GB2470909A - Irrigation control system having a variable height electrode - Google Patents

Abstract

An irrigation control system for determining the amount of irrigation water supply in soil-less cultures or hydroponics, comprises an accumulator10for sampling drainage from a lysimeter. The accumulator10includes two electrodes50,40, one of which is adjustable40in height, the other being static50, an openable lid30, at least one upper aperture80, a lower side aperture100and a lowest drain aperture110. The system also comprises a main irrigation valve, a stop irrigation circuit and an irrigation control centre (ICC). Drainage water enters the accumulator10via the upper aperture80, when the electrodes40,50are short-circuited by rising drainage water, irrigation stops by the stop irrigation circuit sending a message to the ICC to shut the main valve. An irrigation control centre controls the irrigation valves and collects information from the accumulator. One of the electrodes is shiftable, facilitating determining the amount of drainage water that shuts off the irrigation.

Description

METHOD AND APPARATUS FOR IRRIGATING PLANTS

FIELD OF THE INVENTION

The present invention relates to agriculture, in particular to a method and apparatus for controlling the irrigation of plants grown in soil-less cultures.

BACKGROUND OF THE INVENTION

Operation of soil-less culture systems is knowledge based, but also requires the implementation of experience of the grower, typically acquired by trial and error. In such systems, the irrigation water is provided according to the predicted usage of water by the plants. A grower intending to grow plants on soil-less culture system needs to gain knowledge about the local parameters which affect the plants needs with respect to irrigation. Of these parameters some are climatic or microclimatic, notably: temperature variability, extremes and averages around the year, humidity, diurnal and annual radiation distribution and light hours duration. Other parameters are such that relate to the growth medium: type of growth and plant substrate media, the substrates physical structure, chemical characteristics and substrate volume per plant. Yet other parameter relates to the crop: species and variety, plant age and canopy density, number of plant per square meter. Other parameters relate to the irrigation water are salinity, pH, and major soluble ion species. Structural characteristics of the construction in which the crop is maintained, contribute to the micro-climatic conditions in which the plants grow, temperature extremes, temperature variability, radiation intensity, humidity are some important factors determining the success of the crop. Variability of micro climatic conditions within the area in which the crop is grown may be considerable, and the individual plants may require different response such localized irrigation scheme.

In view of the above number and complexity of parameters, understanding and supplying the plants requires of water and fertilizers are based on estimations. Carrying out the grower's planning and calculating, resulting in various alternative irrigation schemes, associated with numerous experiments. Implementing less than optimal irrigation schemes, can possibly result in less than optimal yield, or damage to the crop leading to financial loss.

Today, for successfully applying irrigation and fertilization control systems to soil-less culture one has to rely on data collected from ongoing irrigation and retaining such data for future use. The collected data are taken from records of the irrigation and fertilization control systems, and typically include onset and ending time of irrigating, irrigated area, irrigation system plan, water capacity of the growth media, amount of water used and amount of fertilizer used. Some of this data is made available to the grower only at the end of the irrigation cycle. The sampling of water from the lysimeters is typically made at a limited number of sampling points, due to limitation of manpower and by manual means.

In view of the data collected, the grower makes an assessment of changes in the upcoming irrigation cycles, but does not intervene in the on-going irrigation cycle. The subsequent irrigation cycles include parameters such as the amount of water, the amount of fertilizer and time intervals between irrigation cycles. During the on-going irrigation cycle, the ability of the grower to perform major changes, in case of a noticeable irregular event, is reserved to manual intervention (typically only relates to interruption, total shut down, or renewal of the irrigation).

SUMMARY OF THE PRESENT INVENTION

According to one aspect, the present invention, an apparatus for collecting drainage water from a lysimeter tray of soil less culture is provided.

A narrow bottom accumulator for drainage from soil less culture, has an openable lid into which are inserted two electrodes, one of which is static and the other is of variable height; a pH sensor for measuring pH of the drainage water; EC (electrical conductivity) sensor for measuring conductivity of the drainage water. An uppermost drain pipe proves drainage to the accumulator from the lysimeter, an upper side drain pipe is an alternative entrance port to irrigation drain. In the accumulator, a lower side drain aperture enables also sampling by taking samples of the drainage from the accumulator. A bottom -most aperture from which accumulated water can be evacuated entirely. The apparatus further comprises one electrode positionable at different heights within the accumulator for providing a limitation for the amount of drainage water volume. The drainage volume indication of limit is used to control the amount of irrigation provided to the plants.

According to another aspect, the present invention relates to a method for controlling irrigation in soil-less culture as determined by the actual consumption of water by the plants.

