Autonomous Irrigation Practice

Isaac Klein (PhD)

Tevatronic Chief Scientist

Dr Isaac Klein is a graduate of the Faculty of Agriculture, The Hebrew University, Jerusalem, Israel (1961) and Michigan State University, Mich, USA (1969), followed by post doctorate in the University of Minnesota, Min, USA (1969-1971). During 1971-2002, until retirement, he researched irrigation and nutrition of fruit trees in the Volcani Center, Agricultural Research Organization (ARO) in Israel.

The main research interests of Dr. Klein included:

  • Irrigation of fruit trees.
  • Modeling for consumptive use, and deficit irrigation.
  • Irrigation methods, in relation to nutrient and water use efficiency.
  • Saline and recycled water utilization.

Nutrition of fruit trees:

  • Fertigation, nutrient distribution in the soil.
  • Nutrient supply and demand. Estimating requirement and correcting deficiencies.
  • Foliar fertilization.
  • Effect of nutrition on fruit quality, storage properties and physiological disorders.

Dr. Klein published more than 100 scientific research papers.

Lemon: A lemon orchard was irrigated in the Northern Negev region of Israel with the TevaSens controller in 2012. The irrigation coefficient, and the volume of water recommended by the Israel Extension Service, based on the Pan A evaporation data (a standard reference measure used for irrigation recommendation) in the region for 2012, served as a control for calculating the water saved by our system. The Autonomous irrigation with the TevaSens controller saved 58% water.

Avocado: A young avocado orchard of one ha was irrigated with a single Tevatronic controller for 2 years (25/4/2013 – 9/3/2015). An adjacent commercial one ha plot served as control. The Tevatronic control irrigation saved 25% water in 2013 and 34% water in 2014.

Banana: The Tevatronic irrigation system was installed in a commercial banana ranch near Haifa, Israel in 2013 for one year. Irrigation was maintained at 15 centibar threshold to a depth of 15 cm. Number of irrigations was proportional to the evapotranspiration. The Tevatronic system saved 26% water when the irrigation system in the ranch functioned properly.

Free_ornamental-peppers

Ornamental peppers: An irrigation experiment was carried out on a cultivar of ornamental peppers grown for the production of specialty cut flowers and marketed as a leaf-less shoot with a cluster of terminal fruits. The aim was to optimize commercial yield and water use efficiency. The irrigation experiment was carried out in Kfar Varburg, in the coastal plain of Southern Israel. The Tevatronic irrigation system was compared to a Rivulis Irrigation (John Deere Water / Plastro) Hydro PCND 12mm drip irrigation system and the commercial control used by the farmer. Threshold was maintained at 10 centibar until 11 days before harvest when it was changed to 20 centibar. Irrigation depth was 25 cm. A low volume application with the Tevatronic system saved 39% water and produced more shoots per plant. There were no differences between treatments in the marketable shoot length, the number of fruits per shoot and the terminal growth.

:תקציר
ייצור מכוון של תאנים במהלך כל השנה דורש הבנה מעמיקה יותר של דרישות ההשקיה
והדישון והשפעתם על איכויות הפרי והגבלת הצימוח הווגטטיבי. למרות הידע שפותח
בגידול תאנים, החלטות בנושאי השקיה (עיתוי וכמות) כיום הן בעיקרן אמפיריות. בשנים
האחרונות בחנו בקר השקיה אוטונומי בגידול תאנים במצע מנותק. גידול תאנים בנפח
מצומצם בכלים מחייב תשומת לב והקפדה יתירה על השקיה תכופה לשמירת הרטיבות
במצע. מקובל על כן להשקות ולדשן גידולי מצע מנותק בעודף רב תוך שימוש במחשבי
השקיה אוטומטיים ודישון רציף. במסגרת עבודה זו בחנו לראשונה בקר השקיה המכיל
בתוכו טנסיומטר, פותח ברז השקיה הידראולי כשמתח המים בקרקע מגיע לסף הרצוי ( 0
עד מינוס 50 סנטיבר) וסוגר את הברז לאחר זמן מובנה, לבקרת עומק ההרטבה. הבקר
מודד את מתח המים בקרקע ברציפות, אוגר את הנתונים לצורך הורדה למחשב נייד
ומציגם גרפית. בעקבות התפתחות שורשים בסביבת הבקר ניתן להבין שהצמח הוא הגורם
הבלעדי שקובע את עיתוי ומשך ההשקיה, ללא התערבות החקלאי.

AFigs

The Practice

It is a formidable task to achieve optimal irrigation of a plant for best performance. Decisions has to be taken by the grower as to when and how much water to apply. The lack of accurate information and guidance to make the right decision regarding timing and volume of water to apply cause more often than not under or over irrigation.

Ideal_Control_From_Orig_TEV_WSite

Under-Irrigation

The damage we create in an extreme case of under-irrigation is readily distinguishable: leaves curl in mid-day and scorch, flowers and fruits drop, growth stops and eventually the plant dies. In a more subtle case of under-irrigation the symptoms are not readily obvious and even a professional grower often fails to diagnose the damage to his crop.

