- Author: Ben Faber
At the recent HLB Conference in Florida a paper was given that reinforces the need for appropriate soil and water pH to maximize root density and tree health. The industry there is dominated by a range of rootstocks and by Valencia-like varieties. Jim Graham and colleagues have shown that pH contributes to orchard health in their HLB situation. This should be a reminder for California growers for general tree health. Florida soils tend to be more coarse than soils found in many California orchards. It's much harder to change soil pH with acidified irrigation water with heavier textured soils.
4.b.1 Soil and water acidification sustain root density of huanglongbing-infected trees in Florida
Jim GRAHAM, Kayla GERBERICH, Diane BRIGHT, Evan JOHNSON
University of Florida, Citrus Research and Education Center, Lake Alfred, Florida, USA
Abstract: Early symptoms of HLB include fibrous root loss and leaf blotchy mottle, followed by premature fruit and leaf drop, and yield decline. As a consequence of initial bacterial infection of fibrous roots, a 30-50% reduction in fibrous root density and elevated soil Phytophthora populations were detected in field surveys. Continued sampling of Hamlin and Valencia orange trees on Swingle citrumelo rootstock in different stages of HLB decline revealed that root loss occurs in two stages. The second phase of root loss (70-80%) begins at the early stage of tree canopy thinning resulting from leaf drop and branch dieback. A more extensive survey of HLB-affected groves indicated that greater decline in fibrous root health and expression of HLB symptoms is observed where irrigation water is high in bicarbonates (> 100 ppm) and/or soil pH > 6.5. HLB symptom expression of trees on different rootstocks follows the known intolerance to bicarbonate (Swingle citrumelo > Carrizo citrange > sour orange > Cleopatra mandarin). Acidification of irrigation water in central ridge and south central flatwoods Valencia orange groves on Swingle citrumelo rootstock for three seasons has maintained soil pH below 6.5 on the flatwoods and 6.0 on ridge. Over the last three seasons of survey, root density as an index of root heath has been sustained. Phytophthora populations remain below the damaging level in ridge groves and in flatwoods increase to damaging levels coincident with the fall root flush but drop back to non-damaging levels for remainder of the season. Compared to the 2013-14 season, yields in the ridge blocks have increased up to 4% and on the flatwoods have increased up to 22%.Growers using acidification treatments with sulfuric and/or N-phuric acid for the last 3 seasons report an average cost of $60 per acre. This cost will analyzed in relation to yield response to provide a cost benefit of acidification
Non-Technical Summary: Managements have been implemented to reduce soil, nutrient and water stress, and Phytophthora root rot. They include frequent irrigation cycles, fertigation and acidification of irrigation water and soil to reduce rhizosphere pH, and fungicides. Root density of trees under these practices fluctuates seasonally and annually but has not declined over the past 3 years. Trees managed with soil acidification and fertigation have steadily recovered in health and yield.
http://www.icc2016.com/images/icc2016/downloads/Abstract_Book_ICC_2016.pdf
- Author: Ben Faber
Calcareous soils have often more than 15% CaCO3 in the soil that may occur in various forms (powdery, nodules, crusts etc…). They are relatively widespread in the drier areas of the earth. California is notable for its young soils, that is, soils that have a relatively high level of nutrients because low rainfall means that natural productivity has not been leached out. The potential productivity of calcareous soils is high where adequate water and nutrients can be supplied. Water is the most limiting input to making California soils productive.
The high pH associated with these soils, though, is not the level of calcium present. It is the carbonate in the soil or the bicarbonate associated with the waters found in those soils which controls the pH. The high pH then controls the availability of iron, zinc, manganese and copper. These nutrients need to be added as foliars or soil applied, or better yet, the soil pH needs to be dropped to around 7 to make these nutrients available.
Recently someone asked if replacing the calcium with potassium would change the pH. No, it won't. The carbonate needs to be removed. Calling it a calcareous soil confuses people about what caused the high pH. The carbonate or bicarbonate needs to be removed with acidification, it turning it into CO2 gas. This is done with urea sulfuric acid or sulfuric or sulfurous acid. There are actually magnesium dominated soils in the San Luis Obispo area that have high pHs due to carbonates. They are carbonateceous.
