Chemistry of Variable Charge Soils

1997 ◽  
Keyword(s):  
Soil Pollution ◽  
Management Practices ◽  
Chemical Properties ◽  
Soil Management ◽  
Soil Productivity ◽  
Basic Difference ◽  
The Past ◽  
Variable Charge ◽  
Constant Charge ◽  
Variable Charge Soils

This book, based on research carried out at the Academia Sinica over the past 30 years, explains the basic difference between the variable charge soils of tropical and subtropical regions, and the constant charge soils of temperate regions. It will focus on the chemical properties of the variable charge soils--properties which have important bearing on soil management practices, including maximizing soil productivity and combating soil pollution.

Surface Charge

1997 ◽  
Author(s):  
X. N. Zhang ◽  
A. Z. Zhao
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Clay Minerals ◽  
Chemical Properties ◽  
Surface Charges ◽  
Variable Charge ◽  
Surface Materials ◽  
Two Factors ◽  
Constant Charge ◽  
Variable Charge Soils

The surface of soil colloids carries electric charges, and these surface charges are the basic cause for soil to possess a series of surface properties. Soil surface charges affect the chemical properties of the soil through varying the quantity of electric charge and the surface charge density. For example, adsorptions of cations and anions are caused by negative and positive surface charges of the soil, respectively. The amount of ions adsorbed is determined by the quantity of surface charge, whereas the tightness of adsorption is related to charge density. In addition, the migration of ions in soil, the formation of organo-mineral complexes,and the dispersion, flocculation, swelling, and shrinkage are all affected by surface charge properties of the soil. Therefore, surface charge properties have an important bearing on soil structure and plant nutrition. Variable charge soils are characterized by the high content of iron and aluminum oxides. The clay mineralogical composition is dominated by 1:1-type minerals, such as kaolinite. These two factors make the surface charge properties of variable charge soils distinctly different from those of constant charge soils of temperate regions which chiefly containin 2:1-type clay minerals. However, unlike the case for pure variable charge minerals, in variable charge soils there is generally the presence of a certain amount of 2:1-type clay minerals. Therefore, as a mixture of variable charge minerals and constant charge minerals, the surface charge properties of variable charge soils is more complicated. In this chapter, the origin and factors affecting surface charges of the soil as well as the relationship between these charges and soil type will be discussed. Despite the complexity in composition, a soil may be regarded as a mixed system consisting of constant charge surface materials and constant potential surface materials in different ratios (Anderson and Sposito, 1992; Gillman and Uehara, 1980). Examples of the former type such as montmorillonite and vermiculite carry permanent negative charges, while those of the latter type such as iron oxide and aluminum oxide carry variable charges. Commonly found constant charge clay minerals in soils include those layer silicates such as hydrous mica, vermiculite, montmorillonite, and chlorite.

scholarly journals Factors Affecting Adoption of Sustainable Soil Management Practices among Fluted Pumpkin Producers in Ikorodu, Lagos State

2019 ◽  
Vol 8 (4) ◽  
pp. 43
Author(s):  
Olatomide W. Olowa Omowumi A. Olowa ◽  
Akinkunmi A. Falade Ijiyokun, A.O.
Keyword(s):  
Management Practices ◽  
Family Members ◽  
Soil Management ◽  
Soil Productivity ◽  
Adoption Of Technology ◽  
Factors Affecting ◽  
Fluted Pumpkin ◽  
Vegetable Farmers ◽  
Sustainable Soil Management ◽  
Probability Of Adoption

Proper soil management is germane to sustainable vegetable production. The greatest threat to sustainable agricultural productivity is the declining soil productivity. The reason for this declining soil productivity might not be unconnected with the soil management practices by farmers. This study attempts to isolate factors that are contributing to vegetable farmers’ adoption of soil management practices. Primary data were collected from purposively selected 120 fluted pumpkin vegetable farmers, adopting pre-tested semi-structured interview schedule in Ikorodu Local Government Area. This is predicated on the facts that Ikorodu environment seems to be well adapted for fluted pumpkin production as many hectares of land are cultivated to fluted pumpkin by hundreds of small holders. Probit regression model was used to isolate factors affecting the adoption of sustainable soil management practices. Overall, the model predicted 85.76% of the sample correctly. The findings of the study revealed that number of economically active family members, farmers’ education, livestock holding, membership in farmer's group and credit availability were significantly positive while age of farmer negatively affect adoption of sustainable soil management practice. A unit increased in economically active family members, years of education and livestock standard unit would increase the probability of adoption of technology by 21.3, 5.8 and 7.6% respectively. Likewise, if farmers were made member in the groups and credit made available, the probability of adoption of technology would increase by 46.2 and 46.3% respectively. But a unit increase in the age of household head would decrease the level of adoption by 1.4% indicating old aged farmers do not adopt innovative technologies in agriculture.Keywords: Lagos, adoption, probit, sustainable soil management, vegetable, fluted pumpkin

Acidity

1997 ◽  
Author(s):  
X. L. Kong ◽  
X. N. Zhang
Keyword(s):  
Surface Charge ◽  
Soil Acidity ◽  
Solid Phase ◽  
Hydrogen Ions ◽  
Variable Charge ◽  
Aluminum Ions ◽  
Acid Reaction ◽  
The Relationship ◽  
Constant Charge ◽  
Variable Charge Soils

