Lime movement through soil
By Lisa Miller
Updated 24/9/2015
Take home messages
 Lime takes time to work so it needs to be applied preferably 2 years before acid sensitive
species (barley, canola, faba beans, lucerne) are to be grown.
 Soil pH in the topsoil may need to be higher than 5.5 to allow surface applied lime to move
below 10 cm to treat subsurface acidity.
 Surface applied lime may take greater than four years to move beyond 10 cm depth when
there is sufficient alkalinity within the topsoil.
 Incorporating lime at depth is the fastest way of addressing a subsurface acidity issue and
avoids forfeiting potential production for some years.
Introduction
Lime responses are rarely seen in the year of application. This can be partly explained by how fast
lime works and moves through the soil.
Below is a simplified diagram of chemical reactions that lime needs to undergo to neutralise acidity
in soil (Source: Gazey et al).
In moist soil, calcium carbonate in
lime separates into calcium and
carbonate ions. This reaction is
extremely slow when pH(Ca) > 5.8
CaCO3
(Lime)
CO3--
₊
H+
₊
HCO3-
C02
₊
H20
Ca ++
Calcium ions are taken up plants,
bind to clay particles or leach
Excess bicarbonate ions (alkalinity)
leach into underlying soil layers &
chemical reactions repeat.
H+
Carbonate ions react with excess
hydrogen ions to form bicarbonate
ions
Hydrogen ions (causing acidic soil)
react with bicarbonate ions to form
water and carbon dioxide
Hydrogen ions that were
contributing to soil acidity are
chemically bound in soil water.
Carbon dioxide (gas) is released into
the soil air
Lime needs the soil to be acid (pH < 5.8) and moist so that lime readily dissolves into the soil
solution. This has implications for surface spreading or banding lime rather than mixing it through
the soil as the pH can become too high for the chemical reactions to occur and a proportion of the
lime will sit there undissolved until the soil becomes more acid. Large clumps of lime (approx. 5mm
diameter) have been observed to remain intact for at least 20 years surrounded by high soil pH
(Chris Gazey pers. communication).
Excess alkalinity (bicarbonate) in the soil solution is leached into the underlying soil layers with the
acid neutralising chemical reactions occurring as it goes. Soil pH change from surface applied lime
may be highest in the top 5 cm of soil and is likely to lessen with depth as the lime is used up. Excess
alkalinity from surface applied lime is reported to only move into subsurface layers (> 10 cm) when
then the pH in the topsoil (0-10 cm) is greater than 5.5. Otherwise the lime is used up in the top 10
cm and none is left over to move beyond 10 cm (Fenton, 2003). Where topsoil pH is maintained
greater than 5.5 then lime takes four to ten years to move beyond 10 cm (Gazey et al, 2014).
Bicarbonate movement is also dependent on the pH buffering capacity of soil. Soils with higher clay
content and organic matter give greatest resistance to pH change. This is because hydrogen ions
which are also bound onto the clay particles or organic matter are released into the soil solution to
replace those hydrogen ions that have been neutralised or converted into water.
Fine lime particles can be physically moved by water flow through micro-pores (0.03 mm diameter).
This movement is greatest in coarse textured soils (sandstones and granite). Particulate lime may
move through larger soil pores in heavy and prolonged rainfall events. Worms, ants and soil
organisms can also move lime.
The results of lime movement are reported here from SFS lime response trial sites. Further
monitoring is planned, especially to see if lime is addressing acidity below 10 cm. This is important
because acidification occurs throughout the soil profile, not just the topsoil and subsoil acidity will
develop if lime is not reaching it.
Method
Lime movement is being tracked at the Bellarine trial site on a loam soil classed as a Sodosol, (See
Crop response trials –Bellarine for further details on the trial site). Lime with a 90% neutralising
value was surface applied in mid April before Westminister Barley was sown on 13/6/2014. The site
was sown with a disc seeder with minimal disturbance. Soil pH was monitored by taking 4 soil cores
per treatment (Nil and Lime 3t/ha) across all 4 replicates. Cores were divided into 2.5 cm increments
and like increments were bulked together for testing soil pH by Farmright in 2014 and Nutrient
Advantage in 2015. The soil was tested initially down to 10 cm and then to 20 cm. The site was
harvested on January 22nd. A large rainfall event occurred on January 14th with 33 mm of rain falling.
Lime movement was also monitored at Woady Yaloak catchment group trials in plots where lime 2.5
t/ha was applied in autumn 2012 (see Woady Yaloak Catchment Group trials). In addition the
Mannibadar trial site which was originally an alternative fertiliser trial had lime applied in 2009 to
2011 in 5 applications at 250 kg/ha (total lime applied 1 t/ha) with worm castings 200kg/ha. These
trial sites were initially soil tested 0-10 cm in 2012 and again tested at depths 0-10 cm, 10-20 cm and
20-30 cm in May 2015.
