- Author: Sarah Light
A field in Sutter County was confirmed to have charcoal rot, also known as dry root rot or ashy stem blight, which is caused by the fungus Macrophomina phaseolina. The disease generally occurs under dry soil conditions paired with high temperatures and can be especially problematic when irrigation is delayed during periods of drought stress. This pathogen infects the crown and stem of garbanzo plants near the soil line and produces black cankers, which are sunken with distinct margins and often contain concentric rings. The disease is usually scattered in the field and often occurs during the flowering and pod stages (although infection can occur at all growth stages). The pathogen infects the stems of seedlings at the base of the developing cotyledon near the soil line. In older plants, symptoms include stunting, leaf chlorosis, early defoliation, and ultimately plant death. A sudden drying of whole plants scattered in the field is observed. Additionally, a “charcoal dust” can appear near the soil line on the surface of roots and stems of older plants. Canker development may kill the plant's growing tip and weaken the stem, causing stems to break, separating roots from the rest of the plant when plants are removed from the field. Infection can move into the hypocotyl and root region, as well as primary leaf petioles. The plant taproot often becomes dark, necrotic, and devoid of lateral and fine roots.
Management options in California are limited. This disease affects other legumes like common beans, blackeyes, and limas, as well as other crops that may be grown in rotation (like sunflowers). Inoculum survives in both seeds and soil. A 3-year rotation with a cereal grain (except corn and sorghum, which are hosts) is recommended to reduce soil inoculum levels. The dry, warm weather in the winter months earlier this year were conducive to drought stress for garbanzos, which increased the risk of disease. If possible, irrigate to avoid drought stress conditions. Garbanzos grown in soils that are high in organic matter tend to have more problems with this disease, however, garbanzos in other soil conditions are at risk if the plants are stressed and the environment is conducive to disease development.
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- Author: Sarah Light
Soil compaction is often a problem in field crop production and occurs when soil particles are pressed together, reducing available pore space for air and water. About half the soil volume is composed of particles, the other half is soil pores. At field capacity, these pores are roughly filled to equal parts with water and air. Pores are the spaces where roots grow, microbes live, and water and nutrients move through the soil. For this reason, compaction can lead to poor water infiltration, increased water runoff and soil erosion, restricted root growth, reduced nutrient uptake, and ultimately poor plant growth and lower yields. For example, last spring we visited a dry bean field where there was about an acre of beans along a road that were stunted. When we checked the soil in the affected area, we found it was heavily compacted and root growth was reduced. The areas with healthy plant growth did not show soil compaction problems. Upon talking to the farmer, we learned that the affected area was where water pooled during heavy rains. This was further evidence that there was poor drainage and compacted soil in that part of the field.
Soil compaction can occur at the soil surface or in the subsoil. Surface compaction is caused by water hitting tilled soil, which forms a crust. This can be managed by ring-rolling to break the crust and can be avoided by keeping soil covered during the rainy season, either with plant residue or a winter cover crop. This article will focus on subsoil compaction, which is more challenging to manage. Compaction in the subsoil can be in the form of a hardpan layer or deep compaction. A hardpan forms when the tillage implement presses soil directly below it together, forming a compacted layer. Deep compaction occurs further down in the soil profile and is caused by excessive weight on soil, particularly when soil is wet. It can be hard to break up soil once deep compaction occurs.
How can soil compaction be avoided?
- Do not work or drive over soil when wet. Wet soils are much more susceptible to compaction and depth of compaction can increase with soil moisture.
- Reduce tillage when possible. Tillage breaks up soil aggregates and disrupts soil microbial communities.
- Vary the depth of tillage to avoid a hardpan layer from forming.
- Distribute tractor weight over a larger surface tire area by decreasing tire pressure and/or using radial tires. This will reduce the pressure on specific points in the field.
- Reduce axel load for all machinery.
- Reduce the number of trips over a field. Do not drive over the field unnecessarily.
- Incorporate crops with different rooting depths and types into your rotation.
- Increase soil organic matter with compost, cover crops, or crop residue.
Once compaction occurs, it can be very challenging and costly to fix the problem. One can mechanically break up a compacted layer by ripping or chiseling, which will help improve crop growth in the current growing season, but this will not improve soil structure over time. Additionally, if this practice is repeated year after year, compaction will be made worse. Ripping or chiseling should never be done when soil is wet.
