Potassium in Intensive Cropping Systems on Highly Weathered Soils

2015 ◽  
pp. 1155-1175 ◽  
Author(s):  
L. Vilela ◽  
K.D. Ritchey
Keyword(s):  
Cropping Systems ◽  
Weathered Soils ◽  
Intensive Cropping ◽  
Highly Weathered Soils

scholarly journals Electrochemical attributes and availability of nutrients, toxic elements, and heavy metals in tropical soils

2006 ◽  
Vol 63 (6) ◽  
pp. 589-608 ◽  
Author(s):  
Mauricio Paulo Ferreira Fontes ◽  
Luís Reynaldo Ferracciú Alleoni
Keyword(s):  
Heavy Metals ◽  
Electrochemical Properties ◽  
Toxic Elements ◽  
Chemical Speciation ◽  
Surface Complexation ◽  
Tropical Soils ◽  
Metal Availability ◽  
Ionic Exchange ◽  
Weathered Soils ◽  
Highly Weathered Soils

Electrochemical properties of soils are very important for the understanding of the physico-chemical phenomena which affect soil fertility and the availability of nutrients for plants. This review highlights the electrochemical properties of tropical soils, the behavior and the availability of nutrients, toxic elements and heavy metals in the soil, especially for soils with predominant variable charge minerals. Availability of the elements is related to ionic exchange, solution speciation, and electrostatic and specific adsorptive soil properties. Empirical and surface complexation models are briefly described, and some results of their application in tropical soils are presented. A better understanding of the role of the double diffuse layer of charges and CEC on nutrient cation availability for highly weathered soils is required, as well as a solid comprehension of surface complexation models, in order to improve the knowledge regarding the behavior of anions in soils. More studies have to be conducted to generate results that enable the use of chemical speciation concepts and calculation of several constants used in surface complexation models, especially for highly weathered soils from the humid tropics. There has to be a continuing development and use of computer softwares that have already incorporated the concepts of chemical speciation and adsorption models in the study of nutrients, toxic elements and heavy metal availability in the soil-plant system.

Soil warming effects on tropical forests with highly weathered soils

2019 ◽  
pp. 385-439 ◽  
Author(s):  
Tana E. Wood ◽  
Molly A. Cavaleri ◽  
Christian P. Giardina ◽  
Shafkat Khan ◽  
Jacqueline E. Mohan ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Soil Warming ◽  
Weathered Soils ◽  
Highly Weathered Soils

scholarly journals A carbon-sink in a sacred forest: Biologically-driven calcite formation in highly weathered soils in Northern Togo (West Africa)

CATENA ◽  
2021 ◽  
Vol 198 ◽  
pp. 105027
Author(s):  
Hafeez Ur Rehman ◽  
Rosa M. Poch ◽  
Fabio Scarciglia ◽  
Michele L. Francis
Keyword(s):  
West Africa ◽  
Carbon Sink ◽  
Sacred Forest ◽  
Weathered Soils ◽  
Highly Weathered Soils

Dissolution behaviour of soil kaolinites in acidic solutions

Clay Minerals ◽  
2013 ◽  
Vol 48 (3) ◽  
pp. 447-461 ◽  
Author(s):  
K. Khawmee ◽  
A. Suddhiprakarn ◽  
I. Kheoruenromne ◽  
I. Bibi ◽  
B. Singh
Keyword(s):  
Steady State ◽  
Dissolution Rate ◽  
Initial Period ◽  
Reference Sample ◽  
Stoichiometric Ratio ◽  
Solution Ph ◽  
Weathered Soils ◽  
Dissolution Behaviour ◽  
Georgia Kaolinite ◽  
Highly Weathered Soils

AbstractHighly weathered soils of the tropics and subtropics commonly have kaolinitedominated clay fractions. Under acidic conditions prevailing in these soils kaolinite dissolution occurs, contributing to the high levels of soluble Al in these soils. This study evaluates the dissolution behaviour of kaolinites from subsurface horizons of highly weathered soils from Thailand, along with a soil kaolinite from Western Australia (WA kaolinite) and Georgia kaolinite (KGa-2). Kaolinite-dominated clay fractions were isolated from soils by sedimentation and chemically treated to remove iron oxides. The dissolution rate of kaolinites was measured in 0.01 M NaCl as a function of pH (1–4; HCl) at 25±1°C using non-stirred flow-through reactors. Kaolinite dissolution rates were calculated from the release of Al and Si at the steady state. In most of the experiments and at all pH values, the release of both Si and Al underwent a distinct transition from an initial period of rapid release to significantly slower release at the steady state. Aluminium and Si concentrations at the steady state were higher for soil kaolinites than the reference sample (KGa-2). At the steady state the dissolution of all kaolinites was stoichiometric except for the soil kaolinites from Thailand at pH 4, where the Al/Si ratio was well below the stoichiometric ratio. Log dissolution rate (RSi) of soil kaolinites ranged from –13.75 to –12.51, with the dissolution rate increasing significantly with decreasing solution pH. However, the dissolution rate was similar or pH independent between pH 2 and 3, which is the pH range of the point of zero net charge (PZNC) for both soil and reference kaolinites. The dissolution rate of soil kaolinite was significantly higher than the KGa-2 sample at pH < 3. The results obtained on kaolinite samples from highly weathered soils show that in highly acidic systems kaolinite is a source of soluble Al. Soil kaolinites with poorly ordered small crystals dissolve faster than better crystalline reference kaolinite (KGa-2) with larger crystals.

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