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B. P. Kelly

Publications and source records attributed to B. P. Kelly.

5 recordsLinked to original sources
USGS2005

Preferential flow and transport of nitrate and bromide in claypan soil

The in situ measurement of water flow and chemical transport through clay pan soils is crucial to understanding potential water contamination from agricultural sources. It is important due to the large areal extent of these soils in agricultural regions of the midwestern United States and because of preferential flow paths caused by desiccation cracks, worms burrowing, and root development. A study plot at the Missouri Management Systems Evaluation Area near Centralia, Missouri, was instrumented to determine the rate of preferential flow of water and transport of NO 3 −1 fertilizer in the unsaturated zone through a claypan soil using 15 N‐NO 3 −1 and Br‐1 tracers. The areal distribution of preferential flow paths was between 2 and 20% in the topsoil. Gravity lysimeter flow caused by preferential flow through the claypan was as much as 150 times greater than the estimated average rate of vertical recharge. As much as 2.4% of the volume of the soil below the clay pan may be occupied by preferential flow paths.

Ground Water↗
USGS1996

Movement of nitrate fertilizer to glacial till and runoff from a claypan soil

Although water from 20 to 25% of shallow farmstead wells in northern Missouri has concentrations of nitrate (NO3/-) exceeding 10 mg L-1 as nitrogen (N), many potential sources for this NO3/- are usually present. A field experiment was designed to trace and isolate the amount of a single application of N fertilizer lost to a glacial-till aquifer and runoff from a 400 m2 corn (Zea mays L.) plot with bromide (Br-) and isotopically labeled (15N) fertilizer. Soil at the plot is a Albaquic Hapludalf of the Adco Series containing a 61 cm claypan beneath 41 to 43 cm of topsoil. Groundwater levels ranged from 0.38 to 2.40 m below the land surface. Transport of water and NO3/- to the saturated zone was not substantially retarded by the claypan. Labeled-N fertilizer accounted for as much as 8.6 mg L-1 of the NO3/- (as N) in groundwater, but only in the top 1 to 2 m of the saturated zone. After two growing seasons (16 mo), <2% of the labeled-N fertilizer was lost to runoff, about 30% was in the saturated zone, 27.3% was removed with the grain, and about 5% remained in the unsaturated zone. A large part of the remaining labeled N may have been lost in gaseous N forms. The presence of labeled NO3/- only in the top 2 m of the aquifer, slow horizontal transport, and winter recharge indicate grass crops such as wheat (Triticum aestivum L.) or rye (Secale cereale L.) might be used to extract near- surface N during the winter recharge period. Also, fall fertilizations can be expected to readily leach. Because groundwater concentrations of labeled NO3/- were still increasing after two growing seasons, rotation of crops requiring small N inputs could be expected to limit the cumulative effect of large annual fertilizer applications on groundwater.

Journal of Environmental Quality↗