Premium
Testing the precision of a weighable gravitation lysimeter
Author(s) -
Xiao Huijie,
Meissner Ralph,
Seeger Juliane,
Rupp Holger,
Borg Heinz
Publication year - 2009
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200800084
Subject(s) - lysimeter , collar , casing , debris , environmental science , soil science , geotechnical engineering , geology , meteorology , physics , soil water , structural engineering , engineering , petroleum engineering
Tests were carried out to determine the weighing precision of a 2 m deep lysimeter with a 1 m² cross‐sectional area and a total mass of 3500 to 3850 kg, depending on the soil water content. The weighing mechanism consists on three shear‐stress cells laid out for a load capacity of 1320 kg each. Mass changes as small as 20 g, which is equivalent here to a water gain or loss of 0.02 mm, can be measured with good accuracy and stability under favorable environmental conditions (low wind speed, relatively constant temperature). This precision does not depend on the position on the lysimeter where the mass change occurs and is as good as the best values reported in the literature for other lysimeters. To prevent water and debris from entering the cleavage between lysimeter vessel and pit casing, a rubber collar can be placed across the cleavage. It is attached to the casing and extends about 1–2 cm into the vessel. Although the collar is not supposed to touch the vessel, it does at a few points. This seriously lowers weighing precision, because this contact exerts forces on the vessel, which distort the true weight. Hence, one should refrain from using this type of collar and develop another one. Weighing precision decreases with increasing wind speed, because wind exerts forces on the lysimeter vessel and can thus alter its apparent weight. It is temperature‐dependent, too.