The Effects of Multiple Beneficial Management Practices on Hydrology and Nutrient Losses in a Small Watershed in the Canadian Prairies

Abstract

Most beneficial management practices (BMPs) recommended for reducing nutrient losses from agricultural land have been established and tested in temperate and humid regions. Previous studies on the effects of these BMPs in cold-climate regions, especially at the small watershed scale, are rare. In this study, runoff and water quality were monitored from 1999 to 2008 at the outlets of two subwatersheds in the South Tobacco Creek watershed in Manitoba, Canada. Five BMPs-a holding pond below a beef cattle overwintering feedlot, riparian zone and grassed waterway management, grazing restriction, perennial forage conversion, and nutrient management-were implemented in one of these two subwatersheds beginning in 2005. We determined that >80% of the N and P in runoff at the outlets of the two subwatersheds were lost in dissolved forms, ≈ 50% during snowmelt events and ≈ 33% during rainfall events. When all snowmelt- and rainfall-induced runoff events were considered, the five BMPs collectively decreased total N (TN) and total P (TP) exports in runoff at the treatment subwatershed outlet by 41 and 38%, respectively. The corresponding reductions in flow-weighted mean concentrations (FWMCs) were 43% for TN and 32% for TP. In most cases, similar reductions in exports and FWMCs were measured for both dissolved and particulate forms of N and P, and during both rainfall and snowmelt-induced runoff events. Indirect assessment suggests that retention of nutrients in the holding pond could account for as much as 63 and 57%, respectively, of the BMP-induced reductions in TN and TP exports at the treatment subwatershed outlet. The nutrient management BMP was estimated to have reduced N and P inputs on land by 36 and 59%, respectively, in part due to the lower rates of nutrient application to fields converted from annual crop to perennial forage. Overall, even though the proportional contributions of individual BMPs were not directly measured in this study, the collective reduction of nutrient losses from the five BMPs was substantial.

Relationship between Manure Management Application Practices and Phosphorus and Nitrogen Export in Snowmelt Run-off Water from a Black Chernozem Saskatchewan Soil

“…Soil texture, water infiltration rates and redistribution of crop residues via tillage operations can all have an effect on the amount of NO 3 -N that is retained near the soil surface (Stumborg et al, 2007). The subsurface flow of snowmelt water through thawing soil often results in much greater NO 3 -N removal (Li et al, 2011). Figure 10.…”

“…In regions of the northern Great Plains such as Saskatchewan, spring snowmelt is the major moisture recharge event of the year. Snowfall can account for as much as 30 % of the annual precipitation received (Cutforth et al, 1999) and accumulates through several months, subsequently melting and running over thawing and frozen soil when spring temperatures begin to increase (Li et al, 2011). Snowmelt run-off can exceed rainfall run-off due to frozen soils with limited water infiltration (Granger et al, 1984;Hansen et al, 2000;Young and Mutchler, 1976).…”

“…The kinetic energy generated by the force of raindrops contacting the soil surface can cause more aggregate breakdown, soil particle detachment and movement of particles with the run-off water (Li et al, 2011). Glozier et al (2006) reported that approximately two-thirds of the N and P removal due to run-off from snowmelt in southern Manitoba occurred in a dissolved inorganic form.…”

A Review and Discussion on Modeling and Assessing Agricultural Best Management Practices under Global Climate Change

“…At the watershed scale, BMP evaluation aims to assess the cumulative effects of multiple BMPs implemented at different places and times. Because of the high heterogeneity of watershed conditions, considerable uncertainties could be introduced to the observations and evaluations, and the timing, intensity, and spatial distribution of climatic variables would become key determinants of BMP effects on water quality (Li et al, 2011). Additionally, in-stream processes or improper maintenance of stream management practices may result in a much lower BMP effectiveness at a watershed scale than that observed at site, plot, and field scale.…”

An assessment of vegetation characteristics and hydrologic flow pathways on the effectiveness of vegetated buffer strips for phosphorus reduction in an agricultural watershed

“…For example, a study in the South Tobacco Creek watershed in southern Manitoba found that nearly 70% of annual runoff occurred during this period, and P was primarily exported in the dissolved form (Glozier et al, 2006). Similarly, Li et al (2011) found that total dissolved P exports were 4.7 to 5.0 times as high as particulate P in two sub watersheds in South Tobacco Creek.…”