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The value of lime

Brian G. Davey

Senior Lecturer in Soil Science The University of Sydney, Sydney, N.S.W. 2006.

1. Liming is not a new technique

A Spaniard named Columella who lived in Rome about 45 A.D. wrote the first known treatise on Agriculture. In this treatise, of some twelve volumes, called De re rustica Columella recorded the use of lime to increase plant growth.

The first conscious use of lime in the United States of America to correct soil acidity was made by the Virginian farmer-scientist Edmund Ruffin in the era between 1825-1845. Ruffin also claimed to have fired the first shot in the American civil war.

Many older publications refer to the importance of liming and marling (the name for the process of adding calcium carbonate rich clay to the soil) as a means of improving poor soils -- especially organic soils with their associated higher levels or organic acids.

2. Liming is widely practised overseas

In 1979 some 29,433,636 tonnes of lime were used for agricultural purposes in the U.S.A. In the State of Illinois alone 4,769,310 tonnes were used. The National Limestone Institute of the U.S.A. has estimated that abc’ut half of the area of that country requires regular liming.

Liming is widely practised in Europe and the United Kingdom where it is a regular feature of every rotation.

By contrast the total agricultural lime sales in New South Wales probably did not exceed 40,000 tonnes in 1980. It is scarcely necessary to point out the enormous difference between consumption in this State and overseas. The area of soils known to need lime has been estimated at about 1 000 000 hectares by Cregan (1980) and Bradley (1981) provided the following estimates by districts:

Table 1. Areas needing lime in New South Wales


AREA (hectares)

Albury, Holbrook


Goulburn, Bigga, Taralga


Bathurst, Oberon, Burraga, Lyndhurst






Bradley (1981) also notes that much of coastal N.S.W. requires lime. These figures lead to the simple conclusion that we will soon be witnessing a revolution in farming practice in this State as liming becomes an accepted part of our soil management system.

3. What is the effect of liming?

A. How acid soils develop and some of their properties

The clay particles present in most soils carry significant amounts of negative electrical charge which electrostatically attracts cations which carry positive charge. These cations are the principal sources of the plant nutrients, Ca, Mg and K. They also include some trace elements like Zn, Cu and Mn which occur in cationic form. As soils become more acid increasing amounts of H and Al gradually displace the nutrient cations from the soil reducing the amounts of them available to plants. Aluminium (Al) and H are both known to reduce plant growth and Al is accepted as a toxic element when present in sufficient quantity.

From the previous papers it is obvious that the soil becomes acidified by the addition of hydrogen ions or protons arising from the decomposition or organic matter, the oxidation of NH4 4 NO and from nutrient uptake.

The increased acidity results in greater solubility of Al which is present in all soils in large amounts in the form of clay minerals and other aluminosilicates. The released aluminium becomes both soluble and exchangeable. The Al cations are usually held firmly by the soil and they displace other cations that are essential plant nutrients. These include Ca, Mg and K. The increased acidity also reduces the availability of Mo which is held more strongly by acid soils. The acid condition if coupled with waterlogged conditions in part of the soil profile (often the A2 horizon) lead to the reduction of Mn3 and Mn4+ compounds (usually oxides) to which can cause Mn toxicity in sensitive plants. The more acid the soil the more Mn that is released and the longer it is likely to persist in the soil (Bromfield 1979). This phenomenon is very likely in the Duplex soils of this State which tend to become waterlogged in the A2 horizon in autumn and winter because of the lower hydraulic conductivity of the B horizon. This effect will often be more obvious in the drainage lines and on the lower slopes of the hills where water collects for longer periods of time.

B. What liming does

i) Addition of lime, in any form, calcium oxide (CaO), calcium hydroxide (Ca(OH)2), or calcium carbonates, will convert soluble and exchangeable Al to insoluble forms.

e.g. Al3+ + 3OH Al (OH)3

and any H+ reacts

2H+ +CaCO3 H2O + CO2 + Ca++

Figure 1. Effect of liming on cation exchange capacity and exchangeable cations. Moss Vale District.

