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>Date: Tue, 24 Dec 1996 02:24:37 -0400 >To: <trickle-l@unl.edu> >From: Leonard Ornstein <lenornst@pipeline.com> >Subject: Re: Minute/ultra-low microirrigation >Cc: >Bcc: >X-Attachments: > >>Date: Sat, 21 Dec 1996 13:23:25 -0400 >>To: <trickle-l@unl.edu> >>From: Leonard Ornstein <lenornst@pipeline.com> >>Subject: Re:ultra-low microirrigation & Irristats >>Cc: >>Bcc: >>X-Attachments: >> >Tricle-L and SOWACS list members: > >The WebSite I promised to launch (below), though still under >construction, is now online as of this evening: > ><http://www.pipeline.com/~lenornst/index.html> > >It conects to my Irristat page and, at present, 4 down-loadable Acrobat >documents on the Irristat technology. > >Len Ornstein > >>>The concept of "Minute" irrigation is not necessarily new but has been >>>impractical until approximately three years ago.> >> >>Well, this gives me an oportunity to introduce Trickle-L list members to >>a drip technology, the use of moisture-sensitive, self-regulating >>irrigation valves,Irristats, (typically, but not necessarily, one to a >>plant, bush or tree) for delivering water at rates which exactly match >>evapotranspioration, and therefore is as "Minute" as you would want to >>get! Like other forms of "Minute", it typically uses a water-supply >>continuosly pressurized at up to 15 lbs/in^2, and requires quality >>filtration. But it has a lot more to offer. >> >>As indicated below, I had planned to delay this "announcement" until my >>Web site is ready, (in about two weeks), but this discussion cries out >>for this respons: >> >>X-Sender: lenornst@pop.pipeline.com >>Mime-Version: 1.0 >>Date: Sat, 30 Nov 1996 13:58:15 -0400 >>To: SOWACS@aqua.ccwr.ac.za >>From: Leonard Ornstein <lenornst@pipeline.com> >>Subject: Measuring Evapotranspiration/Lysimeters >>Sender: owner-sowacs@aqua.ccwr.ac.za >>Precedence: bulk >> >>Greetings to all: >> >>On Nov. 20, Dean Reynolds initiated a thread on methods that might be >>useful for updating crop-ET numbers. Because of the expense of lysimeters >>and lysimetry, he was interested in the pros and cons of using neutron >>probes and TDR as alternatives for such purposes. >> >>Terry Howell quickly responded with a very helpful discussion. He correctly >>noted that since evapotranspiration modifies the moisture content of the >>air above soil and foliage, strictly speaking, lysimetry, neutron probe >>measurements and TDR only provide an indirect measures of ET, whereas eddy >>correlation can measure ET directly. However he indicated that it probably >>wasn't a practical alternative at this time. He neatly reviewed the hazards >>of crop-ET assessment; rain, deep percolation, etc. >> >>On Nov. 22, Dean replied with thanks to all for their contributions to the >>discussion, and revealed just why he had raised the subject; namely the >>economic factors that governmental bodies, like the State of California >>face as farmers choose to sell their State-assigned water rights to one >>another (and municipalities). >> >>To oversimplify, it appears the allowed selling price depends upon a >>State-approved estimate of crop-ET and acreage. If the estimated crop-ET is >>too high, the State essentially is giving away (and wasting) valuable >>public resources. >> >>What Dean in fact wants to assess is the crop water consumption, which of >>course results mainly from ET, but THAT is directly measurable by lysimetry. >> >>Dean believes, for the reason reviewed above, that updating crop-ET with >>lysimetry would have substantial desirable economic consequences, but >>apparently judges that the costs of the equipment and labor for the job >>will be unacceptable to the officials of the California Department of Water >>Resources for whom he works. >> >>The problems he raises are rather universal. >> >>I believe I can offer an inexpensive solution: >> >>I am the inventor and manufacturer of the Irristat, a moisture-sensitive, >>self-regulating valve, designed to control the delivery of water to a "drip >>emitter". The Irristat is a device with which few if any of the SOWACS >>List's members will be familiar. Although the Irristat was developed as an >>automated irrigation-scheduling device, it also works fine as an >>alternative to a lysimeter to "measure" evapotranspiration: >> >>It was introduced in: >> >>The Irristat: A Moisture-Sensitive, Self-Regulating, Water