LimeR Series
Analyzing Lime in Container Substrates
Overall Limestone Model
Understanding pH dynamics of liming
materials in container substrates.
Jinsheng Huang and Paul Fisher
pH drift is common.
Multiple factors and low buffering.
BASIC (increase pH)
Nitrate NO-3
ACID (lower pH)
Ammonium NH+4
Alkalinity
Media
Lime
pH
balance
Species
Purposes of Liming
• Initial pH
• pH buffering
• Supply Ca, Mg
• Lime pH effect depends on:
– Reactivity
– Requirement
– Residual
Generalized model of lime reaction
Substrate-pH
7
6
pH=pHinit + pHMax(1-EXP(kt))
5
pHMax
k = f(particle size, chemical form,
temperature, moisture)
4
pHinit
pHMax = f(lime acid neutralizing value,
lime concentration, lime solubility,
media buffering)
3
0
20
40
Days (t)
60
80
Objectives
• Predict and understand pH response
of lime in a container substrate.
• Applications
• Lime, media analytical tests
• Match lime rate and type to substrate
• Assist in R&D of substrates
Lime Reactivity: solubility
8
pH
7
6
5
4
3
0
50
100
150
200
CaCO3 (meq/L)
250
300
350
Solubility: model with two-phase function
8
Plateau
7
6.3
pH
6
5
Linear
4
3
0
50
100 150 200 250 300 350
CaCO3 (meq/L)
Lime Reactivity:
particle size
Particle Size Efficiency (PSE) factors
= pH response at day 7/pH response from reagent CaCO3
Particle size (µm)
Calcitic
limestone
Dolomitic
limestone
850-2000 µm (10-20 mesh)
0.18
0.18
250-850 µm (20-60 mesh)
0.45
0.44
150-250 µm (60-100 mesh)
0.79
0.66
75-150 µm (100-200 mesh)
0.91
0.83
45-75 µm (200-325 mesh)
0.98
0.93
<45 µm (passes 325 mesh)
0.99
0.96
Lime Reactivity: particle size
PSE = A(1-EXP(kt))
1.0
Particle size (µm)
k
A
75-150 µm
(100-200 mesh)
0.91
1.0
250-850 µm
(20-60 mesh)
0.85
0.91
850-2000 µm
(10-20 mesh)
0.38
0.56
PSE
0.8
0.6
0.4
100-200 mesh
20-60 mesh
10-20 mesh
0.2
0.0
0
14
28
42
Day
56
70
84
Lime Reactivity:
substrate moisture and temperature
Relative pH change at day 7
500
0.9-1
400
0.8-0.9
Moisture
300 (mL water/
L substrate)
0.7-0.8
0.6-0.7
200
0.5-0.6
2
7
12
17
22
Temperature (C)
27
100
32
Lime Requirement:
substrate buffering
8
pH
7
6
5
∆pH
(meq CaCO3/L substrate)
4
3
0
50
100
150
200
CaCO3 (meq/L)
250
300
350
Lime Residual
Example of one lime source and substrate
Substrate-pH
7
6
5
4
3
0
5
10
Applied lime rate (g/L)
15
Lime Residual
Not all lime reacts. What is left is residual lime.
Reacted or residual lime (g/L)
16
14
12
Residual lime
Reactive lime
10
8
6
4
2
0
0.0
3.2
6.4
9.6
Applied lime rate (g/L)
12.8
16.0
Lime Residual: provides buffering
Impatiens
Acid fertilizer
Residual
No residual
General procedure
CO2
• 50 ml substrate + 75 ml
deionized water in flask
25 mL
6M HCl
• Close system and dispense 25
ml 6M HCl
• Moles of CO2 by volume
displacement
• Residual lime in substrate can
be calculated using Ideal Gas
Law
HortScience 42(7): 1685-1689. 2007
CO2
50 mL
sample
5.3
1.4
5.1
1.2
4.9
1.0
pH
4.7
Substrate-pH
4.5
4.3
0.8
0.6
Residual Lime
4.1
0.4
3.9
3.7
0.2
3.5
0.0
0
5
10
15
20
Day after liming
25
30
Residual CCE (g.L-1)
Lime Residual: change over time
LimeR application
Thank You
Jinsheng Huang
Kate Santos
Angelica Cretu
Connie Johnson
Ernesto Fonseca
Easton Horner
Becky Hamilton
Dustin Meador
Bill Argo, Blackmore Co.
Paul Nelson, North Carolina State Univ.
2008 Donors
• Research partners (Univ. of Florida, Univ. of Minnesota)
– Leading Media and Fertilizer Companies:
PINDSTRUP MOSEBRUG A/S
– Leading Growers:
- AgriStarts (FL), Altman Plants (CA), D.S. Cole Growers (NH),
Four Star (MI), Florida Plant Specialists (FL), Knox (FL), Kube Pak
(NJ), Lucas (NJ), Pleasant View Gardens (NH), Spring Meadow
(MI), Smith Gardens (WA), Twyford (FL), Wagners (MN), Welby
Gardens (CO)