Autonomous Irrigation
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Monday, March 6, 2017
How does the Tevatronic system handles fertilizer application?
Fertilizer
is applied by the Tevatronic system as in other systems, by continuous
fertigation, injecting diluted liquid fertilizer using fertilizer pumps
Traditionally tensiometer use requires usually averaging of several locations. How can the use of a single tensiometer overcome the variability in the field?
Traditionally tensiometers are positioned in 2-3 depths at several locations to obtain a statistically average value of tension because of soil and root density variability.
Tevetronic eliminate these variability, therefore it can use a single controllers. How the variability is eliminated?
a. By positioning the tension control at a shallow soil layer close to the dripper (15 cm deep, up to 15 cm from a dripper) where a dense root system exist.
We exploit the existing dense root layer and actively developing and maintaining it.
b. By controlling precisely irrigation depth.
The Tevatronic company developed the mathematical algorithm to irrigate precisely any soil depth while monitoring the tension at a shallow soil position.
When we aim to develop the root system at certain depth by precise irrigation and water percolate somewhat bellow (because of soil variability), it is not lost because the root system adjust and grow after the water. Soil variability is not eliminated but adjusting the soil layer to be explored by the root system and precisely irrigating that layer accommodate it.
Can precise irrigation without leaching cause salinity?
It is
customary to maintain a leaching fraction to avoid salinity. In the Tevatronic system increasing
irrigation depth is equivalent to a leaching fraction.
An alternate approach is to irrigate precisely and apply
periodically an extra volume of water for leaching, when needed. Precise irrigation reduces salt and
fertilizer input and periodical leaching can be as efficient as continuous
leaching while wasting less water. Pepper was successfully irrigated with
2.8-3.5 dSm water
What is the maximal area that can be irrigated with a single controller?
A single controller normally irrigates a size of a field covered by a single valve.
In practice there are various consideration that dictates what actually is the
size of a plot that is controlled by a single valve: technical consideration can
limit the size of a plot (i.e. rate of water delivery), topography limitation and
uniformity of soil and plant size. Where there are no limitations on plot size, a
single controller/valve can irrigate as much as 20 ha.
In practice there are various consideration that dictates what actually is the
size of a plot that is controlled by a single valve: technical consideration can
limit the size of a plot (i.e. rate of water delivery), topography limitation and
uniformity of soil and plant size. Where there are no limitations on plot size, a
single controller/valve can irrigate as much as 20 ha.
How does the Tevatronic controller handles sequential irrigation?
The valve switch controller is programed to open a single valve at any time.
The first sensor to reach the threshold tension starts the sequence. Other
sensors will wait their turn. The sequential order is not fixed, it depends on the
soil water tension of the various sensors at any moment.
The first sensor to reach the threshold tension starts the sequence. Other
sensors will wait their turn. The sequential order is not fixed, it depends on the
soil water tension of the various sensors at any moment.
Why tension controlled irrigation is preferable to other soil sensor controllers?
Soil sensor probes are relatively cheap, require minimum maintenance and can
be automated for feedback irrigation but they have to be calibrated for water
content. Calibration is specific for the substrate (soil type, soil-less media) and
some of them are affected by temperature and salinity. In contrast, soil water
tension does not require calibration and it is not affected by salinity and
temperature. Furthermore, the water movement in the soil-plant- atmosphere
continuum is governed by tension difference. Soil water tension, plant water
tension and plant photosynthesis are directly related. Soil water tension is
therefore a direct measurement of plant performance, contrary to indirect
measurements by other soil sensor.
be automated for feedback irrigation but they have to be calibrated for water
content. Calibration is specific for the substrate (soil type, soil-less media) and
some of them are affected by temperature and salinity. In contrast, soil water
tension does not require calibration and it is not affected by salinity and
temperature. Furthermore, the water movement in the soil-plant- atmosphere
continuum is governed by tension difference. Soil water tension, plant water
tension and plant photosynthesis are directly related. Soil water tension is
therefore a direct measurement of plant performance, contrary to indirect
measurements by other soil sensor.
Do we need to fit threshold tension to plant and cultivar (vegetable, fruit trees, flowers, turf)?
Very likely yes because of the hydraulic resistance to water flow in
transpiration. More research is needed to evaluate the quantitative aspects of
the relation between hydraulic resistance and water potential in various plant
species. Water flows trough the plant in xylem vessels. The hydraulic
resistance is dependent on the anatomy of xylem vessels and the length for
water transport that are different in various plants. The higher the hydraulic
resistance a lower water tension is required to enable sufficient transpiration
and stomatal opening for photosynthesis.
transpiration. More research is needed to evaluate the quantitative aspects of
the relation between hydraulic resistance and water potential in various plant
species. Water flows trough the plant in xylem vessels. The hydraulic
resistance is dependent on the anatomy of xylem vessels and the length for
water transport that are different in various plants. The higher the hydraulic
resistance a lower water tension is required to enable sufficient transpiration
and stomatal opening for photosynthesis.
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