A lysimeter is a measuring device that can measure plants’ actual evapotranspiration by recording the amount of rainfall that an area receives and the amount lost through the soil. Vessels for lysimeters are usually located at a special lysimetric station with access for functional inspection and for placing measurement, control, and weighing devices. In most cases, an expensive concrete or steel basement is used for such a station. A polyethylene (PE-HD) lysimeter station in a container has been developed to reduce cost and ensure mobility. Variations in the number and location of lysimeters are possible (usually one or two lysimeters in a container).
Lysimeters are primarily devices, usually reservoirs or containers, that define a specific boundary for soil water retention and measure either the balance of soil and water or the volume of water percolating vertically, as well as its quality. Lysimeters are also related to percolation lysimeters (they are called drainage lysimeters) and weight lysimeters. Both can serve the purpose of determining the soil-water balance, vertical percolation flow (drainage), and the chemical composition of the infiltrated water. Percolation lysimeters can be installed to detect vertical soil-water flow (drainage) or chemical movement. in the soil at a certain border. Soil aqueous solution sampling lysimeters have small holes in them.
It is used to take out the soil’s water by vacuum, and they have an allowance for good sampling (i.e., the water table). Percolation and weighing lysimeters have some differences in measurement methods for telling us vegetation water consumption and soil water evaporation. Percolation lysimeters should be used with the method of measuring the water soil. Weighing lysimeters allows you to determine the mass or volumetric change in the soil’s water content by weighing the lysimeter and determining the change in its mass over time. Thus, weighing the lysimeters can determine the “net” infiltration from rain or irrigation and the amount of evaporation between humidification events. Properly designed, weighing lysimeters can simultaneously measure drainage rate as well as evaporation rate. The accuracy of the evaporation water balance analysis using a percolation lysimeter is directly related to measuring water in the soil and its integration in the root zone of vegetation. The accuracy of a weighing lysimeter depends on many factors: balance resolution, equilibration, and area-to-volume ratio.
A new “microlysimeter” method for assessing soil evaporation involves pushing a 76 mm thin-walled cylinder into the field soil, removing the soil-filled cylinder from the field, and closing the bottom to make it waterproof, determining the mass of the microlysimeter, replacing it in the field with its upper surface even with the surrounding soil, leaving it in ambient conditions for a certain period (usually one day) and re-determining its mass. Deviations are quantified by comparing short micro lysimeters with effectively “infinitely long” ones. The deflection is influenced by the time during which the microlysimeter is exposed to environmental conditions and the length of the soil sample. For silty clay loam under evaporation conditions from 2 to 9 mm/day, the measurement error for micro lysimeters with a length of 70 mm turns out to be <0.5 mm for 1 or 2 days whether the initial state of the soil is equal. “Wet” or “dry” respectively (0.26 or 0.13 g H2O per gram of dry soil in the top 20 mm).
Therefore, for many applications, this method is valid for 1 or 2 days. Correction equations for deviations up to 0.5 mm are given. This method requires little equipment and makes it possible to measure evaporation in some conditions (for example, in many areas or areas of partial shade of crops) when micrometeorological methods, water balance methods, and traditional lysimetric methods are impractical or impossible.
Lysimeter Working principle
A sampling lysimeter, also known as a pore water sampler, is a device for sampling moisture from the soil. Moisture is transferred from the soil through a porous ceramic cup to a container for collection. The movement of water is due to the vacuum created by the ceramic cup. The sample is then sent to a laboratory for further chemical analysis. There are many types of sampling lysimeters depending on whether you want to sample a solution close to the surface, deep in the profile, or use unique chemicals. The sampling lysimeter is used in continuous monitoring applications such as testing under tailings dams, under crops, or even laboratory experiments with soil columns. A lysimeter with a soil moisture sensor provides for installing one or more sensors for the volumetric water content in the soil profile. The number of sensors depends on the depth of the soil and how moisture penetration is to be monitored.
The lysimeter’s design was simple, consisting mainly of an inner reservoir, an external reservoir, and strain gauges. The cost of each lysimeter was approximately US $ 1,700, excluding construction labor costs.