Valve for >>Drip Irrigation Systems: Drip/Trickle Irrigation in Action Vol. 2 >>ASAE Pub. 10-85, St. Joseph, Mich., pp.623-629; (Proceedings. of the >>Third International Drip/Trickle Irrigation Congress, Nov. 18-21, 1985, >>Fresno, CA). >> >>The article contains a description of the Irristat and a general >>discussion of its applications in agriculture and horticulture, >>including a description of an installation for 60 mature cherry trees at >>Washington State Uniersity Irrigated Agriculture Research Center, >>Prosser, WA (WSU). >> >>Temporarily, an Abode Acrobat version of that publication, irrst2.pdf, >>as well as another document, irrist1.pdf, which describes the Irristat >>technology in greater detail, can be read and/or downloaded (thanks to >>Bruce) from: >> >> <http://www.icfrnet.unp.ac.za/~metele/sowacs/irristat.html> >> >>Adobe Acrobat Readers for PC, Unix or Mac platforms can be downloaded FREE >>from: >> >> <http://www.adobe.com/acrobat/> >> >>I am in the midst of preparing a Web Page which will describe the >>technology briefly and will contain URL's for downloading these two >>papers as well as four others, including an unpublished paper by Robert G. >>Evans, documenting the performance of the Irristats that I installed for >>him and Ed Proebsting for the 60 mature cherry trees at WSU. I had expected >>to introduce the Irristat to SOWACS and Trickle-L when my Web Page is >>ready. That should be before the new year. And I will post its address here >>as soon as possible. >> >>Briefly, this is how the Irristat works: >> >>The Irristat uses a uniquely formulated, synthetic polyacrylamide gel as >>its moisture-sensing element. The valve is buried near a plant's roots, in >>intimate contact with the soil,. >> >>Water is conducted by capillary tubing from a water supply, through a >>thin-walled rubber tube within the body of the Irristat and then through >>another attached length of capillary tubing to, or near to the soil >>surface. On its way past the roots, the water spreads by gravity and >>capillarity through the soil, passes through the Irristat's porous >>polyester fiber membrane, and reaches the moisture-sensing element, the gel. >> >>As the gel becomes more moist, it swells, pushing the Irristat's piston >>against the rubber tube. When the moisture in the soil surrounding the >>Irristat reaches a predetermined set-point, (typically -0.15 bars) the >>swollen gel causes the piston to pinch the rubber tube closed, cutting off >>the supply of water. >> >>As the plant draws moisture from the soil, the gel shrinks, reversing >>the cycle. As the moisture level falls below the Irristat's set-point, >>the piston moves back, relieving the pressure on the rubber tube, and >>water begins to flow. >> >>Buried in the soil, Irristats will function reliably for many years, >>PROVIDING AUTOMATED DRIP/TRICKLE IRRIGATION. The Irristat itself is >>about 2 cubic centimeters in volume. It, and its connections, are >>usually encased in a protective polypropylene shell in the form of a >>spear-tip, which simplifies insertion into the soil. The body parts and >>piston of the Irristat are molded of polypropylene; the internal water >>conduit is made of silicone rubber; the semi-permeable membrane, of >>Dacron-like polyester fibers; and the moisture-sensitive gel, of >>slightly-cross-linked polyacrylamide. All are chemically, biologically >>and physically durable. With 0.125-inch inside-diameter capillary >>tubing, and a water supply at 15 pounds per square inch, an Irristat can >>deliver up to about 1.7 liters of water per minute. Therefore, one Irristat >>can service any plant, up to a medium-size tree; a few Irristats, in >>parallel, can service a large tree. >> >>The Irristat delivers to its plant, EXACTLY THE AMOUNT OF WATER NEEDED >>TO REPLACE LOSSES DUE TO EVAPOTRANSPIRATION, (plus any additional amount >>incorporated into new growth). >> >>If it is set up with a gravity-feed water supply from a tank, after it >>has been working for a few days, the measured amount of water drawn from >>the tank per unit time (e.g., per 24 hours) is an accurate measure of >>evapotranspiration plus "growth water". >> >>Alternatively, if the water supply is a typical drip-lateral, a second >>Irristat can be installed in parallel with, and directly adjacent to the >>first, with an outlet capillary line of the same inside diameter and length >>as the first, delivering