Calcium in soil

The extraction method for prohexadione-calcium in soil was developed using alluvial soil and volcanic ash soil. Extraction by shaking the soil with a mixture of 1N sulfuric acid-acetonitrile (1 3, v/v) and/or of 1N sulfuric acid-acetone (1 3, v/v) showed an acceptable extraction recovery efficiency. 

Fig. 16.3 Replicated field trial in Wadenswil, Switzerland where higher bacteria biomass (expressed as microbial bound carbon (Cmic) was found in the organically managed orchard soils (crosses = organic squares = conventional, integrated) than in orchards managed according to integrated farming practice. Higher bacterial biomass was correlated with increased content of water-extractable calcium in soil samples...

Xing-Chu and Yu Sheng [79] have described a spectrophotometric method for the determination of exchangeable calcium in soil. In this method, a portion of an aqueous extract of the soil is treated with ammoniacal ammonium acetate and an aqueous solution of chlorophosphonazo-mA. The solution is evaluated spectrophotometrically at 630 nm. Recoveries of calcium are 99% and relative standard deviations of between 0.9% at the 11 mequiv/lOOg of soil level and 3.1% at the 2 mequiv/100 g soil level are obtained. 

Crapper MacLachlan D. R., MacLachlan C. D., Krishnan B., Krishnan S. S., Dalton A. J., and Steele J. C. (1989) Aluminum and calcium in soil and food from Guam, Palau, and Jamaica implications for amyotrophic lateral sclerosis and parkinsonism-dementia syndromes of Guam. Environ. Geochem. Health 11, 45-53. 

W6. Williams, C. H., The use of lanthanum chloride to prevent interferences in the flame photometric determination of exchangeable calcium in soils. Arud. Chim. Acta 22, 163-171 (1960). 

Calcichrome has been used for determination of calcium in soil extracts [81] and in poly(ethylene terephthalate) [82], Calcium has been determined in river water with Propyl Orange after extraction with a crown ether [67]. 

Usually, a series of standard NaCl solution is prepared containing 0.1-0.5 meq/1 Na by dilution from 0.05(N) NaCl solution using saturated calcium sulphate solution in place of water. Since mostly the calcium in soil extract is associated with sulphate these solutions contains about 30 meq/1 calcium as sulphate. Next to this, the flamephotometer is calibrated with pure NaCl standard and subsequently the standard containing the calcium sulphate is sprayed and any interference effect due to calcium is measured. 

Calcium is relative abundant in soils, and calcium rarely limits crop production per se. Low levels of exchangeable calcium in soils result in increased soil acidity, which usually results in reduced growth of most crops. Using lime applications to correct soil acidity to recommended soil pH levels will provide sufficient calcium for crops because liming materials contain calcium (Table 17.1). 

Gypsum amends and reclaims soils high in destructive sodium and magnesium. Sodium and magnesium act the opposite as calcium in soils by destroying structure and reducing water and air movement, and root growth (Ilyas et al., 1997). 

Calcium. Soil minerals are a main source of calcium for plants, thus nutrient deficiency of this element in plants is rare. Calcium, in the form of pulverized limestone [1317-65-3] or dolomite [17069-72-6] frequendy is appHed to acidic soils to counteract the acidity and thus improve crop growth. Such liming incidentally ensures an adequate supply of available calcium for plant nutrition. Although pH correction is important for agriculture, and liming agents often are sold by fertilizer distributors, this function is not one of fertilizer manufacture. 

Generally, the most common cations in the soil solution are potassium, sodium, magnesium and calcium. Alkali soils are high in sodium and potassium, while calcareous soils contain predominantly magnesium and calcium. Salts of all four of these elements tend to accelerate metallic corrosion by the mechanisms mentioned. The alkaline earth elements, calcium and magnesium, however, tend to form insoluble oxides and carbonates in nonacid conditions. These insoluble precipitates may result in a protective layer on the metal surface and reduced corrosive activity. 

The exposure of calcium carbonate soils by erosion in early stages of desertification may contribute to the paucity of available nitrogen by ammonium volatilization. In soils of high pH, ammonium is converted to NH3 which is lost to the atmosphere by ... 

Menzel, R.G. and Heald, W.R. 1959 Strontium and calcium contents of crop plants in relation to exchangeable strontium and calcium in the soil. Proceedings of the Soil Science Society of America 23 110-112. 

Methyl parathion is only slightly soluble in pH 7 water (55-60 ppm). This affects its mobility in water and its ability to be leached or solubilized into the water phase of a soil-water system. Factors most likely to affect the adsorption of methyl parathion in soil are organic matter content and cation exchange capacity. In soils of low organic matter (e.g., subsurface soils), calcium concentration, which affects the hardness of the water, may also be important (Reddy and Gambrell 1987). Several studies have shown... 

Since prohexadione-calcium degrades rapidly in soil, soil samples should be analyzed or frozen immediately after sampling. ... 

Sample storage stability Prohexadione-calcium in strawberry, rice grain, rice straw, wheat grain and barley grain is stable at -20 °C for 40, 140, 60, 80 and 100 days, respectively. Approximately 88% of the applied prohexadione-calcium remained in soil when stored at —20 °C after 80 days. 

In arid and semi-arid soils with a pH range of 6-9, free calcium is the major Ca speciation form in soil solution. When pH > 9.2-9.5, CaP04 becomes a major calcium species in soil solution of neutral and calcareous soils, especially when the activity of H2P04 is > 10 5 M (Lindsay, 1979), such as after phosphate fertilizers are used. Lindsay (1979) further pointed out that CaS04° contributes significantly to the total calcium in solution when S042- is > 10 M. 

In arid and semi-arid soils, calcite, dolomite, leonhardite (Ca2Al4Si8024.7H20) and lawsonite (CaAl2Si208.2H20) can be possible minerals. Calcium carbonate strongly influences soil properties in arid and semi-arid soils. Most calcareous soils have soil a pH in the range of 7.3-8 5. When sodium is predominant in soils, soil pH is above 8.5. In most arid and semi-arid soils, calcium carbonates (calcite and dolomite) generally accumulate and are most likely to control the Ca2+ and Mg2+ solubility in these soils (Lindsay, 1979). 

The effects of the pH of the NaOAc-HOAc solutions on the subsequent fractions are related to the partitioning patterns of elements in soils. Calcium and Cd in the calcareous soils are predominately present in the CARB fraction (Banin et al., 1990). Cadmium and Ca in the CARB fraction of the soils studied accounted for 40-50% and 75-99%, respectively. Even NaOAc-HOAc solutions at pH 7.0 extracted 3-6% and... 

Smith E, Naidu R, Alston AM (2002) Chemistry of inorganic arsenic in soils II Effect of phosphorus, sodium, and calcium on arsenic sorption. J Environ Qual 31 557-563... 

Morgan, J.E. and A.J. Morgan. 1990. The distribution of cadmium, copper, lead, zinc and calcium in the tissues of the earthworm Lumbricus rubellus sampled from one uncontaminated and four polluted soils. Oecologia 84 559-566. 

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