Nitrate Leaching from Two Kentucky Bluegrass Cultivars as Affected by Nitrate Uptake Capacity and Subsurface Soil Compaction

Abstract

ABSTRACTThere are a number of strategies to minimize NO3– leaching from turfgrass, including planting turfgrass cultivars with higher NO3– absorption abilities. This column lysimeter study was conducted to examine NO3– leaching from two Kentucky bluegrass (Poa pratensis L.) cultivars differing in NO3– uptake capacity. Subsurface soil compaction was included as a second factor. Tillers of Julia and Midnight Kentucky bluegrass, previously identified as having high and low NO3– uptake capacity, respectively, were grown in column lysimeters. Each column was filled with Wagram loamy sand with or without a subsurface compaction layer 8.5 cm below the surface. The two cultivars were established and then treated to impose moderate N deficiency. Potassium nitrate was applied in solution at 49 kg N ha–1 followed by daily heavy irrigation. Leachate was collected and analyzed for NO3–‐N. Cumulative N leaching loss of applied N ranged from 2.6 to 19% and 2.8 to 21% for Julia and Midnight, respectively. In two out of three trials, both cultivars absorbed NO3– very efficiently in noncompacted soil, with only trace amounts of NO3– leaching. While NO3–‐N loss averaged 4.7% of applied N in noncompacted soil across all trials, subsurface soil compaction increased that to 8.9%. Results indicated that despite being identified as more efficient for NO3– uptake, NO3– leaching from Julia was generally similar to that from Midnight. Soil conditions and differences in root morphology and/or architecture may played a more important role than root uptake capacity in determining NO3– leaching from these Kentucky bluegrass genotypes.