SUBSURFACE DRIP IRRIGATION: HERE TODAY, HERE TO STAY Freddie Lamm Professor and Research Irrigation Engineer KSU Northwest Research-Extension Center, Colby, Kansas flamm@ksu.edu

SDI, a definition 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. Soil wetting pattern. Installation of SDI driplines. Most driplines in Great Plains are at depth of 12-18 inches.

What is Subsurface Drip Irrigation? 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. This is SDI This is subirrigation

What is Subsurface Drip Irrigation? Some shallow subsurface systems (< 8 inch depth) are retrieved and/or replaced annually and are very similar to surface drip irrigation (DI). Many research reports refer to these systems as DI, and reserve the term SDI for systems intended for multiple-year use that are installed below tillage depth. This is DI This is SDI

Irrigation Systems and Water Savings No irrigation system can save water without good management imparted by the producer. 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.

Microirrigation in USA Microirrigation is the overarching term that includes surface drip irrigation (DI), subsurface drip irrigation (SDI), microsprinkler and bubbler irrigation. The rate of growth of DI and SDI is quite high in the USA. In the Great Plains, we are most interested in SDI because it allows us to consider microirrigation for lesser-value commodity crops such as cotton and corn.

SDI is also of major interest in several other states. SDI in USA SDI is also of major interest in several other states. 2013 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.

Economics for SDI The components of SDI systems can be easily and economically designed to accommodate the field size. 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.

SDI System Life Pressure and flow tests were conducted annually on the system installed in 1989. Results indicate that plot flowrates could be maintained within +/- 5% of their initial first annual value.

What is the Number One Cause of SDI System Failure in the World? Like all other microirrigation systems, the number one cause of failure is emitter clogging. Emitter passageways are very small. Physical hazards: soil particles, crop residue, PVC pipe filings, debris, etc. Chemical hazards: precipitates, compounds, and interactions with injected chemicals. Biological hazards: algae, bacteria, slimes, hatchlings, etc.

What is the Number One Cause of SDI System Failure in the World? The water quality of some water resources used for SDI may require constant or periodic water treatment. Don't cut corners on selection, management, and maintenance of the filtration and water treatment components of your SDI system.

Efficiency Concepts with SDI 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 evaporation Improved infiltration, storage, and use of precipitation Improved in-field uniformity and targeting of plant root zone Improved crop health, growth, yield, and quality

Does SDI really increase crop per drop? Water Savings with SDI Does SDI really increase crop per drop? 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.

Water Savings with SDI In four different K- State studies at Colby, Kansas, spanning the period 1989 through 2004, corn grain yield and crop water productivity both plateaued at ≈80% of full irrigation.

Water Savings with SDI An early K-State SDI study (1989-1991) indicated we could maintain yields at ≈75% of full irrigation and that one of the major reasons was through reduction of early season drainage losses.

Does SDI really improve nutrient management? Nutrient Management with SDI Does SDI really improve nutrient management? Our studies have shown that using 75% of full irrigation with SDI, our corn yields plateaued at approximately 80% of typical nitrogen applications.

Nutrient Management with SDI SDI Phosphorus Fertigation for Corn, 2015 - 2016 Treatment 2015 Yield (bu/a) 2016 Yield Mean Yield (bu/a) Water Use 15 (in) Water Use 16 (in) Mean Water Use (in) WP 15 (lb/a-in) WP 16 (lb/a-in) WP Mean (lb/a-in) 1 Control 246 258 252 29.0 25.2 27.1 476 575 526 2 + P Fertig. 1 278 276 277 28.7 25.3 27.0 544 612 578 3 + P Fertig. 2 260 284 272 29.1 25.4 27.3 501 624 563 4 + P Fertig 1 + Inseason Zinc 273 274 27.5 25.5 26.5 555 602 579 5 + P Fertig. 3 266 269 27.7 25.6 26.7 539 595 567 All trts received same total irrigation amount and same total N (220 lbs/a) and P (40 lbs/a). The 8% yield benefit of Phosphorus Fertigation is shown.

Available from ASABE or the K-State SDI in the Great Plains website. Cotton, Tomato, Corn, and Onion Production with Subsurface Drip Irrigation – A Review Freddie R. Lamm Lamm, F. R. 2016. Cotton, Tomato, Corn, and Onion Production with Subsurface Drip Irrigation - A Review. Trans. ASABE Vol. 59(1):263-278. Available from ASABE or the K-State SDI in the Great Plains website. Caveat: Any time you do a relatively complete review of the literature, you will find at least some conflicting results.

Cotton 16 studies were found in the literature that allowed ≈ equal comparisons of cotton lint yield under SDI and alternative irrigation systems. Lint yield increases when using SDI ranged from negative 1% to positive 65% with an average increase of 18% across all studies. SDI cotton lint yields were 2, 15, and 19% greater than DI, surface gravity, and sprinkler irrigation, respectively.

Cotton Cotton lint yield increases averaging 19% as compared to sprinkler irrigation are illustrative of why SDI is increasingly being adopted in Texas. The yield increases tended to be greatest for SDI when irrigation was limited. Crop water productivity with SDI was almost always greater, particularly where SDI was compared to surface gravity irrigation methods.

Tomato 16 studies were found in the literature that allowed ≈ equal comparisons of tomato yield under SDI and alternative irrigation systems. SDI tomato yield increases ranging from negative 32% to positive 205% with an average increase of 12% across all studies. SDI tomato yields were 7, 17, and 23% greater than DI, surface gravity, and sprinkler irrigation, respectively.

Tomato More than one-half of the studies had tomato yield increases of 10% or greater for the most productive treatments. SDI has become the commercial standard for processing tomato with large SDI land areas in California.

Corn 12 studies were found in the literature that allowed ≈ equal comparisons of corn yield under SDI and alternative irrigation systems. SDI corn yield increases ranging from negative 51% to positive 30% with an average increase of 4% across all studies. SDI corn yields were 7, -16, and 0% greater than DI, surface gravity, and sprinkler irrigation, respectively.

Corn Economic competitiveness for SDI as compared to center pivot sprinklers arises from SDI being able to irrigate a greater fraction of the field area and would therefore be improved when corn selling prices are greater and when greater grain yields are obtainable.

Onion The current commercial use of SDI for onions is focused primarily on increasing the fraction of larger onions that can command a premium market price and has a much smaller focus on water conservation.

Onion Only 4 studies were found in the literature that allowed ≈ equal comparisons of onion yield under SDI and alternative irrigation systems. SDI onion yield increases ranging from negative 7% to positive 24% with SDI usually having greater proportion of larger onions. Shallow (≈ 0.10 m depth) SDI for onion has steadily grown in eastern Oregon and was anticipated to reach 50% of the irrigated onion area by 2013.

What are the Greatest Barriers to SDI Adoption in the Great Plains? 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.

System Cost as Barriers to SDI Adoption 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

Germination/Crop Establishment Barrier to SDI Adoption 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.

And bad news travels fast………………………… Rodent Damage as a Barrier to SDI Adoption 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. And bad news travels fast…………………………

Rodent Damage as a Barrier to SDI Adoption 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.

Closing Thoughts Modern SDI is relatively new to the Great Plains 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.

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 on their farms. Government cost sharing is being provided to advance the adoption of the technology. Many talented research and extension teams all across the world are committing time and effort with SDI.

So, I conclude: SDI is here today and SDI is here to stay Presentation available at http://www.ksre.ksu.edu/sdi/underground/LammCWR16.ppt So, I conclude: SDI is here today and SDI is here to stay Google SDI in the Great Plains http://www.ksre.ksu.edu/sdi