Abstract
Phosphorus (P) loss to freshwater is a key driver of eutrophication, and understanding the scale and spatial distribution of potential P sources is a key pre-requisite for implementing policies for P management to minimize environmental impacts. Soil test P (STP) is a useful indicator of the accumulation of P in soils, but these data are not readily available for most agricultural land in Canada, so the cumulative P balance (P inputs as manure or fertilizer minus removal of P in crops) is calculated as a proxy for this value. Cumulative P balance is an important calculation within the indicator of risk of water contamination by P, so allocations of manure and fertilizer P to cropland were updated within the calculation of P balance, and for Ontario, data from 1961 to 1980 were added to account for P applications during that period. The STP concentrations were calculated from the resulting cumulative P balances. When compared with reported STP concentrations, the predicted concentrations showed a statistically significant regression at the national (R2 = 78%) and provincial scale (Ontario, R2 = 36%; Prince Edward Island, R2 = 36%; Manitoba, R2 = 72%; British Columbia, R2 = 40%). There was significant variation in the cumulative P balance across Canada, with the highest values corresponding with areas of high livestock density, whereas large zones of P deficit were detected across the Prairies.
Highlights
This paper presents the results of an updated methodology for calculating the cumulative P balance since the paper by van Bochove et al (2012), and extends the analysis for an additional five years to 2011
The cumulative P balance was calculated at the Soil Landscape of Canada (SLC) scale as the sum of estimated manure and mineral fertilizer P applications minus the P removed in the harvested portion of the crop, accumulated over the time period from 1976 to 2011
The allocation of mineral fertilizer P according to crop requirements and modified by relative fertilizer expenditures assumes that all fertilizer decisions are completely rational, which we know is not the case for any purchasing decision
Summary
Phosphorus (P) loss to surface freshwater is a key driver of environmental degradation (Jarvie et al 2013; Scavia et al 2014), including blooms of both harmful (e.g. microcystis) (Conroy et al 2014; Simic et al 2017; Steffen et al 2014) and nuisance (e.g. cladophora) algae (Howell and Dove 2017), along with contributing to the development of hypoxic zones that impact fish habitat (Bouffard et al 2013; Scavia et al 2014). One of the key source parameters for P loss from agricultural runoff is the accumulation of P in the soil, as measured with an agronomic soil test (Sharpley et al 2002; Vadas et al 2005; Wang et al 2015). This directly influences the concentration of dissolved P in runoff (Wang et al 2010), the concentration of bio-available particulate P (BAPP) (Sharpley 1985), and indirectly, the accumulation of P in plant biomass that could be released over-winter from frozen plant tissue (Maltais-Landry and Frossard 2015; Roberson et al 2007; Sharpley and Smith 1989). The original calculations by van Bochove et al (2012), assumed that manure P displaced mineral fertilizer P from land application, which generated zero fertilizer P applications for some areas despite the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
