Soil Chemical Analysis

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Mitigation and Adaptation Strategies for Global Change

In most soils, inorganic phosphorus occurs at fairly low concentrations in the soil solution whilst a large proportion of it is more or less strongly held by diverse soil minerals. Phosphate ions can indeed be adsorbed onto positively charged minerals such as Fe and Al oxides. Phosphate (P) ions can also form a range of minerals in combination with metals such as Ca, Fe and Al. These adsorption/desorption and precipitation/dissolution equilibria control the concentration of P in the soil solution and, thereby, both its chemical mobility and bioavailability. Apart from the concentration of P ions, the major factors that determine those equilibria as well as the speciation of soil P are (i) the pH, (ii) the concentrations of anions that compete with P ions for ligand exchange reactions and (iii) the concentrations of metals (Ca, Fe and Al) that can coprecipitate with P ions. The chemical conditions of the rhizosphere are known to considerably differ from those of the bulk soil, as a consequence of a range of processes that are induced either directly by the activity of plant roots or by the activity of rhizosphere microflora. The aim of this paper is to give an overview of those chemical processes that are directly induced by plant roots and which can affect the concentration of P in the soil solution and, ultimately, the bioavailability of soil inorganic P to plants. Amongst these, the uptake activity of plant roots should be taken into account in the first place. A second group of activities which is of major concern with respect to P bioavailability are those processes that can affect soil pH, such as proton/bicarbonate release (anion/cation balance) and gaseous (O2/CO2) exchanges. Thirdly, the release of root exudates such as organic ligands is another activity of the root that can alter the concentration of P in the soil solution. These various processes and their relative contributions to the changes in the bioavailability of soil inorganic P that can occur in the rhizosphere can considerably vary with (i) plant species, (ii) plant nutritional status and (iii) ambient soil conditions, as will be stressed in this paper. Their possible implications for the understanding and management of P nutrition of plants will be briefly addressed and discussed.

Bioavailability of soil inorganic P in the rhizosphere as affected by root-induced chemical changes: A review

Composting of animal manures and chemical criteria for compost maturity assessment. A review

B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

http://link.springer.com/content/pdf/10.1007/BF01976688.pdf

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

In areas that remain unaffected by industrial pollution soil acidification is mainly caused by the release of protons (H+) during the oxidation of carbon (C), sulphur (S) and nitrogen (N) compounds in soils. In this review the processes of H+ ions release during N cycling and its effect on soil acidification are examined. The major processes leading to acidification during N cycling in soils are: (i) the imbalance of cation over anion uptake in the rhizosphere of plants either actively fixing N2 gas or taking up NH 4 + ions as the major source of N, (ii) the net nitrification of N derived from fixation or from NH 4 + and R-NH2 based fertilizers, and (iii) the removal of plant and animal products containing N derived from the process described in (i) and losses of NO3-N by leaching when the N input form is N2,NH 4 + or R-NH2. The uptake of excess cations over anions by plants results in the acidification of the rhizosphere which is a “localized” effect and can be balanced by the release of hydroxyl (OH−) ions during subsequent plant decomposition. Nitrification of fixed N2 or NH 4 + and R-NH2 based fertilizers, and loss of N from the soil either by removal of products or by leaching of NO3-N with a companion basic cation, lead to ‘permanent’ acidification.

Processes of soil acidification during nitrogen cycling with emphasis on legume based pastures

Losses and transformation of nitrogen during composting of poultry manure with different amendments: An incubation experiment

Fluoride (F) is an essential element for animal growth, not readily taken up by plants from soils, yet cases of acute fluorosis in grazing animals caused by ingestion of phosphatic fertilisers, volcanic ash, and industrial wastes remind us of its potential hazard. Fluoride concentrations in topsoils slowly increase where annual inputs through atmospheric pollution and phosphatic fertilisers exceed losses. This paper reviews information on the fate of F in grazed pasture systems with the aim of assessing the potential toxicity of accumulating soil F. A preliminary F‐cycling model for grazed pastures, based on the review of international literature and F concentrations in selected New Zealand pasture soils, indicated that grazing sheep and cattle obtain over 50% of their dietary F (and this may be >80% during winter) from soil ingestion. The model suggests that at the extremes of the ranges of the measured winter soil ingestion (143–300 g d‐1 for sheep and 900–1600 g d‐1 for cattle) and dietary F a...

https://www.tandfonline.com/doi/pdf/10.1080/00288233.2000.9513430

Fluoride: A review of its fate, bioavailability, and risks of fluorosis in grazed‐pasture systems in New Zealand

Environmental hazards of fluoride in volcanic ash: a case study from Ruapehu volcano, New Zealand

A simplified procedure for determining the amount of phosphate (P) extracted from soils by ion exchange resin membranes is reported. Strips of anion (HCO3- form) and cation (Na+ form) exchange membrane were shaken with suspensions of soil in deionised water for 16–17 hours. After shaking, the strips were thoroughly rinsed in deionised water before the phosphate retained on the anion exchange resin strip was determined by shaking the strip directly with phosphate reagent. Compared to the common use of resin beads in nylon mesh bags, this resin membrane procedure is simpler, more convenient, and because an elution step is omitted, less time consuming.

M. J. Hedley

Papers

Processes of soil acidification during nitrogen cycling with emphasis on legume based pastures

Losses and transformation of nitrogen during composting of poultry manure with different amendments: An incubation experiment

Fluoride: A review of its fate, bioavailability, and risks of fluorosis in grazed‐pasture systems in New Zealand

Environmental hazards of fluoride in volcanic ash: a case study from Ruapehu volcano, New Zealand

A simplified resin membrane technique for extracting phosphorus from soils