Good soil aggregation is required to prevent and alleviate soil compaction in the long term. Soil aggregates are clumps of soil particles that are bound together, leaving more available space for air and water. Aggregates are held together by organic matter (like roots), organic compounds (produced by soil microbes), and fungal hyphae. Microbes get nutrients and energy from the carbon found in soil organic matter. This is the reason that increased soil organic matter can make soil more resistant to compaction—it provides food for soil microbes which increases their activity and population.
Finally, gypsum can increase water infiltration in soils that are high in sodium (sodic soils) but does not alleviate soil compaction. Sodium ions disrupt the clay structure in soil which causes the clay particles to destabilize and clog available pore space, resulting in slower water infiltration. The calcium in gypsum will replace the sodium in the soil, which helps improve water infiltration. Therefore, gypsum can improve soil structure, but cannot reduce compaction of existing hardpans. Other management practices discussed above need to be implemented to improve and prevent soil compaction problems.
Client's Situation and Question: My rhubarb tends to die back in the summer much earlier than I think it should or expect. I know that the soils where it is planted are marginal and I haven't fertilized the rhubarb. I do give it regular water. What is causing the early summer die back? and how can I improve the health, vigor, and survival of my rhubarb?
UC MGCC Program's Help Desk Response: We believe that the rhubarb's early die back may be due to a combination of lack of fertility and Contra Costa County's hot summer temperatures. Rhubarb plants do best if fertilized regularly. If you want to grow organically, you can use a six-inch layer of good compost around the base of the plant. The compost will provide a continuous nutrient source that may last for several months. Rhubarb also responds well to manure, but be sure that it has been well composted since applying fresh manure will burn the plant. You can purchase composted manure at a nursery or home supply store. It can be mixed into the compost before you put it around the plant.
Another contributing cause of the summer die back could be hot summer temperatures. Die back is a common response to temperatures that are too high. Although rhubarb likes plenty of sun, providing some shade on hot summer afternoons may help.
Hope this info helps your rhubarb thrive. It's a great perennial vegetable to have in your garden—does well in desserts but can also be used in savory dishes.
UC Master Gardener Program of Contra Costa's Help Desk (TKL)
Editor: Although this response is written for Contra Costa County gardeners, thanks go to the UC Master Gardeners of Sonoma County for input.
Don't miss our 2016 Great Tomato Plant Sale:
@ http://ccmg.ucanr.edu/EdibleGardening/GreatTomatoPlantSale/
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog at http://ucanr.edu/blogs/CCMGBlog/.
- Author: Alison Collin
- Remember to winterize irrigation systems before the heavy freezes start. If you have a “frost free” faucet attached to the wall of your house, make sure to disconnect any hoses from it, especially those with a pressure nozzle attached. The mechanism is inside the house wall, and the stretch between the mechanism and the actual faucet is prone to bursting in cold weather if water cannot drain from it. The same applies to “splitters” or Y connectors – either remove completely or make sure that the nozzles are in the open position.
- If you banded trees with Tanglefoot for insect control, remove the bands for the winter.
- Check any plant ties to make sure that they have not become too tight over the summer and loosen or reapply as necessary.
- If you did not harvest bush or climbing beans when fresh, leave them to dry on the vines and then harvest them as dry beans for use in soups. Put them in the freezer for a couple of days after shelling them to kill off any bugs.
- If you are planning to use straw mulch over the winter, make sure that you buy straw and not hay. Hay contains seeds of grasses, oats or alfalfa and although these are nutritious for stock they will rapidly grow in the garden – and who needs all that weeding?
- Author: Georgia Luiz
Ah terrariums! How I love this tiny little worlds. In my experience, which is somewhat limited, the easiest ones are the dry cactus types. So little water involved. Just add some rocks, sand, and you have an itty bitty desert in that cognac snifter you never use. Stick with shade succulents like gasterias and haworthias. Don't put them too close to a window as the glass from the terrarium will magnify the suns rays and cook them, unless you're going for the desert apocalypse look.
Another cutie is the moss habitat. These kind remind me of my sister-in-law's back yard in Washington state. Very wet, just a clearing in a forest with some fallen logs. Mosses and mushrooms and tiny flowers everywhere. Very Jurassic. So, I got brave, and made one. Mine contains babies tears, Irish moss, scotch moss, an African violet, which is normally also an outside ground cover for shade, some tilandsias, and some dinosaurs figurines for effect. Also a maiden hair fern, that is ailing, but in my defense, it's not me, it's my kitten, Vespa. She's been getting in there and piddling on it. That can't be good.