July_August_PCC_2016_Web

Progressive 

Crop Consultant 

The Leading Magazine For CA Ag Professionals 

July - August 2016 

Advancing the Next Generation of 

Groundwater Management in California 

Organic Blueberry Production 

Weedy Red Rice Update 

Potassium Deficiency in Vineyards 

PUBLICATION 

Volume 1 : Issue 2

Publisher: Jason Scott 

Email: jason@jcsmarketinginc.com 

Editor: Kathy Coatney 

Email: kathy@jcsmarketinginc.com 

Production: Logan Willems 

Email: logan@jcsmarketinginc.com 

Phone: 559.352.4456 

Fax: 559.472.3113 

Web: www.progressivecrop.com 

Contributing Writers & Industry Support 

Timothy Blank 

Certified Seed Program Representative, 

California Crop Improvement Association 

Mark Gaskell 

Farm Advisor, University of California 

Cooperative Extension, San Luis Obispo, CA 

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Progressive 

Crop Consultant 

The Leading Magazine For CA Ag Professionals 

In This Issue 

4 

10 

Spotted Wilt Virus Management in Tomatoes 



David Guy 

President, Northern California Water Association 

Cecilia Parsons 

Contributing Writer 

Thomas A. Turini 

University of California Agriculture and Natural Resources, 

Vegetable Crops Advisor in Fresno County 

Stephen Vasquez 

Research Agronomist – West of the Rockies 

Tessenderlo Kerley, Inc. Crop Vitality 

15 

22 

24 


Nutrient Management Requirements in 

Mild-Winter Areas of California 


Weedy Red Rice Rivals Watergrass as being the 

Worst Weed in Rice Production Worldwide 

Post Harvest Nutrition in Almonds 

UC Cooperative Extension Advisory Board 

Kevin Day 

County Director and Pomology 

Advisor, Tulare/Kings County 

David Doll 

UC Farm Advisor, Merced 

County 

Dr. Brent Holtz 

County Director and Pomology 

Farm Advisor, San Joaquin 

County 

Steven Koike 

Plant Pathology Farm Advisor 

Emily Symmes 

Integrated Pest Management 

Advisor, Sacramento Valley 

Kris Tollerup 

Integrated Pest Management 

Advisor, Parlier, CA 

26 


The articles, research, industry updates, company 

profiles, and advertisements in this publication are the 

professional opinions of writers and advertisers. 

Progressive Crop Consultant does not assume any 

responsibility for the opinions given in the publication. 

Page 2 Progressive Crop Consultant July/August 2016

26 

22 

4 

15 

24 

10 

July/August 2016 www.progressivecrop.com Page 3

Tomatoes 

Photo Credit: Thomas A. Turini 

TSW symptom fruit. Fruit distortions and 

irregular color are associated with TSWV. 

Spotted Wilt Virus Management in Tomatoes 

Thomas A. Turini 

University of California Agriculture and 

Natural Resources, Vegetable Crops Advisor 

in Fresno County 

Tomato spotted wilt virus (TSWV) is 

a thrips-transmitted virus that can 

infect many crops and weeds. In California’s 

Central Valley, in an important 

processing tomato production area, this 

virus disease may cause substantial economic 

damage. The most recognizable 

symptoms include fruit with protruding 

oval deformities or irregular concentric 

ring color patterns and this virus can kill 

shoots and plants, so both quality and 

Page 4 Progressive Crop Consultant July/August 2016 

yield are affected. The host range of this 

virus includes many common crops and 

weeds and likely survives the winter on a 

few weed or crop plants, but quickly amplifies 

on tomatoes in spring. Therefore, 

risk increases during the season. The 

virus is transmitted by thrips; primarily 

Western Flower Thrips, Frankliniella 

occidentalis in the Central San Joaquin 

Valley. The vector must feed on an infected 

plant as a nymph to be capable of 

transmitting the virus as an adult. Risk 

of loss due to TSWV can be reduced 

but management in high risk situations 

is going to depend upon several tactics. 

Resistance to the virus is available in 

both fresh market and processing tomato 

varieties; however, in some production 

areas, resistance-breaking TSWV has 

been reported and is likely to develop in 

regions where the gene is heavily relied 

upon. A few foliar insecticides have been 

shown to bring down thrips population 

densities and reduce incidence of TSWV 

symptomatic plants, but will not keep 

the virus down to commercially acceptable 

levels under high disease pressure. 

Under situations where there is a history 

of the virus, identify risk factors, which 

may include weed or crop sources of 

the virus in early spring, ensure that 

transplants are not arriving with in-

fection, consider variety susceptibility, 

plant date, thrips management programs 

to calculate your risk of experiencing 

damage. Once there is an appreciation 

for your risk factors, you have capacity 

to mitigate disease risk by modifying any 

of these components that contribute to 

a situation in which this disease causes 

economic damage. 

Tomato spotted wilt virus was present 

at low levels and was largely regarded 

as a curiosity 15 years ago, but by 2005, 

this severity and incidence of this virus 

increased to levels that caused severe 

economic damage in the Central San 

Joaquin Valley. In response the California 

Tomato Research Institute funded 

a comprehensive research project to 

better understand and control this viral 

disease. 

Identification is critical to implementation 

of an effective program because 

management of TSWV requires different 

tactics than other diseases. This virus 

disease is associated with several striking 

symptoms, but also has symptoms 

that can be confused with other virus 

diseases or even diseases caused by very 

different pathogens. Symptoms of TSWV 

vary by stage of crop development when 

infection occurs and by other factors. 

The most recognizable symptoms of 

TSWV in tomato include fruit with 

protruding oval deformities or irregular 

concentric ring color patterns. Plants 

infected shortly after transplant will 

produce foliage with dead spots or have 

more superficial patterns on the upper 

leaf surface giving a bronzing appearance 

and the entire plant will die before 

producing fruit. When fruit are forming 

at the time that infection occurs, fruit 

will be deformed and discolored, foliage 

will show bronzing symptoms and 

dieback. Plants infected at late stages of 

development will have symptoms limited 

to shoots. There are quick tests that are 

easily preformed in the field or office 

available for purchase from AgDia at 

www.agdia.com or EnviroLogix at www. 

envirologix.com. 

An awareness of virus and vector 

characteristics is helpful in considering 

control program components. The virus 

has a wide host range that includes sow 

thistle, prickly lettuce, mustard, London 

rocket, malva, Russian thistle and many 

others. Crops that also may be infected 

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Continued from Page 5 

Table 1. Summarized processing tomato variety response to Tomato spotted wilt virus. 

includes beans, eggplant, lettuce, pepper, 

potato, and spinach. The virus does not 

survive outside of a living host, so it is 

likely to be surviving in winter weed or 

crop hosts while there are no tomatoes 

in the area. In central California the 

primary vector is Western flower thrips 

(WFT), Frankliniella occidentalis. The 

thrips must acquire TSWV by feeding on 

an infected plant as a nymph, pupate in 

the soil in the case of WFT, and emerge 

as an adult capable of transmitting the 

virus. The thrips may survive for more 

than 45 days and is capable of transmitting 

the virus. During most years, thrips 

movement is very low from November 

through January, and the levels observed 

in weeds and crops in January and 

February are very low, so all indications 

are that after winter, this virus is present 

in very low levels in the environment. 

In March and early-April, there are low 

levels of TSWV present in the processing 

tomato production areas, but the virus 

quickly amplifies on the large and concentrated 

areas of tomatoes so that by 

June, the virus is present at much higher 

levels and risk of economic damage due 

to TSWV is much higher than early in 

the season. 

In addition to crop and weed sources, 

recent research suggests that adult thrips 

with TSWV emerging from pupae in 

the soil are another potential source of 

early season TSWV inoculum. In this 

case, the immature thrips that fed on an 

infected plant prior to pupating in the 

fall harbor the virus through the winter. 

As soil temperatures increase in spring, 

the infectious adults may emerge and 

serve as a source of the virus early in the 

season. 

Varieties resistant to TSWV are 

available for both processing and fresh 

market production. Commercial varieties 

with resistance are using a single 

gene resistance, Sw5. With repeated and 

widespread use of single gene resistance, 

virus strains with capacity to reproduce 

within resistant plants will be selected 

for. In the event that a strain or strains 

with resistance breaking capacity is 

present in the population, selection for 

an increase of that strain or strains will 

occur in the presence of dense use of 

this single gene resistance. Therefore, 



Low Variable or Medium High 

BQ 163 paste, peel H 2005 multi use H 8004 multi use 

H 2206 multi use SUN 6366 multi use BOS 602 multi use 

UG19406 multi use H 1015 early multi H 8504 paste 

SUN 6368 peel, solids NDM 5578 multi use HM 6898 multi use 

H 4007 multi use CXD 282 multi use H 2601 pear 

K 2769 ----------- AB 2 multi use AB 3 multi use 

H 3044 multi use H 9780 multi use NUN 672 Viscosity 

N 6397 multi use K 2770 ----------- APT410 Multiuse 

UG 15308 Peel CXD 255 multi use 

BQ 205 multi use HMX 7885 pear 

UG 4305 multi use PX 1723 dice, peel 

Ring spots may be obvious on green fruit and blister-like protrusions 

may be obvious on red or partially colored fruit. 

