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Guidelines for abandonment of irrigated acres from groundwater
systems
7/23/2002
Joel
Schneekloth
Regional Extension Specialist (AgricultureWater
Quality/Management)
Colorado State University
Extension
Golden Plains Area |
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Many irrigation systems that in the past have been able to
adequately irrigate an entire field have not been able to keep up with the
demand of the crop under current drought conditions. The following worksheet is
designed to help determine how many acres a given system is capable of
adequately irrigating with the assumption of depleted soil moisture and minimal
rainfall. These guidelines are compiled from the most current scientific
information available from the Central Plains region including Colorado,
Nebraska, and Kansas. Site specific factors and management constraints must be
considered in this decision process. These guidelines are for the cropping
year of 2002 only due to the extenuating circumstances of this
year.
The decision to abandon acres or to continue irrigation should
be based upon economic considerations. You must evaluate what additional inputs
are required to complete the current crop/irrigation season, the yield
potential of the crop if irrigation stops or if irrigation continues on fewer
acres, the future insurability of that field, and what level of risk do you
wish to assume. Producers with higher risk tolerance may assume that it will
rain and irrigate more acres, while a producer with low risk tolerance will
irrigate fewer acres with the assumption that significant rainfall will not
occur in time to help the crop.
Some of the questions that need to be
addressed to determine whether to abandon acreage are as follows:
- Will continuing to irrigate the entire irrigated acreage
result in a harvestable yield? If yes, then irrigation should continue on the
entire irrigated acreage. Even though the crop may be under stress, it will
respond to an additional input of water.
- What will happen to your insurability in the future if a
portion of the irrigated acreage is abandoned? If abandoning a portion of the
field reduces the future insurability of the entire field, it is questionable
as to whether or not to abandon the entire field. This is a question that must
be addressed between the producer and the insurance agent. Additionally, the
crop yield history for insurance purposes will be recorded based upon the yield
of the entire field, irrigated and non-irrigated. Future insurance claims will
be affected by this decision.
- What is the current growth stage of the crop? If the crop
is past the flowering or tassel stage and under severe stress, continuing
irrigation is questionable. Will irrigation allow the crop to properly
pollinate? If crop is past the flowering stage and prior to pollination, it is
unlikely that proper pollination will occur under severe water stress.
Several agronomic questions
must also be answered as to which acreage to abandon and which to irrigate.
Here are several questions to help clarify that decision:
- What crop growth stage are portions of the field in? If
the field is uneven in crop development it may be more advisable to choose the
acres that are close to flower or tassel emergence to irrigate. This is the
most critical time period for irrigation and will typically have the greatest
yield response to water. If portions of the field are past silking, these may
be the most desirable to abandon. See CSUCE Fact Sheet # 4.715
Crop Water Use and Growth Stages for
additional information on critical growth stages for various crops.
- Which portion of the field will have the greatest yield
potential? Irrigating these acres that will result in the greatest return.
These are the acres that typically have the better soil types and less weed
pressure. If fields are highly variable, choose the most uniform part of the
field to continue irrigating. For example, portions of the field with eroded
hilltops generally have lower yield potential are more logical to abandon.
Other areas of concern may include high pH regions, very sandy areas, large
areas with weed infestations or areas that are generally low yielding in normal
years.
- It may be advantageous to discontinue the use of end-guns
on center pivots if they are used. End-guns typically have low efficiencies of
application and are non-uniform in the application of water. Discontinuing the
use of these systems will allow for more efficient use of water under the main
portion of the center pivot.
Several concerns may come up
with the potential yield of stressed crops. Work done in Nebraska and Kansas
with limited water has generally shown that although the yield potential may
not be as high as when fully irrigated and not stressed, satisfactory grain
yields can still be achieved if crop ET is met during the reproductive growth
stage. The key to limited water management is applying adequate water just
prior to (within 2 weeks prior to tassel emergence) and during the reproductive
growth stage.
The following worksheet has been compiled with the best
research information available at this time. You will need to supply realistic
site-specific information on system efficiency and well capacity. The worksheet
contains typical averages and ranges of system efficiencies. The efficiency of
impact sprinklers versus in-canopy sprinklers is not significantly different
unless runoff is observed. This will require a trip into the field to observe
the area that the sprinklers are immediately over, with the end of the system
being the most important. Observe if water is moving within the field and note
that as runoff. Even though water is staying in the field, it is moving from
where it is intended to be applied to other regions that now may be over
watered.
If well capacity is not known with certainty, it is necessary
to measure the output of the well. Under-estimating well capacity will result
in under-estimating the acreage that can be irrigated, while over-estimating
well capacity will mean that you are irrigating more acres than the system can
realistically irrigate. The worksheet also provides information to calculate
the irrigated acreage for center pivots and furrow irrigate fields.
If
you have any questions on irrigation system capacity and efficiency, please
contact one of the CSU Extension faculty in your area.
Joel
Schneekloth (Akron - Northeast Region) (970) 345-0508
Reagan Waskom (Ft.
Collins) (970) 491-2947
Bruce Bosley (Sterling) (970) 522-3200 ext
285
Ron Meyer (Burlington) (719) 346-5571
Jerry Alldredge (Greeley) (970)
356-4000 ext 14474
Mike Bartolo (Rocky Ford) (719) 254-6312
Tim Macklin
(Southeast Area) (719) 336-7734
Randy Buhler (Logan) (970) 522-3200 ext
284
Steve Norberg (Morgan) (970) 867-2493
Troy Bauder (Ft. Collins) (970)
491-4923
Grant Cardon (Ft. Collins) (970) 491-6235 |
Page Created and Maintained by: Perry D. Brewer, Area
Extension Agent (Technology Education/Youth)
1/16/2003 |
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State University, U.S. Department of Agriculture, Kit Carson, Phillips,
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