Subtropical Fruit Crops Research & Education
University of California
Subtropical Fruit Crops Research & Education

Posts Tagged: irrigation

It's NOT Just Heat Stress, It's Lack of Water for Cooling

Plants lose water through their leaves and it's called transpiration.  People lose water off their skin and it's called evaporation or sweating.  When a plant stops losing water and when people cant produce enough sweat to cool off, both overheat.  The weather influences that drive this water loss - water that needs to be replaced or the bodies begin to go into heat stress - are the amount of light (day length, cloud cover), relative humidity (it dries faster when air is dry and slower when humid - think desert versus Florida),  and windy (more wind, more drying).  Temperature is important, but not as much as these other drivers. Think freeze-drying  - a very successful process for removing water from food.  Often humans respond more to temperature than these other factors and figure, when it's cool. it's not necessary to water their plants, themselves or their workers.

Heat stress is more complicated than this, of course, but below are some helpful guidelines to follow to avoid heat stress:

https://www.dir.ca.gov/dosh/heatillnessinfo.html

Cal/OSHA HEAT ADVISORY

When employees work in hot conditions, employers must take special precautions in order to prevent heat illness. Heat illness can progress to heat stroke and be fatal, especially when emergency treatment is delayed. An effective approach to heat illness is vital to protecting the lives of California workers.

California law requires employers to identify and evaluate workplace hazards and take the steps necessary to address them. The risk of heat illness can be significantly reduced by consistently following just a few simple steps. Employers of outdoor workers at temporary work locations must be particularly alert and also plan for providing first aid and emergency medical services should they become necessary. All workers should be accounted for during and at the end of the work shift. Heat illness results from a combination of factors including environmental temperature and humidity, direct radiant heat from the sun or other sources, air speed, and workload. Personal factors, such as age, weight, level of fitness, medical condition, use of medications and alcohol, and acclimatization effect how well the body deals with excess heat. 

Heat Illness Risk Reduction

1. Recognize the Hazard. There is no absolute cut-off below which work in heat is not a risk. With heavy work at high relative humidity or if workers are wearing protective clothing, even work at 70oF can present a risk. In the relative humidity levels often found in hot areas of California (20 to 40 percent) employers need to take some actions to effectively reduce heat illness risk when temperatures approach 80 F. At temperatures above 90 F, especially with heavy work, heat risk reduction needs to be a major concern.

    2. Water. There must be an adequate supply of clean, cool, potable water. Employees who are working in the heat need to drink 3-4 glasses of water per hour, including at the start of the shift, in order to replace the water lost to sweat. For an eight-hour day this means employers must provide two or more gallons per person.  Thirst is an unreliable indicator of dehydration. Employees often need ongoing encouragement to consume adequate fluids, especially when the workload or process does not encourage breaks.

3. Shade. The direct heat of the sun can add as much as 15 degrees to the heat index. If possible, work should be performed in the shade. If not, employers where possible, should provide a shaded area for breaks and when employees need relief from the sun. Wide brimmed hats can also decrease the impact of direct heat.

  1.  Acclimatization. People need time for their bodies to adjust to working in heat. This “acclimatization” is particularly important for employees returning to work after (1) a prolonged absence, (2) recent illness, or (3) recently moving from a cool to a hot climate. For heavy work under very hot conditions, a period of 4 to 10 days of progressively increasing work time starting with about 2 hours work per day under the working conditions is recommended. For less severe conditions at least the first 2 or 3 days of work in the heat should be limited to 2 to 4 hours. Monitor employees closely for signs and symptoms of heat illness, particularly when they have not been working in heat for the last few days, and when a heat wave occurs. 
  2.  Rest Breaks. Rest breaks are important to reduce internal heat load and provide time for cooling. Heat illness occurs due to a combination of environmental and internal heat that cannot be adequately dissipated. Breaks should be taken in cooler, shaded areas. Rest breaks also provide an opportunity to drink water.
  3.  Prompt Medical Attention. Recognizing the symptoms of heat illness and providing an effective response requires promptly acting on early warning signs. Common early symptoms and signs of heat illness include headache, muscle cramps, and unusual fatigue. However, progression to more serious illness can be rapid and can include unusual behavior, nausea/vomiting, weakness, rapid pulse excessive sweating or hot dry skin, seizures, and fainting or loss of consciousness. Any of these symptoms require immediate attention.

Even the initial symptoms may indicate serious heat exposure. If medical personnel are not immediately available on-site, and you suspect severe heat illness, you must call 911.

Regardless of the worker's protests, no employee with any of the symptoms of possible serious heat illness noted above should be sent home or left unattended without medical assessment and authorization.