its output at the same point. After they have been >>working together for a few days, the outlet of either one can then be >>placed into a container, and the amount of water delivered per unit time >>will be an accurate measure of the evapotranspiration associated with that >>plant, bush or tree. (The Irristat has a time-constant of about 2 hours, so >>an "instantaneous measurement" usually reflects the evapotranspiration that >>occurred 2 hours earlier.) >> >>Of course, this description of how to use Irristats to measure >>evapotranspiration is a bit oversimplified; (e.g., if the bottom of the >>root ball is at the water table, if it has just rained or if the plant is >>growing in such coarse sand that, at -0.15 bars matric potential, a >>substantial portion of the delivered water percolates down past the roots), >>my method works poorly. With two tensiometers; one beside the Irristat in >>the root ball, and the other inserted to a depth somewhat below the root >>ball, you can easily check whether the water table is too high or the >>irrigation water is perciolating too deep. >> >>You will of course wonder why I have kept this a "secret" so long? >> >>In order to compete with pressure-compensating emitters, we had planned to >>manufacture the Irristat at a unit cost of under $1.00, with most of the >>cost coming from the labor of manual assembly. But that depended upon >>essentially 100% manufacturing-yield of correctly functioning Irristats. >>And over the years, the best we've been able to do is a bit better than >>90%. That means that EACH finished Irristat needs to be checked by cycling >>it a few times between wet and dry states, and this turns out to be quite >>expensive. We (and others) judged that the resulting $6.00 unit selling >>price, for a spear-tip mounted Irristat, would severely restrict the range >>of its application. With rather limited resources, we have been (very >>inadequately) trying to enter markets, like landscaping, which might >>tolerate the higher, cost. I hope the Web will help us change this. >> >>But, clearly, for use as an ET-measuring tool, our current manufacturing >>cost should pose no problem!. >> >>I'll be happy to discuss various other details of use and performance, in >>this forum, or privately. >> >>Hope you find this useful. >> >>Leonard Ornstein, Ph.D. >>Irristat International Inc. >> >>lenornst@pipeline.com >> >> >> >>>The concept of "Minute" irrigation is not necessarily new but has been >>>impractical until approximately three years ago. The idea is to apply water >>>at a very slow rate. To achieve this we would require a drip emitter with >>>extremely small passages and considerably higher filter requirements. This >>>emitter would be highly susceptible to clogging. To date there is no >>>emitter >>>or tape product that is capable of delivering water at a rate which >>>approaches that considered to be minute irrigation. However, there are >>>a few >>>individual components that when used together can create this minute >>>irrigation. I consider minute irrigation to be in the range of 100 - 400 cc >>>per hour. >>> >>>The heart of this system is a pulsating device which contains a silicone >>>sleeve seated upon a specially designed piston. As this sleeve or bladder >>>swells with water it reaches a critical point where the stored water is >>>released and then the process repeats itself. This continual action creates >>>the pulsing effect. The rate of flow through the pulser is determined by >>>either a compensated or non-conpensated emission device. It is when this >>>pulser is connected to a secondary emission device that we are able to >>>achieve minute irrigation. In Israel when using the term minute irrigation >>>they are referring only to the use of drip emitters. Pulsated >>>micro-sprinklers or jets is a different concept. >>> >>>Most applications of this system have been used in green houses. There are >>>two types of systems of minute irrigation. One system connects about 20 >>>individual pot type drippers (stakes with a labyrinth) to one single pulser. >>> If the pulser has a discharge rate of 4 LPH or 4,000 cc/hour we divide >>>this >>>number by the number of outlets and have an individual discharge rate of 200 >>>cc/hour/pot. The second system uses our (Drip In) 1/4" (6mm) soaker >>>dripline >>>with emitters spaced anywhere from 15cm to 30cm connected to the same >>>pulser. >>> We