California Avocado Growers Seminars Series 2023

Scheduled Topics

You missed this in-person meeting, but see it here

 

From: February 15 (10 AM - 12 PM)

In-Person and Zoom

Get Down - Fertilizers

 
in-person meeting was at:

United Water Conservation District offices (1701 N. Lombard ST., Oxnard)

and zoomed for those who would prefer that option.

click here: https://californiaavocadosociety.org/seminars.html

NITROGEN DEFICIENT AVOCADO LEAF

Healthy Soils Week is a campaign by the California Department of Food and Agriculture to highlight the importance of soil health. We thought our readers might be interested in some of the common questions our UCCE Stanislaus County Master Gardener Help Line receives about soils and fertilizers.

Do I need to test my garden soil?

The short answer is, “no.” Although many gardening magazines and websites advise gardeners to “test” their soil, it's unnecessary unless you suspect a major problem such as lead contamination or excess salts.

For a list of soil laboratories located in Stanislaus, Merced, Fresno, and Merced Counties, visit https://cemerced.ucanr.edu/ClimateSmartAg/HSP/SoilTest/Soil_Testing_Laboratories_in_Fresno_Madera_Merced_and_Stanislaus_Counties/

I think I have bad soil; nothing grows! What should I do?

The most common reason gardeners have trouble with soil is compaction, which results in poor drainage. This is often caused by compaction from heavy machinery or foot traffic. To improve soil, Master Gardeners recommend adding 4-6” of compost and mixing it into the soil. This is best done when soil is not wet. Since compost is an organic material that breaks down, continue to add it each season.

I think there are diseases in my soil, what should I spray?

Plant diseases do live in the soil, in fact, they are everywhere! However, these diseases need an opportunity to infect plants, such as a wound. Overwatering is a common cause of plant disease. Changing watering practices usually solves this problem.

Should I add manure to my vegetable garden soil?

Manure is a great addition to prepare your soil for a vegetable garden. However, it's best to use composted manure and to incorporate it into the soil several weeks before you plant. If fresh manure is used, plants may turn yellow due to the high concentration of salts.

How often should I fertilize my fruit trees?

Fruit trees work hard to produce a crop and do benefit from applications of fruit tree fertilizer in spring. Always follow the instructions on the package and never apply more than is recommended.

Have a soil, fertilizer, or other question topic we didn't answer?

Our Master Gardeners are available on Wednesdays from 9:00 a.m. to noon in person or by phone (209) 525-6802. You can also drop off a sample during business hours and we will get back to you, or fill out this survey (you can also attach photos if needed):

http://ucanr.edu/ask/ucmgstanislaus A Master Gardener will get back to you within 5 days of your request.

UCCE Stanislaus County Master Gardeners
3800 Cornucopia Way Ste A
Modesto, CA 95358

If you live in another county in California, you can find your local Master Gardener program by using this link https://mg.ucanr.edu/FindUs/

 

RIVERSIDE, Calif. -- Beautiful things can happen when plants surround themselves with the right microbes. A study on Acmispon strigosus, a plant in the pea family, showed a 13-fold growth increase in plants that partnered with a highly effective strain of the nitrogen-fixing bacteria Bradyrhizobium.

The ability of plants to use beneficial microbes to boost their growth is not lost on agronomists. Some breeders think understanding the traits that enable crops to recruit top-performing microbes is key to the future of sustainable agriculture.

A roadblock in capitalizing on the beneficial work of microbes is the complex genetic and environmental factors that govern their role in plant growth. Left unattended, plants don't always recruit beneficial microbes, instead surrounding themselves with a mix of both helpful and ineffective bacteria. Attempts to manage the microbial populations plants encounter in the soil--by inoculating with beneficial strains--have largely failed.

"It is very difficult to predict which combinations of microbes will be successful under field conditions, since the microbes that are beneficial to plants in the lab do not always compete successfully against microbes that already exist in the field," said Joel Sachs, a professor of evolutionary ecology at the University of California, Riverside and member of the university's Institute for Integrative Genome Biology. "A promising alternative is to breed plants that are better at managing their own microbial partners, an advancement that will be passed down to future generations."

In a study published today in New Phytologist, Sachs' team has advanced our understanding of how plant genetics and environmental factors affect microbial soil populations in the field. The paper's first author is Camille Wendlandt, a graduate student in Sachs' research group.

The researchers investigated whether Acmispon strigosus (the pea plant) changes how it associates with different strains of nitrogen-fixing bacteria when its environment changes. Surprisingly, they found that changing the plants' environment by fertilizing the soil did not change how plants associated with microbes. Instead, the researchers found that genetic variation between the pea plants was most important in explaining whether plants invested in relationships with the most beneficial microbes. In other words, some variants of the plant are better than others at developing these beneficial partnerships.

