Estimating Dissolved Reactive Phosphorus Concentration in Surface Runoff Water from Major Ontario Soils

Abstract

Phosphorus (P) loss from agricultural land in surface runoff can contribute to eutrophication of surface water. This study was conducted to evaluate a range of environmental and agronomic soil P tests as indicators of potential soil surface runoff dissolved reactive P (DRP) losses from Ontario soils. The soil samples (0- to 20-cm depth) were collected from six soil series in Ontario, with 10 sites each to provide a wide range of soil test P (STP) values. Rainfall simulation studies were conducted following the USEPA National P Research Project protocol. The average DRP concentration (DRP30) in runoff water collected over 30 min after the start of runoff increased (p < 0.001) in either a linear or curvilinear manner with increases in levels of various STPs and estimates of degree of soil P saturation (DPS). Among the 16 measurements of STPs and DPSs assessed, DPS(M3) 2 (Mehlich-3 P/[Mehlich-3 Al + Fe]) (r2 = 0.90), DPS(M3)-3 (Mehlich-3 P/Mehlich-3 Al) (r2 = 0.89), and water-extractable P (WEP) (r2 = 0.89) had the strongest overall relationship with runoff DRP30 across all six soil series. The DPS(M3)-2 and DPS(M3)-3 were equally accurate in predicting runoff DRP30 loss. However, DPS(M3)-3 was preferred as its prediction of DRP30 was soil pH insensitive and simpler in analytical procedure, ifa DPS approach is adopted.

Degree of phosphorus saturation threshold for minimizing P losses by runoff in cropland soils of Southern Brazil

“…Moreover, several studies have shown high correlation between dissolved reactive P in runoff and WEP (Pote et al, 1996;Sharpley et al, 2001;Davis et al, 2005). According to Wang et al (2009), these relationships are soil-specific and vary with soil type, soil clay content, slope, and soil management. Because it is impractical to implement a specific environmental soil test P for each soil type, several efforts have been made to find an agri-environmental soil test that can be applied to the major soils of a given region, considering some soil properties (Ige et al, 2005).…”

“…Because it is impractical to implement a specific environmental soil test P for each soil type, several efforts have been made to find an agri-environmental soil test that can be applied to the major soils of a given region, considering some soil properties (Ige et al, 2005). Wang et al (2009) Pesq. agropec.…”

“…There is a lack, however, of studies regarding the assessment of P losses by surface runoff in these soils. In the present study, it is expected that the DPS, successfully tested in other regions of the world, might be suitable to estimate the risk of those losses in soils of Southern Brazil (Ige et al, 2005;Casson et al, 2006;Guérin et al, 2007;Wang et al, 2009).…”

“…Therefore STP has been used to estimate potential P losses or been incorporated as a PI factor because it has shown high correlations with dissolved reactive P in runoff waters (Wang et al, 2009). The constraints of using only this index, however, are due to the fact that it does not account for soil-specific P reactions and for other relevant soil properties, such as soil sorption capacity, indicated by the PSI (Beck et al, 2004).…”

“…Wang et al (2009), for example, used the STP and PSC estimated both by Mehlich-3 extractable Al and Fe+Al to calculate the DPS in soils of Ontario.…”