learning objectives: effect of soil ph on wheat diseases
TRANSCRIPT
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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
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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?