Fallow fields can serve as sources of both thrips and TSWV. 

Photo Credit: Thomas A. Turini



while plant resistance is a critical tool in 

managing TSWV, exclusive reliance on 

this tactic should be avoided. In addition, 

careful attention to any evidence of 

the presence of plant resistant strains is 

critical. If typical fruit and foliar TSWV 

symptoms are present on more than 3% 

of the plants that have Sw5 resistance, 

there may be resistance breaking strains 

present. 

Some susceptible varieties are more 

susceptible than others. In the absence of 

genetic resistance, differences in TSWV 

expression were documented in susceptible 

varieties. In studies conducted at 

the University of California West Side 

Research and Extension Center (UC 

WSREC), 10 to 16 varieties were compared 

in 13 trials conducted from 2007 

to 2012. Based on TSWV incidence in 

susceptible varieties, entries were placed 

into three categories (Table 1, Page 6). 

It is notable that there are factors aside 

from variety that influence performance 

of these varieties. 

Insecticide use to control thrips can 

be challenging, but use of some foliar 

insecticides reduced TSWV incidence in 

studies conducted at UC WSREC. Thrips 

concentrate in flowers or other protected 

location, have tremendous reproductive 

potential and may develop resistance to 

insecticides; however, as a component 

of a management program, they may be 

useful in reducing economic impact due 

to TSWV. 

In foliar insecticide efficacy comparison 

experiments conducted from 

2007-2012 the only insecticides that 

consistently reduced WFT densities were 

Radiant, Dimethoate and Lannate (data 

not shown). Insecticide program evaluations 

conducted at UC WSREC included 

drip injected materials as well as transplant 

drenches and foliar applications as 

detailed in Figures 1 and 2. Under the 

conditions of comparisons of program 

studies over five years, drip injected materials 

were ineffective, but foliar applications 

were generally helpful in reducing 

TSWV disease incidence. No significant 

differences were documented with drip 

injected materials (Fig 1 and 2) while 

foliar programs reduced TSWV incidence 

in 2009, 2011 and 2012 (Figure 2). 

In 2010, no significant differences were 

observed between any treatments (foliar, 

drench or control) (Figure 2). In 2010, 


Figure 1. Drip irrigation applied materials had no significant effect (P=0.05) on Tomato spotted 

wilt virus symptom incidence 2009-2012 at University of California West Side Research and 

Extension Center. 

TSWV infected weeds, like this sow 

thistle, may show symptoms, or 

they may be symptomless. 

Moderate necrosis and yellowing. 

Irregular necrotic spots and yellowing 

is common on leaves of TSWV 

infected tomato plants. 

Green fruit with blister like 

protrusions are typical of TSWV. 

TSW bronzing symptom. A bronze 

coloration of the foliage is a typical 

symptom of Tomato Spotted Wilt 

Virus (TSWV). 

Photo Credit: Thomas A. Turini

Photo Credit: Thomas A. Turini 

Severe yellow and necrosis. 

Figure 2. Effect of transplant drench and foliar insecticide programs on Tomato spotted wilt 

virus symptom incidence at University of California West Side Research and Extension Center, 

2009-2012. 

Performance of Verimark as a transplant 

drench was inconsistent. In comparison 

to the program lacking the Verimark 

application, the Verimark transplant 

drench reduced TSWV symptom 

incidence in 2011, but not in 2010 and 

2012 (Figure 2) ). In 2010, regardless of 

the treatment, there were no differences 

between treatments and the untreated 

control, which was likely due to very 

high population densities of thrips from 

an infected tomato field near the experiment. 

This highlights the limitations of 

what can be accomplished with insecticide 

treatments and that without other 

strategies also implemented, the likely 

failure to provide commercially acceptable 

levels of control under high disease 

pressure. The insecticide treatments 

are effective largely in that they reduce 

secondary spread, or spread of the virus 

within the field, to prevent spread from 

external sources of infective thrips is 

unlikely with infield applications. 

Rogueing, which is removal of TSWV 

symptomatic plants, may be effective 

and even economical under some 

circumstances. However, if substantial 

external sources of infective thrips are 

contributing to the disease increase or 

there are already substantial levels of 

TSWV infected plants in the field, this 

is not likely to be effective. Also, it may 

be difficult to economically justify this 

approach depending upon the market 

for the tomatoes or the value of labor. 

Integrated Pest Management can be 

applied specifically to TSWV for the 

greatest sustainable levels of success 

under high pressure situations. Careful 

inspection of the area for potential 

sources of inoculum and avoiding 

planting crops near sources, to prudent 

selection of varieties to starting with 

virus-free transplants are important preplant 

steps. Following planting, continue 

to monitor not only your field but fields 

in the vicinity for TSWV symptoms. At 

the first detection of the virus in the area 

or in the field, begin treatments with 

insecticides. Generally, few applications 

will be needed and under the conditions 

of the studies in Central California, two 

applications were as effective as more 

treatments. After harvest of tomatoes or 

any crop, quick and complete removal 

of the crop and weeds are critical and 

weed control throughout the year in the 

production area can reduce pressure. 

PCC 


Water 



David Guy 

President, Northern California Water 

Association 

The past four dry years in California 

have brought into sharp focus the 

importance of groundwater resources 

for farmers, cities and rural communities 

throughout the state. The California 

Department of Water Resources (DWR) 

has found that “groundwater is a vital 

resource in California, providing close to 

40 percent of the state’s water supply in 

an average year. In some regions of the 

state, groundwater accounts for as much 

as 60 percent of the supply during dry or 

drought years.” In the past several years, 

certain parts of the state have received 

no surface water, instead relying upon 

groundwater for 100 percent of supplies. 

Extended drought conditions typically 

result in an increase of groundwater 

well activity and pumping to compensate 

for surface water supply shortages. 

Increased groundwater pumping can 

lead to adverse conditions including dry 

wells, land subsidence, water quality 

impacts, seawater intrusion, and stream 

depletion. 

In the midst of this recent drought, 

the California Legislature passed and the 

Governor signed into law on September 

16, 2014 the Sustainable Groundwater 

Management Act, now being referred 

to as SGMA or pronounced as “Sigma.” 

The passage of SGMA raises some 

fundamental questions for California’s 

farmers and ranchers and the rural areas 

throughout the state as they plan for the 

future. The central question is whether 

farmers and ranchers, as well as the 

various overlying local agencies (water 

districts and counties), will step up and 

take the actions that are truly necessary 

for sustainable groundwater management. 

In some parts of the state, it is generally 

acknowledged that there is overdraft 

as shown by the map on page 12, which 

suggests that groundwater pumping is 

out of balance and exceeds the available 


supplies. To bring these basins back into 

balance will require aggressive water 

management strategies (both surface 

and groundwater), an adjudication of 

the rights to pump groundwater, more 

stringent land use policies, or some combination 

of these measures. 

In other areas, the groundwater is 

currently in balance and the available 

supplies exceed pumping. Here, the 

strategy will be for local agencies to 

manage the surface and groundwater 

resources to keep and maintain the 

balance. 

For all areas, SGMA provides a process 

and guidance for how local agencies 

can develop groundwater sustainability 

plans, but the real question is whether 

there will be local leadership to drive a 

cultural change that will be necessary 

for sustainable groundwater management. 

For success, the next generation of 

groundwater management will require 

a different mindset where farmers and 

other landowners look beyond the 

borders of their land and recognize the 

need to work collectively as the best way 

to protect and manage the groundwater 

resources for their benefit and the longterm 

value of their land and the various 

functions it supports. In the alternative, 

there are many adjudicated basins in 

California and there will continue to be 

adjudications in areas where SGMA and 

these cultural shifts do not take form. 

What is Sustainable Groundwater 

Management? 

Although sustainability is a difficult 

term to define with any precision, SGMA 

has a sustainability goal for groundwater 

management and planning to avoid 

“undesirable results” that include: 

“(1) Chronic lowering of groundwater 

levels indicating a significant and unreasonable 

depletion of supply if continued 

over the planning and implementation 

horizon. Overdraft during a period of 

drought is not sufficient to establish a 

chronic lowering of groundwater levels 

if extractions and groundwater recharge 

are managed as necessary to ensure that 

reductions in groundwater levels or 

storage during a period of drought are 

offset by increases in groundwater levels 

or storage during other periods. 

(2) Significant and unreasonable 

reduction of groundwater storage. 

(3) Significant and unreasonable seawater 

intrusion. 

(4) Significant and unreasonable 

degraded water quality, including the 

migration of contaminant plumes that 

impair water supplies. 

(5) Significant and unreasonable land 

subsidence that substantially interferes 

with surface land uses. 

(6) Depletions of interconnected 

surface water that have significant and 

unreasonable adverse impacts on beneficial 

uses of the surface water.” 

