Irrigated Agriculture: Introduction to Irrigation Technologies and Applications

1. Irrigated Agriculture: Introduction to Irrigation Technologies and Applications • Alon Ben-Gal, PhD • Senior Scientist • Institute for Soil, Water and Environmental Sciences • Environmental Physics and Irrigation • Agricultural Research Organization (Volcani) • Gilat Research Center, Israel Visiting Scientist Institute for Water and Environment and College of Dryland Agriculture and Natural Resources MekelleUniversity, Ethiopia

2. Irrigated Agriculture: Introduction to Irrigation Technologies and Applications • Objectives: • To introduce general methods and technologies available for irrigation delivery and scheduling with focus on smallholder farming…. • while recognizing the complexities and site/system specific needs involved in the use of irrigation and irrigation technology in sustainable agricultural development Alon Ben-Gal, 19 Jan 2019

3. Irrigated Agriculture: Introduction to Irrigation Technologies and Applications • Outline: • 1) General background on the importance of irrigated agriculture for smallholder farming • 2) Irrigation technologies and their operation 2.1 Gravity (flood, basin, furrow) 2.2 Pressurized (sprinkle, drip) 2.3 Smallholder drip • 3) Water use efficiency and water saving considerations in irrigated agriculture 3.1 Water storage and distribution systems 3.2 Irrigation systems 3.3 Irrigation scheduling 3.4 Precision irrigation 3.5 Externalities and economics • 4) Management and sustainability of irrigation systems, with focus on community/society Alon Ben-Gal, 19 Jan 2019

4. 1.1. General background on the importance of irrigated agriculture for smallholder farming • What can irrigation offer? • Yield security – dry seasons, drought • Economic opportunity – increased yields, choice of high value market driven crops, multiple cropping seasons annually, out of season production, protected agriculture, beneficial to nutrient management • Food/nutrition (personal/family/community) security – crops, quality Alon Ben-Gal, 19 Jan 2019

5. 1.2General background on the importance of irrigated agriculture for smallholder farming • Problems / disadvantages of irrigation • Confounding water scarcity (depletion of water supplies) • Competing sectors for water • Environmental concerns • Pollution • Salinity, water logging • Cost • Equipment, labor, maintenance, water, energy Alon Ben-Gal, 19 Jan 2019

6. 1.3General background on the importance of irrigated agriculture for smallholder farming • Prerequisitesto smallholder irrigation • Water supply and storage • Energy supply • Capital – investment • Community organization • Support: subsidies, investment, knowledge Alon Ben-Gal, 19 Jan 2019

7. 2.0Irrigation technologies and their operation • Gravity, surface – flood, furrow irrigation • Pressurized irrigation • Sprinkler • Micro-irrigation - drip Alon Ben-Gal, 19 Jan 2019

8. 2.1Irrigation technologies and their operationGravity fed irrigation systems • Water source and storage • River, lake, pond, reservoir, tank • Pump (if necessary) • Channels/pipes • Field • Challenge • Losses • Uniform delivery • Scheduling • At worst – whenever there is water, however much there is • At best – soil-crop-weather based • Maximum water per irrigation event, minimum number of events Alon Ben-Gal, 19 Jan 2019

9. 2.2Irrigation technologies and their operationGravity fed irrigation systems – flood irrigation Start of application – from channel to field Closing the delivery channel End of water application Photo credits: Moshe Broner, NevaTeam Closed ridge aperture Alon Ben-Gal, 19 Jan 2019

10. 2.3Irrigation technologies and their operationSprinkler irrigation • Water under pressure (pump) • Stationary / moving • Pipes • Laterals • Emitters / sprinklers • Design – pressure-flow relationships in pipes, • in laterals between sprinklers • Concept and challenge – “just like rain” (uniform application) • Scheduling – similar to flood: return of • plant available water in soil each event Alon Ben-Gal, 19 Jan 2019

11. 2.4Irrigation technologies and their operationThe move to drip Micro-irrigation: paradigm shift in how we provide water to crops Other methods Micro-irrigation • Complete soil wetting • Replace depleted plant available water in soil • Interest to invest in irrigation events as least often as possible • Large wetting – drying cycles • Fertilization - separate • Partial soil wetting • Provide plant water needs • High frequency application • Maintain relatively high water content in root zone • Fertigation!