Results
The graphs below show the pH change at the mid point of each increment eg 0-2.5 cm is 1.25cm.
Soil pH had changed from 4.3 to 4.6 within the top 2.5 cm of soil after approximately 2 months
following lime application (see Fig 1). After four months, lime had moved into the 2.5 to 5 cm depth
as soil pH had changed from 4.0 to 4.4.
Bellarine - Soil pH (CaCl2)
3.5 4.0 4.5 5.0 5.5 6.0
0
0
2
2
Soil depth (cm)
Soil depth (cm)
Bellarine - Soil pH (CaCl2)
3.5 4.0 4.5 5.0 5.5 6.0
4
6
4
6
8
8
Nil - August 2014
3 t/ha - August 2014
Nil - June 2014
10
3 t/ha
10
Figure 1. Soil pH change 7 weeks (June) and 17 weeks (August) after lime application in 2014.
After approximately 6 months soil pH change had now occurred within the 5 to 7.5 cm increment of
soil and had increased from 4.1 to 4.5. Soil pH in the lime treatment had now increased in the top
2.5 cm to 5.5.
Bellarine - Soil pH (CaCl2)
3.5 4 4.5 5 5.5 6
0
Soil depth (cm)
2
4
6
8
Nil - October 2014
3 t/ha - October 2014
10
Fig 2. Soil pH change 23 weeks (October) after lime application in 2014.
A total of 489 mm of rainfall occurred in 2014 which was below the long term average at
Portarlington of 611 mm. Below average rainfall occurred in September and October 2014 and in
February and March 2015.
70
Rainfall (mm)
60
50
40
Rainfall (mm)
30
Mean
20
10
0
J
F
M
A
M
J
J
A
S
O
N
D
Fig 3 Monthly rainfall at Portarlington in 2014 compared to the mean.
70
Rainfall (mm)
60
50
40
Rainfall (mm)
30
Mean
20
10
0
J
F
M
A
M
J
J
A
S
O
N
D
Fig 4 Monthly rainfall at Portarlington from January to July 2015 compared to the mean.
After nearly 12 months (March 2015) the lime treatment was stalled as there was probably little
moisture to allow the chemical reactions to occur. Also pH had slightly declined compared to
previous recordings in October 2015 which can be attributed to temporal variation which is
strongest following a long dry spell.
By late June, moisture has allowed the chemical reactions to resume and the pH in the top 2.5 cm of
the lime treatment has risen to 6.2 compared to 4.3 in the control. The lime treatment seemed to be
working up to 5 cm and there was no obvious change from 5 to 10 cm. There appear to be
differences between soil pH in the limed and unlimed plots beyond 10 cm but it’s likely this is not
lime movement and due to site variation or sampling contamination from the more alkaline surface
soil.
3.5
Bellarine - Soil pH (CaCl2)
4
4.5
5
5.5
6
Bellarine - Soil pH (CaCl2)
3.5 4 4.5 5 5.5 6 6.5
0
2
2
4
4
6
6
Soil depth (cm)
Soil depth (cm)
0
8
10
12
8
10
12
14
14
16
16
18
18
Nil - June 2015
3 t/ha -June 2015
20
Nil - March 2015
3 t/ha -March 2015
20
Figure 3. Soil pH change nearly 12 months (March 2015) and 15 months (June) after lime application.
The majority of the Woady Yaloak lime sites show that lime hasn’t moved after 3 years into the 1020 cm soil layer (Table 1 and 2). Only the Mannibadar site looks like lime might have moved beyond
10 cm layer with a pH difference of 0.2 units compared to the nil treatment.
The sandy loam soil at Illabarook remains unchanged in the 10-20 cm layer and yet its soil pH in the
top 10 cm was 6.2. This indicates that lime needs greater than 3 years to move beyond 10 cm even
in sandy loam soils which are more leachable than heavier textured soils.
Table 1. Soil testing results for Woady Yaloak Catchment Group lime pasture response trials
Site
Texture
Illabarook
Sandy loam
Starting pH
Pittong
Sandy Loam
pH 4.9 (2012)
Mannibadar
Clay Loam
Mt Mercer
Clay
pH 5.2 (2012)
pH 4.8 (2009)
pH 4.8 (2012)
Depth
cm
Nil
Lime
Nil
Lime
Nil
Lime
Nil
Lime
0-10
5.3
6.2
5.1
5.5
4.9
5.6
4.5
5.1
10-20
4.9
4.8
4.6
4.6
4.7
4.8
4.5
4.7
20-30
5.1
5.1
4.5
4.5
4.9
4.9
4.7
5.1
Table 2. Soil testing results for Woady Yaloak Catchment Group lime crop response trials
Site
Texture
Werneth
Clay loam
Starting pH 2012
Rokewood West
Clay loam
pH 4.7
Rokewood Nth
Loam
pH 4.8
pH 4.8
Depth
cm
Nil
Lime
Nil
Lime
0-10
4.5
5.2
4.7
5.1
10-20
5.1
5.0
5.1
5.4
4.6
5.6?
