In reading an old Water Right Decision from the State Water Resources Control Board, I came across two interesting points about drip irrigation. Basically, a well owner near Escalon was pissed that their well was running dry in 1977 because of (allegedly) new pumping in the area, so they complained, and the SWRCB investigated. In order to check for reasonableness of use, they investigated how farmers were irrigating, and found that some were still flooding fields (border-check irrigation is a form of flood irrigation with tailwater recapture). Why not drip or sprinkler irrigation? The Board answered with the following:
Border check irrigation is a less efficient method of irrigation than sprinkler irrigation. However, peaches cannot be irrigated with sprinklers because water on the fruit causes spoilage.Bottom Line: Be wary of those who want to impose more efficient irrigation on farmers.
Drip irrigation is a more efficient method of irrigation than sprinkler irrigation. However, it is not feasible to utilize drip irrigation for existing orchards because the roots are not developed in such a manner to use the water from drip emitters. Consequently, in the area of concern drip irrigation is being utilized only for new orchards.
12 comments:
It's definitely a crop-by-crop issue. On my way out to visit family in Isleton, for example, I could swear I saw a pear orchard being converted to drip irrigation, and those trees could easily have been over 100 years old.
Trees adapt. Roots grow. They will find the water, however it is applied.
The bigger problem with drip, or any "efficient" irrigation, is soil salinity. Periodic flushing is necessary to prevent salt buildup. This is only a problem in places with a net evaporation debit and too little winter rain - like, say, the San Joaquin Valley...
I'm not really surprised that there is no mention of innovation, let alone existing alternatives such as mini-sprayers or soaker hose; both widely used in other applications.
Bottom Line:
When somebody tells you there is only a single correct way to do something, be assured there are at least one or more superior methods that can work for said situation.
I would appreciate seeing some competitive economics for the various ways to irrigate.
Numbers please.
I'm still not convinced that the more efficient irrigation system actually provides better opportunity time for the crop to use the water and actually can, in some (most?) cases, INCREASE consumptive water use compared to the old system. This has been discussed many times in the micro-irrigation listserve Trickle-L and has been suspected on various crops including grapes, tomatoes, cotton, wheat and corn. If true, without a subsequent reduction of acreage irrigated, or switching to a less, water intensice crop, the consumptive water use under the better irrigation system may end up costing you water. More crop yield, for sure, but more water use, too. If there is data out there to quantify these thoughts - either way - I'd like to see it.
Data - perhaps look at some of Zilberman's early work, but more recently, this paper: here has info on drip increasing water use. Havent read it fully yet but it looks promising.
@Eric - for numbers, this article may do. But a search of google scholar ought to turn up some stuff - this has been studied quite a lot.
@Damian,
Very useful article. Thanks.
Tim's comment about soil salinity is just part of the unintended consequences that may result with broad application of increased irrigation efficiency. The salinity concentration and recharge rate of the entire regional groundwater resource may be affected if the scale of change is broad (ie, "effective") enough.
I just attended a talk about water management in Australia, where they are dealing with 1000 year drought conditions. They have instituted a broad based effort to improve irrigation efficiencies on farms from 75% to 85% to extend their water supply. I asked if they were concerned that such a move cuts the groundwater recharge rate to about 50% as much, and also increases the salt concentration in the recharge water by about 200%. The answer (paraphrased) was no, it was not a concern because the groundwater quality is already too saline to use, so it is in effect being written-off. They want to keep groundwater levels low and away from the crop roots.
I don't think we are ready for such a trade-off on a broad scale in the central valley yet....but the day may come.
Drip is a great technology, but has all the disadvantages mentioned by the other posters; and it requires considerable energy, when gravity works for free. I heard today from a good farmer who had been growning an orchard on drip, and chipping all his walnut prunings, like a good boy should (air quality and all that). Because they were not getting enough surface moisture, the chips would not break down and were raising Cain with his harvest.
Not a knock on drip or any other technology; just on those drive-by enviro-nannies who think farmers are simpletons.
'groaning an orchard'
good description for the environinnies.
Imposing drip irrigation can be tricky but certainly education and incentives seem in order. I seem to recall that in Israel approximately 90% of crops receive drip irrigation, in the U.S., only about 10% and in India, less than 1%. Meanwhile the groundwater levels in India are falling by several feet each year and the poor (anyone who can not afford deep wells) are literally being hung out to dry.
JDF, in many cases, drip recovers its cost in better yields and lower operating costs. However, when the economics are less compelling, the best incentives are allowing water districts to sell water conserved by drip (or other water saving practices), then using the proceeds to improve their own distribution systems, and to make grants and low cost loans to growers who install water saving technologies. This is legal, and is already happening in some districts, but needs to be encouraged. Some people have wanted to create another government entitlement program to accomplish the worthy aim of water conservation. That is bad policy for all the familiar reasons.
The country-to country comparisons are a little misleading because places like Wisconsin and Georgia are so radically different (soils, weather, crop mix) from Israel and India. A lot of American farm land will never be drip irrigated, nor would it be practical to try. The land holdings in India are so small, access to capital for farmers so meager, and the infrastructure so appalling I am amazed even 1% is drip irrigated. A great pity.
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