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Efficient Irrigation Practices

Laura Garza, Ph.D.

Water and Climate Change advisor

UC Cooperative Extension

Mendocino and Lake Counties

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1) Irrigation 101

Water Budget /Evapotranspiration

2) Irrigation and Crop Requirement

3) Irrigation Efficiency

4) Efficient Irrigation Practices

System Design and Application Uniformity
Irrigation Scheduling
Monitoring and Maintenance

5) Benefits

CONTENT

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IRRIGATION 101

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IRRIGATION 101

Water Budget

Runoff

Precipitation

Irrigation

Evaporation

Transpiration

Infiltration

The foundation and the basics of irrigation systems and the effective use of water resources is the Water Budget!

It all begins with precipitation and/or irrigation– water falling into our crop
When precip/applied water hits the ground, some of it soaks into the soil through a process called infiltration. Not all water infiltrates the soil. Excess water that cannot be absorbed creates runoff.

The soil acts like a sponge, absorbing water., this water will reach the root zone
Now this is when the Plants play its role too! They absorb water through their roots. That water is then used for growth, development, photosynteis and release it into the air through small pores in their leaves in a process called transpiration.
At the same time, the heat from the sun is evaporating water from the surface of the soil
These two components of the water budget are really important in irrigation

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IRRIGATION 101

Evapotranspiration (ET)
�Loss of water through
Evaporation + Transpiration

ET = Crop water needs

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IRRIGATION 101

Water Budget

Soil

Plants

Precipitation

Irrigation

Evaporation

Transpiration

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IRRIGATION 101

Factors Affecting Evapotranspiration (ET)

Temperature
Wind
Soil Moisture
Solar Radiation
Region / Altitude

ET = Crop water needs

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IRRIGATION 101

Water Budget

Precipitation

Irrigation

Evaporation

Transpiration

ET is very specific to the types of crops and even to where are they grown.

There are some key Factors that affect the rate of evapotranspiration include the amount of solar radiation, atmospheric vapor pressure, temperature, wind, and soil moisture.

The same crop grown in the cost and more inland will have different ET or crop requirements.

Estimating the amount of water that plants evapotranspirate is a necessary initial step in figuring out the total amount of your crop water needs

Temperature:

Warmer temperatures generally lead to increased evapotranspiration as higher temperatures enhance the energy available for water to transition from liquid to vapor.

Wind Speed:

Increased wind speed enhances evapotranspiration by removing the moist air around plants or water surfaces, creating a gradient that encourages more water vapor to move into the atmosphere.

Soil Moisture Content:

The availability of soil moisture directly affects evapotranspiration. When soil is dry, evaporation rates may be higher, but transpiration rates from plants can be limited. Soil properties, such as texture and composition, influence how well water can be retained or drained. Sandy soils typically allow for faster evaporation compared to clayey soils.

Solar Radiation:

Intense sunlight provides the energy needed for evapotranspiration. Cloud cover or shading can decrease solar radiation, thereby affecting the rate of evapotranspiration.

Vegetation Type and Density:

Different plants have varying rates of transpiration. Dense vegetation cover tends to increase transpiration rates, influencing overall evapotranspiration.

Altitude:

At higher altitudes, the air pressure is lower, and water evaporates more easily. This can affect evapotranspiration rates in mountainous regions.

Urbanization:

Urban areas with extensive impervious surfaces, such as asphalt and concrete, may experience altered evapotranspiration patterns compared to natural landscapes.

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CROP/IRRIGATION REQUIREMENT

Crop Requirement: Amount of water supplied by irrigation to satisfy crop needs in terms of evapotranspiration
Irrigation requirement = crop + other requirements

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CROP/IRRIGATION REQUIREMENT

Frost Protection

Evapo-transpiration

(ET)

Leaching

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IRRIGATION EFFICIENCY

Volume of water applied to the crop compared to the volume of water required by the crop for its irrigation requirement.

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IRRIGATION EFFICIENCY

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IRRIGATION EFFICIENCY

Volume of water applied to the crop compared to the volume of water required by the crop for its irrigation requirement.

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IRRIGATION EFFICIENCY

Crop requirement = 12 inches �Applied water = 16 inches

Irrigation Season

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IRRIGATION EFFICIENCY

Volume of water applied to the crop compared to the volume of water required by the crop for its irrigation requirement.

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IRRIGATION EFFICIENCY

Irrigation requirement = 12 inches �Applied water = 16 inches

How efficient was our irrigation application?

Irrigation Season

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IRRIGATION EFFICIENCY

Volume of water applied to the crop compared to the volume of water required by the crop for its irrigation requirement.