The present invention provides a foundation for an irrigation system in which the crop itself, in a soil -less culture, determines the amount of water dispensed in an irrigation cycle and affects the amount of water dispensed in the subsequent irrigation cycle. In the accumulator, the drainage water efflux from the root medium is summed up and the electronic system sends an indication to the control unit when to stop the irrigation. The logic behind this concept is that for a given amount of water dispensed to the crop, a cetain amount is lost to the drainage, and a certain, much larger amount is taken up by the plants. Some of the amount taken by the plants remain in the plants but most evaporates to the atmosphere. The total amount of evaporation (often referred to as evapotranspiration) dictates to a large degree the amount of water that the crop requires. This amount is a function of many factors, some physical, some climatic and microclimatic and some physiologic, cultural and phenological etc. The irrigation system featuring the present invention allows that the grower sets an estimated minimal irrigation volume for the plants, for each irrigation cycle from which the drainage percentage is calculated, but does not require a direct intervention of the grower in setting the limit to the irrigation water actually required by the plant. Moreover, changing conditions are translated automatically by the system of the invention to a correlated water volume to be dispensed. For example for specific irrigation cycle, a rise in temperature to and irradiation may cause an increase in evapotranspiration. This increase causes a parallel decrease in drainage water efflux. The accumulated amount of drainage water in the accumulator will require more time to indicate the control system to stop irrigation. If on the other hand, the temperature and irradiation decrease, less of the irrigation water will be diverted to evapotranspiration and the accumulator will receive more rapidly the amount of water that will set off the termination of irrigation.

The present invention promotes the irrigation principle according to which a variety of parameters such as climate, micro-climate, growing media and plant type are integrated into a simple mechanism which controls the amount of water dispensed to the crop and the intervals between irrigation cycles, automatically by the plant itself.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the following drawings, in which: Fig. 1 is a sectional view of an apparatus for irrigating plants, according to an embodiment of the present invention; Figs. 2A-2C are isometric views of the apparatus of Fig. 1, connected to a lysimeter of a soil less culture; and Fig. 2D is an isometric view of the apparatus of Fig. 1, connected to a tank of a hydroponic system.

Fig. 3 is a block diagram describing schematically the functional connections between the irrigation control center and the irrigation system affecting the control methods of the invention.

Fig. 4A is a flow chart describing the steps carried out in an irrigation cycle demonstrating the method of the invention; Fig. 4B is a flow chart describing the steps carried out in an irrigation cycle that alter the interval to the next irrigation cycle.

The following detailed description of the invention refers to the accompanying drawings referred to above. Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The principles and operation of the apparatus and a method for its use according to the present invention may be better understood with reference

to the drawings and accompanying description.

Fig. 1 depicts an exemplary apparatus in accordance with an embodiment of the present invention comprising a drainage water accumulator that includes: an openable lid 30 having five apertures, electrodes 40 and 50, a pH sensor 60, an EC sensor 70, an uppermost drain aperture 80, a upper side drain aperture 90, a lower side drain aperture 100, and a lowest drain aperture 110 onto which an optional bottom drain pipe 120 is connectable.

Drainage water narrow bottom accumulator 10 referred to hereinafter as accumulator, is suitable for collecting drainage, in accordance with the present invention. Due to the internally slanting walls of the accumulator, even small amount of drainage water occupy a large column of water in the bottom part of the accumulator making it available to the electrode and sensors positioned within the accumulator. In addition, the drainage water when discharged from the bottom drainage aperture, evacuates the accumulator entirely, and quickly disengages the sensors. Openable lid 30 is placed on top of accumulator 10, allowing access to the inside of accumulator 10 for maintenance. Typically, five apertures are distributed across the surface of lid 30 wherethrough electrodes 40 and 50, pH sensor 60, EC sensor 70, are insertable. Into drain aperture 80 a drain pipe is insertable. The height of electrode 40 is adjustable, so that its bottom can assume different levels with respect to electrode 50, within accumulator 10. Variable height electrode 40 can be manually or mechanically/electrically moved up and down, typically by shifter 85 housed on the lid, typically utilizing electric power to position electrode 40 in the height determined by the system as will be described later on. The height of the electrode can be altered manually by employing an adjustable screw with a securing capability, for changing the height and stabilizing it relative to accumulator 10. Whether operated manually or electrically, the actual height is determined by the irrigation control center as will be explained later on. In order to monitor the height of the variable height electrode 40, visible markings are typically inscribed on the side of the electrode, preferably correlating the change in height with the volume of water within the accumulator. However, in some embodiments, both electrodes are variable in height. The accumulator in accordance with the present invention, may assume any shape complying with the definition of internally slanted or converging walls, for example the shape depicted in Fig. 1, an inverted pyramid, a spheroid, an inverted cone or any symmetrical or non symmetrical containers in which water will accumulate at a single lowest point, as forced by gravity.

