Dr. Kelly T. Morgan
University of Florida
Soil and Water Science Department
Southwest Florida Research and Education Center, Immokalee
239 658 3400
conserv@ufl.edu
Effect of soil pH and soil application of
Calcium, Magnesium and
Alkalinity
•
Primarily determined by presence of
bicarbonates (HCO
3
-
), Carbonates (CO
3
-
), and
hydroxides (OH
-
) in water.
•
A measure of the capacity of water to
neutralize acids.
•
Alkaline compounds in water remove H
+
ions
and lower the acidity of water (increase pH).
Bicarbonates in Water
•
Water above pH 7.5 is usually associated with high
bicarbonates.
•
Recommend levels of 100 ppm or less
•
Forms bicarbonate salts with Ca, Mg, Na, and K.
•
High Ca concentrations will react to form Calcium
carbonate or line.
•
Higher calcium carbonate in soils increases pH making
many nutrients less available.
•
Particulates can drop out of water and plug emitters or
microsprinklers.
•
Soils with excess Ca forms CaCO
3(lime).
•
Treatments:
–
calcium or gypsum (calcium sulfate) to increase calcium availability to
plants and soil,
–
elemental sulfur can be used to reduce soil pH,
Effect of Soil pH on Nutrient
Availability
• Macronutrients (N, K, S, Ca and Mg) highly available between soil pH 6.5 and 8 • Micronutrients (Mn, Zn B, and Fe) most available below soil pH 6.5 • Best soil pHrange for most crops is 6 to 6.5
Plant Uptake
Bicarbonate induced chlorosis is caused by transport of
bicarbonate into the plant leading to reduced nutrient
uptake.
Lime-induced chlorosis effects many annual crops and
perennial plants growing on calcareous soils.
Horneck, D. 2006. Acidifying Soil for Crop Production East of the Cascades. Oregon State
Survey of groves on Swingle and
Carrizo
Well water pH and bicarbonate levels are related in Central Florida citrus groves
Data from Davis Citrus Management
Well water bicarbonate
0 50 100 150 200 250 W el l w a ter pH 3 4 5 6 7 8 9 Ken Ten Cham Water 3 Glen Water 2 Water 1 Three Sachs Smith ButlerN ButlerS Reedy Wal Weig Cole Ruvin Steph Hugh Col Mama Web18 Parker Coke
MaxS Web19Rhapp
Bent Swan Moody Sweet Hen McCann MaxN Con Shallow wells Deep wells
J.H. Graham, 2014- 2016 survey of central Florida citrus groves for effect of bicarbonates
Lower Root Density is related to
higher pH
Well water pH 3 4 5 6 7 8 9 F ibr ou s r oot den s it y ( m g/ c m 3 ) 0.0 0.2 0.4 0.6 0.8 1.0 Soil pH 4.5 5.0 5.5 6.0 6.5 7.0 7.5 F ibr ou s r oot den s it y ( m g/ c m 3 ) 0.0 0.2 0.4 0.6 0.8 1.0Well water pH Soil pH in the wetted zone
J.H. Graham, 2014 - 2016 survey of central Florida citrus groves for effect of bicarbonates
Field Study: Effect of Soil
pH on Nutrient Uptake
Effect of soil pH on Nutrient status
•
Mature Hamlin/Swingle – initial soil pH 7.3
•
Irrigation water acidified for 3 years
•
Soil pH range from 4 to 7.3
•
Methods of pH moderation
–
Irrigation water acidification
–
Application of slow release sulfur product
Effect of Acidificaiton on Water pH
•
Irrigation
water within
half a pH
unit of target
Irrigation Water pH Sampling DateJan Jul Jan Jul Jan Jul Jan Jul Jan
irri gat ion W at er pH 3 4 5 6 7 8 9 No Acid pH 6.0 pH 5.0 pH 4.0
Effect of pH on water Bicarbonates
• Suggested bicarbonate limit = 100 ppm • Little reduction in bicarbonates below pH 5 • Soil applied S has no effect of irrigation water pHIrrigation Water Bicarbonates
Sampling Date
Jan Jul Jan Jul Jan Jul Jan Jul Jan