can not use a dripline with a larger ID because the line will always be >>>partially filled with air. The 1/4" because of its small ID is constantly >>>charged with water. This system is either stretched on top of the pots or >>>laid directly on the bed. The number of emitters varies but is >>>generally not >>>more than 60. I recently installed a system where I used an 8 LPH pulser >>>with 60 emitters or an individual discharge rate per emitter of 133 cc/hour. >>> These emitters normally are 2 LPH. >>> >>>The beauty here is that we are able to reduce the flow per emitter to minute >>>amounts of water and yet maintain large passageways and relative clog >>>resistance. Like any new technology there are advantages and >>>disadvantages. >>> In fact this technology is considered by some to be revolutionary. Similar >>>to what drip was 20 years ago. Most pots are irrigated by spray stakes or >>>some type of emitter. Water applied at a rate of 2 LPH will form a sausage >>>near the middle of the pot and drainage will begin within a few minutes. >>> Irrigation will continue approximately 7-15 minutes. During this time >>>water >>>will begin to move upwards closer to the sides of the pot pushing the salts >>>further into the root zone. This mandates frequent flushing and an >>>additional waste of water and nutrients. With the pulsated drip system the >>>water will move almost twice as fast laterally until the upper area is >>>completely wetted. Then the movement will be downward as a front until >>>drainage occurs. When the first drops drain the pot is at pot capacity and >>>the irrigation can be shut off. This movement is constantly washing the >>>salts >>>downward. Additional flushing of the salts is only required when the EC of >>>the drainage water exceeds the established limits. >>> >>>Specific advantages of this system include: >>>1. Water and fertilizer savings up to 40-50% >>>2. Optimum growing conditions due to the ability to maintain an optimum >>>balance of air, water and nutrients in the soil. >>>3. Better utilization of available space; plant density can be increased. >>>4. Quicker turn around of plant material; reduced growing cycles. >>>5. Higher yields >>>6. Better quality >>>7. Lower system costs; smaller PVC sizes, reduced horsepower >>>requirements.... >>> >>>This system poses significant challenges and requires us to change our >>>way of >>>thinking. >>>For one, the discharge rate of the emitters at the end of the lateral is >>>higher than the rate at the begining. This is completely opposite from what >>>we expect with conventional drip technology. Second, we are talking about >>>using up to 40-50% less water then existing drip systems. If this is true >>>than we need to reevaluate crop requirements. We applied this technology on >>>a small scale to 40 almond trees in the Sacramento Valley this summer. From >>>mid june through October we applied 1 GPH/tree. The dripline was our 1/4" >>>soaker dripline with emitters spaced at 12". The water was never shut off >>>except for one day at harvest. The surface wetted area was on average 1 >>>foot >>>wide and there was no runoff. These trees received no more than 24 gallons >>>per day. These were mature trees with a full crop. Visual inspection >>>indicated good growth and yields comparable to the rest of the orchard. We >>>intend to expand this system and do a small area of grapes in 1997. >>> >>>We do not have all the answers to these questions yet. Actually we are not >>>sure what questions we should be asking. While the concept has broad >>>applications the technology to apply this on a large scale to field crops is >>>in its infancy. For the present we will be promoting this minute irrigation >>>technology to the greenhouse industry and evaluating its application in the >>>broader agricultural market. We would like to invite those interested in >>>this technology to explore the possibilities and ramifications along >>>with us. >>> A few papers have been written on the subject in Israel. They have been >>>translated into english and are available in Israel by contacting Jacob >>>Levin >>>at Lego Irrigation or contacting me at Drip In Irrigation. >>> >>>I hope that I have been able to answer a few of the questions. >>> >>>Philip Lubars >>>Drip In Irrigation >>>2836 N. Larkin Ave. >>>Fresno, CA 93637 >>>Tel: (209) 294-8008 >>>Fax: (209)294-8809 >>>e-mail figali@aol.com >> >> >> > >