The absolute amount of each cation is given on the horizontal axis.
The areas represent the percentage of each cation in each soil.
Data collected by M.K. Conyers.

There is universal agreement that soils with a pH in water greater than 5.5 contain little exchangeable Al.

ii) The higher pH brought about by addition of lime reduces the amount of Mn++ formed in the soil when it is waterlogged. The higher pH of the soil means that the microorganisms which convert Mn++ to Mn3+ and Mn4+ work more rapidly thus reducing the period that the soil contains the toxic divalent form. Oxidation of Mn is very rapid in soil with pH in the range of 5.6-7.5.

iii) Addition of lime to acid soils results in the release of Ca to exchangeable and soluble forms. It restores the essential Ca lost during the acidification process. Ca is essential for plant growth and some workers believe it helps to protect some plants from the effects of Al toxicity.

iv) In some soils addition of lime may increase the cation exchange capacity cf the soil thus increasing the soil’s capacity to retain essential plant nutrients. Figure 1 illustrates this effect for the Al and A2 horizon of a soil from the Moss Vale district of N.S.W. The date was obtained by M. Conyers, a member of my research group. Notice how liming has reduced Al to a negligible amount in the surface soil. Calcium has increased proportionally. Some reduction in Mg has occurred and most of the exchangeable Na has been displaced. Very little effect is seen in the A2 horizon because lime does not move readily. There is some reduction in exchangeable aluminium and a slight increase in exchangeable Ca. The clear increase in the cation exchange capacity of the Al horizon is partly due to increased charge from the increased organic matter in the surface soil following liming. While decreased Al and increased Ca would be observed in most acid soils following liming increase in cation exchange capacity does not always take place.

v) In acid soils containing sufficient Na to cause soil structural instability addition of lime will reduce exchangeable Na and lead to enhanced structural stability.

vi) The role of lime in determining the availability of phosphate in soil has been the subject of argument for many years. While increase availability is observed on some soils, on others the effect is either not observed or some reduction in availability takes place. Smith (1979) showed that liming increased the pH of soils in the Henty-Albury district and resulted in increased levels of available phosphorus. Experience around the world suggests that liming probably does not change phosphorus availability a great deal. If it occurs it should be regarded as a bonus rather than normal expectancy.

vii) Care needs to be taken not to over lime as this can cause a number of undesirable effects including deficiencies of trace elements like Zn and Cu as well as reduced levels of Mg.

viii) The effect of liming on soil potassium (K) status is also debated. Both increased and reduced availability have been recorded. There is little doubt that increasing Ca status will tend to cause displacement of K from exchange positions. The role of pH and Ca status in the release of K from micaceous clays is less well understood. Release of K from some micaceous clays requires both H and Ca ions to be present. The best checks on K status are soil tests and field strips to see if response to K is taking place on your soil.

Figure 2. Distribution of pasture plants and bare patches in an old pasture fertilized for 20 years at Cobbitty N.S.W. Data collected by I.McClennan.

4. How much lime should be applied?

There are many well established procedures for determining the lime requirement of soils. Most are based on methods where base is added to the soil in the laboratory. It has been recently shown by Tran and Van Lierop (1981) that each method provides a good prediction of lime requirement if it is used on the soil for which it is developed. They have re-calibrated all methods and recommend the use of single buffer methods because of their simplicity. The SMP - or the Shoemaker, McLean and Pratt (1961) buffer method proved the best procedure. These tests were based on liming to pH 6.5 in water but can be adapted to give predictions for liming to pH 5.5 in water.

An alternative procedure is that due to Kamprath (1970) and Reeve and Sumner (1970) based on the amount of exchangeable Al in the soil. Fox (1981) summarized the controversy which ensued by stating, “it is reasonable to conclude that there can be no single criterion for liming if the objectives are diverse and the soil varied”.