Organizing: Forming Groundwater 

Sustainability Agencies (GSAs) 

The first task under SGMA is for local 

public agencies or a combination of local 

public agencies overlying a groundwater 

basin to decide whether to become 

a Groundwater Sustainability Agency 

(GSA). This is a big decision as local 

agencies look at the tremendous responsibility 

and potential costs that will inevitably 

come with GSAs. As local agencies 

consider whether to declare as a GSA it 

will be important that they fully understand 

the requirements for developing a 

Groundwater Sustainability Plan that is 

the heart of SGMA, as described in more 

detail below. 

The requirements in SGMA apply to 

basins designated as high and medium 

priority that have not been adjudicated, 

as shown on the map on page 13. In 

some areas there is already a local or 

regional agency that can serve as the 

GSA. In areas where multiple agencies 

overlie a groundwater basin, multiple 

agencies may come together and act as a 

single GSA through a memorandum of 

agreement (MOA), a joint powers agreement 

(JPA), or other legal agreement. In 

addition to public agencies, SGMA also

allows a water corporation regulated by 

the Public Utilities Commission or a 

mutual water company to participate in 

a GSA through similar agreements with 

the local public agencies. 

Importantly, in areas that are not 

covered by local water agencies acting 

as a GSA (generally referred to as “white 

spaces”), the county will be presumed 

to be the GSA for these areas unless 

it formally notifies DWR that it will 

not take on this responsibility. County 

participation in SGMA and coordination 

with local water agencies may be very 

difficult: yet, it may be the most important 

element of forming meaningful 

GSAs that can effectively work towards 

sustainable groundwater management. 

After a local agency submits a formal 

GSA notification to DWR, the agency 

is presumed to be the exclusive GSA in 

the area covered by the notification if no 

other local agency submits a notification 

within 90 days for all or any portion of 

the same area. For additional details 

regarding the current GSA formation 

notifications submitted to DWR, visit 

the following website: http://www.water. 

ca.gov/groundwater/sgm/gsa_table.cfm 

So what happens if local agencies do 

not submit the formal process for GSA? 

The simple answer is that this provides 

an opportunity for state intervention. 

Under SGMA, when local or regional 

agencies cannot or will not manage their 

groundwater sustainably in a mediumor 

high-priority groundwater basin, 

SGMA provides for state intervention 

until the local agencies are prepared to 

assume responsibility. The State Water 

Resources Control Board (SWRCB) 

may intervene if a GSA is not formed 

or if a GSA fails to adopt or implement 

compliant plans by certain dates. Thus, 

if no GSA is established by June 30, 

2017 for all or a portion of a high- or 

medium-priority basin, the basin may 

be designated as a probationary basin by 

the SWRCB. This is the first date where 

the state can intervene and may develop 

an interim plan for managing the 

basin until the local agencies can reach 

agreement and identify a GSA or GSAs. 

If the basin is designated as probationary, 

there are reporting requirements 

for groundwater pumpers and the state 

may also assess fees to provide funding 

required to develop an interim plan. 

There are many resources to assist 

local agencies in this process. To assist 

in coordinating GSA formation, DWR 

has provided facilitation services to 

support local public agencies. Further 

information on facilitation services is 

available at: http://www.water.ca.gov/ 

irwm/partnership/facilitation_services. 

cfm. Additionally, there is more information 

on the DWR website regarding 

formation: http://www.water.ca.gov/ 

groundwater/sgm/pdfs/GSA_Notification_Requirements_v2_2016-01-06.pdf. 

The Water Education Foundation has a 

handbook available at: http://www.watereducation.org/publication/2014-sustainable-groundwater-management-act. 

and the California Water Foundation 

has a guide: http://waterfoundation.net/ 

wp-content/uploads/2015/09/CF_GSA_ 

Guide_09.30.15_web.pdf. 

Planning: Developing the Groundwater 

Sustainability Plan (GSP) 

Following GSA formation, the next 

step is for the GSA(s) to develop a 

Groundwater Sustainability Plan (GSP). 




Critically Overdrafted Critically Water Overdrafted Basins - Groundwater January 2016 Basins – January 2016 

For high- and medium-priority basins 

that are not critically over-drafted, the 

GSPs are due by January 1, 2022. For 

areas with critical overdraft (see map), 

the GSPs are due on January 31, 2020. 

Where multiple agencies agree to form 

a single GSA through a legal agreement, 

the agencies may develop a single 

GSP. However, multiple GSAs may also 

coordinate to develop a single GSP or 

multiple GSPs for a single groundwater 

basin or sub-basin. In groundwater 

basins where there will be more than one 

GSP, the responsible GSAs must coordinate 

management of the basin through 

a single coordination agreement that 

covers the entire basin. 

On May 18 the California Water 

Commission (Commission) approved 

DWR’s GSP regulations. 

The regulations specify the components 

of GSPs, acceptable alternatives 

to GSPs, and coordination agreements 

among local agencies. The regulations 

also describe the methods and criteria 

used by DWR to evaluate those plans, alternatives, 

and coordination agreements, 

and information that DWR requires for 

evaluation, which is to be based on a 

substantial compliance standard provided 

that the objectives of SGMA are 

satisfied. 

In sum, a local agency “shall have the 

responsibility for adopting a GSP that 

defines the basin setting and establishes 

criteria that will maintain or achieve 

sustainable groundwater management.” 

DWR will “have the ongoing responsibility 

to evaluate the adequacy of the 

GSP and the success of its implementation.” 

A GSP will be evaluated, and its 

implementation assessed with the objective 

that a basin be sustainably managed 

within 20 years of GSP implementation 

without adversely affecting the ability of 

an adjacent basin to implement its GSP 

or achieve and maintain its sustainability 

goal over the planning and implementation 

horizon. 

The full text of the GSP regulations 

and additional information are available 

at: http://www.water.ca.gov/groundwater/sgm/gsp.cfm 

The Importance of Surface Water for 

Sustainable Groundwater Management 

Although SGMA focuses upon 

groundwater, successful implementation 

Crescent City 

Eureka 

Fort Bragg 


Ukiah 

San Francisco 

Willows 

Napa 

Redding 

Red Bluff 

Chico 

Sacramento 

Oakland 

San Jose 

Santa Cruz 

Monterey 

Critically Overdrafted Basins 

Basin Number 

Basin/Subbasin Name 

3-01 Soquel Valley 

3-02 Pajaro Valley 

3-04.01 180/400 Foot Aquifer 

3-04.06 Paso Robles Area 

3-08 Los Osos Valley 

3-13 Cuyama Valley 

4-04.02 Oxnard 

4-06 Pleasant Valley 

5-22.01 Eastern San Joaquin 

5-22.04 Merced 

5-22.05 Chowchilla 

5-22.06 Madera 

5-22.07 Delta-Mendota 

5-22.08 Kings 

5-22.09 Westside 

5-22.11 Kaweah 

5-22.12 Tulare Lake 

5-22.13 Tule 

5-22.14 Kern County 

6-54 Indian Wells Valley 

7-24 Borrego Valley 

Total number of Basins/subbasins: 21 

January 1, 2016 

Oroville 

Marysville 

Quincy 

Auburn 

Antioch 

Stockton 

Susanville 

Downieville 

Placerville 

Modesto 

Truckee 

Merced 

Santa Barbara 

Mariposa 

Fresno 

Visalia 

Bakersfield 

Los Angeles 

Miles 

0 25 50 100 150 200 

Long Beach 

Groundwater basin/subbasin 

Critically Overdrafted Groundwater Basins 

DWR Region Office boundary 

County boundary 

North Central 

Region Office 

South Central 

Region Office 

Lancaster 

Oceanside 

San Diego 

San Bernardino 

Riverside 

Anaheim 

Northern 

Region 

Office 

Southern 

Region 

Office 

Cadiz 

El Centro 

Needles 

of SGMA and sustainable groundwater 

management will rely upon the availability, 

utilization and integration of surface 

water. 

Under SGMA, DWR was directed 

to prepare a report on water available 

for replenishment. DWR has prepared 

a White Paper to provide an initial response 

to the “water available for replenishment” 

requirements under SGMA, 

including background information and 

next steps for completing the analysis. 

This White Paper is available for public 

review and comment at: http://water. 

ca.gov/groundwater/sgm/wafr.cfm. The 

report will be completed by December 

31, 2016. 

In addition to the DWR report, there 

is new thinking and more concerted 

efforts around groundwater recharge 

opportunities and the ability to recharge 

groundwater is receiving increased attention 

in California. The Legislature in 

SGMA found that “sustainable groundwater 

management in California depends 

upon creating more opportunities 

for robust conjunctive management of 

surface water and groundwater resources. 

Climate change will intensify the 

need to recalibrate and reconcile surface 

water and groundwater management 

strategies.” Furthermore, the Legislature 

expressed its intent “to increase groundwater 

storage and remove impediments 

to recharge.” (Water Code §10720.1)(g).) 

Looking forward, sustainable 

groundwater management will thus be 

dependent in large part on the effective 

management of surface and groundwater 

supplies in an integrated manner. This 

includes the recharge of groundwater--either 

directly or through in-lieu 

opportunities--by maximizing the availability 

and use of surface water supplies.

