DESIGN, INSTALLATION, AND PERFORMANCE OF PERCOLATION LYSIMETERS FOR WATER-QUALITY SAMPLING

Lysimeters are the primary research tool for measuring percolation and water quality. Monolithic percolation lysimeters were evaluated for m easuring the quantity and quality of leachate from the root zone of ir rigated crops. Six percolation lysimeters were installed in a continuo us corn (Zea Mays, L.) cropping system near North Platte, Nebraska, du ring the fall of 1988 and spring 1989. The lysimeters were 0.9 m in di ameter and 2.4 m deep. They were filled with undisturbed soil using a hydraulic pull-down method. Porous stainless steel extractors were ins talled vertically upward into the lysimeter bottoms, and leachate was extracted from the unsaturated soil. Leachate volume, volumetric soil water content, soil temperature, and soil bulk density were measured. Isolation of a large soil monolith in the lysimeter did not significan tly affect plant growth, soil bulk density, or temperature. Soil water content near the lysimeter bottoms was greater than in the surroundin g field after a wet spring in 1991. However, extractors removed most e xcess water and adequately matched unsaturated drainage in the field. Though leachate varied among lysimeters, they behaved similarly over t ime. Results will help relate irrigation management and scheduling str ategies to potential leaching of soil water and associated chemicals i nto groundwater.