Journal ArticleDOI
Amelioration of Al toxicity and P deficiency in acid soils by additions of organic residues: a critical review of the phenomenon and the mechanisms involved
Richard J. Haynes,Mokolobate +1 more
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TLDR
In this paper, an integrated overview of the probable mechanisms responsible and their implications is presented and discussed, and the practical implication of the processes discussed is that organic residues could be used as a strategic tool to reduce the rates of lime and fertilizer P required for optimum crop production on acidic, P-fixing soils.Abstract:
High rates of lime and fertilizer-P are characteristically required to obtain high crop yields on highly weathered acid soils. Much of the agriculture in the southern tropical belt, where acid soils predominate, is carried out by resource-poor, semi-subsistence farmers who are unable to purchase large quantities of lime and fertilizer. There are, however, a number of reports that additions of organic residues to acid soils can reduce Al toxicity (thus lowering the lime requirement) and improve P availability. The literature regarding these effects is sparse and disjointed and an integrated overview of the probable mechanisms responsible and their implications is presented and discussed. During decomposition of organic residues, a wide range of organic compounds are released from the residues and/or are synthesized by the decomposer microflora. The two most important groups in relation to Al toxicity and P availability are soluble humic molecules and low molecular weight aliphatic organic acids. Both these groups of substances can complex with phytotoxic monomeric Al in soil solution thus detoxifying it and they can also be adsorbed to Al and Fe oxide surfaces consequently blocking P adsorption sites. During residue decomposition, there is often a transitory increase in soil pH and this induces a decrease in exchangeable and soil solution Al through their precipitation as insoluble hydroxy-Al compounds. It also confers a greater negative charge on oxide surfaces and thus tends to decrease P adsorption. The increase in pH has been attributed to a number of causes including oxidation of organic acid anions present in decomposing residues, ammonification of residue N, specific adsorption of organic molecules produced during decomposition and reduction reactions induced by anaerobiosis. There are also mechanisms specific to either Al detoxification or improved soil P status. For example, regular applications of organic residues will induce a long-term increase in soil organic matter content. Complexation of Al by the newly-formed organic matter will tend to reduce the concentrations of exchangeable and soluble Al present. As organic residues decompose, P is released and this can become adsorbed to oxide surfaces. This will, in turn, reduce the extent of adsorption of subsequently added P thus increasing P availability. The practical implication of the processes discussed is that organic residues could be used as a strategic tool to reduce the rates of lime and fertilizer P required for optimum crop production on acidic, P-fixing soils. Further research is, therefore, warranted to investigate the use of organic residues in the management of acid soils.read more
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Journal ArticleDOI
A quantitative review of the effects of biochar application to soils on crop productivity using meta-analysis
TL;DR: In this paper, a statistical meta-analysis was performed with the aim of evaluating the relationship between biochar and crop productivity (either yield or above-ground biomass) with an overall small, but statistically significant, benefit of biochar application to soils on crop productivity, with a grand mean increase of 10%.
Book ChapterDOI
Labile Organic Matter Fractions as Central Components of the Quality of Agricultural Soils: An Overview
TL;DR: In this paper, the authors considered the sensitivity of individual organic matter fractions to changes in soil management and have specific effects on soil properties and processes, and concluded that individual organics are sensitive to changes and have a specific effect on soil function.
Journal ArticleDOI
Competitive sorption reactions between phosphorus and organic matter in soil: a review
TL;DR: In this paper, it was shown that the reported decreases in P sorption are not related to competition from the decomposition products of organic matter breakdown, but are the result of P release from the OM that was not accounted for when calculating the reduction in P-sorption.
Book ChapterDOI
Plant nutrition research: Priorities to meet human needs for food in sustainable ways
TL;DR: In this article, the authors proposed the integration of plant nutrition research with plant genetics and molecular biology is indispensable in developing plant genotypes with high genetic ability to adapt to nutrient deficient and toxic soil conditions and allocate more micronutrients into edible plant products such as cereal grains.
Journal ArticleDOI
Crop residue management and soil health: A systems analysis
TL;DR: In this paper, the authors reviewed crop residue management practices, mainly surface retention, incorporation or removal, describing their advantages and limitations in cereal-based agroecosystems in developing countries.
References
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Book ChapterDOI
An ecosystem approach to soil acidification.
TL;DR: In this paper, an approach to quantify the rate of formation of acidity due to the life processes in the ecosystem is presented, where the soil represents the reaction vessel and the chemical reactions taking place in this reaction vessel are represented by the chemical reaction vessel.
Journal ArticleDOI
Aluminum effects on the kinetics of calcium uptake into cells of the wheat root apex : Quantification of calcium fluxes using a calcium-selective vibrating microelectrode.
TL;DR: Al disruption of Ca2+ transport at the root apex may play an important role in the mechanisms of Al toxicity in Al-sensitive wheat cultivars, and that differential Al tolerance may be associated with the ability ofCa2+-transport systems in cells of theroot apex to resist disruption by potentially toxic levels of Al in the soil solution.
Journal ArticleDOI
Competitive Adsorption of Phosphate with Malate and Oxalate by Tropical Soils1
Journal ArticleDOI
Hydrolysis-precipitation studies of aluminum (III) solutions. 2. A kinetic study and model
TL;DR: In this article, a model based on the structure of the solid was proposed for the hydrolysis process of Al(OH)3 from acidified aluminum nitrate and chloride solutions with a homogeneous alkali injection technique.
Soil acidity and alkalinity.
TL;DR: The pH of the soil strongly affects the availability of nutrients to plants as mentioned in this paper, which is indicated by the pH, which is the negative logarithm of the H-ion concentration.
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