CASGEM Groundwater CASGEM Basin Prioritization Groundwater Basin Prioritization 

Crescent City 

Eureka 

Fort Bragg 

Ukiah 

San Francisco 

Willows 

Napa 

Redding 

Red Bluff 

Chico 

Sacramento 

Oakland 

San Jose 

Santa Cruz 

Monterey 

Oroville 

Marysville 

Quincy 

Auburn 

Antioch 

Stockton 

Susanville 

Downieville 

Placerville 

Modesto 

Statewide Groundwater Basin Prioritization Summary 

Basin Basin count 

Percent of total for State 

ranking per rank GW use Overlying population 

High 43 69% 47% 

Medium 84 27% 41% 

Low 27 3% 1% 

Very Low 361 1% 11% 

Totals 515 100% 100% 

Truckee 

Merced 

Santa Barbara 

Mariposa 

Fresno 

Visalia 

Bakersfield 

Los Angeles 

Long Beach 

North Central 

Region Office 

South Central 

Region Office 

Lancaster 

Oceanside 

Groundwater basin/subbasin 

Basin prioritization ranking 

High 

Medium 

Low 

Very low 

San Diego 

San Bernardino 

Riverside 

Anaheim 

DWR Region Office boundary 

Hydrologic region boundary 

County boundary 

Northern 

Region 

Office 

Cadiz 

El Centro 

Southern 

Region 

Office 

Needles 

tions for fish and wildlife.” Several areas 

took advantage of this opportunity, including 

the Yolo County Flood Control 

and Water Conservation District. 

There are also several other programs 

underway to explore and encourage 

groundwater recharge opportunities. 

This includes: 

A recent study conducted by scientists 

with University of California, Davis and 

the University of California Cooperative 

Extension, where they investigated 

the value deliberate winter flooding of 

fields during rainy years would have in 

recharging groundwater in California. 

According to the study, “flooding agricultural 

land during fallow or dormant 

periods has the potential to increase 

groundwater recharge substantially. 

The study identified 3.6 million acres 

of agricultural land statewide as having 

Excellent or Good potential for groundwater 

recharge. The index provides 

preliminary guidance about the locations 

where groundwater recharge on 

agricultural land is likely to be feasible. 

A variety of institutional, infrastructure 

and other issues must also be addressed 

before this practice can be implemented 

widely.” http://californiaagriculture. 

ucanr.edu/landingpage.cfm?article=ca. 

v069n02p75&fulltext=yes. 

A recent study by RMC that “evaluates 

the potential benefits of recharging 

groundwater through flooding of 

agricultural lands using excess winter 

river flows, focuses on a portion of the 

east side of the San Joaquin Valley in 

Merced, Madera, and Fresno counties.” 

http://waterfoundation.net/wp-content/ 

uploads/2015/09/Creating%20an%20 

Opportunity%20On%20Farm%20Recharge%20Summary%20Report%20 

(00306326xA1C15).pdf. 

The Almond Board of California is 

working with Sustainable Conservation 

to work with San Joaquin Valley farmers 

to accept flood flows from storms to 

help replenish groundwater, California’s 

underground “savings account,” for dry 

seasons. See: http://plantingseedsblog. 

cdfa.ca.gov/wordpress/?p=9570. 

Water resources managers throughout 

the state have and will continue to explore 

various ways to recharge groundwater 

and conjunctively manage water in 

this manner. 

Basin Prioritization results — June 2, 2014 

Miles 

0 25 50 100 150 200 

In other words, sustainable groundwater 

management will largely depend upon 

sustainable surface water management. 

In November 2015, the Governor 

issued an Executive Order encouraging 

new recharge opportunities: “To 

demonstrate the feasibility of projects 

that can use available high water flows to 

recharge local groundwater while minimizing 

flooding risks, the State Water 

Resources Control Board and California 

Regional Water Quality Control Boards 

shall prioritize temporary water right 

permits, water quality certifications, 

waste discharge requirements, and 

conditional waivers of waste discharge 

requirements to accelerate approvals 

for projects that enhance the ability of a 

local or state agency to capture high precipitation 

events this winter and spring 

for local storage or recharge, consistent 

with water rights priorities and protec- 

Conclusion 

Sustainable groundwater management 

is and will be hard work and require new 

levels of collaboration. The passage of 

SGMA now provides an opportunity for 

local leaders to come together to develop 

plans and implementation strategies 

that will help advance sustainable water 

management in California. In places 

where sustainable local groundwater 

management does not emerge, there will 

be regulatory (i.e., SWRCB action) or 

judicial (adjudication) actions leading to 

sustainable groundwater management. 



Blueberries 


Photo Credit: Mark Gaskell 


Nutrient Management Requirements in 

Mild-Winter Areas of California 

Mark Gaskell 

Farm Advisor , University of California 

Cooperative Extension, San Luis Obispo, CA 

The expansion of California organic 

blueberry production area targets 

growing demand for fresh organic fruit 

all over the US. Early and out of season 

blueberry markets tend to maintain higher 

prices and organic fruit often receives an 

additional price premium. Organic blueberry 

production also requires specialized 

management — and often higher costs 

— primarily associated with challenges for 

efficient nutrient management and higher 

costs for weed control. 

Fresh blueberry acreage and production 

has increased annually in California 

since the late 1990s. Prior to 2000, California 

was not known as a fresh blueberry 

production area and California blueberry 

volumes were not sufficient for USDA 

to report prior to 2005. Between 

2010 and 2015, California 

blueberry market volume 

increased 250% to nearly 9 

million trays and California 

had become the leading 

fresh blueberry shipping 

point of all domestic or import 

sources (US Berry Report, 

USDA Market News Service). The 

percentage of US fresh produce consumption 

that is organic, increased 

from 5% in 2010 to 8.4% in 2015 

(The Packer 5/2/16) and organic 

blueberries are typical of that trend. 

Soil and Climate Conditions Dictate 

Critical Blueberry Cultural Practices 

In mild areas of California, there is 

relatively low chill hour accumulation, 

but earlier blueberry production. Specific 

blueberry types predominate in these areas 

— typically Southern Highbush (SHB) 

cultivars or rarely, Rabbiteye cultivars 

(RE). More traditional blueberry production 

areas in the eastern, northern, and 

Pacific Northwestern US primarily grow 

Northern Highbush (NHB) types. The 

NHB cultivars by nature are larger plants 

that require more chill hours to fruit and 

lose their leaves during a dormant winter 

period. Growing seasons are generally 

shorter in those areas than milder areas of 

the southern and western US. 

Organic fertilization of blueberries has 

been more thoroughly studied with NHB 

cultivars in Oregon, Michigan, and New 

York. These studies are helpful in guiding 

organic management of SHB cultivars, but 

the mild-winter conditions of California’s 

coast present special challenges. Studies 

with conventional nutrient management 

of SHB blueberry cultivars from the 

Southeastern US also provide insight into 

effective organic fertilization programs. 

Some SHB cultivars will begin flowering 

and fruiting in September and October 

with little or no chilling hour accumulation. 

While these cultivars begin flowering in 

fall of the prior season, they remain green 

and active during the cool winters. This 

is described as the evergreen production 

system. There may be periods of relatively 

slow growth in the shorter, cooler days of 

winter, but plants do not lose their leaves. 

If regular banded applications or pre-plant 

broadcast nutrient applications were made 

the prior season, little or no fertilization 

may be required during this wetter winter 

period from November to February—especially 

in higher organic matter soils (> 3%). 

The SHB plants in the evergreen system, 

are pruned in mid-summer following 

harvest as opposed to winter pruning of 

dormant plants with the NHB cultivars. 

California blueberry growing areas are 

predominated by soils with higher pH than 

traditional blueberry production regions— 

pH 7-8 as opposed to pH 4.5 to 6.5—and 

the California blueberries require careful 



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attention to soil and water acidification to 

maintain productivity. Organic blueberry 

cultivation generally in California requires 

applications of acidification agents to soils 

and irrigation water. These are typically sulfur, 

or weak organic acids approved by the 

National Organic Program (NOP). There 

are approved granular sulfur materials 

for soil application and approved organic 

acids—primarily citric and acetic acid—for 

maintenance of low pH in irrigation water. 

The use of sulfur burners is also approved 

for acidifying irrigation water and may be 

the most cost effective and efficient option 

for organic blueberry production. Occasionally, 

foliar or fertigated minor elements 

may be used to correct short-term minor 

element deficiencies (e.g. iron, zinc, etc.) 

resulting from higher soil or water pH. 

Major and Minor Nutrients 

Organic production systems place an 

emphasis on turnover of nutrients from 

soil organic matter (SOM), and the related 

cultural practices for enhancing SOM combined 

with nutrient applications can supply 

most major and minor elements with the 

exception of nitrogen. These practices in 

effect raise overall background soil levels to 

medium to high levels, and with periodic 

soil tests for these levels, they can be 

maintained via banded applications. Soil 

levels of most major and minor elements 

can be managed with timely soil testing 

and broadcast or banded incorporation 

of NOP-compliant nutrient sources such 

as compost and various other potential 

nutrient sources. 

