RECOVERY OF N-15-LABELED FERTILIZERS APPLIED TO BARLEY ON 2 ARTIFICIALLY ERODED SOILS IN NORTH-CENTRAL ALBERTA

Soil erosion induces variability in soil properties which may influenc e nutrient use efficiency. A 2-yr field study was conducted with the f ollowing objectives: (1) to determine the recovery of N-15-labelled fe rtilizers applied to barley growing on artificially eroded soil, and ( 2) to compare N losses from nitrate-and ammonia-based N fertilizers. F ield experiments were conducted in north-central Alberta in 1991 and 1 992 on an Orthic Gray Luvisol (Site 1) and on an Eluviated Black Chern ozem (Site 2) soil. At each site, a factorial experiment of three leve ls of artificial erosion (0, 10 and 20 cm) and three N sources (KNO3, urea, and control) was laid out as a split-plot design with four repli cations. The SN-labelled fertilizers (5.63 atom % abundance) were band ed in June 1991 at 150 kg N ha(-1) within 46-cm by 46-cm steel frame m icroplots. The proportion of added N recovered by barley (Hordeum vulg are L.) was not affected by erosion level. Periodical water saturation and NO3- availability suggested denitrification as a major mechanism of N loss. The N losses ranged from 12 to 51 kg N ha(-1) in 1991 and 2 0 to 80 kg N ha(-1) over the 2-yr period, but the N losses did not rel ate to erosion level. The N losses after 2 yr were greater from KNO3 t han from urea at Site 1. Most of the added N-15 was found in the surfa ce 0- to 15-cm layer, but amounts of N-15 were detected in the 15- to 30-cm or 30- to 45-cm layers. The results call for continued developme nt of N management techniques geared to optimize crop growth and minim ize losses from fields.