Liming rates cannot be determined without consideration of the plants involved. Cregan (1980) has proposed that liming rates should be adjusted to the crops and pastures being sown. The effect of soil pH on the distribution of various pasture species is shown in Fig. 2. The data collected by Ian McLennan, a member of my research group, shows that there is a well defined lower limit to the pH range occupied by each species in the pasture. Medicago sp. is least tolerant of acid conditions, Trifolium repens moderately tolerant and Paspalum dilatatum the most tolerant. It is interesting to note that the data of McLennan suggests that some parts of the pasture are even too acid for Paspalum dilatatum. This effect seems to be primarily related to soil p11 as the effects of soil structure and physical conditions have been eliminated.

FIGURE 3 Pasture response to superphosphate with and without lime and the percentage of lucerne in the pasture with and without lime at three sites in the Goulburn district.

(data from Vimpany and Bradley, 1979)

Trikkala subterranean clover is moderately tolerant of aluminium toxicity (Scott 1980) and only the most acid soils would respond to lime application. On the other hand lucerne is highly sensitive to aluminium and excellent responses to lime would be expected on soils that would not affect the growth of trikkala sub clover. The response of lucerne to lime is shown in Fig. 3 taken from Vimpany and Bradley (1978). Within wheat there is a considerable variation in sensitivity to aluminium and varieties like Egret, Condor, Durati, Kite and Timgalen have been shown to be highly sensitive by Scott (1980). Teal, Songlen, Shortim and Olympic were found to be less sensitive. The situation becomes more complicated when the effects of manganese are also taken into account. Egret is tolerant of Mn arid sensitive to Al and Teal sensitive to Al and Mn.

The effects of acid soil conditions on wheat. yield is under study within my research group, by P. Slavich, and is funded by the Wheat Industry Research Council.

Figure 4 shows the relationships obtained between dry weight. of wheat plants and pH, pAl (the negative logrithm of the A13+ in 0.10 M CaCl2 extract). This data illustrates the principles enunciated earlier, namely that acid soil conditions lead to high Al, high Mn and low Mg levels. This date collected from Mr. Colin Campbell's property, “Avondale”, Pleasant Hills is typical of a number of sites that were sampled in October 1980. We have been able to show in later work that plant dry weight is very strongly correlated to grain yield. It is therefore reasonable to interpret the dry weight axis as grain yield.

The effects of liming the soil on yield are shown in. Table 2 for four of the 77 varieties under study. The increase in average yield is dramatic and their statistical significance is indisputable. The average pH of the soil was 4.48 and was limed to an average target of pH in 0.01M CaCl2 which was accurately predicted by a buffer procedure.

Table 2 Grain yields of wheat on limed and unlimed plots as Hawkesbury Agricultural College.

Mean yield per plant (grams of grain).





















Liming this soil has effectively eliminated Al and Mn toxicities as well as restoring Ca levels. While our data analysis is not yet complete we are aware that about 50 of the 77 varieties of wheat under test gave visual yield responses to lime. It is worth emphasizing that these results were obtained under field conditions in 1979, a dry year which necessitated irrigation to ensure crop survival.

Figure 4. Samples collected from an acid soil yellow patch on Colin Campbell’s property Avondale Pleasant Hills October 1980. pH measured in 1/5 soil/0.01m cacl2 solution. Data collected by P. G. Slavich.

5. Sources of lime in New South Wales and cost

The current sources of lime in Southern New South Wales are:

i) Molong Limestone manufactured by Cabbone Shire Council. The amount produced is geared to demand and can be increased at any time.

a) Sieve analysis

Sieve No.

% passing bagged

% passing bulk
















b) Price




Per tonne privatebuyer



c) Chemical composition:







Iron oxide or Alumina


Water and undetermined


The Council is currently investigating changes to provide 80% passing 50 mesh sieve and 50% passing 100 mesh to meet a new demand for finer material.

