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Tuesday, January 3, 2017

What is the optimal irrigation depth?

Root growth and exploration of the soil volume is dependent on available

water and nutrients therefore irrigation depth strongly affects rooting depth.

The choice of irrigation depth is based on several factors. Woody plants have

as a rule deeper rooting system (0-100 cm) than annuals (0-60 cm). Plant

species differ in rooting pattern, some tend to be shallow rooting (i.e. pepper,

lawn) and others deeper (i.e. maize). Soil texture, aeration and the existence of

a hard pen have to be taken into account when choosing an optimal irrigation

depth. The top soil layer contains organic matter and it is rich in nutrients

compared to the deeper soil layers. Wherever water is readily available,

adopting a strategy of minimal soil depth irrigation is a good practice from the

standpoints of increasing irrigation efficiency and exploiting the top soil layer

rich in nutrients and aeration.

How much water can be saved by the Tevatronic controller?

In an olive irrigation experiment an extreme case of 75% water was saved. In a

lemon orchard 58% water was saved, as compared to the extension service

recommendations. In a tomato irrigation experiment we saved 24% water,

compared to the best irrigation practiced today, based on previous

experiments. A 30% saving of water, without loss of yield, and sometimes an

increase in yield, is a conservative estimate of the water that can be saved.

Does the Tevatronic system improves yield and how much?

With the Tevatronic irrigation system it is possible to achieve the optimal

balance between vegetative and reproductive growth for top yields. An

increase of 4%-8% yield was achieved in many cases as a result of the precise

irrigation that prevented stress or water-logging. Furthermore, the ability to

impose precise stress for any length of time at any stage of the plant growing

cycle is a powerful tool that can be exploited to increase yield beyond what we

have achieved so far.

What consequences have precise and reduced irrigation on fruit quality?

Precise irrigation is essential to achieve maximum fresh fruit size when there

are no other limiting factors (i.e. light, photosynthesis, nutrient availability).

Reduced irrigation to a level when water becomes a limiting factor, reduce

yield and affects fruit composition. Changes have been found in dry weight,

oil content, soluble solids, titratable acidity, pH, juice viscosity and vitamin C

of fruits grown under stress. Using precise tension control it is possible to

maximize water saving without yield loss and alternately compensate yield

reduction by enhanced quality to avoid financial loss.

Can we incorporate the Tevatronic controller in existing irrigation controllers of other companies?

The Tevatronic irrigation system use solenoid valves, water and fertilizer

counters and fertilizer pumps available on the market and may exist in

controllers of other companies. All other components are unique and specific

for the Tevatronic irrigation system.

What is the unique aspect of the tension controlled irrigation of Tevatronic compared to conventional and other tensiometer in use?

Tevatronic tension controlled irrigation is autonomous, due to the integration of hardware and software developed by the company and the adoption of an appropriate method of operation.
Traditional tensiometers are analogs. The incorporation of pressure transducers into tensiometers enabled digital output,
continuous readings, processing the data and taking advantage of up to date communication for viewing the data.
The technology to couple tension readings to solenoid valves to initiate irrigation is already known for several decades.
More recently the ability to terminate the irrigation when a pre-set tension is reached, at the position where the tensiometer is located, was also introduced.
The next step of development was missing until Tevatronic developed a propriety algorithm that control precisely irrigation depth, independent of the tensiometer location.
The control of irrigation depth enabled a revolutionary change in the method of operation that finally transformed the system to fully autonomous:
initiating and terminating the irrigation without human intervention using shallow monitoring of tension combined with irrigation to any desired depth.
The Tevatronic system does not rely on statistical averaging of root density and soil variability, as common in other tension controlled irrigation systems,
but actively eliminate the root density variability (shallow monitoring) and bypass the existing soil variability (irrigation depth control). 

Do we need to fit threshold tension to soil type (sand, light soil, heavy soil, soil-less media)?

- Yes we do. The question is why. Soil water tension is a measure of suction, it

is the force by which the soil particles bind water and quantitavely is

expressed in units of Paskal (i.e. kPa – kilo Paskal). The force is negative and

absolute and therefore it is independent of the soil type. A -30 kPa is the same

potential energy in sand, light or heavy soil types. It can be argued therefore

that the plant need to invest the same amount of energy to extract water from

all soil types and threshold tension does not have to be adjusted. However,

Soil texture varies in different soil types and volumetric water holding

capacity varies according to soil type. A 20% available volumetric water

content in sand has a much lower water tension (ca. -10 kPa) than a heavy soil

water tension (ca. -80 kPa). To supply the same amount of water needed for a

plant in sand as in heavy soil we need to maintain a lower water tension in