Overview | Water Savings | Applications | Additional Benefits | Resources | Case Studies
Overview
Growers have long been concerned about water quality, but today water quantity has emerged as a leading consideration in managing irrigation. Today we not only have to focus on reducing contaminants caused by leaching and runoff, but irrigation systems have to be managed so that the amount of applied water closely matches crop water requirements. Poorly managed irrigation systems can cause soil damage, environmental problems, and contribute to water shortages. As California’s population increases and water becomes more scarce, irrigation management practices will have to become ever more creative. A great deal of effort and resources have been dedicated to improving irrigation management in recent decades with great success. Yet there is still room for improvement and evolving practices and technologies continue to emerge.
Soil moisture monitoring and irrigation scheduling
One of the most straightforward actions growers can take is to time well the application of irrigation water. There are a variety of methods for determining when to water crops. Simply monitoring soil moisture levels to help determine when to irrigate can significantly improve water and energy conservation, maximize yields, improve water quality, and greatly reduce soil erosion. There are several effective, low-cost methods for assessing soil moisture. Combining soil moisture monitoring with a method of irrigation scheduling can produce substantial water savings.
In irrigation scheduling, different factors related to a specific crop and context are assessed to determine water requirements. There are various techniques and software programs readily available for growers to utilize which will provide the irrigation schedules needed. Irrigation scheduling typically relies on actual weather data in conjunction with crop coefficients to estimate crop water demand. Watering based on evapotranspiration (ET) or plant needs should be used as a method for planning a watering budget and soil/plant-based irrigation schedule for actual scheduling. One issue with irrigation scheduling is that growers may not always be in control of when water will be available to them. However, many of the more advanced software programs will take this into account. Although irrigation scheduling is an effective tool for managing an irrigation system, growers can make their irrigation systems even more efficient with new technologies and practices.
Irrigation systems can be managed by hand or automated. Recent technological developments include the use of sensors and controls to manage irrigation systems. Automated irrigation systems utilize weather station data and/or moisture sensor data to determine when and for how long to water crops. Sensors are placed into the ground to monitor soil moisture and connected to a control system. The control system can use real-time data from the sensor or a combination of inputs to determine irrigation time and amount. The sensor tells the computer how much moisture there is in the soil, which determines if water is required. Automated systems typically save on labor, yet tend to be associated with higher equipment costs. Though automated irrigation systems with moisture sensors and weather stations are being more widely adopted, their cost-effectiveness largely depends on the crop in question and broader market forces.
Drip and micro-irrigation
One of the more effective forms of irrigation is micro- or drip irrigation. Drip irrigation employs drip emitters that slowly apply water to crop root zones. Drip irrigation usually consists of a pressurized tubing system that is run along crop rows. These tubes are fitted with nozzles at specific distances to allow water to drip from the emitters.
Micro-irrigation is typically used on tree and vine crops. It is also becoming popular for row crop irrigation, especially in areas where water supplies are limited or recycled water is used for irrigation. The two distinct features of micro-irrigation are high irrigation frequency and localized water application to only part of the crop’s potential root zone. These two factors are the framework that make up difference between micro-irrigation and traditional surface irrigation methods. Research shows that there is a minimum level of available soil moisture required for plants to maintain growth. A well managed micro-irrigation system should maintain a minimal level above the threshold. Over-irrigation should be avoided, because saturated soils can injure a plant by causing inadequate root aeration or promoting root rot and loss of nutrients.
Another application of drip irrigation is subsurface drip irrigation (SDI). This is the irrigation of crops through buried plastic tubes containing emitters. The tubing and emitters are generally buried 2 to 10 inches (5 to 25 cm) below the soil surface. In the United States, SDI is most widely used for the irrigation of annual row and field crops, but it can be used for permanent crops as well. In other parts of the world, SDI is widely used for the irrigation of permanent crops. SDI is an efficient irrigation system that greatly reduces evaporation from the soil surface, often resulting in substantial water savings when compared with flood irrigation. As with drip irrigation, sub-surface drip adoption has proceeded slowly due to the high initial cost and intensive management requirements.
