Nutrient Loss in Snowmelt Runoff: Results from a Long‐term Study in a Dryland Cropping System

Abstract

Snowmelt runoff often comprises the majority of annual runoff in the Canadian Prairies and a significant proportion of total nutrient loss from agricultural land to surface water. Our objective was to determine the effect of agroecosystem management on snowmelt runoff and nutrient losses from a long-term field experiment at Swift Current, SK. Runoff quantity, nutrient concentrations, and loads were estimated after a change in management from conventionally tilled wheat (Triticum aestivum L.)-fallow (Conv W-F) to no-till wheat-fallow and subsequently no-till wheat-pulse (NT W-F/LP) and to an organic system with a wheat-green manure rotation (Org W-GM). The conversion from conventional tillage practices to no-till increased snowmelt runoff likely due to snow trapping by standing stubble after summer fallow. Relatedly, runoff after no-till summer fallow had higher dissolved P losses (0.07 kg P ha −1 ). Replacing summer fallow with a pulse crop in the no-till rotation decreased snowmelt runoff losses and nutrient concentrations. The Org W-GM treatment had the lowest P loss after stubble (0.02 kg P ha −1 ) but had high dissolved P concentrations in snowmelt following the green manure (0.55 mg P L −1 ), suggesting a contribution from incorporated crop residues. In this semiarid climate with little runoff, dissolved reactive P and NO 3 -N loads in snowmelt runoff were smaller than those reported elsewhere on the prairies (averaging <0.05 kg P ha −1 yr −1 , and <0.2 kg NO 3 -N ha −1 yr −1 ); however, the nutrient concentrations we observed, in particular for P, even without P fertilizer addition for organic production, question the practicality of agricultural management systems in this region meeting water quality guidelines.

Surface runoff and nutrient dynamics in cover crop–soybean systems in the Upper Midwest

“…In southern Ontario, snowmelt runoff from conservation‐tilled wheat–red clover cover crop systems had dissolved reactive P concentrations of 1.06 mg L −1 and loads of 0.15 kg ha −1 (Lozier, Macrae, Brunke, & Van Eerd, 2017). This load was above the 0.07 kg SRP ha −1 observed during cover phase snowmelt events in the current study and above the 0.02–0.04 kg P ha −1 reported for dryland cropping systems in the same Dfb climate region of southern Saskatchewan, Canada (Schneider, McConkey, Thiagarajan, & Reid, 2019). The current study's load matched the median soluble P load of 0.07 kg ha −1 released in runoff between April and November across several fields within the Lake Erie watershed (Smith et al., 2015), which falls just south of the Dfb climate zone.…”

Agricultural Water Quality in Cold Climates: Processes, Drivers, Management Options, and Research Needs

“…A diagram showing key agronomic, biogeochemical, and hydrological characteristics influencing nutrient losses in cold agricultural regions. The papers in this special section investigate different aspects of these characteristics, including the importance of the nongrowing season (Good et al, 2019; Plach et al, 2019; Ulén et al, 2019) and snowmelt (Hoffman et al, 2019; Kokulan et al, 2019; Wilson et al, 2019a) in annual flow and nutrient transport, the impacts of vegetative nutrient release (Cober et al, 2019; Costa et al, 2019; Liu et al, 2019b; Schneider et al, 2019; Vanrobaeys et al, 2019), the impacts of winter and fall nutrient applications (He et al, 2019; Sadhukhan et al, 2019; Smith et al, 2019; Stock et al, 2019; Vadas et al, 2019; Vetsch et al, 2019; Zopp et al, 2019), the influence of soil on nutrient loss (Dharmakeerthi et al, 2019; Liu et al, 2019a; Satchithanantham et al, 2019; Wilson et al, 2019b), and the patterns of nutrient concentrations in streams (Casson et al, 2019). …”

“…Conversion of cropping systems Conversion from conventional tillage to no-till increases snowmelt runoff volumes and nutrient losses (Schneider et al, 2019).…”

“…Using green manures in place of summer fallow increases snowmelt P losses (Schneider et al, 2019).…”

Nitrogen dynamics and nitrogen‐to‐phosphorus stoichiometry in cold region agricultural streams

“…Hydrological connection to upland and cropland areas is highest in the early spring. Snowmelt runoff over frozen soils drives much of the nutrient transport in this region, and the snowmelt rate (Rattan et al., 2017), snowmelt volume (Schneider et al., 2019), and accumulation of chemicals in the snowpack over the winter months (Costa et al., 2018) contribute significantly to this annual nutrient load. However, discharge by itself was not a strong predictor of N concentrations in the spring (Supplemental Table S1).…”