- Author: Mindy Robinson
Coming to citrus orchards?
An ongoing study in hazelnut orchards offers possible electric weed control (EWC) solutions for other tree nut orchards, especially in light of increasing herbicide resistance.
Marcelo Moretti, Assistant Professor at Oregon State University, conducted two studies in 2021 utilizing EWC to manage Italian ryegrass in hazelnut orchards. One study focused on the necessary speed of operation to provide effective weed management. The second, multi-year study focuses on crop safety when using EWC.
Because hazelnuts are harvested from the ground, they are grown conventionally with mostly no cover crops and no tillage. Mowing suppresses the tops of weed plants but requires too many passes to be effective.
For the herbicides used in hazelnuts, growers are seeing resistance to all of the post-emergent herbicides such as paraquat and glufosinate, Moretti says. Thus, a non-chemical weed control alternative is needed.
“The end goal is to control or eliminate (weed) seed production in order to have the benefits of rye grass as a cover crop but be able to kill it when not needed,” Moretti says.
With today's growing herbicide resistance, commercial developers such as Zasso, RootWave, and Crop.Zone have developed EWC units focused on meeting the needs of different agricultural users.
HOW EWC WORKS
EWC kills weeds with thermal energy. A high-voltage electrode touches the foliage of the plant, allowing an electric current to pass through the plant; electric resistance in the plant converts the electrical energy to heat, killing the plant. The higher the plant's conductivity, the less energy it takes to kill the plant.
An EWC unit is typically tractor-mounted, and the unit's generator is connected to a PTO (Power Take Off). The generator is coupled to a transformer that increases the voltage. A module controller connects to the electrodes that are contained in sets of electrical fingers, which provide applicator contact to the plants and the soil. The applicators vary in shape and size, which is dictated by the size of the generator. A 30 kVA generator can treat about four feet at a time.
Along with equipment setup, the target plant and soil conditions play a role in the efficacy of the operation. Plant factors such as morphology, stage of development, water content, and plant density all affect EWC efficacy. Younger, herbaceous plants with high water content and particular root systems are more susceptible to EWC applications.
Soil factors include impedance, mineral composition, texture, moisture, temperature, and porosity. EWC is more effective in soils that have less conductivity, which forces the electricity to stay in the plants longer, creating more thermal energy. Optimum soils with low conductivity are lighter, sandy, dry, and warm.
STUDY RESULTS
Moretti's study on the necessary speed of operation for EWC using a Zasso unit shows that 9,000 volts at 2 mph efficiently kills Italian ryegrass. When soil conditions are wetter, the unit must be run at 5,000 volts to minimize the risks of damage to the EWC unit or the tractor. Although the 5,000-volt setup (at 1 mph) is less efficient, it does kill ryegrass.
Moretti's multi-year study on crop safety looks at variables such as plant variety, electric rates, and application — with and without suckers. The study will monitor tree growth, photosynthesis rate, and yield. Based on the 2021 results, EWC has not adversely affected crop safety.
Although not a part of the study, Moretti observed that yellow nutsedge, Canada thistle, field bindweed, and horsetail were all sensitive to EWC.
As the study progresses, cost factors also will be evaluated.
As expected, the most significant limitation of EWC is the potential for causing fires. In Oregon, EWC is not ideal when it is too dry (usually after July) or too wet.
EWC provides effective weed control at 2 mph, is initially safe to hazelnuts, and is safe to humans. It is compatible with existing production systems, as it does not damage irrigation lines.
The economics are to be determined but initially show to be about $50 per acre to implement — comparable to conventional herbicide application — after the initial equipment investment (Moretti purchased a Zasso unit for $50,000 in 2020 for this study). The benefits to the environment are that it leaves no chemical residue and does not require soil tillage.
From Growing Produce
And see what those folks at UC Davis are doing with electrical weed control - EWC
A Zasso electric weed control unit mounted on a tractor demonstrates its capabilities.