Deficit irrigation
Deficit (or regulated deficit) irrigation can maximize water use efficiency by maintaining or increasing yields per unit of irrigation water applied. In deficit irrigation, the crop is exposed to a certain level of water stress for certain periods or throughout the whole growing season. The expectation is that yield reduction will be insignificant compared to the benefits gained from decreasing water use. However, deficit irrigation may only work for certain crops and the grower must have prior knowledge of crop yield responses to deficit irrigation. One of the greatest obstacles to implementing deficit irrigation is the wide range of crops that one grower may manage in any given season in California. More research on deficit irrigation for specific crops and soils is needed to ensure guidelines for implementation are successful.
The aforementioned methods and technologies are but a small example of the applications available for irrigation management. Growers are encouraged to consult irrigation professionals or farm advisors before implementing significant changes in their irrigation practices.
NOTE: Uniformity vs. efficiency
Water Savings
With the recent drought and water shortages, conserving water has been a major concern in California. The methods and applications mentioned above are just a few irrigation management practices that are being practiced today. The basis of irrigation scheduling is to determine the amount of water to apply to a field and when to apply it. Irrigation scheduling for flood irrigation systems can save growers 25% or more of a grower’s water usage. In drip irrigation, water is slowly but directly applied to the plant root zone. With drip irrigation, water is not wasted on non-growth areas and the plant root zone is maintained at its ideal moisture level. Drip irrigation can maintain an optimum moisture level in the soil at all times with less water lost to the sun and the wind. Drip irrigation typically saves between 30-50% of water used on crops and orchards.(a, b)
“The drip irrigation technology has the ability to reduce water consumption
up to 50 percent compared to overhead(spray) irrigation systems“Subsurface drip further reduces the loss of water due to evaporation or wind. Subsurface drip irrigation, one of the most efficient irrigation technologies, has an estimated 25% or more savings as compared with surface irrigation. Regulated deficit irrigation has been shown to reduce water use by a further 20%. Using the above technologies and methodologies in conjunction can increase water savings even more.
Applications
Irrigation scheduling is a practice that most if not all growers who irrigate should be practicing. It is one of the most standard practices in use today. Irrigation scheduling can be done in various ways and with most if not all crops and scales of production. Free irrigation scheduling software is available, such as the online Wateright program developed by California State University, Fresno.
Drip irrigation is currently being used by permanent crop growers all over the State of California. Due to its high initial cost, it is primarily used by farmers with large acreage. But with the recent drought and California water shortages, more and more farmers are employing this technology, which may become a standard for permanent crops. Subsurface drip on the other hand, is not as widely used. Its high cost and maintenance make it less appealing to growers. This may change as water shortages and the price of water increase.
Soil moisture sensor-based irrigation may be the future of irrigation technology. This technology makes irrigation a real-time consideration, in which decisions are made real time and not based on historical facts. The major setbacks of this technology are availability, cost, and maintenance. But with the ongoing development of computer technology, soil moisture sensor-based irrigation should become more readily available and easier to maintain.
Additional Benefits
The adoption of irrigation practices with the potential to decrease water use is essential to establishing agricultural systems that use available water more efficiently and yet maintain crop production capacity. Changes in irrigation practices will likely require reassessment of fertilizer application rates and delivery practices as well. These changes are key to developing efficient and sustainable cropping systems that will benefit the environment, the grower and consumer. For example, the efficient delivery of water and nutrients to crops will likely lead to less greenhouse gas emissions by reducing available nitrogen and making the soil environment less conducive (less water throughout profile) in producing nitrous oxide, the most potent greenhouse gas. Current agriculture fertilization practices throughout the world contribute significantly to nitrous oxide production. The efficient use of fertilizer and water management will allow growers to enhance and diversify their income sources by enhancing the efficient use of inputs and participating in emerging carbon and greenhouse gas markets.
Research has suggested that many farmers often under-irrigate, some from lack of knowledge and information, while others under-irrigate as a deliberate decision to save water or benefit from the quality of crop. In reality, providing crops with too much water is much more harmful than providing crops with too little. Another important note is that although the initial cost of these systems at the outset are generally high, their relative cost over a life span of 15-40 years is offset by the improved quality, uniformity, and higher production associated with the technology or practices. Secondary benefits include stretched water supply and money saved on energy and water costs.