Nitrogen (N) is an exception however, 

because of dynamic cycling of N during 

SOM turnover the importance of matching 

N availability with plant demand and 

movement of soluble N out of the root 

zone. Nitrogen is often the most critical 

element limiting crop growth and matching 

plant N demand with N availability is 

the most difficult challenge with efficient 

organic blueberry production. Blueberries 

show some preference for ammonium 

forms of N and ammonium is relatively 

plentiful at the lower soil pH preferred by 

blueberries. Nitrate-N however, is the most 

common and abundant form of nutrient 

N in most field soil situations. Studies in 

Florida with SHB blueberries—comparing 

Ammonium-N and Nitrate-N sources— 

confirmed a preference for Ammonium-N, 

but concluded that overall vegetative 


Fertilizer solutions used for conventional fertigation are soluble and 

more uniform compared to most liquid organic fertilizers. 

growth was not limited by N form. The 

most important benefit of efficient N management 

for blueberries is the development 

of a large, vigorous vegetative plant on 

which to hang berries. 

Nutrient Management Requirements of 

Organic Blueberries 

Seasonal needs for N can vary considerably 

for blueberries. Highest NHB blueberry 

yields were observed with approximately 

100 lb. N per acre per season in recent 

studies in Oregon, and those studies also 

showed benefits to low, stable nutrient applications 

throughout the season. In mild 

production areas of California, the SHB 

plants in the evergreen system are growing 

over a longer season, and the overall 

nutrient requirements may exceed those 

of traditional NHB production areas. In 

established California evergreen plantings, 

after the first 6-12 months, blueberries 

will respond to regular N applications 

from spring into late fall. In these areas, a 

seasonal N requirement of 180-220 lb. of N 

per acre, per season, is more typical. Wood 

waste is often incorporated to improve soils 

for blueberry plantings, and there may be a 

need to compensate for additional immobilization 

of applied N by the decaying 

wood waste with application of additional 

periodic or pre-plant N. 

Synchrony of Plant Uptake and Nutrient 

Availability 

Plants have relatively slow nutrient 

uptake initially as new plants become 

established, but root systems are small and 

unable to explore large soil volume. The 

blueberry root system is relatively shallow 

and fibrous, so needed nutrients should be 

concentrated in upper part of soil profile 

(2”-10”), near the developing plant, and in 

contact with moist soil to speed decomposition 

and mineralization of N. 

Pre-plant applications of compost can 

provide uniform amounts of balanced 

nutrients for overall soil improvement. Nutrient 

placement is critical for small plants 

however, and a balanced source of pelleted 

or granular organic fertilizer should be 

added and mixed into the hole at planting. 

Pre-plant incorporation of organic nutrient 

sources such as compost at very high rates 

may also contribute to net losses of soluble 

nutrients such as Nitrate-N during periods 

of slower uptake and higher rainfall typical 

of California winters. Thus, soil nutrient 

and organic matter building programs for 

the first 12-24 months, should rely partly 

on periodic application of banded and 

incorporated compost and/or granular 

NOP-compliant materials. Calculate rates 

of application based on the percent N in 

the material—adjusting for moisture content—and 

do not exceed overall monthly 

application of 30-50 lb. N per acre to avoid 

loss of soluble N. 

As plants become established and new 

growth flushes emerge, N need increases 

rapidly and periodic applications N is 

important to match N demand. Low chill 

SHB blueberries typically are growing year 

around in the evergreen system that typifies 

mild-winter areas. Plants need continual 

nutrition and water but those needs 


Photo Credit: Mark Gaskell

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change. In the second year and beyond, 

blueberries may require 5-8 lb. N per acre 

per week during the periods of most active 

vegetative growth from mid-February to 

early November. Lower N rates can be applied 

in situations with high organic matter 

soils or added N in irrigation water. 

Sources of Nutrients for Organic Blueberries 

Heavier textured and higher organic 

matter soils have higher reserves of 

nutrients and more capacity for cycling of 

nutrients, while sandier soils require more 

frequent and continuous nutrients supplied 

from fertilization. Different soil areas on 

the farm can require different management 

strategies. Pre-plant application of organic 

matter and compost can bring overall levels 

up to optimum and recurrent application 

can be used to maintain a balance of nutrients 

from cycling organic matter—particularly 

in sandy soils. Band or strip incorporation 

of granular materials can be more 

reliable and in some cases more efficient 

then fertigation. These granular fertilizers 

must be applied near the root zone and 

covered with moist soil to accelerate microbial 

decomposition. Organic wood waste 

mulches are often used with blueberry 

plantings to encourage high organic matter 

levels around superficial blueberry root 

systems, and this favors efficient cycling of 

nutrients in this root zone. 

If soil N and moisture are sufficient, 

the SHB blueberries normally respond to 

post-harvest pruning in June with vigorous 

vegetative growth and development of large 

new canes. This new vegetative growth 

is key to the plant’s productivity during 

the following harvest cycle. Ideally, large 

new, thick canes and branches will set the 

stage for high yields of relatively large fruit. 

Higher numbers of larger fruit are set on 

larger canes emerging from the base and 

from larger branches from pruned canes. 

This development will occur between 

pruning and November in mild areas of 

California, and N encourages larger and 

more canes if moisture is adequate. 

Another potential source of N is 

irrigation water. Nitrogen is common 

in irrigation water in many California 

blueberry production areas, and 10-20 

ppm of Nitrate-N is not uncommon. These 

amounts would contribute 2-4 lb. N per 

acre inch of irrigation water applied, so it 

would not be unusual for a blueberry planting 

to be receiving 1-4 lb. N per acre week 

via irrigation water alone. Irrigation water 

should be analyzed and N credits given for 

any N present. 

Recent continuing drought conditions 

in California have affected many fruit crops 

including blueberries when salinity and 

chloride and/or sodium levels rise because 

of lower than normal winter rains to wash 

salts from the root zone. These problems 

have affected fertilization regimes generally 

and more attention should be directed 

toward management of soil salinity in 

addition to maintaining adequate nutrition 

in the root zone. Drip irrigation performs 

better than micro-sprinklers in Florida 

studies, but salt accumulation can occur 

at the edge of wetting zones in more arid 

areas like California. Granular N fertilizer 

can also increase soil salinity over fertigation 

and aggravate salinity problems. 

Uncertain and diminishing water supplies 

and marginal irrigation water quality also 

add to challenges for efficient management. 

Additional leaching irrigations are needed 

to flush the root zone to control salinity and 

potentially harmful ions such as sodium 

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Preplant incorporation of compost and other organic nutrient 

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and chloride among others. This challenges 

N management related to soluble 

N forms like Nitrate-N from N cycling 

and the potential for losses of this N in the 

leaching process. 

Limits of Organic Fertigation 

Fertigation is widely used by growers of 

both conventional and organic fruits and 

vegetables as a means to manage fertilization 

efficiently. Regular fertigation of 

blueberries has been shown to be more 

productive compared to granular fertilization 

in recent Florida studies with conventional 

fertilizer sources. Fertigation with 

NOP-compliant organic fertilizers, however, 

can be a relatively inefficient process. 

Conventional fertigation materials, for the 

most part, utilize soluble fertilizer sources, 

but this is not usually the case with organic 

fertilizers because completely soluble 

NOP-approved organic materials are very 

limited. Chilean nitrate (CN) is soluble for 

example, but CN is limited to no more than 

20 percent of total N application for compliance 

with the NOP. Some studies and 

grower experience have identified potential 

problems with NOP-approved fertigation 

materials related to their uncertainty in 

micro irrigation systems. 

Irrigation engineers are calling attention to 

the potential for “bacterial slimes” forming 

from fertigation with organic nutrient 

sources and the potential for plugging and 

loss of nutrients behind irrigation filters or 

emitters. These problems can contribute 

also to variable irrigation system distribution 

uniformity (DU) and undue plant 

stress due to moisture and/or nutrient 

deficiency. Growers have noted shortened 

intervals between filter cleanings and have 

occasionally responded by eliminating the 

filtering during fertigation, which can be 

devastating to irrigation system DUs. 

It is important that micro irrigation systems 

be maintained for use with fertigation 

regardless of the material. And irrigation 

systems require acidification as maintenance 

also to avoid build-up of precipitates. 

There are NOP-approved materials for 

acidification—usually weak acids—and 

chlorine, and other materials may also be 

used for control of algae and bacteria in the 

lines. Carefully verify limits on chlorine 

concentrations for irrigation systems to 

remain compliant with NOP restrictions. 

For the most efficient use of organic fertigation 

to apply nutrients via micro irrigation 

systems, it is especially important to use a 

filter, clean the filter and the lines often, and 

use NOP-compliant materials with a high 

percentage of N in soluble form. 

