Liming materials

Calcium. Calcium is the fifth most abundant element in the earth s cmst. There is no foreseeable lack of this resource as it is virtually unlimited. Primary sources of calcium are lime materials and gypsum, generally classified as soil amendments (see Calcium compounds). Among the more important calcium amendments are blast furnace slag, calcitic limestone, gypsum, hydrated lime, and precipitated lime. Fertilizers that carry calcium are calcium cyanamide, calcium nitrate, phosphate rock, and superphosphates. In addition, there are several organic carriers of calcium. Calcium is widely distributed in nature as calcium carbonate, chalk, marble, gypsum, fluorspar, phosphate rock, and other rocks and minerals. 

Heavy metals are introduced into the soil mainly by the application of fertilizers, sewage sludge, liming materials, and other industrial and urban waste materials. In recent years, increased anthropogenic inputs of heavy metals in terrestrial environments have caused considerable concern relative to their impact on groundwater... 

Calculation. Determine the amount of hydrochloric acid (y ml) consumed by the sample. This is done by subtracting the titre of 0.5 M NaOH from 50 (the volume of 0.5 M HCI added to the liming material). The reactions for HCI on limestone and the subsequent back-titration of the excess HCI are ... 

Johnson, F.J. (1990a) Agricultural liming materials. In Helrich, K. (ed.) Official Methods of Analysis, 15th edn. Association of Official Analytical Chemists, Arlington, Virginia, pp. 1-8. 

All liming materials, whether oxide, hydroxide, or carbonate, react with soil water and carbon dioxide to yield the bicarbonate form when applied to acid soil. The partial pressure of carbon dioxide in the soil usually is several hundred times greater than that in atmospheric air, and drives the reaction that produces Ca(HC03)2, which is very important in buffering the soil solution (see Equation 3). 

Two attributes are required of any liming material 1) a cation capable of displacing soil colloid-adsorbed H+ and Al+ + + ( also a source of soil acidity) and 2) an anion capable of neutralizing the displaced H+ and Al+ + + (see Equation 4). 

Calcium carbonate, 88-91 Equilibrium with C02, 88 Liming material, 160-162 Calcium phosphates, 342-344,436,458 Carbonates, 88-91, 433 Langelier Index, 417 Mn and Fe carbonates, 440 Ca and Mg carbonates, 449-451 Nickel carbonate, 435 Lead carbonate, 435 Cadmium carbonate, 435 Carbon dioxide, 29-33... 

Empty Fruit Bunches and Fibers and Shells. Traditionally, the empty fruit bunches generated at the palm oil mill are mostly incinerated to produce bunch ash. Bunch ash is considered a good source of potassic fertilizer and is also useful as liming materials because of its high alkalinity (pH 12). However, incineration of EFB could cause air pollution, and this practice is not encouraged by the Department of Environment. 

The earliest geologic deposits used as mineral supplements for agricultural soils seem to be chalk and marl. The beneficial effects of these materials on crops were known to the Celts as early as 2500 B.P. The Romans, who learned this practice from the Greeks and Gauls, even classified various liming materials and recommended that one type be applied to grain and another to meadow. However, liming materials were used for nearly 20 centuries before the beneficial effects were shown to be mainly due to the neutralization of excess soil acidity. 

Annual data on the consumption of agricultural limestone and other liming materials can be obtained from the Agricultural Limestone Institute, of Washington, D. C. 

Data on agricultural limestone and other liming materials consumption, annually. 

In this most common type of experiment, the total quantity of metal in the system, Mt, is held constant while the pH is raised. It pertains to the quite feasible situation in soils where a particular quantity of metal pollutant has to be made less soluble by raising the pH with liming materials. Initially, at very low pH, all of the metal is in solution, but as the pH is adjusted higher, part of the metal is adsorbed. The mole quantity of metal adsorbed is (S—OM X W, where (S—OM has units of moles of metal bonded per unit weight of adsorbent and W is the weight of the adsorbent in the suspension. The mole quantity of metal in solution is [M J X F, where [M J has units of moles per unit volume and V is the volume of solution in the suspension. Mass balance then requires that... 

In the process, Ca is immobilized on the newly formed exchange sites. As a result, when liming materials such as CaCOa and Ca(OH)2 are added to acid soils, Ca mobility is very limited. In less acid soils, Ca added as lime can be mobilized in the form of soluble Ca(HC03)2-... 

Potassium is the third most important fertilizer element, in terms of amounts added as fertilizer, after nitrogen and phosphorus. Many soils of humid and temperate regions are unable to supply sufficient K+ for agronomic crops. Farmers in these areas long ago recognized the benefits of applying wood ash and other liming materials to their acid soils. Both the alkalinity of the ash (to counter Al3+ toxicity) and its K and Ca content are beneficial. 

Redimag. (Nat I. Refiactories Minerals] Agric. liming material with high acid neutralizing effect... 

There are officially accepted methods to determine Al colorimetrically using alumi-non in liming materials, gravimetrically in deodorants using 8-hydroxyquinoline, in sulfate-type soil acidifiers and baking powders by flame AAS optimally at 50-150 mg Al L by titration in plants, in solid wastes using ICP-AES (with a detection limit of 0.045 mg Al L ), and in waters by ICP-MS (with a detection limit of 0.001 mg Al L ) (Horwitz 2000). 

A few of the many manuals on chemical analysis which include instructions on sample collection may be mentioned. For over 100 years, AOAC INTERNATIONAL, has published detailed experimental procedures for sampling, subsampling and pretreatment of natural materials with the latest volume (Horwitz 2000) containing procedures for materials such as agricultural liming materials, fertilizers, plants, animal feed and dairy products in various chapters. A chapter on sampling dairy and related products is in the book edited by Marshall (1993) on Standard Methods for the Examination of Dairy Products. Specific sampling procedures for various food commodities are summarized by Ihnat (1982), based mostly on the AOAC manual. 

The requirements for some of the quarry-produced liming materials are summarised in Table 10.3 [10.3]. 

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