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IRRIGATION EFFICIENCY

Crop requirement = 12 inches �Applied water = 16 inches

Irrigation Season

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EFFICIENT IRRIGATION PRACTICES

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

EFFICIENT IRRIGATION PRACTICES

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Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

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Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Surface�

Sprinklers�

Microirrigation

Factors to think about:

- natural conditions�- type of crop�- type of technology�- previous experience�- required labor inputs�- costs and benefits.�

Application efficiency: 50 – 75%

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Application efficiency: 70 – 90%

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Application efficiency: 85 – 95%

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Irrigation Systems

There are a lot of decisions to consider when optimizing your irrigation system:

What type of system makes the most sense for the plants you’re growing? The typethat you choose will depend on different factors for example: the topography, soil texture and crops to be grown on your farm.

Surface irrigation types include basins, boarders and furrows. Surface irrigation is generally used in fields with moderate slopes. It requires lower is less expensive to operate tends to be the most labor intensive and the least water efficient option for irrigation.

Sprinkler irrigation systems provide more control and higher efficiency than surface irrigation and come in a variety of types appropriate for different cropping systems: center pivot, linear move, big guns, wheel roll

Microirrigation systems consist of laterals containing emitters (drip or trickle irrigation) or microsprinklers, irrigate individual plants or groups of plants rather than the entire soil surface. Microirrigation systems are usually permanently installed and can be expensive.�

Microirrigation is a common choice for many farmers growing vegetables or fruit crops this is a highly efficient irrigation system, and many small-acreage producers find that the cost is worth the control and efficiency that they gain by using this system.

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Distribution Uniformity�

Distribution Uniformity (DU) measures how well irrigation water and fertigation is distributed to different areas in the field.

How to achieve good DU and good IE

Monitor drip emitter flow rates
Check pressure at the pump and drip hoses
Replace plugged emitters or damaged hoses.
Evaluate DU every 3 to 5 years

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Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

A uniform distribution allows the grower more control over the field and the inputs that are applied. DU measures how well irrigation and fertigation is distributed to different areas in the field.

Calculating distribution uniformity involves some in-field work, and growers can do it themselves or contract it out. The flow of the emitters is measured, and distribution uniformity is calculated by the average flow of the lowest 25% emitters divided by the average flow of all the emitters.

1. Poor Irrigation Efficiency and Distribution Uniformity:

Issue: Inefficient system and Uneven distribution leads to overwatering in some areas and underwatering in others, impacting crop health and soil quality.

2. Poor Irrigation Efficiency and Good Distribution Uniformity:

Issue: Despite even water distribution, the system is inefficient, resulting in significant water wastage. Or plants getting too much fertilizer/nitrogen.

3. Good Irrigation Efficiency and Distribution Uniformity:
Ideal Scenario: Efficient system uniformly delivers water. Optimal water usage enhances crop growth, yields, and environmental sustainability. Achieved through modern technologies and proper maintenance.

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Calculating distribution uniformity involves some in-field work, and growers can do it themselves or contract it out. The flow of the emitters is measured, and distribution uniformity is calculated by the average flow of the lowest 25% emitters divided by the average flow of all the emitters.

�DU = Average flow of lowerst 25% emitters / average flow of all emitters

For example, a grower has 16 emitters, and the lowest four of them have an average flow of 0.87 gallons per hour (gph). The average flow of all the emitters combined measures 0.97gph. By using the DU equation, this grower has a 90% distribution uniformity. If the average flow of those same bottom 25% dropped to 0.67gph, with the same 0.97gph field average, this would result in closer to a 70% distribution uniformity – cause for concern

https://nationalnutgrower.com/article/understanding-the-principles-of-irrigation-efficiency-in-pistachio/

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Soil-based

Irrigation scheduling involves planning when and how much water to apply

A major part of any irrigation management is deciding when to irrigate and how much water to apply to the field. This decision-making process is referred to as irrigation scheduling.

Irrigation scheduling offers several advantages:

It enables the farmer to schedule water rotation among the various fields to minimize crop water stress and maximize yields.
It reduces the farmer’s cost of water and labor through fewer irrigations, thereby making maximum use of soil�moisture storage.
It lowers fertilizer costs by holding surface runoff and deep percolation (leaching) to a minimum.
It increases net returns by increasing crop yields and crop quality.
It minimizes water-logging problems by reducing the drainage requirements.
It assists in controlling root zone salinity problems through controlled leaching.
It results in additional returns by using the “saved” water to irrigate non-cash Crops that otherwise would not be irrigated during water-short periods.

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Soil-based

Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Assessing the moisture content in the soil

Types of soil moisture sensors:

1) Volumetric: measure water content

2) Tension: measure soil tension when placed in the soil profile.

It’s important to understand the soil water content at which a crop begins to experience stress.

One of the easiest and most effective ways to improve irrigation efficiency is to implement soil sensor. This method relies on measuring the soil moisture levels in the plant root zone .