NOP-approved fertigation materials from 

organic byproducts that have undergone 

varying rates of fermentation and other 

organic transformation are sometimes 

stabilized with the addition of acids. These 

materials may have acid pH reaction that 

also makes them desirable for blueberry 

production. These materials may nevertheless, 

have elevated levels of salt, chloride, 

sodium, or other ions that may aggravate 

soil salinity, and ion toxicities, and compromised 

water quality exacerbated by extended 

drought conditions in California. 

Blueberry growth, development and 

fruiting have clearly defined patterns in 

mild-winter areas of California. Efficient 

fertilization and nutrient management 

programs for organic blueberry production 

can be built upon a basic understanding 

of organic matter cycling in soils, different 

alterative NOP-compliant cultural practices, 

and the special nutrient requirements of 

blueberries. 



Rice 

Photo Credit: Timothy Blank 


Weedy Red Rice Rivals Watergrass as being the 

Worst Weed in Rice Production Worldwide 


Timothy Blank 

Certified Seed Program Representative, 

California Crop Improvement Association 

In the southern rice growing states, 

where weedy rice is widespread, 

high infestations have resulted in yield 

reductions of over 60%. A 2008 survey 

in Arkansas, which has the largest area 

of rice production in the U.S., found that 

62% of rice fields were infested to some 

degree. Fortunately, California growers 

have had little opportunity to personally 

experience this weed on their own land, 

primarily due to isolation from affected 

rice growing regions, careful import 

protocol for new varieties and breeding 

material, and largescale use of certified 

seed. Over the past 100 years of rice 

production in California, there have 

been periodic infestations. Most of these 

populations were eradicated or taken out 

of rice production. 

After the discovery of six new weedy 

rice populations in 2003, an effort was 

made to eradicate these populations. 

While these efforts bore some success, 

not only has one of these populations 

not been eradicated, several new populations 

have since been discovered. 

With the known economic harm this 

pest can have on the industry at large, it 

is important that growers report infestations 

to their farm advisor or county 

Agricultural Commissioner’s office. Early 

infestations are often confused with 

watergrass, specialty rice varieties, or 

bakanae. While there is abundant phenotypic 

diversity of weedy populations 

in the United States, three characteristics 

that are consistent across weedy U.S. rice 

populations are: 1) red colored bran, 2) 

shattering, and 3) seed dormancy. It is 

the long seed dormancy, in some cases 

remaining viable in the soil for over 10 

years, which makes weedy rice control a 

persistent, long-term effort. Weedy rice 

can be distinguished from most conventional 

rice varieties in that it has lighter 

green leaves, rougher leaves, a wider 

canopy, and is taller. 

Best Management Practices (BMPs) 

have been updated and can be viewed on 

the UC-ANR website, http://rice.ucanr. 

edu/files/240623.pdf. The BMPs outline 

proper equipment cleanout, roguing, 

harvest scheduling, burning of straw, 

avoiding tillage and straw incorporation 

to prevent incorporation of weedy rice 

into soil, and fallowing/irrigating/spraying. 

Other techniques to help reduce 

weedy populations include planting to a 

stale seed bed, using high seedling rates 

to increase competition with weedy rice, 

water seeding, and maintaining a continuous 

flood. The ‘stale seed bed method’ 

is a technique to reduce weeds on the 

soil surface prior to planting by irrigating, 

germinating weed seeds, spraying a 

broad-spectrum herbicide, flooding, and 

then planting. 

The Weedy Red Rice Task Force has 

been reestablished to determine the 

most effective path to form a collaborative 

effort to eradicate weedy rice. This 

taskforce includes representatives from 

the Butte and Glenn Agricultural Commissioner 

offices, University of California 

Cooperative Extension, University 

of California - Davis, California Rice 

Commission, Rice Experiment Station, 

Rice Research Board, and California 

Crop Improvement Association. 

During the 2016 growing season, 

the Task Force would like growers or 

PCA’s to notify their county agricultural 

commissioner office or local UC Farm 

Advisor if they suspect their fields may 

have weedy red rice. Plant samples will 

be taken and compared with samples of 

other populations. At least two genetically 

distinct populations are present in 

California. Plans are in place to publish 

images of different biotypes to aid growers 

and PCA’s while they scout fields. 

For the vast majority of growers who do 

not have weedy red rice on their farms, 

the two best ways to stay uncontaminated 

is to 1) plant only certified seed, and 

2) clean equipment coming from offfarm 

locations, and especially clean used 

equipment purchased from the southern 

rice growing regions. 

The California rice industry is still at 

a stage where this weed can be eradicated. 

The Weedy Red Rice Task Force 

believes this effort will best be achieved 

when growers and PCA’s work voluntarily 

and cooperatively with their local UC 

Farm Advisor and county Agricultural 

Commissioners office. 

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Almonds 

Post Harvest Nutrition in Almonds 

Cecilia Parsons 

Contributing Writer 

Crop yields, leaf tissue analysis and 

timing are all factors in determining 

a successful strategy for providing post 

harvest nutrition to almond trees. 

University researchers and crop care 

managers agree that fall can be an excellent 

time to apply certain nutrients in 

almond orchards, but actual benefits to 

tree health and the bottom line depend 

on calculating exactly what trees need 

and timely delivery of nutrients. 

“The fundamentals remain the same,” 

said University of California farm advisor 

Roger Duncan of post harvest nutrition. 

Rather than applying a set amount 

of fertilizer each year, he stresses a July 

leaf tissue analysis and a hull testing for 

boron at harvest to determine the nutritional 

status of an orchard and a plan 

for delivering the nutrients at a time and 

place where they will be taken up by the 

tree. Knowing the levels of nutrients in 

the trees helps growers avoid over application 

of nitrogen and delivering sufficient 

levels of other nutrients. Annual 

leaf sampling aids in adjusting nutrition 

programs. 

The four materials that are most 

commonly used in post harvest almond 

nutrition applications are zinc, boron, 

nitrogen and potassium. 

In Stanislaus County, boron is often 

deficient in almonds east of the San 

Joaquin River but can reach toxic levels 

on the west side, Duncan reports. Boron 

does not accumulate in almond leaves, 

so hull samples are the best indicator of 

boron status. If hulls have less than 80 

ppm trees are deficient and yields may 

suffer, Duncan warned. This nutrient is 

commonly applied in the fall as a foliar 

spray as long as trees retain functioning 

leaves. Two pounds of a 20% product 

per 100 gallons water is a typical rate. 

Fall applied boron will be remobilized in 

the spring and benefit development of 

healthy flower parts, particularly pollen 

tubules. Boron also aids in the translocation 

of calcium. 

Duncan said boron is best applied to 

the soil in the spring, as fall sprays do 


not have enough boron to correct an 

overall boron deficiency. Boron applied 

to the soil in the fall is subject to winter 

leaching. The fall foliar application acts 

to temporarily replenish boron levels in 

the dormant fruit bud. 

Rapidly growing young trees or trees 

planted in alkaline soils are prone to zinc 

deficiency, especially on Nemaguard 

rootstock. Symptoms are most noticeable 

in the spring with delayed opening of 

flower buds, smaller leaves with chlorotic 

areas between the veins and a wavy leaf 

margin. The most cost effective method 

for delivering zinc is a fall application of 

zinc sulfate, Duncan said. Some growers 

prefer to apply more expensive, less 

phytotoxic formualtions of zinc in the 

spring when it can be tank mixed with 

fungicides or other materials. 

Crop advisor Justin Nay said zinc sulfate 

also helps with disease management 

and helps prevent tree blow over from 

fall rains. Nay said that in many orchards 

gypsum and compost are also applied in 

the fall before winter rains. 

Leaf analysis is also important in 

tracking potassium levels. A research trial 

cited by Duncan showed that almond 

yields decline when potassium levels are 

less than about 1.4 percent in July-sampled 

leaves. Yields decline in potassium 

deficient trees because fruiting spurs die 

prematurely. 

Duncan advises shooting for potassium 

levels higher than 1.4 percent 

because dropping below that threshold 

will put trees in a deficit for next year, 

setting the stage for lower yields. With an 

average reading of 1.4 percent, some trees 

will need more and some less, but wasting 

some fertilizer will ensure sufficient 

amounts of this nutrient across the entire 

orchard. 

Potassium applications can be made 

with sulfate of potash or potassium 

chloride. It can be banded on the soil in 

the fall in flood, solid set or microsprinkler 

irrigated orchards. In orchards that 

are drip irrigated, this nutrient can be 

injected. 

The amount of nitrogen applied post 

harvest depends on yield, said University 

of California researcher and plant science 

professor Patrick Brown. If a tree is still 

growing and soil moisture is adequate, it 

will take up nutrients through the roots. 

If a tree is stressed for water, it has been 

more than a month since harvest or the 

tree is flush with nutrients, it will take up 

less. Soil or foliar application of nutrients 

will give trees a small boost in the fall if 

conditions are right, Brown said. 

Crop yield and tissue analysis will 

show the amount of nitrogen that has 

been removed at harvest. A tendency to 

apply the same amount of nitrogen each 

year post-harvest can lead to over or under 

application. Brown said with higher 

yields there is a greater chance of higher 

uptake of nutrients — and less chance of 

over — application of nitrogen. 

