the data indicated a movement of NO₃-N, since the amounts were reduced in the upper soil layers and increased in the lower ones during the fall–spring period.