Adsorption of Selenite in Tropical Soils as Affected by Soil Management, Ionic Strength, and Soil Properties

ABSTRACT Sorption of selenium (Se) on soils may be influenced by factors that are changed though agricultural practices usually performed for crop production, such as soil pH, competing anion and organic matter contents, among others. This study aimed to evaluate the influence of soil management and ionic strength (IS) on Se retention in Brazilian soils, which is important to predict Se availability in both systems, native and cultivated soils. For that, adsorption and desorption reactions of Se were evaluated in 16 soil samples (eight from cultivated soils and eight from native soils), using solutions containing 100 and 500 µg L-1 Se in the form of sodium selenate and in two IS, 15 and 150 mM. Se adsorption varied as a function of IS for most soils, which may indicate that the adsorption mechanism by outer-sphere complex is important for selenate retention in the studied soils, but future studies involving other techniques, such as spectroscopic studies, are needed to more clearly confirm the adsorption mechanism. In general, adsorption varied in relation to soil characteristics, and native soils adsorbed larger Se amounts than the cultivated soils. In terms of desorption, soils which had larger Se adsorbed amounts also presented larger desorbed amounts. Finally, IS and soil management influenced the availability of selenate in the studied soils.

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Effects of soil properties on the strength of weakly structured tropical soils

Soil and Tillage Research ◽

10.1016/0167-1987(93)90051-p ◽

1993 ◽

Vol 28 (1) ◽

pp. 1-13 ◽

Cited By ~ 20

Author(s):

G.J. Ley ◽

C.E. Mullins ◽

R. Lal

Keyword(s):

Soil Properties ◽

Tropical Soils

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Cropping system effects on soil quality in the Great Plains: Synthesis from a regional project

Renewable Agriculture and Food Systems ◽

10.1079/raf2005125 ◽

2006 ◽

Vol 21 (1) ◽

pp. 49-59 ◽

Cited By ~ 61

Author(s):

B.J. Wienhold ◽

J.L. Pikul ◽

M.A. Liebig ◽

M.M. Mikha ◽

G.E. Varvel ◽

...

Keyword(s):

Organic Matter ◽

Soil Properties ◽

Great Plains ◽

Management Practices ◽

Assessment Tool ◽

Soil Management ◽

Assessment Tools ◽

Soil Functions ◽

Organic C ◽

Environmental Function

AbstractSoils perform a number of essential functions affecting management goals. Soil functions were assessed by measuring physical, chemical, and biological properties in a regional assessment of conventional (CON) and alternative (ALT) management practices at eight sites within the Great Plains. The results, reported in accompanying papers, provide excellent data for assessing how management practices collectively affect agronomic and environmental soil functions that benefit both farmers and society. Our objective was to use the regional data as an input for two new assessment tools to evaluate their potential and sensitivity for detecting differences (aggradation or degradation) in management systems. The soil management assessment framework (SMAF) and the agro-ecosystem performance assessment tool (AEPAT) were used to score individual soil properties at each location relative to expected conditions based on inherent soil-forming factors and to compute index values that provide an overall assessment of the agronomic and environmental impact of the CON and ALT practices. SMAF index values were positively correlated with grain yield (an agronomic function) and total organic matter (an agronomic and environmental function). They were negatively correlated with soil nitrate concentration at harvest (an indicator of environmental function). There was general agreement between the two assessment tools when used to compare management practices. Users can measure a small number of soil properties and use one of these tools to easily assess the effectiveness of soil management practices. A higher score in either tool identifies more environmentally and agronomically sustainable management. Temporal variability in measured indicators makes dynamic assessments of management practices essential. Water-filled pore space, aggregate stability, particulate organic matter, and microbial biomass were sensitive to management and should be included in studies aimed at improving soil management. Reductions in both tillage and fallow combined with crop rotation has resulted in improved soil function (e.g., nutrient cycling, organic C content, and productivity) throughout the Great Plains.

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