Articles
CHANGING OF PLANT GROWTH BY TENSIOMETER CONTROLLED IRRIGATION
Article number
450_50
Pages
405 – 412
Language
Abstract
In experiments with potted herbs, tomato and cucumber seedlings, the parameters for automatic irrigation in an ebb and flood system such as soil moisture tension and damming time were combined for control measures.
Reduced soil moisture caused a reduction of growth, whereby the average tension over the whole growing period – not the highest measured tension – being the point of strongest influence on growth.
With damming systems it turned out that a water consumption reduction could be reached only by raising the control tension, but not by shortening the damming periods.
The growing medium has to get completely wet with every irrigation event to achieve uniform growth.
When the irrigation is controlled by a higher tension, the damming time has eventually to be extended as well.
When using moisture tension for irrigation control, it has to be considered that tension and time are changing exponentially and not linear during moisture reduction.
A moisture reduction in soil and substrate from 0 to 100 hPa requires much more time than for example moisture reduction from 400 to 500 hPa.
Correspondingly, such high tensions are of relatively short duration within an irrigation cycle and is suitable to control watering.
The water holding capacity and the volume of a soil as well as temperature have an influence on the time and tension relationship, so that every substrate has a specific dry-off and moistening behavior.
A drying soil contracts diminishing the contact between substrate and tensiometer become looser.
Because the irrigation control by tensiometers is based on this contact, the tensiometers should be washed in with ground quartz sand.
Reduced soil moisture caused a reduction of growth, whereby the average tension over the whole growing period – not the highest measured tension – being the point of strongest influence on growth.
With damming systems it turned out that a water consumption reduction could be reached only by raising the control tension, but not by shortening the damming periods.
The growing medium has to get completely wet with every irrigation event to achieve uniform growth.
When the irrigation is controlled by a higher tension, the damming time has eventually to be extended as well.
When using moisture tension for irrigation control, it has to be considered that tension and time are changing exponentially and not linear during moisture reduction.
A moisture reduction in soil and substrate from 0 to 100 hPa requires much more time than for example moisture reduction from 400 to 500 hPa.
Correspondingly, such high tensions are of relatively short duration within an irrigation cycle and is suitable to control watering.
The water holding capacity and the volume of a soil as well as temperature have an influence on the time and tension relationship, so that every substrate has a specific dry-off and moistening behavior.
A drying soil contracts diminishing the contact between substrate and tensiometer become looser.
Because the irrigation control by tensiometers is based on this contact, the tensiometers should be washed in with ground quartz sand.
Authors
K. Kell, M. Beck, F.W. Frenz
Keywords
Irrigation, tensiometer, plant growth, ebb- and flood system
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