1

Effect of Soil pH on

Wheat Diseases

Tim Murray

Extension Plant Pathologist

WSU Wheat AcademyDecember 14, 2017

Learning objectives:

What is soil pH?Why do we care?How does it affect crop diseases?

What is pH?

a measure of hydrogen ion (H+) concentration (activity) of a solution

- concept developed in 1909 by a Danish scientist:pH = -log [H+]

For water: H2O = 2H+ + OH- (2 H2O = H3O+ + OH-)

H+ = 0.0000001 M (1 x 10-7 M)

pH = -log [1 x 10-7] = -(-7.00) = 7.0

Acidic solutions have more H+ ions

Basic solutions have more OH- ions

What is pH?

Ranges from 0 to 14

Difference between units = 10X

Why do We Care?

pH of agricultural soils in the PNW is decreasing

< pH 6.6 is considered acidified for ag soils

alarmingly low in some areas (< pH 4.0)

Mahler et al., 1985

A Growing Issue - Soil Acidification

Soil pH at four depths at 76 sites surveyed across Columbia County

Courtesy P. Carter & H. Tao

4.0

5.0

6.0

7.0

8.0

9.0

Soil

pH

3-6 inch 0-3 inch

6-12 inch 12-24 inch

Columbia County, 2013

2

Soil Acidification?

Why?

Application of ammonium-based [NH4+] nitrogen fertilizers

Soil acidity # for # of product:

Anhydrous > Am. Sulfate > Urea > Am. nitrate

Why do We Care?

- in soil, ammonium is converted to nitrate [NO3-] by microbes in a two-step process known as nitrification:

2 NH4+ + 3 O2 2 NO2- + 2 H2O + 4 H+

2 NO2- + O2 2 NO3-

For every # of NH4+ added, 1.9 to 3.6# lime is required to neutralize the acidity

Impact of Soil pH on Crop Productivity

Mahler 1987: Soil pH vs. Max yield- 7 studies with Daws, Hill 81, & Stephens - initial pH 5.0-5.3: 0, 1,000, 2,000, 3,000, & 4,000 lbs Lime or Sulfur

R2 = 0.68

Minimum acceptable pH

0

20

40

60

80

100

120

4.8 4.9 5.0 5.1 5.2 5.3 5.4

% M

ax y

ield

Soil pH

Daws Hill 81 Stephens

Impact of Soil pH on Crop Productivity

4.5

5.0

5.5

6.0

Soil

pH

Minimum Acceptable Soil pH

3 studies, 2 varieties each

Impact of Soil pH on Crop Productivity

Froese et al. 2015

Reasons for Reduced Productivity

• Direct toxicity from Al, Mn, & Fe ions

• Lack of cationic nutrients: Ca, K, Mg

• Low P availability (Fe- and Al-phosphates)

• Altered soil microbiome: e.g. toxicity to Rhizobia in legumes

• Impact on plant diseases?

3

pH 5.5

Nutrient Availability

Courtesy P. Carter

Impact on Soil Microbiome

Well-nodulated plants (L) compared with poorly nodulated plants grown in acidic soil (R)

Measuring Soil pHExtech PH100 Waterproof

ExStik pH Meter

Recommended pH Meter

Source Price

Tequipment.nethttps://www.tequipment.net

$71.99

Amazon.comhttps://www.amazon.com

$82.39

Spectrum Technologieshttps://www.specmeters.com

$159.00**

Plant Disease

A harmful alteration of the normal biological development of a plant that results in harmful morphological and/or physiological changes (sypmtoms)

Biotic = living causes; spread from plant to plant

Abiotic = non-living causes; don’t spread from plant to plant

Are nutrient deficiencies/toxicities diseases?PathogenPlant

Environment

‘Disease Triangle’

ResistanceSusceptibility Virulence

Pathogenic specialization

Inoculum potential

TemperatureMoistureSoil pH

Disease

4

Fungal Diseases of Wheat in the PNW

Common name Pathogen

Stripe rust Puccinia striiformisEyespot Oculimacula yallundae, O.

acuformisCephalosporium stripe Cephalosporium gramineumRhizoctonia root rot Rhizoctonia solani, R. oryzaeFusarium foot rot Fusarium culmorum,

F. pseudograminearumPythium seed/root rot Pythium spp.Snow molds Typhula ishikariensis,

Microdochium nivalisTake-all Gaeumannomyces graminisSoilborne wheat mosaic Wheat soilborne mosaic virus

?

