Author
|
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/25/2016 Publication Date: 9/29/2016 Publication URL: http://handle.nal.usda.gov/10113/63189 Citation: Jabro, J.D., Stevens, W.B., Iversen, W.M., Allen, B.L., Sainju, U.M. 2016. Suction cup samplers for estimating nitrate-nitrogen in soil water in irrigated sugarbeet production. Soil Science. 7(10):1342-1354. doi:10.4236/jep.2016.710117. Interpretive Summary: Contamination of surface and ground waters with nitrate-nitrogen (NO3-N) from farmland is a major environmental issue and an important public health concern. Nitrate-N levels at and above 10 mg L-1have been shown to pose health risks to humans and particularly to infants, causing a condition called blue baby syndrome. Seasonal NO3-N leaching losses beyond the rootzone under irrigated sugarbeet did not differ significantly between conventional tillage (CT) and strip tillage (ST) practices for all three N application rates in 2006, 2007, and 2008 due to soil variability and heterogeneity across the field. Soil variability among plots within each tillage treatment had a major impact on soil physical, chemical and biological properties that influenced water movement, N dynamics and NO3-N leaching losses beyond the 76 cm depth. Variations in soil texture, internal drainage, water content, porosity and other properties among field plots can significantly impact soil temperature and microbial activity which sequentially affect soil N dynamics and nitrate leaching. The findings from this study concur with those from previous research studies that using suction cup lysimeters for monitoring and quantifying nitrate leaching losses is limited in heterogeneous soils with preferential flow and macropores characteristics. Further research is needed to evaluate the use of suction cup samplers in broader range of soil types and cropping systems. Using better farming practices and site specific management for N fertilizer and irrigation management can significantly reduce nitrate leaching potential from agricultural production farms to groundwater. Technical Abstract: 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. |
