Author
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Schmidt, John |
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LIN, H - PENN STATE UNIV |
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Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/3/2006 Publication Date: 1/15/2008 Citation: Schmidt, J.P., Lin, H. 2008. Water and bromide recovery in wick and pan lysimeters under conventional and zero tillage. Communications in Soil Science and Plant Analysis. 39:108-123. Interpretive Summary: Solute transport through soils and the landscape is difficult to quantify; yet, management decisions are developed and selected based on results from sampling devices that have inherent biases. The objective of this study was to evaluate water and bromide movement in no-tilled (NT) and conventionally tilled (CT) corn using two different types of in situ lysimeters - pan and capillary wick, for single rainfall events. Bromide applied on the soil surface or with the initial 25 to 27 mm of irrigation was used as a tracer in evaluating the performance of zero-tension pan and capillary wick lysimeters, under NT and CT, for a single rainfall event. After drainage began and until irrigation was discontinued, the water drainage rate was, on average, greater in NT (7.2 mm per h) than in CT (5.6 mm per h) based on results from the pan lysimeters. By contrast, the water drainage rate for the wick lysimeters was, on average, greater in CT (7.3 mm per h) than in NT (3.0 mm per h). The wick lysimeter appears to have behaved as a sink under the CT conditions, while greater discharge observed with the pan lysimeter under NT implicates drainage from larger channels. This study illustrates, that contrary to the conventional understanding about preferential flow in NT, water flow and Br transport to the 1.2-m depth was as great as or greater with CT than with NT based on results from the wick lysimeter for single rainfall events. Technical Abstract: Quantifying in situ solute transport through soils and the landscape has been widely acknowledged as important and yet challenging. The objective of this study was to evaluate water and bromide movement in no-tilled (NT) and conventionally tilled (CT) corn using two different types of in situ lysimeters - pan and capillary wick, for single rainfall events. Four zero-tension pan and four capillary wick lysimeters were installed at the 1.2-m depth on opposite sides of four soil pits. Two were under NT and two were under CT corn. Bromide was either surface applied or applied with an initial 25 to 27 mm of irrigation (33 to 34 g Br per m2). A total of 120 to 147 mm of irrigation was applied continuously at 8.8 mm per h. Leachate was collected on 15-min. intervals for 24 h and on greater intervals for up to 350 h. Lysimeter discharge and Br concentration were determined for each interval. After drainage began and until rainfall was discontinued, the water drainage rate was, on average, greater in NT (7.2 mm per h) than in CT (5.6 mm per h) based on results from the pan lysimeters. By contrast, the water drainage rate for the wick lysimeters was, on average, greater in CT (7.3 mm per h) than in NT (3.0 mm per h). The wick lysimeter appears to have behaved as a sink under the CT conditions, likely representing water flow in smaller channels. Under NT conditions, greater discharge observed with the pan lysimeter implicates the response from larger channels as the conduit for water flow. Flow-weighted mean Br concentration was less when Br was applied on the soil surface (17.9 mg per L) than when Br was applied with the irrigation water (50.6 mg per L). Implications from preferential flow studies are often determined based on a single method of evaluation for solute transport, which are likely subject to the limitation of the method used. This study illustrates, that contrary to the conventional understanding about preferential flow in NT, water flow and Br transport to the 1.2-m depth was as great as or greater with CT than with NT based on the results from the wick lysimeters for single rainfall events. |