Photo by Marcelo Moretti, Oregon State University
- Author: Ben Faber
There's a lot of new trees going into the ground, both citrus and avocado. Especially avocados are getting tucked into lots of little corners. There's money to be made and maybe there will be in the future. One of the many issues of planting trees is you want to make sure that ground has been surveyed/evaluated/tested for various problems like salts and pH before planting. It's always easier to correct these issues before trees go in the ground. Once there, it can be a wild experience trying to figure out the problem, and by the time a plan of action has been worked out, trees are dead or stressed and it can be difficult to correct. Read a bit more about this HERE
However, the reason for this blog is really to point out that attention needs to be paid when planting trees. They cant be planted too deep. Burying the stem below the level at which they come from the nursery, can lead to serious problems like tree death. The most physiologically active portion of the root system is the crown, the point at which the roots start spreading out from the stem. Bury that area lower than it had been growing in the nursery, and it causes asphyxiation.
Planting can be a manic process of getting trees out and then moving across the landscape to get them into the ground and watered and adjusted to their new environment. It needs to be methodical and if the hole is too big and too much loose soil, or a planting mix is incorporated that eventually decomposes and allows the tree to sink below grade over time, the stem will get buried. Planting on mounds and berms can add to the problem when the planting site gradually settles over time and buries the stem. So many ways it can happen. The rule of thumb is if planting right doesn't work, it's better to plant high and allow time to settle the tree.
Following is a sequence arriving at a buried stem. Slow down, you move too fast, you want the planting to last.
It's tough planting on rocky hillsides
Something is not going well up there, one or two are dying
Tree is not doing well, and whitewash isn't helping much at this point
Where are the roots, just coarse ones? Notice the dirty paper trunk guard that has been buried
No small roots, this stem was buried too deep. Dieback in the root, means dieback in the canopy
- Author: Nicki Anderson
Community Education Specialist
A Fresh Soil Health Resource
In 2015, a group of graduate students at the University of California, Davis attended a hearing on California's Healthy Soils Initiative. They witnessed firsthand the power of storytelling to captivate an audience, as well as the challenges of communicating uncertainty and nuance regarding the dynamic nature of soil.
They started a seminar to discuss and develop science communication, which evolved into a campaign to raise awareness about the value and importance of soil, which caught the attention of the Natural Resource Conservation Service, and ultimately led to a collaboration to produce educational resources (links below).
Their mission is:
- To inspire the next generation of soil explorers for the benefit of all
- To educate that soils are living bodies that harbor a diversity of life, and support and sustain life as we know it
- To empower young power with solutions to some of our greatest global challenges; solutions that lie right beneath our feet!
After years of work, the Soil Life website has officially launched.
The site includes
1) An interactive, graphics-based introduction to soil science;
2) A media hub of soils-related content, and
3) Clear, actionable ways for people to 'get involved' protecting and promoting soils in their everyday lives.
They have also launched the first video in a 6-part series highlighting the connection between soil and life.
Check out their website,
Watch "The Story of Soil and Food," and
Share with your networks (especially the educators and young people in your lives!)
The website and videos were produced under a UC Davis/USDA-NRCS collaborative project and are part of a national campaign to raise awareness about the value and importance of soil.
- Author: Ben Faber
Why guess how much water to apply to reduce salt damage by going to a simple graphical interface with pull down menus and get a pretty good idea of how to use that water to improve tree performance. Most mature crops are listed, soils, water qualities, and irrigation systems. From UC Riverside - SALEACH Try it, you might like it.
