PH in soils

R. W. Smiley and R. J. Cook, Relationship between take-all of wheat and rhizosphere pH in soils fertilised with ammonium vs. nitrate-nitrogen, Phytopathology 63 882 (1983). 

Figure 3.13 Solubility of Zn versus pH in soil at four Zn levels. The straight lines indicate the solubilities of possible precipitates at atmospheric CO2 pressure (McBride, 1994). Reproduced by permission of Oxford University Press...

Patrick WH, Jr, Williams BG, Moraghan JJ. 1973. A simple system for controlling redox potential and pH in soil suspensions. Soil Science Society of America Proceedings 37 331-332. 

Table III. Mean Total and Nitrate Nitrogen, Organic Matter, and pH in Soil Beneath Black Walnut Planted in Mixture with Nitrogen-fixing Species...

Limewater is a saturated aqueous calcium hydroxide, Ca(OH)2, solution. To make limewater, a small amount of calcium hydroxide is needed. Calcium hydroxide is marketed commercially as slaked lime or hydrated lime. It is used for cement, increasing the pH in soils, and water treatment. Lime may be obtained from building material stores in the cement section and in agricultural stores. The smallest quantities sold are generally 5- or 10-pound bags, which cost a few dollars. Because only a teaspoon of lime is needed (the solubility of calcium hydroxide in water is 0. Ig per 100 mL), ask the sales clerk if there are any broken bags from which you can take a tablespoon of lime. Often there will be enough lime dust where it is stored to obtain an ample amount for this activity. 

How migiit a below-normal pH in soil lead to nutrient deficiencies in plants ... 

Table I. Cation Exchange capacity (CEC), Redox Potential (Eh), and pH in soil after 672 hrs...

Goulding, K. W. T. and O. Talibudeen. 1984. Thermodynamics of K-Ca exchange in soils. II. Effects of mineralogy, residual K and pH in soils from long-term ADAS experiments. J. Soil Sci. 35 409-420. 

A survey by Strain etal. (1981) of 3000 first-draw water samples in the US showed that about 18% of the samples (or about 540) had a selenium content that exceeded the EPA standard of 10pgL and the highest measured level was 450 pgL b These same samples showed elevated concentrations of elements associated with corrosion of household plumbing by soft, acidic water. The potential impact of acid precipitation on selenium was discussed by Mushak (1985) who suggested that altered acidity by both soil and aquatic systems poses a risk for altered biotransformation processes. Lowered pH in soils reduces selenium availability. In the pres-... 

F. Cui, E. H. Hansen, and J. Rdiidka, Evaluation of Critical Parameters for Measurement of pH by Flow Injection Analysis. Determination of pH in Soil Extracts. Anal. Chim. Acta, 169 (1985) 209. 

In mineral wetland soils, A1 and Fe are major constituents, which regulate phosphorus solubility by forming insoluble phosphate minerals. These minerals are sensitive to changes in soil pH, whereas phosphorus minerals associated with Fe are redox sensitive. Phosphate minerals associated with A1 and Fe are stable under acidic soil conditions, and their solubility increases with an increase in pH. Solubility of calcium phosphates decreases with an increase in pH. In soils dominated by CaCOj (calcareous soils), when Ca + activity is depressed, phosphorus solubility increases. 

A useful guide to the measurement of soil pH in soil is found in Test Methods for Evaluating Solid Waste Physical Chemical Methods, SW-846 (Washington, DC Environmental Protection Agency, 1995, Volume 1, Section C, Method 9045C, Revision 3). 

Soil acidity, or its pH, is the most important measured parameter. Details for conducting field measurements of pH in soils for use in corrosion testing are covered in ASTM Test Method for Measuring pH of Soil for Use in Corrosion Testing (G 51). Two electrodes, glass tind calomel, of a standard pH meter are pressed on undisturbed soil at a given site, and the vedue of their potential difference is linearly related to pH. Salts such tts fertilizers in the soil can affect the correct value. 

Udagawa, S., and T. Nakada, 1969. Molecular structure of allophane as revealed by its thermal transformation. Proc. Int. Clay Conf, Tokyo. 1 151-160. de Villiers, J. M., and M. L. Jackson, 1967. Cation-exchange capacity variations with pH in soil clays. Proc. Soil Sci. Soc. Amer. 31 473-476. 

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