In some embodiments of the present invention only the variable height electrode is threaded through a solitary aperture of the lid of the accumulator. The static electrode may be made as a part of the accumulator or protrude from it to inside the lumen, for example horizontally, but must be kept in touch with the water accumulated in the accumulator, preferably at the bottom part.

As pH sensor and EC sensors, any product usable for irrigation purposes can be used, as long as it fits physically and geometrically in the accumulator and or its lid.

In an exemplary functional arrangement of the sensors within the accumulator, electrodes 40 and 50 are positioned such that the bottom end of variable height electrode 40 is higher relative to the bottom of static electrode 50. The bottom of electrode 50 is positioned near the bottom of accumulator 10. pH sensor 60, and EC sensor 70 are both positioned inside accumulator 10 in such a position as to enable measurements of pH and EC even when only a small volume of drainage water is available. Accumulator 10, has a substantially see-through wall or a portion of it is, or it may include a transparent window, thus enabling a visual perception of drainage water parameters within accumulator 10 (such as amount, color, rate of collecting). Although the pH and EC sensors were describes as components adjunct to the accumulator, in some embodiments they may not be used, or may not be associated with the accumulator.

Three apertures are typically distributed across wall 20 of container 10, each of which is associated with a corresponding drain pipe, namely upper side drain aperture 90, lower side drain aperture 100, and lowest drain aperture 110. Drainage water may be introduced to accumulator 10 through uppermost drain aperture 80 or through upper side drain aperture 90, or through lower side drain aperture 100 when accumulator 10 is connected to hydroponic tank.

Lower side drain aperture 100 may be also used for taking samples of the drainage water within the accumulator, and for connecting to an auxiliary accumulator. Lowest aperture 110 is used for totally evacuating drainage water accumulated in accumulator 10, bottom drain pipe 120 may be used for supporting accumulator 10 on the ground. Electronically controlled valve 122 is associated with a lowest aperture 110 at the bottom of the collector. This controlled aperture is used as an on-off open/shut outlet mechanism for evacuating drainage water from accumulator 10. Upon exiting accumulator 10, drainage water is typically conveyed to a main drain pipe. Except for the bottom drainage outlet the accumulator may include an aperture through which the static electrode or its wiring can be inserted.

Drainage in soil-less culture results from the excess of irrigation over consumption and evaporation. As drainage water enters accumulator 10 and reach the sensors, pH and EC are measured, data collected and sent to irrigation control center (ICC). Data collected from pH meter and EC sensor are used as indications for monitoring processes taking place inside the plant and in the growing media. Such processes are dependent among other parameters, on the amount of irrigation and fertilizers available. As the drainage water within accumulator 10 reaches upper electrode 40, electric circuit is closed subsequently causing the ICC to stop irrigation. Monitoring the time taking for drainage water to reach upper electrode 40 can be used as input for further information. For example, if the time needed for reaching the pre-calculated amount of drainage water is shorter with respect to the pre-calculated average time, an interpretation can be made, that the plant consumption is reduced due to changes in climatic condition and/or micro-climates condition, and in such case a decision can be made to postpone the next irrigation.

Figs. 2A-2C illustrate various configurations of accumulator 10 connection with a lysimeter tray 130. Fig. 2A shows accumulator 10 connected is with an uppermost drain aperture 80 for collecting drainage water from lysimeter tray 130. Pipe 120 conveys drainage water from accumulator 10 to optional main drain pipe (not shown), and also provides support against the ground. In Fig. 2B, drainage water accumulator 10 is connected to lysimeter tray 130 by upper side drain pipe 90. In Fig. 2C, pipe 132 connects between drainage water accumulator 10 and auxiliary accumulator 140. The two-accumulator configuration increases the amount of collected drainage water the two connected accumulators should have an opening at the top allowing for identical water level. In Fig. 2D, accumulator 10 is connected to hydroponic tank 144 through a lower side aperture 100.

To explain the method of controlling the irrigation offered by the present invention, reference is first made to Fig. 3 schematically describing the appliances to which the irrigation control center (ICC) is functionally connected.

ICC 180 is connected to controlled appliances: main irrigation valve 182, and to a multiplicity of secondary irrigation valves 184. Input data providing appliances are typically all associated with the accumulator, namely: pH sensor 190, EC sensor 192, static electrode 194 and variable -hight electrode 196. Other appliances are controlled by the ICC, namely electrode shifter 198, and valve 122 at the bottom of the accumulator.