12. 2.5Irrigation technologies and their operationdrip irrigation systems • Water under pressure • Irrigation head • Filtration • Automation • Fertigation • Mains, laterals • Emitters • Pressure compensation • Non-leakage • Design – maximum lateral length • Maintenance • Clogging

13. 2.6Irrigation technologies and their operationDrip irrigation systems and operation From Moshe Broner, NevaTeam Energy Source Fertilizing System Filtration System Automation system Control Valves Regulating Valves Main Pipes Submain Pipes Laterals Emitters Alon Ben-Gal, 19 Jan 2019

14. 2.7Irrigation technologies and their operationdrip irrigation systems LATERAL EMITTER EMITTER MANIFOLD SUBMAIN LINE BACKFLOW PREVENTOR AUTOMATION MAIN LINE CONTROLSTATION PRESSURE GAUGE PRESSURE REGULATOR PUMP From Moshe Broner, NevaTeam INJECTORPUMP FILTERS WATERMETER CHEMICAL TANK

15. 2.8Irrigation technologies and their operationTechnology for smallholder drip irrigation • Site-system-situation specific • Appropriate technology and maintenance • Examples • Family drip gravity systems • Solar pumps

16. 2.9Irrigation technologies and their operationTechnology for smallholder drip irrigation • “family” drip • Lower tech solutions – has all the components of high tech systems • automation • filtration • fertigation • mains, submains • laterals • emitters Alon Ben-Gal, 19 Jan 2019

17. 2.10Irrigation technologies and their operationTechnology for smallholder drip irrigation • Solar driven pumps Alon Ben-Gal, 19 Jan 2019

18. 3.0Water use efficiency and water saving considerations in irrigated agriculture • Water storage and distribution systems • Irrigation systems • Irrigation scheduling • Other considerations: externalities and economics Current estimation:- some 65% of water used for agriculture is not utilized by plants! Alon Ben-Gal, 19 Jan 2019

19. 3.1Water use efficiency and water saving considerations in irrigated agricultureWater storage and distribution systems Leaching, evaporation • reservoirs

20. 3.2Water use efficiency and water saving considerations in irrigated agricultureWater storage and distribution systems Leaching, evaporation • channels Alon Ben-Gal, 19 Jan 2019

21. 3.3Water use efficiency and water saving considerations in irrigated agriculture • Irrigation systems • Delivery efficiency • Evaporation • Water in soil but not available to plants • Leaching less efficient more efficient surface/flood sprinkler drip/micro Partial soil wetting Uniform between emitters Uniform application wetting of entire soil Alon Ben-Gal, 19 Jan 2019

22. 3.4Water use efficiency and water saving considerations in irrigated agriculturescientific (knowledge –based) irrigation management • Benefits • Meet crop ET demands – maximize yields • Control soil water depletion in the rootzone • Reduce ET during non-critical growth stages (deficit irrigation) • Optimize crop water productivity • Conserve water • Decrease deep percolation • Reduce runoff • Prevent non-point source pollution • Eliminate water waste • Irrigation scheduling • Plant available water in soil + weather + crop factor • Return of evapotranspiration • Soil and/or plant sensing Howell and Evett, 2005. Pathways to effective applications. Alon Ben-Gal, 19 Jan 2019

23. 3.5Water use efficiency and water saving considerations in irrigated agricultureSoil + weather based irrigation scheduling • Crop available soil water – maximum available depletion • Potential (reference) evapotranspiration • Crop factors Feddes, R.A. et al. 1978. Simulation of Field Water Use and Crop Yield; Centre for Agricultural Publishing and Documentaion: Wageningen, The Netherlands, 1978. Yield From Veihmeyer, ~1927 pwp permanent wilting point fc field capacity θ water content pwp S fc  Water Content Alon Ben-Gal, 19 Jan 2019 From Veihmeyer, ~1927

24. 3.7Water use efficiency and water saving considerations in irrigated agricultureSoil + weather based irrigation scheduling Crop available water A.W. – available water (mm). D - soil depth (mm). qf.c.- field capacity. qw.p.- wilting point. C – coefficient Alon Ben-Gal, 19 Jan 2019