By increasing the use of every drop of water we are also supporting agricultural jobs. With a large portion of California’s population dependent on these jobs, water is essential to keeping California’s economy flourishing.
The energy use associated with agricultural water is a substantial problem in California. Significant amounts of energy are used to pump, treat, deliver, and heat our water. In California approximately 20% of the electricity and 30% of natural gas use is for moving and treating water. By maximizing the use of every drop of water, we can contribute to energy conservation as well. In addition, the combined use of reduced tillage practices with efficient irrigation practices likely will reduce fuel requirements.
Resources
Soil Moisture Monitoring | Irrigation Scheduling | Drip Irrigation | Subsurface Drip Irrigation | Support Organizations
Soil Moisture Monitoring
Soil Moisture Monitoring: Low-Cost Tools and Methods. Published by ATTRA.
A good overview of soil moisture monitoring, with a focus on lower-tech direct monitoring.
Measuring and Conserving Irrigation Water”:http://attra.ncat.org/attra-pub/PDF/irrigation_water.pdf. By Mike Morris and Vicki Lynne.
This ATTRA manual describes how to find the net water application rate for any irrigation system and how to calculate the number of hours the system should be operated. Also offers suggestions for irrigating with limited water supplies.
Measuring Soil Moisture for Irrigation Water Management. By Hal Werner.
An overview of various methods of soil moisture monitoring using direct methods.
Water & Nutrient Management: Soil Moisture-Based Irrigation Systems.
Acknowledging that sensor-based measurement systems are a key factor in effective water management, this “Virtual Field Day” website from the University of Florida includes a range of good publications and videos on soil moisture monitoring and irrigation management. Several types of soil moisture sensors are also described in detail.
A Practical Way of Measuring Soil Moisture. By Esteban Herrera, Extension Horticulturist
One direct method of measuring soil moisture from the College of Agriculture, Consumer and Environmental Sciences, New Mexico State University.
Utilizing Soil-Moisture Monitoring to Improve Alfalfa and Pasture Irrigation Management. UC Davis.
This management guide provides information on soil moisture monitoring, a relatively simple and effective method for managing irrigation on alfalfa and irrigated pasture.
Making Sense of Soil Moisture Sensors. UC Davis.
UC Davis Cooperative Extension evaluation of soil moisture sensors in Kern County.
Soil Moisture. CSU Fresno.
An article about testing and findings of soil moisture sensors carried out at Fresno State.
Irrigation scheduling
Wateright. CSU Fresno.
The WATERIGHT site was developed by the Center for Irrigation Technology at California State University, Fresno with significant support from the US Bureau of Reclamation. WATERIGHT is designed to be a multi-function, educational resource for irrigation water management. The site is designed for three audiences: homeowners, commercial turf growers, and agriculture.
UC Drought Management
A web resource covering irrigation scheduling (includes evapotranspiration scheduling, soil moisture monitoring and plant-based irrigation scheduling) and individual crop deficit irrigation information.
Irrigation Scheduling: A Guide for Efficient On-Farm Water Management. By David A. Goldhamer.
This guide discusses how to measure soil, atmospheric, crop, and irrigation factors to determine the most efficient irrigation schedule.
Automatic Irrigation Based on Soil Moisture for Vegetable Crops. By Rafael Muñoz-Carpena and Michael D. Dukes.
A University of Florida paper on soil moisture monitoring and automated irrigation scheduling.
Water Budget Method of Irrigation Scheduling
A short description of the water budget method of irrigation scheduling, and how to use CIMIS ETo to help determine irrigation schedules.
Efficient Irrigation Scheduling. By Dr. Clint Shock, Oregon State University Malheur Experiment Station
Irrigation scheduling tips, using potatoes as an example.
Best Management Practices for Irrigation Management
An article about best management practices as recommended by Colorado State University.
Irrigation Scheduling
Facts and calculations about irrigation scheduling by Colorado State University.
Irrigation System Selection
The intent of this paper is to summarize considerations for the most common types of irrigation systems.
Drip Irrigation
Drip Irrigation: An Introduction. Oregon State University.
The ins and outs of drip irrigation, including management of drip systems.
Drip Irrigation. Washington State University.