7. Training. Supervisors and employees must be trained in the risks of heat illness, and the measures to protect themselves and their co-workers. Training should include:

  • Why it is important to prevent heat illness
  • Procedures for acclimatization
  • The need to drink approximately one quart per hour of water to replace fluids.
  • The need to take breaks out of the heat
  • How to recognize the symptoms of heat illness
  • How to contact emergency services, and how to effectively report the work location to 911.

Photo: Heat Stress to avocado leaves.

heat damage to avocado leaves
heat damage to avocado leaves

Posted on Friday, April 12, 2019 at 3:18 PM

Citrus? Water? How Do They Go Together?

Advances in Citrus Water Use

                         Workshop & Field Day

Tuesday, March 26, 2019

8 Am - 3 PM

Strathmore, CA

 

Attend the Advances in Citrus Water Use Workshop & Field Day and join UC Davis Irrigation Specialist Daniele Zaccaria as well as other water experts and specialists from the University of California Cooperative Extension, the California Department of Water Resources, and the Citrus Research Board to learn about research advances in water use and irrigation for citrus production. Gain firsthand practical knowledge of the latest developments in the citrus industry and become familiar with methods and tools to measure evapotranspiration (ET) and crop coefficients (Kc), tree water status, and monitor soil moisture to inform irrigation planning and scheduling decisions for citrus. 

 

What to expect?

Session topics include:

  • Current research
  • Water management and regulation
  • Optional Field Session on irrigation technology

View a tentative agenda here.

 

 

Registration Details

 

$35 registration fee includes admission to the field day, coffee, refreshments, and lunch.

 

 

 

Register online, here. Fee will increase on March 13.

 

 

Limited to the first 150 participants

 

 

Logistics and Registration

ANR Program Support, Julia Kalika, (530) 750-1380 or Shannon Martin, (530) 750-1328

citrus cornucopia
citrus cornucopia

Posted on Friday, March 8, 2019 at 1:44 PM
Tags: citrus (304), irrigation (75), water (47)

Water is Life and Watering Citrus is Critical - Come Learn

Advances in Citrus Water Use

               Workshop & Field Day

Tuesday, March 26, 2019

8:00 AM-3:00 PM

Strathmore, California

Register NOW!!!

 https://ucanr.edu/sites/citrusfieldday/Registration/

About the Field Day

 

Attend the Advances in Citrus Water Use Workshop & Field Day and join UC Davis Irrigation Specialist Daniele Zaccaria as well as other water experts and specialists from the University of California Cooperative Extension, the California Department of Water Resources, and the Citrus Research Board to learn about research advances in water use and irrigation for citrus production. Gain firsthand practical knowledge of the latest developments in the citrus industry and become familiar with methods and tools to measure evapotranspiration (ET) and crop coefficients (Kc), tree water status, and monitor soil moisture to inform irrigation planning and scheduling decisions for citrus. 

 

What to expect?

Session topics include:

  • Current research
  • Water management and regulation
  • Optional Field Session on irrigation technology

View a tentative agenda here.

Registration Details

$35 registration fee includes admission to the field day, coffee, refreshments, and lunch.

 

Register online, here. Fee will increase on March 13.

 

Limited to the first 150 participants.

Contacts for More Information

 

Logistics and Registration

ANR Program Support, Julia Kalika, (530) 750-1380 or Shannon Martin, (530) 750-1328.

 

Course Content 

Daniele Zaccaria, UC Cooperative Extension Specialist, Agricultural Water Management

 

citrus cornucopia
citrus cornucopia

Posted on Friday, March 8, 2019 at 1:26 PM
Tags: citrus (304), field day (4), irrigation (75), water (47)

Frost and Rain?

It is that time of year and we should be alert to threat of freezing weather and damage to trees. Last winter was one of the warmest on record, but there was still a sneak cold blast around December 25 that caused some problems in some areas. Wet winters tend to have lower frost threats, and even though wet is forecast for this winter, the forecast is erratic, as usual. That still leaves January which historically is when most of our damaging frosts occur. Fox Weather on the CA Avocado Commission is forecasting some cold weather coming up, so growers need to be prepared for the worst.

http://www.californiaavocadogrowers.com/articles/30-day-weather-outlook-december-7-2015-january-7-2015

 

Here are some links to frost information, preparing for frost and managing frost damage to trees.

