Field Scale Evaluation of Water and Nitrogen Management Impacts on Ground Water Quality

摘要

Excess application of nitrogen fertilizer and irrigation water in Nebraska's central Platte River Valley has resulted in a high accumulation of nitrate-N in shallow ground water. Concentrations are typically 20-40 mg/1. A major emphasis of the Nebraska MSEA(Management Systems Evaluation Area) project was to evaluate the impact of improved management on ground water quality at a filed scale.There management systems were imposed on 13.4 ha fileds under mono-culture corn: conventional practice with furrow irrigation and pre-plant N, improved surface irrigation practice with surge flow irrigation and split N applications, and center pivot irrigation with irrigation scheduling and N applications split between pre-plant and fertigation scheduled chlorophyll metter measurements. Data from suction lysimeters indicated that the management package under the center pivot system reduced the nitrate concentration of root zone drainage. in comparison to the conventional system. Thsi was also reflected in data from multilevel sampling wells, which showed a reduction of nitrate-N in the upper ground water. While water and N inputs were reduced on the improved surface irrigation field, this seemed to have little positive effect on ground water nitrate concentration. This was complicated by an attempt to fertigate using surge irrigation on this field, which resulted in significant leaching loss of N.