(Sample error) 4.8
20-30
5.8
5.7
6.4
6.5
5.1
Nil
5.3
Lime
4.8
Discussion
The results at the Bellarine trial site shows that the topsoil pH responds quickly to liming within the
first year. However, the pH change is not distributed evenly within the 0-10 cm depth and is
concentrated within the top 5 cm and highest in the surface (0-2.5 cm) where the soil pH had
increased to 6.2 after 15 months.
In this soil band we know through CaCO3 testing that some lime remains unreacted and probably
won’t dissolve until the site becomes more acid. Generally 70% of lime is thought to dissolve in the
first year. Lime was visible on the soil surface one year after application at many of the SFS trial sites.
Lime movement was similar to results found from 20 paddock trials in South West Victoria
conducted as part of the SGS program by Cam Nicholson. In those trials soil pH change was generally
detected down to 5 cm after 16 months. Further changes were detected 12 months later to
approximately 7.5 cm (Nicholson, 2011). See Long term effects of surface applied lime in the Woady
Yaloak Catchment.
There was very little pH change that occurred between October 2014 and March 2015 indicating the
importance of moisture to drive chemical reactions of lime. There is also some evidence at the
Bellarine site that there may be temporal variation occurring in pH in March 2015 as pH levels were
slightly lower than in the previous October. Conyers et al reports pH(Ca) variation of up to 0.45 pH
unit can occur following more extreme weather events than normal such as following the break of
season after a hot dry summer. Most soil testing occurs in March and therefore pH should be used
as a guide for making liming decisions rather than using absolute values.
Surface applied lime movement beyond 10 cm appears to have not occurred after 3 years from
testing at the Woady Yaloak trials. In the Corangamite Catchment Soil monitoring Program (CCSMP),
liming does not always appear to address soil acidity occurring below 10 cm. Paddock histories from
CCSMP found that of 36 of paddocks that had been limed in the last 10 years, 13 still had subsurface
acidity (pH< 4.8).
Lime has been reported to move below 10 cm only if the topsoil pH is maintained greater than 5.5.
Seven limed paddocks in the CCSMP had surface pH greater than 5.5 and none of these had
subsurface acidity. Lime in these paddocks was applied 3 to 10 years earlier and often in multiple
applications. Further evidence is required to convince both producers and agronomists that surface
pH targets might need to be above 5.5 to ensure lime movement from surface applied lime.
There does appear to be a slight pH increase (0.2) in the 10-20 cm depth compared to the nil
treatment at the Mannibadar site where lime was applied at low rates from 2009 to 2011 but this
could easily be due to trial site variation. At this site low rates of lime (250 kg/ha) were applied over
4 years. Generally low rates are deemed ineffective at creating pH change due to the buffering
capacity of the soil but if applied in consecutive years they might be beneficial for soil microbiology
and avoid large increases in pH in the top 2.5 cm.
Scott et al, 2000 reported on movement of lime into soils in NSW, Gippsland and NE Victoria and the
results were quite variable ranging from no movement to movement occurring after 13 years. Scott
et al generalised that the higher the limestone rate, the greater the depth of pH increase and the
longer the time period the more movement was detected. Very little movement of lime movement
was recorded at rates less than 3 t/ha and for at least 2 years.
Where a site has subsurface acidity issues, incorporating lime will be the fastest way of ensuring that
potential production is not forfeited for a number of years. Scott et al, 2000 estimates the lag time
of surface applied lime is five years compared to incorporated lime. How to get lime into the 10-20
cm soil layer or deeper in a minimal till cropping system is a question that requires further
investigation. Growers might need to strategically till every 10 years to incorporate lime which could
also be beneficial for breaking up compaction layers, distributing phosphorus or burying weed seeds.
Acknowledgements
Funding by GRDC and Corangamite Catchment Management Authority by support from the
Australian Government is gratefully acknowledged. Thank you to farmers at the lime trials for
allowing us to monitor their soils, Cam Nicholson from the Woady Yaloak Catchment Group and Jim
Caldwell.
References
Conyer M, Uren N, and Heylar K, 1997. Temporal variation in soil acidity. AJSR Vol 35, pp 115-29.
Fenton G, 2003. Planning on liming, 2nd edition, leaflet number 4, NSW Agriculture.
Gazey C, Davies D, & Masters R, 2014. Soil acidity a guide for WA farmers and consultants (2 ed).
Department of Agriculture and Food, Western Australia
Nicholson C, 2011. Long term effects of surface applied lime in the Woady Yaloak Catchment.
Scott B, Ridley A, and Conyers M, 2000. Management of soil acidity in long term pastures of south –
eastern Australia: a review. AJEA, Vol 40. pp 1173-1198.
Quigley P and Schroder P, 1998. Liming pastures for wool production in the high rainfall zone,
Natural Resources and Environment, Brochure.