25. 3.8Water use efficiency and water saving considerations in irrigated agricultureSoil + weather based irrigation scheduling Days till next irrigation: A.W. = available water ETP = potential evapotranspiration = ET0 = reference evapotranspiration KC = crop (cover) factor Weather based – meteorological station Experimentally determined Alon Ben-Gal, 19 Jan 2019

26. 3.10Water use efficiency and water saving considerations in irrigated agricultureIrrigation scheduling for drip systems / advanced scheduling • Return of ET + high frequency • ETp x Kc • ETp Potential (reference) ET from weather data • Kc Crop factor (experimental, experiential, literature) • Highly frequent small applications allow to not consider soil water holding capacity or plant available water Alon Ben-Gal, 19 Jan 2019

27. 3.11Water use efficiency and water saving considerations in irrigated agricultureIrrigation scheduling for drip systems / advanced scheduling • High frequency • pulses / low flow rates • Smaller wetting/drying fluctuations • Less water stress • Less need to invest in roots • Higher efficiency water uptake • Higher efficiency nutrient uptake Alon Ben-Gal, 19 Jan 2019

28. 3.12Water use efficiency and water saving considerations in irrigated agricultureSoil plant and remote sensing methods • Irrigate according to water status • Set points for irrigation from any data that responds/correlates to water status or stress • Can use any point in the soil-water-plant-atmosphere continuum that is measurable Alon Ben-Gal, 19 Jan 2019

29. 3.13Water use efficiency and water saving considerations in irrigated agricultureSoil plant and remote sensing methods Water status/stress Canopy size Crop growth stage Fruit load Driving force Demand-climate (weather) Water potential Radiation, temperature, humidity, wind Capability for transpiration Leaf/canopy temperature Water content Stomatal closure/resistance Plant water potential turgor photosynthesis Changes in leaf, stem, trunk or fruit size (shrinking/swelling + growth) Sap flow Soil water content Soil water potential Alon Ben-Gal, 19 Jan 2019

30. 3.14Water use efficiency and water saving considerations in irrigated agricultureSoil plant and remote sensing methods Water status/stress Canopy size Crop growth stage Fruit load Driving force Demand-climate (weather) Water potential Radiation, temperature, humidity, wind Capability for transpiration Leaf/canopy temperature Water content energy of water Stomatal closure/resistance Physiological mechanisms Plant water potential symptoms amount of water turgor photosynthesis Changes in leaf, stem, trunk or fruit size (shrinking/swelling + growth) Sap flow Soil water content Soil water potential Alon Ben-Gal, 19 Jan 2019

31. Plant Leaf/stem water potential Changes in circumference/width (dendrometers) Sap flow Stomatal behavior (conductance/resistance) Turgor behavior 3.15Water use efficiency and water saving considerations in irrigated agricultureSoil plant and remote sensing methods • Soil • Water content (various electrical property based sensors) (capacitance, conductance, dielectric resistivity) • Water potential (tensiometers) continuous continuous

32. 3.16Water use efficiency and water saving considerations in irrigated agricultureSoil plant and remote sensing methods • Remote • Leaf/canopy temperature, other indices • Drones, planes, satellites Alon Ben-Gal, 19 Jan 2019

33. 3.17Water use efficiency and water saving considerations in irrigated agricultureOther considerations: externalities and economics • Soil health and nutrition – soil management • Salinity – leaching requirements • Dual/multiple cropping • Cost benefit • Deficit irrigation • How to best use water when insufficient for full irrigation/crop needs • Regulated deficit irrigation: recognizing phenological stages where water deficit (stress) has low or no effect on yield, may raise product quality, and is economically beneficial • Tools for farmers - calculators • Scheduling coupled with economics • Region/crop/system specific Alon Ben-Gal, 19 Jan 2019

34. 4.0Management and sustainability of irrigation systems, with focus on community/society Community/society management/involvement “…technology (i.e. drip irrigation hardware) acquires its characteristics only through, and within, the network of institutions, discourses and practices that enact it.” Venot, J-P., et al. BEYOND THE PROMISES OF TECHNOLOGY: A REVIEW OF THE DISCOURSES AND ACTORS WHO MAKE DRIP IRRIGATION, Irrigation and Drainage, 2014 Alon Ben-Gal, 19 Jan 2019