To avoid leaching of nitrogen, Duncan 

said that only 10-20 percent of annual nitrogen 

needs should be applied post-harvest. 

Timing is an important consideration 

in nitrogen applications. October 

may be too late for significant uptake, 

Duncan said. Trees that are losing their 

canopy will not be efficient in uptake. 

Soil type can play a part in uptake of 

nutrients. In sandier soils, nitrogen may 

leach below the root zone. Some growers 

may consider a fall foliar spray of lo-biuret 

urea instead of a traditional ground 

application. 

Type of irrigation can play a part in 

efficient use of nutrients. If an orchard 

is flood irrigated and is not scheduled to 

receive water for more than a month post 

harvest, the trees will not be able to take 

up soil-applied nutrients. Drip or micro 

sprinkler systems allow for better uptake 

by keeping the soil profile filled. 

The post harvest nutrition picture is 

fairly similar from northern to southern 

almond growing regions, Brown said, 

but in the south, the sooner after harvest 

is best. Once signs of defoliation appear 

there will be little uptake of nutrients. 

With early harvested varieties like 

Nonpareil and Independence, growers 

or managers have about a month after 

harvest is completed to apply their post 

harvest nutrients. Trees that are actively 

growing and healthy will make the best 

use of applied nutrients. PCC

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Vineyards 


Stephen Vasquez 

Research Agronomist – West of the Rockies 

Tessenderlo Kerley, Inc. Crop Vitality 

The past four years have been challenging 

for California grape growers 

with persistent drought. In 2015, 

vineyards were displaying a variety of 

foliar and fruit symptoms as a result of 

insufficient water, poor water quality, 

high soil salts, pests and diseases as 

well as many other abiotic and biotic 

causes. Although El Nino brought 

more precipitation to the state in 2016, 

unusual foliar symptoms continue to 

be expressed this season, including 

potassium deficiency symptoms and 

some that resemble potassium deficiency. 

It’s important to properly identify 

foliar symptoms so solutions can 

be implemented as soon as possible. 

Potassium deficiencies, when properly 

identified using visual and lab analysis 

can be corrected in-season, allowing 

fruit to mature properly. 

Role of Potassium in Grapevine Health 

Potassium has many roles in 

maintaining plant health. Taken up 


by plants as K + , an important role is 

its activation of at least 60 enzymatic 

events within grape plants. Potassium 

“activates” enzymes by changing their 

shape, which then initiates one or 

more metabolic activities important 

for grapevine health. For example, 

the uptake of other macro and micro 

nutrients are dependent on potassium 

for their movement into the plant 

and final incorporation into proteins, 

sugars and cell structure by way of enzymes 

initially activated by potassium. 

Another important potassium role is 

the translocation of sugars made in 

the leaves during photosynthesis to 

maturing berries. Without adequate 

potassium, the energy needed to 

transport sugars decreases, resulting 

in a surplus of sugars in the leaves and 

a reduction in photosynthesis. Potassium 

also has a role in water management 

within the plant by controlling 

the opening and closing of stomata 

guard cells found on the underside of 

leaves; allowing the diffusion of water 

vapor out of and carbon dioxide into 

the leaf. Under drought conditions, 

grapevines with sufficient K + will close 

stomata, reducing water vapor loss, 

carbon dioxide passage into the plant 

and photosynthesis. However, when 

water and potassium are abundant, 

the making of sugars becomes an efficient 

process. 

Some Essential Functions of Potassium 

Include: 

• Activation of enzymes 

• Regulation of stomata opening 

and closing 

• Regulation of phototropism 

(tracking of light) 

• Production and translocation of 

proteins and sugars 

• Maintenance of cellular pH and 

electrical charge 

• Promotion of root growth 

• Uptake of other elements 

• Winter hardiness 

• Pest and disease resistance 

Potassium Deficiency Symptoms and 

Causes 

Potassium is a mobile element, 

which allows the plant to move K + 

Continued on Page 28

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Contact a Tessenderlo Kerley 

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©2016 Tessenderlo Kerley, Inc. All rights reserved. KTS ® is a registered trademark of Tessenderlo Kerley, Inc. 



from locations of low demand (older, 

shaded leaves) to high demand sites, 

such as maturing grape bunches. 

When soil potassium is inadequate, 

grapevine foliage becomes the potassium 

source for new leaves and clusters. 

Foliar symptoms begin to appear in 

late spring or early summer on mature 

leaves by displaying a light yellow 

(white varieties) or red (red varieties) 

hue along the leaf blade and fading 

green color between veins under mild 

deficiencies. A more pronounced deep 

yellowing (chlorosis) or reddening 

between veins as well as leaf curling 

and leaf blade necrosis signals a more 

significant potassium deficiency. 

In addition to older leaves showing 

symptoms, a transition between veins 

from green to yellow in young leaves 

indicates severe potassium deficiency, 

which often begins at bloom/berry set 

and worsens as harvest approaches. By 

harvest, potassium deficient grapevines 

will have low yields, reduced 

fruit quality and low vigor with significant 

leaf drop, exposing fruit that will 

raisin (Figure 1). 

Identifying potassium deficiency 

solely by grapevine canopy visual 

observations can be tricky, given that 

foliar symptoms can be confused with 

other maladies. One common disorder 

known as “spring fever” or “false 

potassium deficiency” is caused by the 

vines inability to metabolize nitrogen 

during cool spring weather; resulting 

in high levels of ammonium and the 

amino acid putrescine (Figure 2). Lab 

tissue analysis is the best method for 

correlating symptoms with either 

spring fever or a true potassium deficiency. 

Grapevines expressing spring 

fever symptoms will not be deficient 

in potassium when lab tissue analysis 

is used for confirmation. Bloom time 

petiole levels should be greater than 

1.5% potassium to properly mature a 

crop (Table 2). 

Additional foliar symptoms often 

confused with potassium deficiency 

are water stress, other nutrient deficiencies 

that may initially resemble 

potassium deficiency (i.e. Mg), pest, 

disease (i.e. Pierce’s disease), and herbicide 

damage, as well as others. 

Absolute Deficiency 

When potassium is absent or 

inadequate amounts exist in the soil 

profile to support a crop, deficiency 

symptoms will appear early and persist 

throughout the season. Such cases 

arise when potassium is mined season 

after season without replenishing the 

soil profile with the minimum amount 

of potassium removed with the crop. 

On average, between 6-13 lbs. K 2 

O is 

removed with each ton of grapes that 

needs to be replaced each season. In 

general, vineyards planted to sandy 

soils with low cation exchange capacity 

will display potassium deficiency 

much sooner than those planted to a 

clay soil. However, soil texture is not a 

definitive indicator as to the amount 

and availability of potassium. Some 

soils will “fix” potassium, making it 

unavailable to the vines, even when 

soil lab analysis indicates it exists in 

the root zone. Therefore, potassium 

fertilization programs should take 

into account a soil’s ability to fix 

potassium as well as past cropping 

history and occurrence of potassium 

deficiency. 

Additionally, vineyard sites that 

were leveled to make use of flood or 

furrow irrigation may show deficiencies 

in the areas where the top soil was 

removed to fill-in low lying areas. This 

is often the case at vineyard sites developed 

prior to drip irrigation, which 

now makes fertigation much easier on 

sites with uneven ground. 

Induced Deficiency 

When soil has adequate potassium 

and is not being fixed, other factors 

may impact uptake. Soil pests, like 

nematodes and phylloxera (Figure 3) 

can cause considerable root damage, 

influencing root growth and nutrient 

and water uptake. Vineyards planted 

to their own roots often suffer the 

most damage since they have little 

to no tolerance to soil pest feeding. 

The selection of a proper rootstock 

with resistance to nematodes and/or 

phylloxera can minimize root damage. 

However, there isn’t a single rootstock 

that has all the characteristics 

for all vineyard sites. Table 1 shows 

how some rootstocks might perform 

when planted to different soil conditions. 

Freedom and 1103P are popular 

rootstocks used for raisin, table and 

wine grape production. Freedom has 

relatively good resistance to nematodes 

but poor resistance to phylloxera, 

while pest resistance is reversed 

for 1103P. Differences can also be 

found with respect to nutrient uptake 

amongst rootstocks. Freedom is 

better at foraging for potassium when 

compared to 1103P. However, in the 

presence of nematodes, Freedom will 

probably be the best choice and can 

be supplemented with liquid potassium 

injected into the drip irrigation 

Photo Credit: Stephen Vasquez 

Figure 1. Potassium deficient grapevines displaying 

significant leaf drop and dried fruit. 

Figure 2. “False potassium deficiency” (spring 

fever) resulting from cool spring weather. 

Figure 3. Root damage from nematodes 

limits water and nutrient uptake. 


Table 1. Rootstock characteristics under different soil situations. Adapted from Rootstock Selection 2003, L. Peter Christensen, in Wine Grape 

Varieties in California. 

*Represents root knot/dagger nematodes. 

