A University of Cordoba and Spanish National Research Council research team validated an indicator based on using a tree's temperature to calculate relative water consumption at an almond tree plantation
In 1995, the severe drought that devastated Spain left some farms using irrigation agriculture without water supplies. Though it has not happened again since, climate change increases the chance of this threat. For farmers growing annual crops, an occurrence such as this one would mean losing a year's work but those who have groves of trees risk losing not only their year's production, but their long-term investment as well.
A research team from the University of Cordoba and the Institute for Sustainable Agriculture at the Spanish National Research Council in Cordoba has been working for years on several projects to improve water management and maximize the productivity of tree crops such as olives, almonds and citrus fruits. One of their lines of research is based on the fact that when there is a water shortage, trees transpire less, get warmer, and end up producing less.
In their latest research project, they studied how an indicator called Crop Water Stress Index (abbreviated to CWSI), based on detecting temperature increase in trees with water stress, is related to relative water consumption in an almond grove. Tree water consumption or transpiration is very difficult to measure whereas a tree's temperature is easily taken using remote sensors, similar to those used on a daily basis during the pandemic to detect people with fevers. In their latest work, this group experimentally demonstrated for the first time that there is a relationship between relative transpiration and the CWSI in almond trees. So, farmers can find out at any moment if the trees are consuming water at 80-90% of their capacity, meaning within optimal levels, or if they have high levels of stress and urgently need to be supplied with more water.
"This indicator, the CWSI, has the advantage that relative water consumption can be determined via remote sensing, using drones or manned planes and a map of the transpiration in different areas of a plantation can be obtained. In the future, satellites will most likely be used to do this work very precisely on big plantations", explains Elías Fereres, Professor Emeritus of the Agronomy Department at the University of Cordoba and a member of the research team, which is led by Victoria González Dugo from the Institute for Sustainable Agriculture at the Spanish National Research Council.
Therefore, these CWSI maps will allow for irrigating different areas of a farm in different ways in terms of the water level needed at each moment, thus maximizing production with the minimal necessary water resources or those available at the time. This research is within the framework of the technique known as precision irrigation, a new system that uses the most advanced technology to irrigate at an optimal level, supplying the exact amount of water to every part of the grove and circumventing losses. "The aim is to use water effectively and where it is most needed", points out Elías Fereres.
Though the research was performed on almond plantations, this research could be used on other tree crops such as olive trees, which are so important to the economy in Andalusia and on many occasions suffer from times of water shortages.
A related project on which the group is also working is being led by Professor Francisco Villalobos from the University of Cordoba. It is called Project Olive-Miracle, which aims to develop a model to forecast how olive trees behave to climate change, which would provide more information in order to make decisions in the sector in the future.
V. Gonzalez-Dugo, L. Testi, F.J. Villalobos, A. López-Bernal, F. Orgaz, P.J. Zarco-Tejada y E. Fereres. "Empirical validation of the relationship between the crop water stress index and relative transpiration in almond trees". Agricultural and Forest Meteorology
DOI: https://doi.org/10.1016/j.agrformet.2020.108128
A is for Almond but also for Avocado
avocados on a tree picture
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Friday, November 6, 2020 at
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Focus Area Tags: Agriculture
If you have an ash, Chinese pistache, crape myrtle, flowering pear, ginkgo, liquidambar or any...
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Thursday, September 24, 2020 at
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Old crop, new crop. What's up there in the trees? Are they big enough to sell? Is there a good set for next year? These are questions every avocado grower has every year, and often all year long. What is up there in the trees is confounded by what is called the "Avocado Illusion".
In a Science Magazine Letters to the Editor in Dec 1990, Paul Sandorff commented on a book written by Maurice Hershenson called The Moon Illusion. In the book Hershenson described the illusion of why the moon seemed so much larger when it was on the horizon than when it rose to its zenith on the same night. http://science.sciencemag.org/content/250/4988/1646.1
Sandorff said that this illusion applied to avocados since it was so hard to gauge the size of avocados when they were in the tops of the tree canopy. It is the surrounding environment that puts a context to size according to this theory of illusion.
Hershenson added to this observation in the March 1991 Science letters section with the comment that the leaves surrounding the fruit changes our depth perception and so changes our idea of the fruit size.