35. 4.1 Management and sustainability of irrigation systems, with focus on community/society • Obstaclesto smallholder irrigation • Lack of infrastructure(s) • Lack of investment opportunity • Shortage of skilled personnel • Low cost of water – lack of inspiration for conservation • Lack of monitoring and evaluation systems • Lack of holistic local support for cropping systems: breeding, quality seed (varieties), nurseries, plant protection, marketing….. • Lack of knowledge /access to knowledge • Lack decision making tools • Insufficient data needed for smart scheduling • infrastructure of meteorological stations • crop factors for local crops/varieties • locally proved/calibrated methods for calculating potential ET • Insufficient consideration of local soils, cropping systems, irrigation systems and methods, and available resources for decisions concerning irrigation scheduling • Insufficient consideration of additional variables interacting with and influencing water use and the effect of irrigation on crops. These may include: plant nutrition-fertilization, cultivation practices, water quality, etc. • Insufficient understanding of risk of depletion and pollution by irrigation practices Alon Ben-Gal, 19 Jan 2019

36. 4.2Management and sustainability of irrigation systems, with focus on community/society • Equity • Sustainability • Challenge – development of simple, accessible, affordable but scientific and data-knowledge based methods and systems for irrigation delivery and scheduling Societal / community management (contribution / responsibility) micro macro • Investment • Maintenance • Market driven decision making and management • Support • Knowledge + data to drive decision making • Water storage and allocation • Energy • Appropriate (location, system, time, crop) technologies • Purchase and maintenance or equipment, fertilizer, seed, seedlings….etc • Extension – knowledge transfer • Market access Alon Ben-Gal, 19 Jan 2019

37. Concluding message • While irrigation and irrigation technologies appear to present opportunity for smallholder agricultural development, economic advancement and poverty alleviation, technology should not and can not be separated from systems and policies. • Appropriate technology for irrigation will always be site and system (crop, economic, social, institutional) specific. • Sustainable development of agriculture will be a result of system changes and adjustments. Technology can likely play some role in this. Alon Ben-Gal, 19 Jan 2019

38. Reading: Irrigation technology and development of smallholder agriculture – underlying issues • Albinson, B. and Perry, C.J. 2002. Fundamentals of Smallholder Irrigation: The Structured System Concept. Research Report 58. Colombo, Sri Lanka: International Water Management Institute. • Bjornlund, H. et al. 2017. Profitability and productivity barriers and opportunities in small-scale irrigation schemes. Int. J Water Resour. Develop. 33: 690-704. • Burney J.A. et al. 2012. The case for distributed irrigation as a development priority in sub-Saharan Africa. PNAS 110: 12513-12517. • Mutambara, S., et al 2016. A comparative review of water management sustainability challenges in smallholder irrigation schemes in Africa and Asia. Agric. Water Man. 171: 63-72. • Haileslassie, A. et al. 2016. On-farm smallholder irrigation performance in Ethiopia: From water use efficiency to equity and sustainability. LIVES Working Paper 19. Nairobi, Kenya: International Livestock Research Institute (ILRI). • Jägermeyr, J. et al 2016. Integrated crop water management might sustainably halve the global food gap. Environ Res. Letters 11: 125002. • Mwamakamba, S. 2017. Irrigating Africa: policy barriers and opportunities for enhanced productivity of smallholder farmers. Int. J. Water Resour. Develop. 33: 824-838. • van Rooyen, A.F. et al. 2017. Theory and application of agricultural innovation platforms for improved irrigation scheme management in southern africa. Int. J. Water Resour. Develop. 33: 804-823. • Venot, J-P., et al 2014. Beyond the promises of technology: a review of the discourses and actors who make drip irrigation. Irrig. and Drain. 63: 186–194. • You, L. et al. 2010. What Is the Irrigation Potential for Africa? A Combined Biophysical and Socioeconomic Approach. IFPRI Discussion Paper 00993. Alon Ben-Gal, 19 Jan 2019