Quantifying Nitrate Leaching under Commercial Red Raspberry Using Passive Capillary Wick Samplers

Abstract

Core Ideas NO3 leaching was quantified by passive capillary wick samplers over 2 yr. NO3 leaching was three times greater in Year 1 than Year 2 (240 vs. 80 kg N ha−1). Increased Year 1 NO3 leaching reflected field renovation prior to monitoring period. There was strong seasonality in NO3 leaching from the field. Despite fertilizer banding in rows, 60% of NO3 leached from alleys between rows. Groundwater NO3–N contamination in the Abbotsford‐Sumas Aquifer in British Columbia, Canada, has been attributed primarily to NO3–N leaching from red raspberry (Rubus idaeus L.); however, direct estimates of NO3–N leaching are lacking. This study quantified the magnitude and timing of NO3–N leaching under a commercial red raspberry field over 30 mo (October 2010–March 2013) using passive capillary wick samplers installed below the root zone at three row locations (irrigated row, nonirrigated row, and alley) after the critical period of field renovation and replanting. Substantial NO3–N leaching (240 kg N ha−1) during the first year of monitoring was attributed to the effects of field renovation (including autumn chopping and incorporation of raspberry canes and soil fumigation and spring poultry broiler manure application) in the year prior to the initiation of monitoring. Lower NO3–N leaching (80 kg N ha−1) occurred in the second year of monitoring under typical mineral fertilizer management practices. Strong seasonality of NO3–N leaching was observed in both years, with ∼48% in autumn, 34% in spring and summer, and 17% in winter. Approximately 60% of the NO3–N leaching was attributed to the alleys between raspberry rows, which did not receive mineral fertilizer or irrigation. The high proportion of leaching during spring and summer and from the alleys suggests that growing‐season irrigation practices and alley vegetation management, respectively, would be good targets for the development of improved practices. The samplers were effective in quantifying the magnitude and timing of NO3–N leaching from a commercial agricultural field and informing the development of improved practices.

Quantification of Groundwater Nitrate Loading after Raspberry Field Renovation Using High‐Resolution Passive Diffusion Sampling

“…The annual recharge estimates were between 65 and 75% of the annual measured precipitation, which was consistent with the proportion of precipitation occurring outside of the growing season and with previous estimates that 37 to 81% of annual total precipitation typically contributes to groundwater recharge (Kohut, 1987; Scibek and Allen, 2006). The annual recharge estimates from this study were consistent with other recharge estimates for the ASA (Kohut, 1987; Scibek and Allen, 2006; Holländer et al, 2016) and water balance estimations for the same field and period (Loo et al, 2019).…”

“…The NO 3 loading in Year 1 (97 kg N ha −1 ) was ∼35% higher than the average NO 3 loading in nonrenovation years, and this additional NO 3 loading presumably reflects the fall renovation practices (cane chopping, fumigation, and tillage). The NO 3 loading in Year 2 (246 kg N ha −1 ) compared well with the NO 3 leaching from the root zone measured using passive capillary wick samplers over the same period from the same study field (239 kg N ha −1 ; Loo et al, 2019). The Year 2 NO 3 loading rate was ∼3.4 times higher than the average NO 3 loading in nonrenovation years and was attributed primarily to manure application in early 2010.…”

“…The NO 3 loading in Year 3 (84 kg N ha −1 ) compared well with the NO 3 leaching from the root zone measured using passive capillary wick samplers over the same period from the same study field (79 kg N ha −1 ; Loo et al, 2019). The Year 3 NO 3 loading rate was ∼20% greater than the average NO 3 loading in nonrenovation years and was attributed to a residual effect of the manure application that was consistent with the decay series for poultry manure (Pratt et al, 1973; Klausner et al, 1994).…”

“…Manure was only applied during renovation, when an unknown quantity of poultry broiler manure was surface broadcast over the entire field and incorporated by rototilling on 9 Feb. 2010 before replanting. Irrigation was applied to the field with buried drip irrigation lines from June through September, depending on precipitation (Loo et al, 2019). The irrigation application rates and the daily timing were not provided by the grower.…”

Key Components and Contrasts in the Nitrogen Budget Across a U.S.‐Canadian Transboundary Watershed

“…We did not directly quantify N flux to groundwater due to its complexity and instead included it as part of watershed N retention, but we acknowledge that some portion of the N applied leaches into groundwater. For example, rates of nitrate leaching from the soil were substantially below raspberry fields in the area (80–240 kg N ha −1 yr −1 ) (Loo et al, 2019). Combining crop area data with published soil nitrate data in this area or in watersheds with similar land use and weather, we did a back‐of‐the‐envelope estimation of the range of N flux leaching under different land uses.…”