A further addendum to the avocado illusion theory is that since the fruit are the same color as the leaves (they are both dark green and the fruit unlike most other fruit continues to photosynthesize), it is hard to actually make out the fruit. You can be looking right at the fruit and not see it, confusing it with a leaf.
This illusion makes for difficult fruit estimation. To compensate for this illusion, I will eye the canopy in quadrants, counting the number of fruit, then arbitrarily doubling that total number. It usually gives a pretty close number to the real number of fruit that are in the tree.
Photo:
Can you count the number of fruit in this canopy?
canopy fruit avocado
Posted on
Wednesday, May 10, 2017 at
5:43 AM
The first years of a tree's life are for building a structure for the future. Many varieties of trees are precocious and will bear fruit when they should be building structure. Letting a tree carry fruit when it is too young (under 2 years of age in the ground and some say 5 depending on the tree species) delays future good production and distorts the tree's architecture. A young avocado tree can be completely humbled (brought to ground literally) by the weight of the 12 ounce fruit. ‘Lamb Hass' wants to grow upright, but if the young tree is burdened with fruit early on, it will grow squat and twisted.
Another problem with precocious trees recently came up with ‘Meyer' lemon. Along the coast, this is a tree that will carry fruit throughout the year. It is a small tree naturally, but also because it puts so much energy into fruit production. If allowed to fruit to its full potential early, the canopy development is delayed and the fruit grows unprotected from winds. It is much more subject to wind scarring. Imagine the wind flailing the fruit around with no branches or leaves to protect it. Now the grower has a small, twisted fruit tree and fruit that can't be sold.
Give your young trees a chance to grow without the burden of carrying fruit to early. They are your children.
Imagine all this fruit on a one year old canopy
And this fruit is fully exposed to the elements and wind scarring
Lamb Hass pulling on tree
meyer lemon wound
Posted on
Wednesday, September 2, 2015 at
12:12 PM
Transpiration is essentially a function of the amount of leaves present. With no leaves, there is no transpiration and no water use. The extreme case is tree removal. If canopies are pruned there is reduced water use. The more canopy reduction, the more transpiration reduction. Most citrus produces terminal flowers, so there is also a reduction in yield, but there is also typically an increase in fruit size as competitive fruit growing points are removed. There is a balance between yield reduction and tree water use, but typically a 25% canopy reduction results in a 25% decrease in tree water use (Romero, 2006).
The severity of the drought will determine how drastic the canopy should be trimmed. The trees can be skeletonized so that only the main structural branches are left. The tree is whitewashed to prevent sunburn and the water is turned off. As the tree gradually leafs out, the water is gradually reapplied in small amounts. It's important to check soil moisture to make sure the tree do not get too much or too little water. The trees if pruned in the winter will often flower a year later in the spring, but normal production will often take three years for the trees to recover their previous yields.
Skeletonizing should first be practiced on orchards that are the poorest producing. In those areas that get too much wind and have lots of wind scarring or elevated water use, those areas that are most prone to frost damage, those areas that have been always problematic, such as fruit theft. In areas that are healthy and a new variety has been contemplated, this is the time to topwork and replace that old variety. In areas that have been poor producing from disease, this is the time to get rid of those trees.
Canopy sprays of kaolinite clay have shown some promise in reducing transpiration with negligible yield reduction (Skewes, 2013; Wright, 2000). If these are used, they should be done under the advisement of the packing house to make sure the clay can be removed in the packing house.
With a reduced canopy, there are often other benefits besides water reduction. There is better spray coverage for pest control. There is also reduced fertilizer use. New growth is normally coming from nutrients that are now being mined by a large root system and fertilizer applications can be significantly reduced or eliminated altogether for a year until fruit set recommences.
Citations
Kerns, D. and G. Wright. 2000. Protective and Yield Enhancement qualities of yield of kaolin on lemon. In: Eds. G. Wright and D. Kilby, AZ1178: "2000 Citrus and Deciduous Fruit and Nut Research Report," College of Agriculture and Life Sciences, University of Arizona. http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1178_3.pdf
Skewes, M. 2013 Citrus Drought Survival and Recovery Trial. HAL Project Number CT08014 (16/12/2013). SARDI. http://pir.sa.gov.au/__data/assets/pdf_file/0004/238414/SARDI-Citrus-Drought-Survival-Recovery-Trial.pdf
Navel trees skelotinized and topworked, ready for rain and more profits in the future.
navels skeletonized and grafted
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Wednesday, August 5, 2015 at
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