.. S.M.Alam, S. Shamshad, M. Naqvi
1999
Citations
2
Influential Citations
53
Citations
Journal
Journal name not available for this finding
Abstract
The pH of the growth medium has significant effects on the properties of soils and consequently on the nutrient uptake by crop plants. Soil pH is one of the most indicative measurements of the chemical properties of a soil. Whether a soil is acidic, neutral, or basic has much to do with the solubility of various compounds, the relative bonding of ions to exchange sites, and the activity of various microorganisms in the soil systems. Thomas [1] noted that three soil pH ranges are particularly informative: a pH less than 4 indicates the presence of free acids generally from oxidation of sulfides; a pH less than 5.5 suggests the likely occurrence of exchangeable Al; and a pH from 7.8 to 8.2 indicates the presence of calcium carbonate, an important agent of calcareous soil. Soils with pH values ranging from 4 to 7 [2] are extensively distributed throughout the tropical and subtropical regions of the world. Soils with pH values less than 4 also exist and are commonly found as acid sulfate soils and in mine soils. Plant growth in acid soils may be limited by a variety of factors, including the direct effect of pH (excess H ion concentration) as well as pH-induced toxicities (e.g., Al, Mn) and/or insufficiencies (e.g., Ca, Mg, P, Mo) [3]. Increase in the hydrogenion concentration of the medium generally causes a decrease in the rate of absorption of cations, probably as a result of competition between the similarly charged ions for binding and carrier sites. Similarly, the role of high pH has often been considered to be detrimental in causing deficient nutrient availability and ionic imbalance.