Ir ri ga ti o n W a te r B ic a rb o na te s ( pp m ) 40 60 80 100 120 140 160 pH 7.3 without S pH 7.3 with S pH 6 without S pH 6 with S pH 5 without S pH 5 with S pH 4 without S pH 4 with S
Effect of Irrigation Water pH on Soil pH
• Three years to reach target pH • Applied soil S lowered pH by less than half pH unit Soil pH Sampling DateJan Jul Jan Jul Jan Jul Jan Jul Jan
S oi l pH 4 5 6 7 8 9 No Acid pH 6.0 pH 5.0 pH 4.0
Effect of Soil pH on Leaf Calcium
•
Leaf
calcium
increased
with lower
soil pH
•
Calcium
increased
above
optimum
level below
pH 6.5
Calcium Soil pH 4 5 6 7 8 9 Leaf N ut ri ent C onc ent rat ion (% ) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Low OptimumEffect of Soil pH on Leaf Magnesium
•
Increased leaf
Mg with lower
soil pH
•
Leaf Mg
concentrations
above
optimum
below pH = 6.5
•
Leaf Mg in high
optimum or
higher below
soil pH = 6
Magnesium Soil pH 4 5 6 7 8 9 Leaf N ut ri ent C onc ent rat ion (% ) 0.0 0.2 0.4 0.6 0.8 1.0 Optimum Low HighEffect of Soil pH on Leaf Manganese
• Increased leaf Mn with lower soil pH • Leaf Mn concentration s above optimum below pH = 7 • Leaf Mg in high optimum or higher below soil pH = 6 Manganese Soil pH 4 5 6 7 8 9 Leaf N ut ri ent C onc ent rat ion (m g k g -1 ) 0 20 40 60 80 100 120 140 Optimum High LowEffect of Soil pH on Leaf Zinc
• Increased leaf Zn with lower soil pH • Leaf Zn concentrati ons above optimum below pH = 7 • Leaf Mg in high optimum or higher below soil pH = 5.5 Zinc Soil pH 4 5 6 7 8 9 Leaf N ut ri ent C onc ent rat ion (m g k g -1 ) 0 20 40 60 80 100 120 140 Optimum High LowSoil Calcium and Magnesium Applications
• Study started in Jan. 2017, set as zero day of
the three years study.
• 10 year old Hamlin on Cleo and Hamlin on Swingle
• Treatments (T): control (T1), full Ca dose
(T2), full Mg dose (T3), and half Ca and half
Mg doses (T4), (full dose=45 kg ha
-1
).
Effect of Calcium and Magnesium on Leaf
Area
Hamlin citrus tree on cleopatra rootstock 0 60 240 420 600 780 960
L
ea
r a
re
a i
n
d
ex
2.4 3.6 4.8Hamlin citrus trers on swingle rootstock
Days in three years
0 60 240 420 600 780 960 Control Ca Mg Ca and Mg
Irma
Hamlin citrus tree on cleopatra rootstock 0 60 240 420 600 780 960 C an o p y v o lu m e ( m 3 ) 16 24 32
Hamlin citrus tree budded on swingle rootstock
Days in three years
0 60 240 420 600 780 960 Control
Ca Mg
Ca and Mg
Effect of Calcium and Magnesium on
Canopy Volume
Spring 2017 L ea f M g (%) 0.18 0.36 0.54 Cleo Swingle Spring 2018
Secondary macronutrient treatments
1 2 3 4 0.18 0.36 0.54 Summer 2017 Summer 2018 1 2 3 4
Effect of Magnesium on Leaf
Concentration
Treatments (T):
control (T1),
full Ca dose (T2),
full Mg dose (T3), and
half Ca and half Mg doses
(T4)
Effect of Magnesium on Leaf
Concentrations
Spring 2017 L ea f C a ( % ) 0 2 4 6 Cleo Swingle Spring 2018Secondary macronutrient rate
1 2 3 4 0 2 4 6 Summer 2017 Summer 2018 1 2 3 4
Treatments (T):
control (T1),
full Ca dose (T2),
full Mg dose (T3), and
half Ca and half Mg doses
(T4)
Conclusions
Soil pH affects crop plants ability to extract
nutrients, including N, P, K, Mg, Ca, Mn, Zn
Higher soil pH reduce plant nutrient uptake by
reducing soil water nutrient solubility,
Water and soil bicarbonates should be
addressed to allow for proper nutrient uptake,
Irrigation water acidification or application of
acidifying fertilizer materials should be used to
reduce soil pH in the irrigated area,
Soil application of Ca and Mg improves leaf area