The variants of pea plant that were best at investing in beneficial microbes also had very high growth benefits, in contrast to other pea plant variants that did not invest as much and gained less growth benefit.

"The fact that the traits that govern these partnerships vary between plants of the same species and are heritable shows that they can be selected for by breeders," Wendlandt said. "Ultimately, we hope that agronomists will use this research to develop plant varieties that make the most of the soil microbes they encounter. This could reduce reliance on chemical fertilizers, which are expensive for growers and can pollute the environment."

Future work in the lab will focus on whether the pea plants still show genetic differences when they interact with much more complex microbial communities, similar to what they encounter in field soils. The lab is also expanding its research to ask similar questions with cowpea plants, which are an important legume crop in sub-Saharan Africa.

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The title of the paper is "Host investment into symbiosis varies among genotypes of the legume Acmispon strigosus, but host sanctions are uniform." In addition to Sachs and Wendlandt, contributors are John Regus, Kelsey Gano-Cohen, Amanda Hollowell, Kenjiro Quides, Jonathan Lyu, and Eunice Adinata, all at UC Riverside. The work was funded by the National Science Foundation.

https://www.eurekalert.org/pub_releases/2018-08/uoc--tsm080718.php

Photo: UC Riverside,  Can you pronouce Acmispon?

The researchers studied Acmispon strigosus, a plant in the pea family that is native to the Southwestern United States.

What do the numbers on fertilizer sacks indicate?

The “big three” nutrients show on bags are nitrogen, phosphate, and potash which provide N, P, and K elements. They are the ones declared on a bag of fertilizer. If you see the combination of 5-10-5, it means that the bag contains 5% nitrogen, 10% phosphate, and 5% potash by weight. These aren't in a pure form but with other material.

How do each of the “big three” fertilizer elements help a plant?

1)    Nitrogen is an essential element of chlorophyll that helps a plant produce starches and sugars. Since nature seldom provides it in sufficient quantities, fertilizers are used to augment what is naturally available.

If a plant is deficient in nitrogen it will be small, the older leaves turn from green to yellow, then finally brown but remain attached to the plant. Stalks are slender and few new ones develop.

2)    Phosphorous is associated with cell division. It contributes to stiff stems, flowering, and seed production. In acid or alkaline soils it becomes unavailable to plants so it is important to manage the pH of the soil for efficient uptake as well as providing adequate amounts of supplemental phosphate. Fertilizers bags show the amount of phosphorus content in terms of percent rock phosphate (P₂O₅) for historical reasons.

Phosphorus deficiency causes the whole plant to be dwarfed. The foliage is a dark. dull green, and often the stems turn purple. Areas between the leaf veins also can become purple, while the edges turn yellow. Loss of lower foliage follows.

   3) Potassium is essential for movement of the sugars in the plant, the utilization of nitrogen, root development, and it also hastens maturity. It can be depleted over time in soils as plants grow.

A potassium deficiency results in the leaves becoming mottled with yellow between the veins, then turning brown and dropping. Plant growth will be stunted. Potassium in fertilizers is measured in potash form (K₂O).

What is the best fertilizer for perennials and annuals?

The best fertilizer is the one that provides just enough of the elements lacking in the soil and no more. A balanced fertilizer—one with no zeros in the analysis like 15-5-10—will usually work.

Should I buy organic fertilizer?

The “big three” elements in organic fertilizers can be highly complex and are unavailable to plants until they have been broken down into simpler forms by soil organisms. Since these organisms are partially dormant at temperatures below 60 degrees and grow progressively more active up to 90 degrees they are not very effective in early spring. However, some add organic matter, an advantage not provided in synthetic or mineral fertilizers.

In either type of fertilizer the plant nutrients must be in a usable form before they can be used by the plant. This process of conversion happens naturally based on environmental conditions for both types, but organic materials are usually slow to release.

The choice is also driven by one's philosophy toward gardening.

My friend has horses and will give me manure. What should I know about using it in the garden?

It can be a valuable soil amendment. One caution: Many owners use pesticides to control insects or parasites, or feed hay that has may have been treated with an herbicide, so manure should be well composted in a separate pile before being applied to the soil. Cow manure can be a valuable soil amendment if allowed to rot in a compost heap during the winter in preparation for spring use. Check out: http://smallfarms.oregonstate.edu/sfn/f09Herbicide In the Eastern Sierra we tend not to have issues with local animals.

Remember that un-composted manure can carry human pathogens. You should take measures to ensure that plenty of time passes before harvest after using raw manures. 

When should one apply fertilizer?

For permanent plantings such as trees, shrubs, evergreens or perennial flowers , fertilizer may be applied in the fall or spring with equal success. For annual flowers or vegetables it is recommended that fertilizers be applied just prior to planting.