LAUSR

Identifying seasons sensitive to nutrient losses could help farmers and policymakers to formulate effective nutrient loss reduction strategies. This long-term study monitored water percolation, and nitrate (NO3 -N), and total phosphorus (TP) leaching from liquid swine manure and chemical fertilizer applied to intact core lysimeters in a sandy loam soil in Manitoba, Canada. Water percolation, NO3 -N and TP leaching were monitored from 2005 to 2016. Chemical fertilizer showed greater averaged annual mean water percolation (p = 0.01), annual flow-weighted mean concentration (FWMC) of NO3 -N (22 mg L-1 ; p < 0.001)), and annual NO3 -N leaching (36 kg N ha-1 ; p = 0.002) compared to the manure treatment (FWMC NO3 -N 15 mg L-1 ; NO3 -N leaching load 22 kg N ha-1 ). Averaged annual mean TP loss did not differ between treatments (p = 0.86). Spring (April to June) was the most sensitive season where > 75% of annual percolation, > 80% of annual NO3 -N and > 68% of annual TP leaching losses occurred from both manure and chemical fertilizer. The annual NO3 -N and TP leaching increased exponentially with cumulative winter and spring precipitation (r2 : Control = 0.69; Manure = 0.79; Chemical fertilizer = 0.63) and decreased with winter and spring air temperatures. The largest spring NO3 -N and TP leaching losses were observed in 2013, which followed the dry year of 2012, indicating the potential for nutrient flushing. The findings emphasize the need for environmentally sound N and P management strategies in cold, North American regions underlain by coarse textured soils, particularly during the spring season. This article is protected by copyright. All rights reserved.