?

?

51 lb/bu

U.S. #5

60 lb/bu

U.S. #1

Courtesy of R. Smiley

Fusarium crown rot

Courtesy of T. Paulitz

Fusarium Crown Rot Influence of Soil pH on Fusarium Crown Rot

Smiley et al., 1996:

- Long-term plots at Pendleton; pH changes due to N fertilization

- Soil pH inversely proportional to rate of applied N, organic N & C

- Disease inversely proportional to soil pH

bulk soil pH

Organic N (g N/kg soil)C

row

n r

ot

-%

wh

iteh

ead

s

F. CULMORUM DISEASE RATING (0-8)

Courtesy K. Schroeder

Rhizoctonia Root Rot

•Decay of root cortex and “spear-tipping”

•Bare patches and erratic stands

5

R. ORYZAE DISEASE RATING (0-8)

Courtesy K. Schroeder

Pythium Root Rot

•Loss of root hairs and fine rootlets, discolored roots

•Reduced and erratic stands

Pythium Root Rot

Embryo infection- pH adjusted with lime

and H2SO4

- embryo infection was measured 48 hrs after planting seed- treatment with

antibiotic resulted in greater infection at higher pHMicrobial involvement

Fukui et al. 1994

• Larkin silt loam, pH 4.6 o Pedigo silt loam, pH 7.6

Pythium Seed Decay - Chickpea

Colton, WA23 May 2014

Pythium Seed Decay - Chickpea

Courtesy H. Tao & W. Chen

Eyespot or Strawbreaker Foot Rot

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Influence of Soil pH on Eyespot

Smiley et al., 1996: Incidence of eyespot inversely proportional to soil pH from 4.6-5.2

- only report in the literature

- no data provided size of response not known

Soil pH

Eyes

po

t,%

infe

cted

ste

ms

Take-All

W.W. Bockus, KSU E. De Wolf, KSU

W.W. Bockus, KSU

Influence of Soil pH on Take-all

Smiley & Cook, 1973:

- Disease severity is related to soil pH and form of nitrogen

- Disease increases with increasing pH

- Ammonium (NH4+)-N resulted in less disease than nitrate (NO3-)

acidification of the rhizosphere

bulk soil pH

Rhizosphere pH

Dis

ease

rat

ing

Dis

ease

rat

ing

Puyallup

Ritzville

o None Ca(NO3) NH4SO4

Cephalosporium stripe

Cephalosporium Stripe Influence of Soil pH on Cephalosporium Stripe

WA 1964: - antibiotic production by C. gramineum

WA 1968: - survival of C. gramineum enhanced at low soil pH

KS 1985: - low soil pH favors disease development

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Effect of Soil pH on Cephalosporium Stripe and Take-all

4.8 4.84.6 4.6 4.6

4.8 4.8 4.7 4.6 4.54.8

6.36.6 6.6 6.5

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

SUMMER 1981 FALL 1981 SPRING 1982 FALL 1982 SUMMER 1983

So

il p

H

Control Sulfur, 430 #/A Lime, 5000#/A

Bockus & Classen, 1985

Effect of Soil pH on Cephalosporium Stripe and Take-all

27.7

32.5

15

19.817.5

0.7

10.2

6.4

51.1

6.8

11.8

56.1

0

10

20

30

40

50

60

CONTROL SULFUR LIME

% D

isease

Treatment

Ceph str '82 Ceph str '83

Take-all '82 Take-all '83

Bockus & Classen, 1985

pH

4.8

pH

4.7

pH

6.6

pH

4.5

pH

4.6

pH

6.5

Influence of Soil pH on Cephalosporium Stripe

pH 4.5 pH 7.5

Control ControlInoculated Inoculated

Confirmed pH response in Washington

Love & Bruehl, 1987

Soil pH after Amendment with Lime or H2SO4

WSU Plant Pathology Farm, Pullman, WA

Confirm the effect of soil pH on Cephalosporium stripe under PNW field conditions

- Adjust soil pH by adding acid or lime

Incidence of Cephalosporium Stripe in Relation to Soil pH

Mean of 3 cultivars (Brevor, Nugaines, Daws) in 1987 and 2 cultivars (Daws, Stephens) in 1989

