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"David Marshall" <agrimgt@televar.com> writes We have been providing a Scientific Irrigation Scheduling service in Central Washington for over 30 years. We do not use instrumentation for the main core of our irrigation scheduling service. Neither do we rely on the "feel method". Call us old fashioned, but we "feel" that our approach is simple, inexpensive, yet scientifically accurate. Each week, or every other week, we'll visit the field equipped with air tight canisters and soil probes. These are capable of coring to 4' or 5' depth, depending on the crop or location of the hard pan. Yes, our agronomic and horticultural "shields" are up and aware and general scouting information is recorded. Rather than coring at a single location, we walk the field in a pre-defined "representative sample strip". The soil collected in cans will be a composite over a geographic area for a given foot depth. We have found advantages and flexibility to this over single point sampling. As the sampler fills the canisters, he can feel the actual soil and give an estimate of percent water (which is important for ground truthing - pun intended - but we don't rely on it). He can also estimate field capacity (much more of an art). The canisters are then weighed, baked in an oven, then weighed again. This "percent water by weight" (gravimetric approach) is reported to the grower in terms relative to the field capacity, along with our scouting information. We also project crop water use (ETP x crop coefficient). Our own computer program maintains the historical database and generates a report with a chart. I am curious... how unique is our approach in the industry? Maybe it is something of a hybrid between what Richard calls the "subjective - non-scientific" approach and the instrumentation approach? It has all of the advantages to the feel method mentioned by Richard and only one of the down sides (labor intensive -- but then we hire young strong ag students home for the summer...). We have used this method since about 1967, back in the day when the whole concept of "scientific irrigation scheduling" was a hard sell, to say the least. It's interesting how times change. Don't get me wrong, we are not "anti-instrumentation". There are situations (especially permanent crops) where a "widget" can be used very effectively. At this point, we have used both TDR and Watermarks and are open to others. (We appreciate SoWaCS a lot, BTW!!! I'm afraid we mostly just take it in rather than contribute...) COMMENTS BY OTHERS I appreciate Bill Pogue's advise to keep "your footprints in the soil and your shadow on the ground." I like that little saying. It seems like one consensus from this discussion is that every farmer (or irr scheduler) ought to at least have a shovel or soil probe (even a push probe) in the back of his truck, no matter how many widgets he has out in the field. Jean: we could also verify your testing of extension officers with our own informal observations over these many years; some folks can estimate the percent water fairly accurately, while others struggle with it. (Cool is often interpreted as wet...) This of course is why we couldn't rely on their estimates, but we do feed back the actual numbers as compared to their estimates, which helps to train them. Robin Wells: when you talk about those agronomy consultants who partially use the feel method, I think you are talking about folks like us. BTW, if I understand your concept of "fuzzy logic", we have been doing that in our report format. Our own ET projection is compared with inches remaining in the root zone (above wilting pt) and we can get at the approx. number of days before a refill to the soil profile is needed. It's the consultant's and farmer's job to translate this into mgt decisions like increasing on-time or going to 8-hour sets. Cheers to all! - Dave ---------------------------------- David W. Marshall Agrimanagement, Inc. P.O. Box 583 Yakima, WA 98907 email: agrimgt@televar.com "Measuring Crop Needs For Greater Profits..." -----Original Message----- From: owner-sowacs@aqua.ccwr.ac.za Sent: Monday, December 21, 1998 6:27 PM To: Cc: Subject: Hand feel vs instrumentation: Pros and Cons of Both Dear Soil Moisture Fellows: I've always wanted to pose a question regarding the effectiveness of instrumentation vs the traditional method of the hand feel method and using weather based evapotranspiration models. So without further ado..... Here in Central California, there are a number of individuals and companies making their living poking the soil with an auger, feeling the sample and estimating the amount of 'available moisture'. They then apply this knowledge to current ETo conditions/crop coefficients and calculate an irrigation schedule for their clients. Coming from a research background, I am not personally familiar with the soil-feel procedure. The method is not considered to be 'scientific' nor sufficiently quantitative. In research, we always used instrumentation (neutron probe, FDR, TDR, tensiometry, heat dissipation or lysimeters). I can understand that the soil-feel method has several advantages over instrumentation; - One can cover much more territory and hence integrate the field's irrigation needs a tad better than point source instrumentation - For annual or row crops, there are no wires or widgets sticking out of the field to encourage tractor blight - It is 'potentially' a more cost effective method from the grower's perspective However, I see some down sides too: - Feeling the soil is subjective - It is labor intensive (some of the soil feel schedulers begin to wonder how long their bodies will hold up in later years) - For deep rooted crops, it would be hard to assess how deep irrigations have penetrated the soil profile So what about instrumentation? Pros: - One can use instruments as a dummy gauge, some what like a fuel gauge on a car, more or less 'feeling/sensing' the soil electronically through time - Instrumented data can be integrated with computer software - One can detect crop stress or on set of stress, especially if data is monitored continuously Cons: - Placement of the sensor is KEY; does the instrument represent the root zone? - With annual/row crops, the tractor blight problem mentioned above - Maintenance or longevity issues - Accuracy - Soil type idiosyncrasies (2:1 cracking soils etc.) I would like to hear (objectively) from all the experts out in soil instrumentation 'cyberspace'. Many of you are either in the widget selling business or possibly in research. Hence, your perspective might be different than mine, maybe not. I truly believe instrumentation is the way to go, providing it can compete economically and agronomically with the soil-feel method. Comments folks............ Cheers! Richard Mead United Agri Products mPower Specialist http://www.mpower3.com