Lime - the foundation for soil fertility David P. Wall1
T. Sheil2, M. Plunkett1 & S.T.J. Lalor3 1,Teagasc, Johnstown Castle, Co Wexford
2, Alltech Crop Science, Dunboyne, Co Meath
3, Grassland AGRO, Dock road, Limerick
1 2 3 4 5 6 7 8 9 10 11 12 13 14
• Soil pH is the single most important chemical property of the soil (like soil texture is to the physical properties)
• pH is a measure of hydrogen ion concentration (H+) soil solution.
• The pH scale ranges from 0 to 14, where 7 is considered neutral
• The pH scale is exponential
pH 6 is 10X more acidic than pH 7
pH 5 is 100x more acid than pH 7
Therefore every 0.1 pH drop is a significant
Typical pH range for Irish soils
What is soil pH?
Acid Neutral Alkaline
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
Plant root injury:(H+ & Al3+)
• changes in root membrane permeability
• leakiness or loss of organic substrates & absorbed cations
• Increases Al3+ availability which is toxic to plant roots)
• root tips can die and lateral root development is supressed
Plant tops:
- reduced transport of nutrients from roots
What effect does too much acidity have?
` 3 4 5 6 7 8 9 Soil pH
Acidic Soils Alkaline Soils
Ph
osp
ho
rus F
ixati
on
High
Med
Low
Fixation by
Iron &
Aluminium
Fixation
by
Calcium
Plant
Available
P
D.P. Wall, 2015
Effect of soil pH on soil P availability
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
Why is lime important ?
Neutralises acidity to
correct soil pH
Supplies essential plant
nutrients Ca (and Mg)
Enhances soil biology
and fertility
• Organic activity in soil
depends on soil pH
• Release of nutrients from
organic matter in soil
• Optimises nutrient
availability (stored and
freshly applied nutrients)
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
0
500
1000
1500
20001
97
01
97
11
97
21
97
31
97
41
97
51
97
61
97
71
97
81
97
91
98
01
98
11
98
21
98
31
98
41
98
51
98
61
98
71
98
81
98
91
99
01
99
11
99
21
99
31
99
41
99
51
99
61
99
71
99
81
99
92
00
02
00
12
00
22
00
32
00
42
00
52
00
62
00
72
00
82
00
92
01
02
01
12
01
22
01
32
01
4To
nn
ag
e o
f L
ime (
'000 t
/yr)
Year
Lime usage 1970 -2014
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
Lime CaCO3 + Acid 2H+ = Calcium Ca+2 + CarbonDioxideCO2+ Water H2O
1. Ground Limestone (60% carbonate CaCO3)
• Finely ground to react with soils
• (35%) <0.15mm & (65%) <3.35mm
2. Magnesium Limestone (40% MgCO3 60%CaC03 = 64.5% carbonate)
• Higher neutralising value /slower to react / Use on Mg deficiency soils
3. Granulated Liming Products
• Seasonal soil pH regulation / Similar to Fertilisers
4. Burnt Lime (CaO)
• Reacts faster?.
5. Hydrated lime (Ca (OH2))
• Reacts very rapid.
Main lime sources available
Ground limestone effect on soil pH Grazed grassland with 200kg N fertiliser
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.4
6.6
1 6 12 18 24 30 36 42
Months after application Lime
Applied Spring ‘11
So
il p
H level
Target pH range
D.P. Wall et al., 2015
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
3
4
5
6
7
8
9
10
1 6 12 18 24 30 36 42
Months after application Lime
Applied Spring ‘11
Ground limestone effect on soil P levels Grazed grassland with 200kg N fertiliser
So
il t
es
t P
(m
g/L
)
D.P. Wall et al., 2015
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
4.5
5.0
5.5
6.0
6.5
12 24 36 42
Control
Ground limestone
Calcium Oxide
Granulated Lime
Months after application
So
il p
H level
Efficiency of Bag Lime Products Ground limestone 7.5 t/ha
Calcium oxide 2.5 t/ha (1:3 ratio)
Granulated Lime 2.5 t/ha (1:3 ratio)
D.P. Wall et al., 2015
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
Effect of P and Lime of soil P availability
Sheil, Wall & Lalor,
2015, FAI
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
-250
-200
-150
-100
-50
0
50
100
150
200
Ch
an
ge i
n s
oil A
lum
iniu
m
Al3
+ (m
g/k
g)
Control Lime Only P only P & Lime
Treatments applied to soil
Average change in soil test P across 16
Irish soils at 12 months after application
* Increasing soil pH (less acidity) decreases available Al concentrations and reduces Al-P bonding (fixation)
Effect of Lime on Aluminium availability
Sheil, Wall & Lalor,
2015, FAI
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
Average response across 2 sites Effect of P and Lime of grass yield
Average soil pH: 5.2 6.4 5.2 6.4
D.P. Wall et al., 2015
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
• Target mineral soils is pH of 6.3 for grassland (for peats pH 5.5)
• Apply lime based on the soil test report
• Split lime applications when required rates exceed 7.5 t/ha
• Caution! reduce lime rates on high molybdenum (Mo) soils so that pH does not exceed 6.2.
• Ground limestone is the most cost effective source of lime and can be applied throughout the year when the opportunity arises.
• As a rule of thumb: leave ≥3months between lime application and following with Urea or slurry application
• Maintaining soil pH at the target level will increase the release of soil nutrients.
• Lime is the foundation of soil fertility and is a primary step to take following soil sampling.
Lime - Best Management Practice
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