- Author: Ben Faber
A call from a small grower, surprised at the sudden decline of the avocado trees. It must be a disease was the grower's thought. Well driving up to the site, there were numerous trees with canopies indicating drought stress. In fact most of the trees looked like they had had the water turned off. When I got to the orchard, all the trees had a similar look (see photo below). The fringe of the canopy had turned brown/red where the leaves had collapsed rapidly, while the interior leaves were often still green. All the trees had a similar cast. It turns out the water district had required a cutback just when temperatures were going into the 100's. NO water, no cooling effect of transpiration and the outer fringe of leaves collapsed. This is called the “clothesline” effect. It's like a sheet on a clothesline where the margins of the sheet dry first and gradually the body of the sheet dries. The same thing happens in a canopy. The outside leaves are the first to dry out and then the rest of the canopy goes. When you see a whole orchard go down suddenly, that does not fit into a disease pattern. There's usually an epicenter where it starts – where it's colder, wetter, dryer, hotter, more overgrown, etc. and spreads out from there if it is going to spread. It turns out that the automatic irrigation system had gone down and the grower hadn't noticed until too late. When you see reddish tinged leaves, it means the leaves went down fast. When they are brown, it means they slowly went down over weeks or months.
With all the dead points in the tree, it is now open to disease – twig/leaf blight caused by one of the Botryosphaerias. These decay fungi are everywhere in an orchard decaying organic material on the orchard floor. With the dead material in the tree, now the tree becomes a potential feast for the fungi. The dead stuff has to come out, or the fungus will start eating into the tree. I suggested that instead of pruning out all those little points of death, that they cut back the whole canopy to major scaffold branches. In doing so, it would rapidly and cheaply remove the dead material and reduce the water demand.
- Author: Ben Faber
CACHUMA RESOURCE CONSERVATION DISTRICT
FOR SANTA BARBARA COUNTY GROWERS AND FARMERS
WATER CONSERVATION FUNDING AND TECHNICAL SERVICES WORKSH0P
Agenda
8:00 Sign-In
8:15 Breakfast and Technical Displays
9:00 Grower and Funding Talks
10:40 Discussion and
Monday, June 27, 2016 8:15 -11:30 am
Rincon Beach Club
Carpinteria
3805 Santa Claus Lane
Hear from growers who have used State and Federal funds to improve water use and operational efficiency and lern about new resouce conservation technologies from local agricultural and technical service providers.
Advance registration not required. For more information:
Anne Coates 805-455-2820 www.waterwisesb.org
Jamie Whiteford 805-764-5132 www.vcrcd.org
- Author: Ben Faber
http://ucanr.edu/blogs/confluence/
Water woes are probably not going to go away, so readup on how to best manage water at this new blog.
- Author: Rachael Long
Guest post from Rachael Long, UC Cooperative Extension Farm Advisor, Yolo County
The Yolo County Flood Control and Water Conservation District (YCFC) is an agency that supplies water to farmers in northern California. The agency is at the forefront of innovative efforts aimed at banking groundwater by diverting flood waters into their unlined canals. This gives flood waters time to infiltrate soils and recharge groundwater.
Using a water right permit that they recently obtained from California's State Water Resources Control Board, flood waters from recent storms are being captured from Cache Creek as it enters the Sacramento Valley. YCFC recently opened their lateral gates, allowing the flood waters to...
- Author: Faith Kearns
Groundwater wells can fail in many ways. Sometimes the water table sinks below the level of the well. Sometimes minerals cause buildup in well systems. And, sometimes, wells get clogged with lots and lots of microbes.
Microbes can form large, jelly-like mats that lead to well failure from what is known as biofouling. Biofouled wells can be both expensive and technically challenging to repair. There are even times that repair is not possible and replacement is the only option. In Washington State, for example, researchers have encountered well pipes completely clogged by mats of bacteria....
- Author: Faith Kearns
California's Sacramento-San Joaquin River Delta region, commonly referred to simply as the Delta, is often described as a unique part of the world. Although it is located between two big urban centers – the greater Sacramento and San Francisco Bay areas – the Delta can feel like another world altogether.
This is something Michelle Leinfelder-Miles, a farm advisor with UC Agriculture and Natural Resources, knows well. She comes from a sixth-generation farming family in San Joaquin County and, after accepting her position several years ago, was happy to return “home”...
- Author: Faith Kearns
The California drought has shined a spotlight on stories of people and communities living without water. Unfortunately, lack of access to clean and affordable water is not a new issue. Water security has been an enduring challenge across the state in wet and dry years alike, particularly for disadvantaged communities. Trying to meet concerns about water availability and affordability with pragmatic action is where things get both complicated and interesting.
One approach that the state has invested a great deal in exploring is known as integrated regional water management. While it is a complex topic, the basic idea is that there are multiple needs for water throughout the...
- Author: Faith Kearns
Street-side stormwater facilities are turning runoff once seen as a nuisance into a resource. Also known as bioretention areas, rain gardens, and bioswales, these small stormwater facilities provide a decentralized approach to alleviating peak stormwater runoff and subsequent flood damages. These are particularly critical functions in cities like San Francisco where the storm and sanitary sewer systems are combined because they help managers to prevent dreaded “combined sewer overflow” events. As a bonus, stormwater facilities have also proved useful in promoting groundwater recharge and filtering pollutants as water percolates through soils.
While street-side facilities are effective in helping to manage...