Rootstock 

Resistance Tolerance Influence on Scion 

Mineral 

Phylloxera *Nematode Drought Wet Soil Salinity Vigor 

Nutrition 

5C high med/low low low/med med low/med 

420A high med/low med low/med low low 

1103P High med/low med/high med/high med med/high 

3309C High low/low low/med low/med low/med low/med 

Harmony low/med med/med-high low/med low Low/med med/high 

N:low 

P,K:med 

Mg:med/high 

Zn:low/med 

N,P,K:low 

Mg:med 

Zn:low/med 

N:med/high 

P,Mg:high 

K,Zn:low/med 

N: low/med 

P,Ca:low 

K,Mg,Zn:med 

N:low 

P: med 

K:high 

Zn:low/med 

Soil 

Adaptation 

Performs well in 

moist, clay soils 


fine-textured, 

fertile soils 

Performs well 

in drought and 

saline soils 


deep soils 

Performs well 

in sandy loams 

to loamy sand 

soils 

Freedom low/med high/high med low low/med high 

N,P,K:high 

Mg:med 

Zn,Mn:low 


sandy to sandy 

loam soils 

Table 2. Laboratory potassium analysis values for grape petioles at bloom and veraison. Adapted from L. Peter Christensen, 2005. 

*80-100 petioles should be collected at bloom (≈60-70% cap fall) opposite a cluster and veraison (≈50% berry softening). Postharvest K levels have not been determined but should 

increase to > 0.8 once fruit has been harvested. 

**No values have been set for excessive or toxic levels of potassium. 

Tissue* Deficient Adequate Excessive** 

Bloom K (Total) % 1.0 1.5 n/a 

Veraison K (Total)% 0.5 0.8 n/a 

system. 

Low soil moisture, elevated levels of 

other cations (i.e. sodium, magnesium, 

etc.) and sometimes soil pest root 

feeding can be overcome by applying 

water more frequently and employing 

fertigation (aka fertilizer irrigation 

injections) management strategies. 

Soil and Tissue Analysis 

Soil analysis is not generally the 

best tool for determining grapevine 

potassium need for an established 

vineyard. Soil texture (sand, silt, clay 

and organic matter) and its overall 

characteristics can have varying 

effects on potassium availability and 

uptake. As previously mentioned, soils 

that test “high” for potassium, may 

also “fix” potassium; making it unavailable. 

However, general soil analysis 

prior to vineyard establishment 

can be valuable. The best information 

obtained from a lab soil analysis 

includes problems related to chemical 

imbalances or excesses. Problems such 

as pH (alkalinity and acidity), high 

salts, cation imbalances (Mg:Ca:K), 

and high boron levels can be identified 

through soil analysis prior to vineyard 

establishment, cautioning a grower 

as to the need for correction pre- or 

post-planting. Previous crop history 

and practices—like deep ripping— 

will dictate how a particular soil and 

grapevine cultivar responds to current 

farming operations, including fertilizer 

and soil amendments. 

Another useful and free tool is 

the National Resources Conservation 

Service (NRCS) Soil Web Survey, 

which gives general information about 

a site without digging a hole. The Soil 

Web Survey contains nationwide soil 

information for all 50 states and can 

be found here: http://websoilsurvey. 

sc.egov.usda.gov/App/HomePage.htm. 

Your local NRCS and/or UC Cooperative 

Extension advisor can help access 

and interpret the Soil Web Survey 

results. 

Since only general information is 




available about a given site, a detailed 

soil analysis should be completed 

by a local lab or consultant prior to 

planting. Some factors to consider 

when soil sampling a mature vineyard 

or open ground (or site previously 

planted) are: age, variety, rootstock(s), 

soil pests, soil characteristic and other 

unique factors that will help you make 

fertilizer decisions. In a mature vineyard, 

areas that are displaying potassium 

deficiency should be sampled 

separately from areas with normal 

growth so differences and nutritional 

needs can be identified. 

Tissue analysis is a better predictor 

of plant potassium need. Sampling 

should be done at phenological stages 

(i.e. bloom, veraison and harvest) so 

comparisons can be made between 

seasons. Pulling tissue samples from 

a uniform vineyard planted to a 

single variety and rootstock is easy. 

Conversely, a vineyard planted to a 

single variety grafted onto different 

rootstocks, on different soils will 

need multiple collections of petioles 

representing the differences in order 

to make good management decisions. 

Tissue samples can be pulled by you, 

a PCA/CCA or lab technician. It’s important 

to keep in mind that pulling 

samples from the same location within 

the vineyard will give the best results 

over seasons. Doing so will provide 

historical data that will help better 

manage the vineyard site. 

General Tissue Sample Protocol 

• Pull bloom (60-70% cap fall) 

petioles from mature, non-shaded 

leaves opposite basal clusters 

• Collect approximately 80-100 

petioles 

• Wash (removing dirt and foliar 

nutrients) and dry petioles and 

deliver to a lab 

• Have analysis completed for macro- 

and micronutrients and salts 

of interest 

• Interpret results, comparing data 

with past seasons so management 

decisions can be made 

• Potassium levels should be at or 

above 1.5% at bloom. 

• Make potassium corrections by 

injecting liquid potassium into the 

irrigation system at intervals that 


will help mature the crop 

Growers who use tissue analysis to 

monitor for fluctuations in nutrient 

status in coordination with soil and 

water analysis will maximize its benefit. 

Locations within a vineyard that 

have been characterized for differences 

should be mapped and evaluated 

season after season. By understanding 

the variability in the vineyard, fertilizer 

applications can be applied as 

needed, which could be more cost effective 

than simply applying the same 

fertilizer regime to the entire vineyard 

(Table 2, Page 29). 

Fertilizer Management 

Once lab analysis has identified 

a nutrient need such as potassium, 

a grower or PCA/CCA must make a 

choice in the type of fertilizer product 

that will be used. In the case of potassium, 

growers can use dry or liquid 

formulations to supply a vineyard. 

A decision on the type of fertilizer 

product often depends on the style of 

irrigation system that’s installed. 

Vineyards irrigated using flood 

or furrow irrigation are best suited 

for dry fertilizers that can be banded 

in-furrow, close to the root zone and 

watered in. Although this method of 

applying fertilizer has been used for 

decades, it is not very efficient. Depending 

on the soil type and severity 

of the deficiency a typical, flood irrigated 

vineyard will not respond quickly 

enough to correct a deficiency once 

fruit begins developing; when demand 

is at its highest. Additionally, soil 

issues, perched water tables, high crop 

loads, pests and diseases and other 

issues that restrict potassium uptake, 

will make it difficult for grapevines to 

recover. 

Mature or newly established vineyards 

irrigated with drip or micro 

sprinklers have a few more options. 

Solubilizing dry fertilizers can be 

done but have added costs in labor 

that’s needed to maintain fertilizer in 

solution so emitters don’t plug. Products 

like potassium chloride dissolve 

easily and can be injected through 

drip irrigation but add chloride to 

the soil profile, which grapes can be 

sensitive to. Additional products like 

potassium sulfate or potassium nitrate 

add significant costs in handling, 

mixing and the addition of nitrogen 

during fruit development. 

Manufactured liquid products are 

better suited for vineyards using drip 

or micro sprinkler irrigation systems. 

Products like potassium thiosulfate 

(KTS ® ) are easily injected into irrigation 

lines as standalone products or 

blended with other liquid fertilizers. 

Liquid fertilizers allow the option of 

applying small amounts over an entire 

season, maximizing grapevine uptake 

because potassium is available in the 

root zone. As western states continue 

to deal with drought conditions and 

water becomes more limited, growers 

and PCA/CCA’s will find that fertigation 

with the right liquid fertilizer is a 

practice that will maximize yields and 

profits. 


References 

Adams, D.O., Franke, K.E. and Christensen, 

L.P. 1990. Elevated putrescine levels in 

grapevine leaves that display symptoms 

of potassium deficiency. Am. J. Enol. Vitic. 

41:121-125. Print. 

Bettiga, L. J, et al. In: Bettiga, L. J. (ed), 

Grape Pest Management, 3rd ed. Oakland: 

University of California Division of Agriculture 

and Natural Resources, 2002. Publication 

3343, 29-45. Print. 

Fidelibus, M. and Vasquez, S. 2012. Spring 

Fever. http://ucanr.edu/blogs/blogcore/ 

postdetail.cfm?postnum=7244. San Joaquin 

Valley Viticulture-California Viticulture 

Information. Web. 

Ludwick, A. E. et al. Western Fertilizer 

Handbook, 9th ed. Danville: Interstate 

Publishers, Inc. 1995. Print. 

Nutri-Facts: Agronomic fact sheets on 

nutrients-Potassium, No.3. www.ipni.net/ 

nutrifacts. International Plant Nutrition 

Institute. Web. 

Pettygrove, S. et al. Potassium Fixation and 

Its Significance for California Crop Production. 

Better Crops Vol. 95:4 (2011). Web. 

Tindall, T. A. and Musso, G. 2015. Using 

Fluid Fertilizers In Drip Irrigation. The Fluid 

Journal. 23:6-8. Web.

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