Source of information: E.B. Stuckey, Shire Clerk

ii) Cowra Limestone The Council of the Shire of Cowra supplies a waste produce from the crushing of limestone for the purpose of producing various aggregates for road purposes.

The lime “waste" is not refined in any way contains clay and other impurities which may pass through the crusher with the spalls.

No sieve analysis or chemical composition data is available or has even been carried out by the Council.

On June 5, 1981, 1000 tonnes was in store selling at a sale price of $10.00/tonne ex crusher.

Source: J.A. Finemore Shire Engineer

iii) Bathurst Limestone Omya-Minerals expect to commission their plant in mid-August 1981. It will produce about 100 000 tonnes annually, depending to some extent on product mix. A substantial proportion of this capacity is designated to produce agricultural grade products. While the range of grades has not been finally decided it is expected that grades similar to Southern Limestone’s P70 and agricultural grades will be available.

The product will contain approximately 96% calcium carbonate. The ex works prices are expected to be similar to the ex works price at Moss Vale of equivalent Southern Limestone products.

Source: E.B. Thomas Marketing Manager.

v) David Mitchell Estate Ltd., Lilydale, Victoria sells two types of lime:

Ground agricultural lime

92% will pass 850 micrometer sieve

Calcium carbonate equivalent 80%

Magnesium oxide equivalent 4.5%.

Agricultural Lime

Fireground Limestone

Sieve No.

% passing

Sieve No.

% passing













Burnt limestone:

60% passes 850 micrometer sieve

Calcium carbonate equivalent 142%

Magnesium oxide equivalent 8%.

Prices : as at 23/1/1981




Lilydale ground burnt agricultural lime--

truck lots of 11 or 16 tonnes
ex work f.o.r. Lilydale



Core Hill agricultural lime --

truck lots of 11 or 16 tonnes
ex works or f.o.r. Lilydale



Lilydale agricultural limestone --

truck lots of 11 or 16 tonnes
ex works or f.o.r. Lilydale



Source: G.P. Clements Sales Manager

and Victorian Department of Agriculture

vi) Southern Limestone Pty. Limited P.O. Box 9, MOSS VALE. N.S.W. 2577.

Composition: Calcium carbonate 97.00%
Magnesium carbonate 1.00
Other 2.00

Fineness: see attached sieve analyses

Price: ex works Agricultural lime $20 per tonne

ex works Superfine

F70 grade $22 per tonne

Source: K.C. Hoskins Managing Director

6. Evaluation of liming materials

As liming materials are variable in composition it is important to evaluate each one.

i) Chemical evaluation:- If it is assumed that pure calcium carbonate has a neutralizing value of 100% then the relative neutralizing values for other pure materials are:

Molecular Neutralizing

Weight Value %

Calcium carbonate 100 100
Magnesium carbonate 84 119
Calcium hydroxide 74 135
Calcium oxide 56 178

ii) Physical evaluation:- It should be obvious that coarse particles of limestone will take longer to react with the soil than finer material. One rating scale developed by Ohio State University is given below:

Particle Size Efficiency Rating %

Less than 60 mesh USS 100
Less than 20 mesh but plus 60 mesh 60

Less than 8 mesh but plus 20 mesh 20

An example of screen analyses has been provided by Southern Limestone and is given in Fig. 5.

As an example consider evaluation of Southern Limestone Agricultural Grade:


97% x 100



1% x 119



98.19 %



minus 60 m USS 72% x 100%



minus 20 + 60 m 20% x 60%



minus 8 + 20 m 2% x 20%



88.4 %

Total efficiency: 98.19 x 88.4 = 86.8%

By way of contrast take Sample B on sieve analysis a typical “crushed” limestone:


93.7% x 100



2.7% x 119



96 .9 1%

Figure 5. Screen analyses of various liming materials. Data supplied by Southern Limestone Pty. Limited.

