OPTIMIZATION OF DRAINAGE LYSIMETER DESIGN FOR FIELD DETERMINATION OF NUTRIENT LOADS

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  • 1 Horticultural Sciences Department, University of Florida. 1241 Fifield Hall, P.O. Box 110690, Gainesville, FL 32611

Collecting leachate from lysimeters installed in the field below vegetable fields may be used to quantify the amount of nitrogen released into the environment. Because limited information exists on the optimal design type and on the effect of design components on lysimeter performance, the objective of this study were to identify existing designs and their limits, assess cost of design, and test selected designs. Ideally, lysimeters should be wide enough to collect all the water draining, long enough to reflect the plant-to-plant variability, durable enough to resist degradation, deep enough to allow for cultural practices and prevent root intrusion, have a simple design, be made of widely available materials, and be cost-effective. Also, lysimeters should not restrict gravity flow thereby resulting in a perched water table. Previous study done with a group of free-drainage lysimeters (1-m-long, 45-cm-wide, installed 45-cm-deep) under a tomato-pumpkin-rye cropping sequence resulted in variable frequency of collection and volume of leachate collected (CV of load = 170%). Improving existing design may be done by increasing the length of collection, lining the lysimeter with gravel, limiting the depth of installation, and/or breaking water tension with a fiberglass wick. Individual lysimeter cost was estimated between $56 to $84 and required 9 to 14 manhours. for construction and installation. Costs on labor may be reduced when large numbers of lysimeters are built. Labor needed for sampling 24 lysimeters was 8 man-hr/sampling date. Because load may occur after a crop, lysimeter monitoring and sampling should be done year round.

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