A good overview of drip irrigation design and management. Also includes rules and regulations specific to the Washington context.
Practical and Efficient Drip Technology. By Toro.
Information and resources on drip technology by manufacturer Toro.
Drip Irrigation for Home Gardens. Colorado State University.
A complete overview of installing drip systems in home gardens. Useful also for small farms.
Drip vs. Furrow Irrigation
A study on drip irrigation vs. furrow irrigation at the University of Arizona.
Micro-Irrigation Scheduling and Management
A study on micro-irrigation scheduling and management from Fresno State.
Selecting Drip Irrigation for Vineyards
Important considerations for the purchase of a drip irrigation system for vineyards.
Subsurface Drip Irrigation
Subsurface Drip Irrigation. By Kenneth H. Solomon and Greg Jorgensen.
A research report outlining what works and what doesn’t.
SDI On The Great Plains. Kansas State University.
A portal to subsurface drip irrigation resources and information.
Subsurface Drip Irrigation. Colorado State University.
A report covering SDI basics as well as crops, materials, placement, cost, operation and maintenance.
Subsurface Drip Irrigation. University of Nevada.
A publication addressing operation, costs and benefits, and components of SDI systems.
Subsurface Drip Resources for Irrigation Systems. University of Nebraska-Lincoln Extension.
Includes two publications: Advantages and Disadvantages of Subsurface Drip Irrigation, and Drip Irrigation Design and Management Considerations for Windbreaks.
Subsurface Drip Irrigation Advantages & Limitations
An evaluation of subsurface drip irrigation system from Down Under.
Subsurface Drip Irrigation
Information and research on SDI from University of Arizona’s subsurface drip irrigation demonstration and research project.
Support Organizations
Mobile Irrigation Labs
The Department of Water Resources’ mobile irrigation labs help growers across California evaluate their current irrigation systems and make recommendations on improvements.
NRCS Irrigation Page
A comprehensive one-stop-shop that includes information on irrigation components, training, methods, management models, and lots more.
IrrigationTutorials.com
Self-described as the web’s motherlode of irrigation information. Includes free tutorials on drip irrigation design and installation and many other irrigation-related information.
California Water Institute
An academic center of excellence for research, education and policy analysis of issues involving water resources based at CSU Fresno.
The Center For Irrigation Technology
An independent research and testing facility, the Center for Irrigation Technology (CIT) assists designers, manufacturers and users of irrigation equipment to make the technological advances. Based at CSU Fresno.
International Center For Water Technology
ICWT was established in 2001 to educate, promote, and assist in the development and adoption of innovative technologies that improve water utilization, reduce energy demand, and positively impact air quality. Based at CSU Fresno.
CSU Water Resource and Policy Initiative
CSU’s system wide academic excellence into an important resource for addressing the complex issues about water confronting California today and in its future.
Irrigation Training and Research Center at Cal Poly
ITRC provides irrigation training, research and technical support. The website includes many examples of their results, including downloadable papers and reports, valuable public databases, and samples of completed projects.
UC Irrigation Education Material
The UC Department of Land, Air and Water Resources hosts this site that collects UC research-based information on irrigation.
California Irrigation Management Information System
CIMIS is a program in the Office of Water Use Efficiency (OWUE), California Department of Water Resources (DWR) that manages a network of over 120 automated weather stations in the state of California.
Irrigation Association
The Irrigation Association is the leading membership organization for irrigation equipment and system manufacturers, dealers, distributors, designers, consultants, contractors and end users.
Irrigation Management Society
The Irrigation Water Management Society is a non-profit organization dedicated to the wise and efficient use of water in landscape, golf and agriculture.
Case Studies
Red Rock Ranch
A general description of John Diener’s Integrated On-Farm Drainage Management system, which includes both drip tape and new-generation center pivot sprinklers equipped with smart controllers for precise irrigation scheduling. From the California Institute for Rural Studies report California Water Stewards.
Button & Turkovich
Tony Turkovich talks about the use of drip irrigation and other water stewardship practices on crops.
Adragna Ranch
The ranch shifted from using a gated pipe sprinkler system to low-flow buried pipe sprinklers that distribute water uniformly throughout the walnut grove. From the California Institute for Rural Studies report California Water Stewards.
