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Delayed Sample Filtration and Storage Effects on Dissolved Nutrients Measured in Agricultural Runoff

Lentz, Rodrick D.
Communications in soil science and plant analysis 2013 v.44 no.20 pp. 2952
acid treatment, agricultural management, agricultural runoff, ammonium nitrogen, boric acid, cold storage, edge effects, filtration, furrows, irrigation, nitrate nitrogen, nutrients, phosphorus, pollution load
Few research studies have examined the influence of delayed filtration on sample stability or runoff nutrient loss assessments. Runoff samples from irrigation furrows were each split into four volumes: two were filtered (45 μm) in the field and two were filtered 10 days later, with or without boric acid treatment, and stored at 4 °C. Sample dissolved reactive P (DRP), nitrate nitrogen (NO ₃-N), and ammonium (NH ₄)-N concentrations were measured in all filtered samples 10 and 107 days after collection. Samples filtered in the field and those with a 10-day delayed filtration had similar dissolved DRP, NO ₃-N, and NH ₄-N concentrations, whether or not boric acid was added. Boric acid stabilized DRP and NH ₄-N sample concentrations, but not NO ₃-N, during the 107 days of storage (relative to field-filtered samples). The effect of treatments on computed furrow stream concentration and runoff mass losses was similar to that for sample concentrations, except that furrow NH ₄-N parameters were unaffected by treatments. The field-filtered or 10-d delayed filtration without boric acid treatments provided the best dissolved nutrient measurements for comparing agricultural management effects at the field edge; however, results suggest that an incubation-type test for field-edge runoff water may provide a more accurate estimate of field management effects on dissolved nutrient loads in downstream aquatic ecosystems.