The seasonality of nitrate and phosphorus leaching from manure and chemical fertilizer added to a chernozemic soil in Canada
Vivekananthan Kokulan, O. O. Akinremi, Alan P. Moulin
Abstract
Abstract 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 as well as nitrate (NO 3 –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, NO 3 –N, and TP leaching were monitored from 2005 to 2016. Chemical fertilizer showed greater average annual mean water percolation ( p = .01), annual flow‐weighted mean concentration (FWMC) of NO 3 –N (22 mg L –1 ; p < .001), and annual NO 3 –N leaching (36 kg N ha –1 ; p = .002) compared with the manure treatment (FWMC NO 3 –N, 15 mg L –1 ; NO 3 –N leaching load, 22 kg N ha –1 ). Average annual mean TP loss did not differ between treatments ( p = .86). Spring (April–June) was the most sensitive season, when >75% of annual percolation, >80% of annual NO 3 –N, and >68% of annual TP leaching losses occurred from both manure and chemical fertilizer. Annual NO 3 –N and TP leaching increased exponentially with cumulative winter and spring precipitation (control, r 2 = .69; manure, r 2 = .79; chemical fertilizer, r 2 = .63) and decreased with winter and spring air temperatures. The largest spring NO 3 –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.