Transcript Cl Fixen ASA 2003 - International Plant Nutrition Institute

Does Chloride Deserve My
Attention?
American Society of Agronomy
Annual Meeting
Denver, Colorado
November 4, 2003
Paul Fixen
Potash & Phosphate Institute
This slide set available at: http://www.ppi-ppic.org/ppiweb/napro.nsf
Additional Cl information at: www.ppi-ppic.org/chloride/index.html
Related questions
 Can Cl significantly influence crop growth and
development?

Chemical and nutritional basics
 Does Cl influence the crops I manage?
 Crop sensitivity for deficiency and toxicity
 Is Cl an important factor in my trade area?
 Nutrient cycling
 Can Cl be managed economically?
 Dr. Grant and Dr. Lamond
Chlorine the element
One of the halogens
Occurs in nature only as Cl-
Chloride chemistry terminology
 Chlorine (Cl): The name of the element
 Chlorine gas (Cl2): A greenish yellow gas with a
choking odor; used to purify municipal water
 Hypochlorite (OCl-): Forms when Cl2 reacts
with water; A powerful oxidizing agent sold as
laundry bleach
 Chloride (Cl-): The naturally occurring stable
form of the element
Chloride in our environment
 Earth’s crust
 Seawater
 Plants
 Table salt
 Muriate of potash
0.15%
1.9%
0.1-1%
60%
47%
Chloride - an essential plant nutrient
 Earliest report of Cl crop response in mid
1800s in England ... NaCl (salt)
topdressed to stiffen barley straw
 Recognized as an essential micro- nutrient
since the 1950s
 Research in the late 1970s revealed
insufficient levels in many areas
 Phillipines,
Europe, NW USA
Wheat and barley responses to
chloride in the Great Plains
(Over 200 evaluations in KS, MN, MT, ND, SD, SK, TX)
Response expressed as wheat bushels
Range of response:
-3 to +18 bu/A
Average of all:
2.4 bu/A
(includes nonresponsive varieties & high Cl sites)
Frequency of significant response:
Average significant response:
48%
5.2 bu/A
Roles of chloride in plants
 Photosynthesis and enzyme activation
Photosynthetic
electron transport
Due to the accumulation
of Cl in chloroplasts,
this biochemical need is
likely always met under
field conditions
 Transport of other nutrients in plants
 Water movement in the cell
 Stomatal operation
Effects of chloride addition on plants
 Accelerated plant
development
 Increased kernel
size or plumpness
-Cl
+Cl
 Reduced late season lodging
 Disease suppression/enhanced host tolerance
Wheat, barley and millet diseases
suppressed by chloride addition
Common
root rot
Take-all
Septoria
Powdery
Mildew
Stripe rust
Spot blotch
Tanspot
Leaf rust
Tanspot and Septoria suppresion on flag
leaves of Marshall spring wheat near
Watertown, South Dakota in 1985
56 lb Cl/A
No Cl
(Septoria and tanspot incited by Septoria avenae f. sp. triticea and Pyrenophora tritiic-repentis)
Leaf rust suppression on flag leaves of
winter wheat in Bosque county Texas
Pioneer 2158 at anthesis. NH4Cl applied at 40 lbs Cl/A
Miller, Texas A&M Univ.
Other diseases suppressed by
chloride addition
Corn
Stalk rot
Potatoes
Hollow heart, Brown center
Celery
Fusarium yellows
Coconut palm
Gray leafspot
Rice
Stem rot, Sheath blight
Mechanism of disease effects
 Suppression of pathogen
 Increased NH4+ uptake – rhizosphere acidification –
competitive disadvantage for root pathogens
 Increased Mn availability
 Reduced plant NO3- concentrations
 Increased leaf turgor potential
 Enhanced host tolerance
 Increased plant turgor reduces the effect of the
pathogen on crop yield
Chloride accumulates in most plants
20 fold range in
plant concentration
Leaf blade
collar
Chloride toxicity
Soybean
Grape
Shows first
on older leaves,
then works its
way up the plant
Droughted appearance and
pale green marginal necrosis
Fall soil Cl >60 ppm, leaf > 0.9% Cl
for susceptible cultivars (Univ. GA)
Grundon, Univ. of Queensland; Gartel, Germany
Marginal necrosis caused by
spraying Mg or NaCl to prevent
stem necrosis
Toxic effects of chloride
 Some plants are sensitive to Cl excesses:
 Some tree, vine, citrus, vegetable, conifer, and
ornamental plants
 Tobacco
 Certain soybean varieties grown in the SE U.S.
 Conditions where excesses may occur:
 Low-lying poorly drained areas
 Where high water tables occur
 Confined soils - greenhouses
 High Cl irrigation water
Cl deficient leaf spot syndrome
 Leaf spot of previously unknown origin
 First observed in 1991 on Redwin and Manning
winter wheat in Montana
 Appears similar to tanspot disease but is not
caused by a microorganism
 Occurs when wheat tissue Cl < 0.1% and soil
Cl < 10 lb/A (0-24”)