Over-Irrigation

There is a tendency by farmers to over-irrigate when water is readily available. The practice stems from uncertainty of the exact irrigation need. To be on the safe side the farmer prefers to irrigate more than less. Over-irrigation waste water and fertilizers contaminate the ground water and is harmful to plants. The damage is caused by lack of aeration in the root system and root rot in severe cases. The damage to the plant may not be detected in sandy soils where leaching is not a problem. In heavy soils and in soils with a hard pan over-irrigation is more likely to cause damage. The damage is rarely noticeable even in heavy soils, unless over-irrigation is extreme.

irrigation-practices_From_Orig_TEV_WSite

The Agro Metrology Approach

In this approach the evaporation from the plant surface is equated to the evaporation from an open body of water, with appropriate adjustments. Evaporation from an open body of water is affected mainly by an energy balance and wind conditions. The adjustment for the plant takes into account an empirical coefficient (Kc value) since the leaf during development. The soil area coverage (Leaf area) is very difficult to measure and usually is only estimated for approximation. In practice, metrological stations measure the environmental variables for a large geographical area and calculate the potential evaporation (using the Penman Monteith equation). Alternately, the farmer can measure potential evaporation locally in his farm using a Pan A device (1.8 m diameter open water container) with an appropriate coefficient. The agro-metrology approach neglects any measure of soil water content or the plant condition.

Soil Based Systems

Soil based systems used for controlling irrigation rely on water content or soil water tension measures. The soil is the reservoir of water for plant growth and the idea is to maintain the reservoir filled. Scientists use Neutron Scattering (NS) or Time Domain Reflectometry (TDR) measurement for absolute determination of soil water content. Neutron Scattering measure a limited volume of the soil, it is expensive, emits radiation and not applicable for everyday use by a farmer. Several companies are marketing soil probes for soil water measurement. Some of these probes are based on TDR. Soil probes are affected by soil temperature and soil salinity, in addition of measuring only a limited soil volume. Soil water tension measurements use tensiometers. To obtain a usable value of the soil water tension the farmer has to install tensiometers in several locations at 2-3 depths. The tensiometer indicates only when to irrigate. The volume of water is applied by trial and error. Tensiometers used in the past analogue gauges and tension was observed once a day. Today digital tensiometers are available with continuous reading, averaging and plotting the data and downloading to servers. Electro-tensiometer that opens an irrigation valve is available today. The electro-tensiometer does not know when to close the valve, therefore two of them are used in conjunction at two soil depth: one opens and the other close the valve when water lower the tension in the upper soil layer. Water movement from the soil through the plant to the atmosphere is based on water tension difference: water moves from a point of negative tension to where the tension is less negative. Tensiometry is therefore the most logic and valid method to be used in irrigation control. Nevertheless, it is used only to a very limited extent by the farmers for several reasons: a. the need to average several (4-10) units to characterize the soil, which makes it rather expensive. B. The tensiometer indicates when but not how much to irrigate. The farmer does not know where are the plant roots, what is the soil water content at any given time and he has to use trial and error for determining how much water to irrigate. All soil based system neglect the plant itself.

Plant Based Systems

Plant physiologists are looking for plant indicators to determine when to irrigate. Some valid plant indicators were shown to be in correlation with plant performance (stomatal conductance, photosynthesis, plant growth, fruit size, yield, etc.). Mid-day stem water potential, using the Scholander (pressure) bomb, is used mainly in research with an attempt to expand its use in practice (by offering service to the farmer). This technique is destructive, require calibration, affected by environmental conditions, guides the farmer only vaguely and not in real time (once a week measurements) and does not lend itself to automation. Dendrometry, used with woody plants is an alternate system. The stem of trees contracts during the day and expands back at night when stomates are closed and soil water is available. Dendrometers can be automated, but require calibration and it’s use could not be commercialized. In addition, dendrometers cannot be used with herbaceous plants. In recent years the measurement of leaf thickness was introduced in an attempt to measure plant water shortage. Like stems, leaf thickness is reduced in water shortage. However, leaf thickness is oscillating during the day, because of stomatal closure to prevent stress and dehydration, and the change has to be followed for several days and calibrated. Infrared thermometry is explored today for irrigation control. Water shortage causes the plant to close its stomata causing a rise in leaf temperature. Aerial infrared photography can point to water shortage and the need for irrigation but this technique also require calibration and its use is not practical today. The disadvantage of existing plant-based systems is the neglect of the soil and the need to apply water by trial and error.

The Ideal Control Is Here

Precision irrigation requires measurement of several parameters (crop coefficient, leaf area, soil water content, soil surface evaporation, drainage, and environmental conditions) in order to schedule the irrigation and determine the volume of water required in each application. The measurements are complicated and cannot be carried out by an ordinary plant grower (farmer, home owner of a garden, etc.) The demand for water by the plant is changing constantly (daily and seasonally), which makes it impossible to make correct irrigation decisions in real time. Consequently, in spite of the best guidelines that scientific research can offer to the plant grower today, the irrigation in daily practice is basically an empirical endeavour and approximate at best. Only the transfer of the irrigation control to the plant itself can achieve the perfect solution for precision irrigation. We define such a control as Autonomous Irrigation, contrary to Automatic Irrigation (by computers). Can this be achieved? Can it be practical? Tevatronic LTD Company proved it possible, by integrating technology (hardware), software and method of application.

Perfect Irrigation Every Time

The autonomous irrigation transfer the control to the plant. The farmer is no longer has to take decisions as to when and how much to irrigate, thus avoiding erroneous decisions. Not only we are able to sense the plant and the soil water status simultaneously, but also we can precisely irrigate to a specific depth into the soil, such that only the root system of the plant is irrigated. This eliminates waste of water to the depth, reduces the environmental impact of agriculture, reduces the amount of resources to grow the crop, while enhancing its productivity. It is an amazing solution here to revolutionize the entire irrigation system.