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Suction Cup Samplers for Estimating Nitrate-Nitrogen in Soil Water in Irrigated Sugarbeet Production

Jay D. Jabro, William B. Stevens, William M. Iversen, Brett L. Allen, Upendra M. Sainju
Journal of Environmental Protection 2016 v.07 no.10 pp. 1342-1354
Beta vulgaris, agricultural land, ceramics, clay loam soils, conventional tillage, environmental protection, fertilizer rates, groundwater, growing season, irrigation, leaching, measuring devices, nitrate nitrogen, nitrates, nitrogen, nitrogen fertilizers, preferential flow, samplers, soil heterogeneity, soil profiles, soil water, strip tillage, sugar beet, urea
Efforts have been increased to measure nitrate losses from farmland under different management practices due to environmental and public concerns over levels of nitrate-nitrogen (NO3-N) in surface and ground waters. This study evaluated the effect of conventional tillage (CT) and strip tillage (ST) practices and three N application rates on NO3-N leaching below 76 cm depth under irrigated sugarbeet (Beta vulgaris L.) in a clay loam soil. Nitrogen rates were applied as dry urea at 120, 150, 180 kg N ha-1 in 2006; 130, 160, 190 kg N ha-1 in 2007; and 110, 140, 170 kg N ha-1 in 2008. Soil water volumes were measured weekly during each growing season using three ceramic suction cup samplers per plot placed at a 76 cm depth below the soil surface under each tillage. Results indicated that NO3-N leaching losses were not significantly affected by either tillage practice or by N application rate due to soil variability across the field. There were large variations in NO3-N leaching among replicates within each tillage and N rate that caused by variability in soil physical, hydraulic and chemical properties that impacted water movement through soil profile, N dynamics and leaching below the rootzone of sugarbeet. In conclusion, suction cup samplers are point water measurement devices that reveal considerable variability among replicates within each treatment due to the heterogeneity of field soils. Further, these samplers are not recommended in heterogeneous soils with preferential flow characteristics.