Barley flag leaf Cl < 0.09% (Oregon State Univ.)
 Not shown by all varieties that are Cl
deficient

No distinctive deficiency symptoms for all varieties
Cl deficient leaf spot syndrome in
CDC Kestrel winter wheat
No Cl
F
Engel et al., Montana State University
F-1 F-2
20 lb Cl/A
F
F-1 F-2
Cl deficient leaf spot syndrome in winter
wheat at mild stage (left)
20 lbs Cl/A
Engel, Montana State University
Cl deficient leaf spot syndrome on durum
grown hydroponically in a growth room
Western Plant Breeders 881 durum (WB881)
Engel, Montana State University
Bromide does not substitute for
chloride
WB881 Durum
Engel, Montana State University
Crops known to respond positively to
Cl in the field
 Winter wheat
 Potatoes
 Spring wheat
 Rice
 Durum wheat
 Pearl millet
 Barley
 Coconut palm
 Corn
 Celery
 Grain sorghum
Chloride cycling in agroecosystems
 Sources of Cl
 Wet deposition
 Muriate of potash fertilizer (47%)
 Manure
 Irrigation water
 Losses of Cl
 Crop removal
 Leaching
Chloride ion
wet deposition
2000
Cl, kg/ha
2001
2002
Percent of Soils Testing Medium or
Lower in K in 2001
North America
43%
Soil chloride levels in the Northern
Great Plains
10,324 samples collected in 1995
AGVISE Laboratories (Northwood, ND)
52.5% < 30 lb/A
Soil samples with chloride < 30 lb/a
MB
65%
56%
55%
ND
13%
53%
54% 19%
10%
Fall 2002 Samples
(0-24” samples)
82% 51% 44% 30%
14%
47%
77%
35% 28%
78%
63
SD
38% 54%
61%
89%
64%
MN
Cl in Oklahoma soils
Ditribution
80%
69%
<30 lb/a Cl
30-60
>60
60%
40%
29%
68%
32%
20%
2%
0%
0%
0-6"
0-24"
200 sample pairs from 17 counties collected from June to September, 1999
Oklahoma State Univ.
Sampling Depth
Chloride removal by crops
Crop
Plant part
Cl content
Alfalfa
Barley
Wheat
Potatoes
Shoot
Grain
Grain
Tubers
7.6 lb/ton
0.024 lb/bu
0.026 lb/bu
0.06 lb/cwt
Summary: Does Cl deserve my
attention?
 Where K fertilization is minimal
 In non-coastal areas
 Where fungal disease pressure is high
 For responsive crops: wheat, barley, corn,
sorghum
 For crops sensitive to toxicity growing where
soil accumulation is likely
 Where soil and plant analyses indicates low
levels or unusually high levels
It probably deserves more
attention than its getting