Influence of Soil pH on Cephalosporium Stripe

Soil pH- soil microbiome- nutrient availability- soil structure

C. gramineum- inoculum potential- survival

Wheat plant- predisposition- root exudation

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Influence of Soil pH on Cephalosporium Stripe

• Determine the effect of pH on components of inoculum potential- growth, sporulation, and survival and germination of conidia

• Determine the relationship between inoculum density and disease incidence

Objectives:

Effect of pH on Growth and Sporulation of C. gramineum

Mean of 3 isolates and 4 replicates MSA, 7 days, 20°C

pH 4.5 pH 5.5

pH 6.5 pH 7.5

Effect of pH on Growth and Sporulation of C. gramineum

MSA-PB, 7

days at 20°C

Effect of Soil pH on Sporulation of C. gramineum

Mean of two rates in 1989-90 (88 & 177 kg/ha) and one in 1990-91 (233 kg/ha)

Root tip - ‘Daws’

690X

Effect of soil pH on Infection by C. gramineum

36X

500X

Penetration of ‘Stephens’ stem base by C. gramineum

Isolation of C. gramineum from Field-Grown Winter Wheat

Mean of 2 cultivars

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Effect of soil pH on Cephalosporium Stripe

Growth and sporulation are greater at pH 4.5 than 7.5

More spores (inoculum) are produced at lower pH

Fewer spores are needed to cause the same amount of disease at lower pH

Pathogen survival in straw is greater at lower pH

Root infection seems to be greater at lower pH

Courtesy K. Schroeder

Severe Aluminum

Toxicity

Spring wheat – Rockford

23 June 2009

ABIOTIC DISEASES IN ACIDIC SOILS

Scarlet Alikat

June 22, 2010

Courtesy K. Schroeder

ALUMINUM TOXICITY

Scarlet

(sensitive)

Alikat

(tolerant)

Courtesy K. Schroeder

ALUMINUM TOXICITY

Courtesy K. Schroeder

ROOT DAMAGE -ALUMINUM TOXICITY Effect of Aluminum on Wheat Roots

Seedling root tips of Al tolerant and sensitive lines grown without or with 50 mM Al and stained with hematoxylin to show Al accumulation.

Delhaize and Ryan 1995

T

S

T

S

-Al

+Al

Four-day-old wheat root tips grown in 5 µM AlCl3

T S

10

pH (0-6 inch) = 6.6Aluminum = 0

pH (0-6 inch) = 4.8Aluminum = 55%

pH (0-6 inch) = 4.3Aluminum = 62%

Survey for Soil Aluminum, 2008-09

Courtesy H. Tao & R. Koenig

Soil pH vs. Aluminum Toxicity

https://www.agric.wa.gov.au/soil-acidity/effects-soil-acidity

Managing Aluminum Toxicity

•Liming soil to raise pH

•Breeding for tolerance

Managing Aluminum Toxicity

11-day-old barley

seedlings grown

in acidic soil

https://www.agric.wa.gov.au/soil-acidity/effects-soil-acidity

Tara 2002

39 bu/A

Jedd

9 bu/A

Courtesy K. Schroeder

MANAGING ALUMINUM TOXICITY Wheat Varieties for Acid Soils

Spring Wheat:

Alpowa, Alturas, Alum, Babe, Chet, LCS-Antomo, Nick, Otis, Solano, SY Steelhead, Tara 2002, UI-Platinum, WB-1035CL+, WB-6341, WB-9879CLP,WB Hartline, Seahawk, Whit

Winter Wheat:

AP Legacy, ARS Amber, ARS Selbu, Boundary, Brundage CF, Brundage 96, Cara, Chukar, Coda, Crescent, Eddy, Finch, Finley, Hubbard, Mary, Masami, MDM, Moro, Norwest 553,ORCF-102, Paladin, Simon, Tres, Tubbs, WB 528, Weatherford, Whetstone, Xerpha

Hard red, Hard white, Club, Soft white

Froese et al. 2015

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ResourcesAcknowledgements

Paul Carter, WSU Columbia County Extension

Steve Van Vleet, WSU Whitman County Extension

Haiying Tao, WSU Extension Soil Scientist

Kurt Schroeder, University of Idaho

Questions?