Leaching is essential in irrigated croplands where natural precipitation is insufficient to control salinity buildup. Several useful models exist for salinity management; however, leaching requirement (LR) calculations are based on steady-state approaches that only consider salinity tolerance of crops and irrigation water salinity to estimate the LR. In this study, a web-based soil salinity leaching management model (SALEACH) was developed as an online tool to assist growers for better and easier management of soil salinity to sustain agricultural production in irrigated croplands. SALEACH employs the traditional steady-state approach to estimate LRs but improves outputs by not only considering irrigation water salinity (ECiw) and salinity tolerance of specific crops (ECt), but also root water uptake patterns to account for irrigation system differences, and soil types for differences in hydraulic characteristics, as well as water stress and rainfall input. The SALEACH model can calculate the required irrigation water depth by using the estimated LR or any user-specified leaching fraction (LF) values; it can predict the drainage water salinity and soil salinity in the rootzone based on the applied leaching; and it can estimate relative crop yield for a given LF. SALEACH-estimated LRs were assessed in different soil types and irrigation systems by comparing them with LRs, soil water and drainage water salinity values obtained from an existing steady-state model (WATSUIT) and a transient-state model (HYDRUS-1D). Statistical analyses showed that SALEACH-estimated LRs, soil salinity, and drainage water salinity were all in the acceptable ranges of the corresponding values derived from other models. Thus, we conclude SALEACH is reliable and can be employed by practitioners to produce satisfactory estimations of LRs and soil salinity by considering the soil, crop, water quality, and irrigation system. Adoption of the model can improve water use efficiency and reduce groundwater pollution.
- Author: Ben Faber
If you can sell your cowpeas, fava beans and barley, you can make money in Spain and apparently not use any more water than if just growing the mandarins. And coastal growers should look at the fresh market. Have you ever tasted a fresh green cowpea or fava bean? Pretty darn good and consumers think so, as well.
A Diverfarming project study compares the environmental footprint and the economic performance of traditional mandarin monocropping as opposed to growing mandarin intercropped with herbaceous crops and the use of deficit irrigation
The transformation towards intensive agriculture has led to agricultural practices in Europe that have centred on increasing the yield and reducing costs in recent decades, and which involve a major dependence on external sources of agrochemicals and energy. These intensive monocropping systems have generated biodiversity losses, water contamination, and high rates of greenhouse gas emissions, as well as degrading the soil and reducing the ecosystem services.
Faced with this situation, the European Diverfarming project has trialled the diversification of crops throughout the European Union, seeking the best practices to combine crops and focusing on reducing inputs to find the best options to preserve the sustainability of the systems and increase the resilience of the European agricultural sector. To do so, it is also necessary to know the impacts of these practices both at environmental as well as economic level.
With the aim of knowing the environmental footprint and the economic performance of the introduction of herbaceous crops among the alleys of the mandarin trees using controlled deficit irrigation in a mandarin grove located in the Region of Murcia, a team of researchers from the Universidad Politécnica de Cartagena have carried out a life-cycle assessment of the crop and an evaluation of the costs and income of the farm for the three years that the experiment in this case study was carried out.
Although the growing area increased with the introduction of the herbaceous crops (in this case purslane, cowpea, broad beans, and a barley-vetch mix), no detrimental effects occurred in terms of exhausting resources, acidification, or global warming. Therefore, the practice of intercropping did not cause additional contamination or other environmental impacts. This, in addition to the results of the increase in nitrogen and organic carbon content and in the soil and the reduction in erosion and run-off makes the introduction of herbaceous crops in the alleys of the mandarin trees a good sustainable environmental option to cope with the current challenges of the sector.
In economic terms, the financial security of the agricultural community also becomes a key element for successfully adopting diversified systems. This study highlights, through the economic assessment, that intercropping can lead to an increase in production costs, mostly related with a greater demand for labour in comparison with monocropping. However, the study also concludes that “the correct choice of intercropping practices can bring economic advantages”. The results showed that the mandarin crop with purslane and broad beans as intercrops could be profitable and reduce the risk for the grower against volatile prices in the main crop.
In this way, considering all the potential environmental and economic benefits of intercropping practices, these systems arise as a tool to move towards more sustainable and profitable agricultural systems. The valorisation of agricultural products that are more respectful to the environment on the part of consumers and the backing of public funding (e.g., direct help to growers who introduce intercropping) are key aspects to drive the adoption of these practices.