For irrigation scheduling, it's important to understand the soil water content at which a crop begins to experience stress

Sensors that measure volumetric water content and 2) Sensors that measure soil tension

In general, most crops begin to experience stress when soil water depletion/deficit is 30-50% of available water holding capacity (AWC).
Soil water tension indicates the energy required by plant roots to extract water from soil particles. As soil water is removed from soil, soil tension increases. Soil tension is expressed in centibars (cb) or bars of atmospheric pressure. When the soil is full of water, soil water tension is close to zero. For coarse textured soils, AWC is 50% depleted when soil tension is at 25-45 cb. In these soils, a crop should be irrigated before the sensor indicates 25-45 cb.

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Crop water Needs

ET_crop = ET_refx K_crop

_{Evapotranspiration of my crop = is my crop water needs}

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Crop water Needs

ET_crop = ET_refx K_crop

Reference ET is the water needs of grass

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Crop water Needs

ET_crop = ET_refx K_crop

Kc is the crop coefficient. It represents the integrated changes in plant development

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Irrigation Scheduling Tools

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Crop water Needs

ET_crop = ET_refx K_crop

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Crop Requirement

Applied Water

1.1’’

0.7’’

4.2’’

1.7’’

ETc

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Crop water Needs

ET_crop = ET_refx K_crop

Crop Requirement

Applied Water

Crop requirement is 12’’ but initially we applied 16’’

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Irrigation Scheduling

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Weather ET-based

Crop water Needs

ET_crop = ET_refx K_crop

Crop Requirement

Applied Water

Lower applied water

by using irrigation scheduling we can lower the applied water closer to 12’’

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Assess your irrigation system

Install monitoring devices and tools

Inspections and maintenance

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

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EFFICIENT IRRIGATION PRACTICES

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

EFFICIENT IRRIGATION PRACTICES

SUMMARY

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EFFICIENT IRRIGATION PRACTICES

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

EFFICIENT IRRIGATION PRACTICES

SUMMARY

Selecting the appropriate irrigation system will enhance the application uniformity of your irrigation. Allowing more control over your field and the inputs applied.

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EFFICIENT IRRIGATION PRACTICES

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

EFFICIENT IRRIGATION PRACTICES

SUMMARY

Selecting the appropriate irrigation system will enhance the application uniformity of your irrigation. Allowing more control over your field and the inputs applied.

Deciding when and how much to irrigate will:

Achieve high irrigation efficiency
Maximize yields
Save water and fertilizer
Reduce labor and costs

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EFFICIENT IRRIGATION PRACTICES

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

EFFICIENT IRRIGATION PRACTICES

SUMMARY

Selecting the appropriate irrigation system will enhance the application uniformity of your irrigation. Allowing more control over your field and the inputs applied.

Deciding when and how much to irrigate will:

Achieve high irrigation efficiency
Maximize yields
Save water and fertilizer
Reduce labor and costs

Tools such as flowmeters, soil moisture sensors and regular check ups and inspections provide real-time data allowing the grower to make informed decisions.

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BENEFITS �OF EFFICIENT�IRRIGATION

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Conserve Water

Minimize nutrient loss

Reduced costs

Drought Adaptation

Increase yields

Efficient Irrigation Practices

Irrigation System Design

Irrigation Scheduling

Monitoring and Maintenance

Improved Crop Yield and Quality:

Precise irrigation ensures that crops receive the right amount of water at the right time, promoting optimal growth and development. This, in turn, leads to improved crop yields and better quality produce.

Water Conservation:

Efficient irrigation methods, such as drip or precision irrigation, minimize water waste by delivering water directly to the roots of plants. This helps conserve water resources, especially in regions facing water scarcity.

Minimized Mutrient loss and Soil Erosion:

Proper irrigation helps maintain consistent soil moisture levels, reducing the risk of soil erosion. This is crucial for preserving soil structure and fertility.
Some efficient irrigation methods, like drip irrigation, can be combined with fertilization systems to precisely deliver nutrients to the root zones, ensuring that plants receive the required nutrients for optimal growth.

Cost Savings:

Reduced water usage results in lower water bills. Additionally, efficient irrigation systems often require less energy, leading to cost savings in pumping and distribution.
Modern irrigation technologies, such as drip and sprinkler systems, are designed to be energy-efficient, reducing the amount of energy required for water distribution. This is particularly important for sustainable agriculture.

Adaptation to Climate Variability:

With climate patterns becoming more unpredictable, efficient irrigation allows farmers to adapt to changing conditions by adjusting water application in response to weather fluctuations.

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THANK YOU!�

Laura Garza

Water and Climate Change advisor

Mendocino and Lake Counties

legarza@ucanr.edu

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