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THE STATUS OF SDI IN THE CENTRAL AND SOUTHERN GREAT PLAINS Freddie LammProfessor and Research Irrigation EngineerKSU Northwest Research-Extension Center, Colby, [email protected]
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Subsurface drip irrigation (SDI) applies water below the soil surface to the crop root zone with small emission points (emitters) that are in a series of plastic lines typically spaced between alternate pairs of crop rows.
SDI, a definition
Soil wetting pattern.
Installation of SDI driplines.
Most driplines in Great Plains are at depth of 12-18 inches.
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Subsurface drip irrigation is not the same and should not be confused with subirrigation.
Subirrigation applies water below the ground surface by raising the water table to within or near the root zone.
What is Subsurface Drip Irrigation?
This is SDI This is subirrigation
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No irrigation system can save water without good management imparted by the producer.
Irrigation Systems and Water Savings
Additionally, some systems although perhaps more complicated in design and number of components may inherently result in better water management.Generally, farmers obtain improvement by moving to the right in figure above.
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Improved Management with Irrigation Systems
This concept can perhaps be considered as “purchasing improved management capabilities upfront”.
It has been said that one of the principal reasons that pressurized irrigation systems such as center pivot sprinklers (CP) and subsurface drip irrigation (SDI) are considered easier to manage than surface irrigation is because they remove the surface water transport phenomenon from the management.
Both center pivot sprinkler irrigation and SDI are well suited for automation (monitoring and control).
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Microirrigation is the overarching term that includes surface drip irrigation (DI), subsurface drip irrigation (SDI), microsprinkler and bubbler irrigation.
Microirrigation in USA
Year2003 2008 2013
Land
are
a (1
00,0
00 a
cres
)
0
5
10
15
20
25
30
DI SDI
The rate of growth of DI and SDI is quite high in the USA.
In the OAP region, we are most interested in SDI because it allows us to consider microirrigation for lesser-value commodity crops such as cotton and corn.
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SDI is also of major interest in several other states.
SDI in USA
In 2013, the ten USA states with the largest SDI area (716,183 acres) comprise over 93% of the total SDI area but have a wide variation in the ratio of SDI/(SDI+DI) land area. SDI land area in Kansas and Texas has grown 127% and 28%, respectively in the last 5 years according to the USDA-NASS data.
SDI land area has grown 89% in USA during last 10 years.
US StateArizona California Florida Georgia Kansas Nebraska N. Mexico Oregon Texas Washington
Land
Are
a (1
000
acre
s)an
d Pe
rcen
t SD
I0
50
100
150
200
250
300
350
400
Perc
enta
ge S
Di
0
20
40
60
80
100
SDI land areaPercent SDI
2013
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We suspect that NASS is not representing all the SDI area in the Great Plains. For example, in Kansas NASS only projects about 20,000 acres, where we think 35000 acres might be more realistic. NASS data overtime does not match with installation capacities (2000-3000 acres/year) that seem to be occurring.In Texas, NASS reported 170,972 acres, while the single High Plains Water Conservation District (2014) shows physical locations for 4263 SDI systems covering 265,299 acres (http://www.hpwd.org/s/SDI_2013.pdf).
SDI in USA
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The components of SDI systems can be easily and economically designed to accommodate the field size.
Economics for SDI
20 40 60 80 100Percent of full size area
20
40
60
80
100
Perc
ent o
f ful
l siz
e co
st
CPSDI 1:1 unity line
Full size -- 125 acre CP, 155 acre SDI
Lower-valued commodity crops, such as cotton and corn, may only be profitable with SDI because of the ability to amortize SDI system and installation costs over the multiple years of operation.
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SDI can be used for small, frequent, just-in-time irrigation and nutrient applications directly to crop root system.
The primary ways that SDI could increase crop water productivity (WP), More crop per drop are: Reduction and/or elimination of deep drainage, irrigation
runoff, and soil water evaporationImproved infiltration, storage, and use of precipitation Improved in-field uniformity and targeting of plant root
zone Improved crop health, growth, yield, and quality
Efficiency Concepts with SDI
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Does SDI really increase crop per drop?
0.00 0.05 0.10 0.15 0.20 0.25Irrigation capacity (inches/day)
75
100
125
150
175
200
225
250
275
Cor
n yi
eld
(bu/
acre
)
KSU-NWRECColby, Kansas
Incanopy sprinkler, 1996-1999 (Wet years)Incanopy sprinkler, 2000-2001 (Dry years)Subsurface drip, 1996-1999 (Wet years)Subsurface drip, 2000-2001 (Dry years)
Water Savings with SDI
There is growing evidence from our studies and others in the Great Plains that SDI can stabilize yields at a greater level than alternative irrigation systems when deficit irrigated.