Fineness minus 60 m USS

57% x 100%


minus 20 + 60 m

40% x 60%


minus 8+20m

9%x 20%




Total efficiency: 96.91 x 76.8 = 74.43%

Let us assume that a farm requires 2000 kg/hectare of lime rated at 100% neutralizing value.


Sample A - application for Southern Limestone = 2000 - .868 = 2.3047
Sample B - application for crushed limestone = 2000 - .7443 = 2.6875

For application on a farm distant 200 km from works, cartage would be say $15.00/tonne.




price ex works

$ 20.00

$ 24.00

cartage 200 km



Price delivered

$ 35.00

$ 39.00

Lime cost per hectare -- 2.304T x 35 = $ 80.64

2.687T x 39 $104.67

If a finer grade is used, e.g. Southern Limestone Superfine F70 Grade:

Total efficiency

98.19 x 100

= 98.19%


2000 + 98.19

= 2.037T

Cost ex works



Cartage 200 km





Lime cost per hectare = $75.37

It is worthwhile noting that the finer grade would be fully effective in about 6-8 weeks given reasonably moist soil conditions compared to 12-18 months for normal agricultural grade.

The calculation above can also be carried out for a low grade lime. For example for a lime with a neutralizing value of 50% calcium carbonate equivalent and a total efficiency of 43.00%.

To supply 2000 kg/hectare of CaCO3 2000 - 43 = 4.651T

Cost ex works say


Cartage say 30 km




Lime cost per hectare 4.65 x 17.00 = $78.37

The last example illustrates the well known principle that a low grade local limestone will usually prove as cheap or cheaper than high grade materials hauled long distances.


1. BRADLEY, J. 1981. The acid soil problem -- or the rise of aluminium in soil. Notes from farmer prepared by Biological and Chemical Research Institute, Rydalmere.

2. BROMFIELD, S.M. 1979. Transformations of manganese into and out of plant available forms in soils: The importance of pH in these processes and the detection of excessive manganese in soil. Workshop on Acid Soils. N.S.W. Department of Agriculture, Biological and Chemical Research Institute, Rydalmere. N.S.W. March 3, 1979.

3. CREGAN, P.D. 1980. Soil Acidity and Associated Problems --Guidelines for Farmer Recommendations. AG bulletin, 7 October 1980. N.S.W. Department of Agriculture.

4. FOX, R.L. 1980. Soils with Variable Charge. Agronomic and Fertility Aspects. Chapter 11 in B.K.G. Theng. ed. Soils with Variable Charge. New Zealand Society of Soil Science Lower Hutt New Zealand.

5. KAMPRATH, E.J. 1970. Exchangeable aluminium as a criterion for liming leached mineral soils. Soil Science Society America Proceedings 34:252-259.

6. REEVE, N.G. and SUMNER, M.E. 1970. Lime requirements of Natal Oxisols based on exchangeable aluminium. Soil Science Society America Proceedings 34: 595-598.

7. SHOEMAKER, H., McLEAN, E.D. and PRATT, P.F. 1961. Buffer methods for determining lime requirement of soils with appreciable amounts of extractable aluminium. Soil Science Society America Proceedings 25:274.

8. SCOTT, B.J. 1980. Cited by P.D. Cregan 1980 in AG bulletin 7 Soil Acidity and associated problems - Guidelines for farmer recommendations N.S.W. Department of Agriculture.

9. SMITH, A.N. 1979. The effect of lime on the availability of phosphorus in the soil; influence of pH on changes in the response of plants to phosphorus. Workshop on Acid Soils. N.S.W. Department of Agriculture Biological and Chemical Research Institute, Rydalmere. N.S.W. March 3, 1979.

10. TRAN, S. and VAN LIEROP, W. 1981. Evaluation and improvement of buffer-pH lime requirement methods. Soil Science 131:178-188.

11. VIMPANY, I.A. and BRADLEY, J. 1979. Report to Wool Research Trust Fund on project entitled Development of Field and Glasshouse Tests for Potassium and Phosphorus. N.S.W. Department of Agriculture.

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