Nice and very thoughtful question . Equilibrium lime buffer cpacity is still considered very useful in determining the lime requirement of acid soils. however , At present, no single quick-test method for determining lime requirement is suitable for soils with widely varying organic matter contents, nor is there any single method for evaluating lime quality which adequately characterizes limestones, dolomites and chalks. The aim of this study was to develop a method for predicting lime requirement which could (a) be suitable for soils with widely varying organic matter contents and (b) make allowance for the differences in effectiveness among the wide range of commercially available CaCO3— based liming materials. Soils of varying organic matter content were incubated with different rates of both CaCO3 and other liming materials; pH was measured after 8 months of incubation. From the pH-CaCO3rate data a model was developed which related the shape of the pH-CaCO3 neutralization curves to initial pH and sample density. This model was used to predict CaCO3 requirement. A second model was developed which predicted values for a lime-quality correction factor from certain properties of both liming materials and soils. The complete method, comprising both models, appears to provide the most comprehensive method currently available for evaluating the lime requirement of temperate acidic soils. Source : Developments in Plant and Soil Sciences book series (DPSS, volume 45)

Nice and very thoughtful question . Equilibrium lime buffer cpacity is still considered very useful in determining the lime requirement of acid soils. however , At present, no single quick-test method for determining lime requirement is suitable for soils with widely varying organic matter contents, nor is there any single method for evaluating lime quality which adequately characterizes limestones, dolomites and chalks. The aim of this study was to develop a method for predicting lime requirement which could (a) be suitable for soils with widely varying organic matter contents and (b) make allowance for the differences in effectiveness among the wide range of commercially available CaCO3— based liming materials. Soils of varying organic matter content were incubated with different rates of both CaCO3 and other liming materials; pH was measured after 8 months of incubation. From the pH-CaCO3rate data a model was developed which related the shape of the pH-CaCO3 neutralization curves to initial pH and sample density. This model was used to predict CaCO3 requirement. A second model was developed which predicted values for a lime-quality correction factor from certain properties of both liming materials and soils. The complete method, comprising both models, appears to provide the most comprehensive method currently available for evaluating the lime requirement of temperate acidic soils. Source : Developments in Plant and Soil Sciences book series (DPSS, volume 45)

The explanation by Dr. Anoop, regarding lime requirement of acid soils is really impressive. Yes, a complete model has been developed for lime requirement of temperate acid soils. The question here is relatively a quicker and cost effective and efficient method for estimating exchangeable acidity of tropical soils and requirement of lime, because soil acidity has been a serious problem in terms of area coverage and the method and costs to reclaim such soils in tropical regions.

Dr. Anoop has provided very good reply. The model described was capable to predict values for a lime-quality correction factor from certain properties of both liming materials and soils.

Interesting. Lime requirement is hugely deep dent upon the texture of the soil plus quantum of soil pH , you wish to raise an d the fineness of liming materials...

Interesting explanation by Dr. Anoop and Dr Fred Vocasek regarding lime requirement of acid soils

Comparison of Soil pH Methods on Soils of North America

Soil pH, one of the most routine measurements performed, is used to interpret chemical reactions, nutrient availabilities, and the rates of many biological processes in soils. Predominantly, soil pH is measured in soil–water suspensions using a glass H+-sensing electrode and a reference electrode. Soil/water ratios of the suspensions ranging from saturated paste to 1:5 are used in research and commercial soil testing laboratories. Th e objective of this study was to evaluate relationships between pH measured in saturated paste extract (pHsp), 1:1 and 1:2 soil/water suspensions (pH1:1w and pH1:2w), and 1:1 and 1:2 soil/0.01 mol L−1 CaCl2 suspensions (pH1:1CaCl2 and pH1:2CaCl2). In addition, the eff ects of soil suspension electrical conductivity (EC1:1w) on measured values of soil pH were assessed. Analytical results for 120 agricultural soil samples from a laboratory profi ciency program database indicated that the relationship between pH1:1w and pH1:1CaCl2 was highly signifi cant (r2 = 0.984). Similar regressions were found between pHsp and pH1:1CaCl2, and between pH1:2w and pH1:2CaCl2. Th e EC1:1w explained 85.1% of the variation in the diff erence between pH1:1w and pH1:1CaCl. A model comprised of a linear term of pH1:1CaCl and a nonlinear term EC1:1w explained 99.5% of the variation in soil pH1:1w, with the estimated pH of 88% of the soils between ±0.10 pH units of the measured pH1:1w. Results for individual soils indicated that a nonlinear function using matrix EC explained >98% of the variation in soil pH across a range of soil/water ratios and suspension matrices ranging from 0.00 to 0.01 mol L−1 CaCl2. It is our assertion that the current practice of determining soil pH in soil–water suspensions of low ionic strength results in a signifi cant analytical measurement error associated with liquid junction potentials of a glass reference–H+ electrode system. For soil diagnostic analysis purposes, we concluded that the measurement of soil pH using 0.01 mol L−1 CaCl2 solution at a soil/water ratio of 1:1 is a more robust measurement for soils of North America. Source : SSSAJ: Volume 74: Number 1 • January–February 2010

Thank you so much all for the nice discussion we have had since about the last two weeks. However, there is one associated question which has not been yet discussed, i.e. sub-soil acidity and alternative reclamation measures. Would you think gypsum could be one of the amendment options for this problem? Is reclamation of subsoil acidity practically and economically feasible?

Yes , as rightly pointed out Gypsum is one of the amendment for the sub soil acidity problem. Top/ surface soil acidity may be managed by application of lime. However reclaiming the soil acidity in the subsoil is a major limiting factor in crop productivity due to aluminum (Al) toxicity and calcium (Ca) deficiency. Many experiments had shown that the application of gypsum will help in managing the sub soil acidity. The explanation for the same is it will increase the subsoil Ca and forms the complex between Al and SO4 , ligand exchange of SO4 for hydroxyls (OH) on sesquioxide surfaces resulting in the so-called “self liming” effect, precipitation of basic aluminum sulfate minerals which renders the labile Al insoluble and salt sorption in which SO4 is specifically adsorbed which causes the removal of some Al from solution. All these mechansims suggest that it is preactically feasible and with respect to economics, if we go with some industrial waste products containing gypsum then it may be economically also feasible.

@ Getachew Agegnehu I strongly believe that A Lime Requirement procedure for a routine soil test must be area and soil-specific. This is because reactions of acid soils to liming are different among soils (e.g. acid sulfate soils, soils of uplands and hills, red soils,....etc.) with various amount of components that affect liming, i.e. exchange acidity, organic carbon, clay contents, .....The specific procedure must be calibrated using a reference method, such as Dunn (1943) or the field-moist incubation with CaCO3.