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Does SDI really improve nutrient management?
Nutrient Management with SDI
Our studies have shown that using 75% of full irrigation with SDI, our corn yields plateaued at approximately 80% of typical nitrogen applications.
0 40 80 120 160 200 240Applied Nitrogen (lbs/acre)
50
100
150
200
250
Yiel
d (b
u/a)
& A
NU
(lbs
N/a
)100
200
300
400
500
WP
(lbs
grai
n /a
cre-
in)
YieldApparent Nitrogen UptakeWater Productivity
Total 1994 irrigation, 10.9 inches
Unity lin
e for A
pplied vs
. Uptak
e
Total 1995 irrigation, 12.0 inchesTotal 1996 irrigation, 6.0 inches
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What about SDI and Site Specific Irrigation (SSI)?
Irrigation Systems
Well, this topic heavily dives into the semantics here. The SDI system consists of a specific number of zones created in the original design and at the time of installation. Although, not impossible, it may be economically impractical to change the zone configurations at a later time. Breaking the SDI system up into additional zones at the design and installation phases adds costs to the system, but is warranted in some circumstances. Ideally, the zone characteristics are initially carefully considered.
SDI’s technical competiveness with CP systems probably lies more closely with its precise water and nutrient placement.
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In my opinion, the greatest obstacles to adoption of SDI in the Great Plains are: System cost. Germination and crop establishment. Prevention of animal and insect damage to
driplines.Industry, universities, and government agencies are evaluating options that may help reduce these barriers.
What are the Greatest Barriers to SDI Adoption in the Great Plains?
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Potential to increase economic competitiveness:
More generic SDI designs and components
Studies examining system requirements and trying to streamline the design processes
(e.g., Bordovsky et al., 2008 and Rogers et al., 2003)
Government cost sharing
Greater overall yields and crop prices
System Cost as Barriers to SDI Adoption
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Germination and crop establishment can be a problem under drought conditions prevalent in the semi-arid Great Plains.
Cropping and tillage management can help to reduce this problem. (e.g., Bordovsky et al. 2012)
Fortunately, the problem does not occur in every year.
Germination/Crop Establishment Barrier to SDI Adoption
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Rodent damage is probably the largest barrier to greater adoption of SDI systems in the Great Plains.
Of the three mentioned barriers, it is also the one with the least thorough solutions.
It is not that rodent problems are widespread with the majority of systems being greatly affected. The issue is that when a widespread problem occurs on a particular system, it can be frustrating to the irrigator and the damage may lead to system abandonment.
Rodent Damage as a Barrier to SDI Adoption
And bad news travels fast…………………………
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Some partial solutions to reduce or prevent rodent damage are discussed in Lamm et al. (2014).
Industry continues to look for more effective solutions to this problem with a focus on materials that might be impregnated in the plastic or injected into the dripline during the irrigation event to serve as a repellent.
Rodent Damage as a Barrier to SDI Adoption
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Other Research Needs
Scaling the SDI systems to the desired and/or required complexity while addressing the skills of various end-users, locally, regionally, nationally, and internationally.
Optimizing SDI production both in economical and environmentally friendly manners that are socially acceptable.
Breaking the High Tech / Low Tech paradox of SDI that “Never the twain shall meet.”
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Closing Thoughts
Modern SDI is relatively new to our region with cotton research beginning at TAMU in 1963 and our KSU corn research in 1989. It can be noted that first USA research with SDI can be traced to efforts in Colorado in 1913 House (1918).
Some of the persistent barriers mentioned here today have existed throughout its brief history.
Progress continues to be made at addressing and circumventing these barriers.
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Closing Thoughts
Some would say, with 25, 50, or 100 years of research efforts the barriers must be too formidable.
But a growing number of irrigators are voting with their time and money that SDI does have a place in our region.
Government cost sharing is being provided to advance the adoption of the technology.
Many talented research and extension teams all across the OAP region are committing time and effort with SDI.
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Closing Thoughts
So, maybe we should not let these Barrier Bogeymen be so loudly trumpeted as reasons to avoid SDI.Surely, there are enough other technical and social challenges to SDI to keep the conversation continuing.
How about….
Improved irrigation is not synonymous with sustainable irrigation, but both are worthy of our efforts.
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It cannot be overemphasized that management and technology go
hand-in-hand and both can only be optimized in the
presence of the other.
Presentation available athttp://www.ksre.ksu.edu/sdi/underground/LammOAP15.ppt