The functionality of the system of the invention is described in steps with reference to the flow chart in Fig. 4A. in which the sequence of events embodying the method of the invention is described. In step 212 The ICC starts the irrigation by opening the secondary irrigation valves, allowing flow of fertigation to the growing beds. In step 214, the drainage valve at the bottom of the accumulator opens, to evacuate the entirety of accumulated drainage water from the accumulator. In step 215 the drainage water fully evacuates the accumulator. in step 216 the main irrigation valve opens up,. In step 218 the bottom drainage valve previously opened is now shut. In step 220 the irrigation water reach the lysimeter and start flowing through the root medium, and begins to drain. Subsequently water level rises in the accumulator in step 222, pH and EC sensors at step 224 become immersed, and send data to the ICC at step 226. At step 228 the drainage water continue rising in the accumulator, and in step 230 the drainage water reach the upper electrode. A "stop irrigation!! circuit subsequently closes at step 232, indicating the ICC to stop irrigation at step 234. At step 236 the system awaits the next irrigation cycle, in which it repeating the steps 212-236 hence a new signal is sent from the ICC, to the accumulator to release the drainage water of the previous cycle from the accumulator, and start to collect new drainage water.

Another aspect of the present invention is described with reference to Fig. 4B. In this aspect the system is used to effectively alter the subsequent irrigation cycles, as is described next. In an on-going irrigation cycle, at step 252 the ICC opens the main irrigation valve, and at step 254 the ICC starts counting time. When subsequently the "stop irrigation" circuit closes at step 256, the ICC records the total irrigation time at step 258. At step 260, the ICC compares the accumulated time with a predefined time period, the planned irrigation time (PIT). If the accumulated irrigation time (AlT) is larger than PIT, the ICC will apply for the onset of the subsequent irrigation cycle a period, (interval between irrigations or IBI), shorter interval than planned. If AlT was not larger than PIT, in step 264 the system checks if the AlT was smaller than PIT, in which case the interval for the onset of the subsequent irrigation will be set in step 266, to a value larger than IBI. Otherwise, the next interval will remain as planned, i.e. it will equal IBI. Alternatively, instead of changing the subsequent IBI, in response to a AlT different than expected, the system can affect the limitation to drainage within an irrigation cycle, rather than the time between cycles. Thus, if AlT was larger than PIT, the next irrigation cycle can be made longer in advance. This can be effected automatically by raising the variable height electrode by a proper command from the ICC to the electrically actuated shifter moving the electrode or by issuing a report to the grower who then may opt to change the height of the variable electrode manually.

The ICC in accordance with the present invention can be any commercial system adapted to receive readings from the sensors, sense the closing of the stop irrigation!! circuit, and send messages to the various valves.

Benefits of implementing the present invention The preset invention promotes time saving, expenses lowering and provides the grower with realistic water dispensation control while irrigating is in process.

Pre-calculating of the amount of drainage to be collected in the accumulator will result in saving water and fertilizers. As the data collected from the pH meter, EC electrode is sent to main irrigation control, manual changes in the irrigation are possible even during on going irrigation and not in the next irrigation.

The system of the invention can be used in conjunction with any available irrigation system. Applying the system of the invention, the grower can plan ahead the amount of water to be dispensed in any one irrigation cycle in excess, knowing that for a given height of variable height electrode, the need of the crop for water, dictate the total amount of water consumed in one irrigation cycle.

Claims (5)

1. CLAIMSAn irrigation control system for determining the amount of irrigation water supply to soil-less cultures, comprising: * a main irrigation valve; * a narrow bottom accumulator 10 for collecting said drainage from said soil-less culture through a I ysi meter; * an openable lid 30 for said accumulator 10; * a static electrode at substantially the bottom of said accumulator; * an adjustable height electrode; * an irrigation control centre (ICC) having connections to at least said electrodes, and to said main irrigation valve; * a "stop irrigation" circuit for indicating to the ICC the existence of water between said two electrodes; * at least one upper drain aperture for letting lysimeter water drain into said accumulator; * a lower side drain aperture of said accumulator; a lowest drain aperture 110 for discharging the entirety of said drainage water from said accumulator, and wherein said "stop irrigation!! circuit indicates said ICC to shut said main irrigation valve.
2. 2. An irrigation control system as in claim 1 wherein the height of said adjustable height electrode is changed by a shifter.
3. 3. An irrigation control system as in claim 2 wherein said shifter is electrically operated.
4. 4. An irrigation control system as in claim 1 further comprising a conductivity sensor and a pH sensor.
5. 5. An irrigation control system as in claim 1, wherein the wall of said accumulator comprises a see-through portion of a wall.