A Frost Primer

http://ceventura.ucanr.edu/Com_Ag/Subtropical/Publications/Frost/A_Frost_Primer_-_2002_/

Methods of Frost Protection

http://ceventura.ucanr.edu/Com_Ag/Subtropical/Avocado_Handbook/Frost_Control_Freeze_Damage_/Methods_of_Frost_Protection_/


Protecting Avocados from Frost

http://ceventura.ucanr.edu/Com_Ag/Subtropical/Avocado_Handbook/Frost_Control_Freeze_Damage_/Protecting_Avocados_from_Frost_/


Rehabilitation of Freeze-Damaged Citrus and Avocado Trees

http://ceventura.ucanr.edu/Com_Ag/Subtropical/Avocado_Handbook/Frost_Control_Freeze_Damage_/Rehabilitation_of_Freeze-Damaged_Citrus_and_Avocado_Trees_/

The forecast is for north winds, which often means cold, dry air and often with winds. Winds mean no inversion and no warm air that can be introduced at ground level to warm trees. If this occurs, running a wind machine can make the damage worse. Wind machines and orchard heaters work on the principle of mixing that warmer air higher up – 20-100 or so feet higher than ground level which has colder air. When temperatures drop, the air is dry (wet-bulb temp below 28 deg F) and there is no inversion, running a wind machine can just stir up cold air and cause worse conditions (freeze-drying). It's better to not run the machine. The only thing left to do is to run the microsprinklers during the day so that the water can absorb the day's heat. Then turn the water off before sunset so that evaporative cooling from the running water isn't accentuated. Then when temperatures drop near 32 at night and the dewpoint is much below that, it's time to start the water again and let it run until sunrise (when risk is less). Running water works even if the water freezes. This is due to the release of heat when water goes from liquid to frozen state. This 1-2 degrees can mean the difference between frost damage and no damage. Also, ice on fruit and leaves can insulate the fruit. As the ice melts at the surface of the plant, it releases heat, protecting the plants. If there is not sufficient water to run the whole orchard, it's best to pick out the irrigation blocks that are the coldest or the ones you definitely want to save and run the water there continuously. Running the water and turning it off during the night to irrigate another block can lead to colder temperatures in both blocks.

 

Keep warm this winter.

and check out this Wind Machine You Tube:

https://www.youtube.com/watch?v=rwTJveN8cIE

Wind Machine frost
Wind Machine frost

Posted on Wednesday, January 9, 2019 at 4:46 PM
Tags: avocado (272), citrus (304), frost (17), irrigation (75), water (47), wind (5)

Ready! Set! Split! Navel Orange Time.

These are hard days for navel oranges.  Drought stress.  Salt stress due to drought. Then a heat wave in July that messed the trees up.  And now we head into a weird fall with maybe rain. Maybe no rain. Maybe a little rain. This is ripe for navel splitting. This time of year when they are starting to build sugar, they are also ripe for splitting.

Years of drought, and a stressed tree are a perfect set up for navel oranges and fruit splitting.
The days have turned cooler and suddenly out of nowhere there is rain. That wonderful stuff comes down and all seems right with the world, but then you notice the navel fruit are splitting. Rats! No, a dehydrated fruit that has taken on more water than its skin can take in and the fruit splits. This is called an abiotic disease.  Not really a disease but a problem brought on by environmental conditions.

Fruit splitting is a long-standing problem in most areas where navel oranges are grown. In some years, the number of split fruit is high; in other years it is low. Splitting in navel oranges usually occurs on green fruit between September and November. In some years, splitting may also occur in Valencia oranges but it is less of a problem than in navel oranges.

Several factors contribute to fruit splitting. Studies indicate that changes in weather including temperature, relative humidity and wind may have more effect on fruit splitting than anything else. The amount of water in a citrus tree changes due to weather conditions and this causes the fruit to shrink and swell as water is lost or gained. If the water content changes too much or too rapidly the rind may split. In navel oranges the split usually occurs near the navel, which is a weak point in the rind.

Proper irrigation and other cultural practices can help reduce fruit splitting. Maintaining adequate but not excessive soil moisture is very important. A large area of soil around a tree should be watered since roots normally grow somewhat beyond the edge of the canopy. Wet the soil to a depth of at least 2 feet then allow it to become somewhat dry in the top few inches before irrigating again. Applying a layer of coarse organic mulch under a tree beginning at least a foot from the trunk can help conserve soil moisture and encourage feeder roots to grow closer to the surface.  

If trees are fertilized, apply the correct amount of plant food and water thoroughly after it is applied.  If the soil is dry, first irrigate, then apply fertilizer and irrigate again.

navel split
navel split

Posted on Friday, November 2, 2018 at 4:55 AM
Tags: citrus (304), irrigation (75), navel orange (2), rain (17), water (47), weather (8)

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