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The relation of dissolved oxygen, soluble carbon, and redox potential to the movement of nitrate in soil columns and into submerged tile lines was studied. Columns 300 cm long were drained at depths of 180, 240, or 300 cm with the water table in all columns maintained at 175 cm. After adding ammonium nitrate and irrigating, the peak in nitrate concentration moved downward to the 160‐cm depth, but nitrate concentrations decreased at 180 cm and almost disappeared at the 240‐ and 300‐cm depths. The soil solution at 180 cm contained an average of 5.2 ppm nitrate‐nitrogen and a maximum of 16 ppm. In contrast the soil solution at 240 or 300 cm, which had passed through a submerged zone of 65 or 125 cm, averaged 0.5 ppm and had a maximum concentration of 1.1 ppm. Disappearance of nitrate was associated with decreases in redox potential, oxygen content of the soil solution and oxygen levels in the soil atmosphere, and with increases in soluble iron and manganese. Denitrification occurred without submergence if the soil redox potential was sufficiently low. Results of this experiment indicate that nitrate concentrations probably can be reduced in tile effluents by submerging the tile lines.

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A lysimeter system is described which consists of four continuously weighing lysimeters mounted on a portable platform. The lysimeters, made from low pressure PVC irrigation pipe (1.18 m deep by 0.31 m dia), are placed on a hydraulic weighing system that consists of either a water-tilled rubber pillow or an automotive innertube connected to a water column. The sensitivity of the weighing system is 0.1 kg or an equivalent water depth of 1.4 mm. One bar ceramic cups, placed in the center of the lysimeters at 0.25, 0.50 and 0.75 m from the soil surface, are connected to the outside for soil solution sampling. Eight small bolts symmetrically located around the lysimeter at the same depths as the ceramic cups, serve as "four probe" contacts for electrical conductivity measurements. The cost of each set of four lysimeters in 1978 was about $400.

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