For variable charge soils, acidity is a property that is of equal importance as the surface charge. These two properties may affect each other, with the effect of the former on the latter more remarkable than the reverse. In the previous chapters it was shown that pH affects many other properties of the soil by affecting the surface charge. Therefore, soil acidity is more significant than surface charge in some aspects. Owing to a similar reason, the importance of acidity for variable charge soils may exceed that for constant charge soils. Soil acidity generally manifests itself in the form of hydrogen ions. Actually, these hydrogen ions are chiefly the product of the hydrolysis of aluminum ions. Therefore, when examining soil acidity it is necessary to examine the properties of aluminum ions. In the previous chapter the transformation of hydrogen ions into aluminum ions has already been mentioned. In this chapter the relationship between aluminum ions and hydrogen ions will be discussed in greater detail. Another difference between variable charge soils and constant charge soils with respect to acidity is that, not only hydrogen ions, but also hydroxyl ions can participate in chemical reactions between the solid phase and the liquid phase. In constant charge soils the quantity of hydroxyl ions is an induced variable and is determined by the quantity of hydrogen ions in the solution and the ionic product of water. In variable charge soils, on the other hand, the quantity is also determined by the chemical equilibrium of that ion species itself at the solid-solution interface. Thus, hydroxyl ions can, in turn, affect the quantity of hydrogen ions in solution. In this chapter the nature of acidity of variable charge soils will be discussed mainly from these characteristics. In the field of soil chemistry, there has been an interesting history with regard to the nature of soil acidity. Soon after the recognition of the relationship between acid reaction and hydrogen ions in chemistry, this concept of the nature of acidity was introduced into soil science, and the significance of hydrogen ions was invariably associated with it whenever soil acidity was considered.

Reactions with Hydrogen Ions

1997 ◽  
Author(s):  
F. S. Zhang ◽  
T. R. Yu
Keyword(s):  
Ionization Energy ◽  
Alkali Metals ◽  
Chemical Properties ◽  
Hydrogen Ion ◽  
Hydrogen Ions ◽  
Soil Particles ◽  
Variable Charge ◽  
Hydrated Proton ◽  
Characteristic Features ◽  
Variable Charge Soils

Hydrogen ion is one kind of cation which possesses many properties common to all cations. Hydrogen ion also has its own characteristic features which are of particular significance for variable charge soils. The interactions between hydrogen ions and the surface of soil particles is the basic cause of the variability of both positive and negative surface charges of variable charge soils. The quantity of hydrogen ions in soils determines the acidity of the soil while the acidity of variable charge soils is among the strongest in all the soils. This strong acidity of variable charge soils affects many other chemical properties of the soil. In this chapter, the basic properties of hydrogen ions will be briefly discussed. Then, the products and the kinetics of the interaction between hydrogen ions and variable charge soils will be treated. The dissociation of hydrogen ions from the surface of soil particles has already been mentioned in Chapter 2. After the dissociation of an electron, a hydrogen atom becomes a proton (H+ ion). The ionization energy of hydrogen atoms is 1310 kj mol-1, whereas those of alkali metals, Li, Na, K, and Cs, are 519, 494, 419 and 377 kj mol-1, respectively. This difference in the ionization energy between hydrogen and alkali metals indicates that protons have a particularly strong affinity for electrons. Therefore, protons are apt to form a covalent bond with other atoms by sharing a pair of electrons, or to form a hydrogen bond. Because of the absence of an electronic shell, a proton has a diameter of the order of 10-13 cm, while other ions with electronic shells generally have a diameter of the order of 10-8 cm. Because a proton is so small, it is quite accessible to its neighboring ions and molecules. Therefore, there is very little steric hindrance when protons participate in chemical reactions. The above-mentioned features of proton are the basis for its particular properties. Free proton in solution is extremely unstable because it is very active. In an aqueous solution it will react with water molecules to form a hydrated proton, H3O+.

scholarly journals Soil Fertility under Improved and Conventional Management Practices in Sanga, Kavrepalanchowk District, Nepal

2014 ◽  
Vol 9 ◽  
pp. 27-39 ◽  
Author(s):  
Ram K. Shrestha
Keyword(s):  
Soil Fertility ◽  
Management Practices ◽  
Management Practice ◽  
Chemical Properties ◽  
Soil Management ◽  
Available Phosphorus ◽  
Physico Chemical ◽  
Soil Management Practice ◽  
Upland Soils ◽  
Conventional Practice

A study was carried out to compare the fertility of soils under improved soil  management practice with that of prevailing conventional practice and to assess the farmers’ perception on the improved practice in the upland   farming system. The study was carried out in Nasikasthan Sanga of Kavrepalanchok district of Nepal. Soil samples were collected from fields under improved conventional practice. Samples were taken at 0-15 and 15-30 cm depths and were analyzed for various physico-chemical properties to  compare the fertility status of the soils under both the practices. Altogether 68 farmers were interviewed to have information on farming practices and information pertinent to improved soil management practice being adopted by them. Results from soil physico-chemical analysis showed higher fertility of soils under improved practice in terms of more favorable pH level,  contents of exchangeable bases, available phosphorus and soil organic matter compared to prevailing conventional soil management practice. Moreover, majority of the farmers believed that soil fertility and physical condition of their upland soils had improved and that the productivity of major upland  crops had also increased after the adoption of improved soil management practice. Improved practice could play an important role in the sustainable management of upland soils in the mid hills of Nepal. It is however, desirable to conduct long-term research to further ascertain the effect of the practice on soil fertility of different soil types and land uses.Nepal Agric. Res. J. Vol. 9, 2009, pp. 27-39DOI: http://dx.doi.org/10.3126/narj.v9i0.11639 

scholarly journals Spatial Variability of Physical and Chemical Properties in Northern Himalayas of Kashmir Province

2021 ◽  
pp. 193-202
Author(s):  
Ayman Javed ◽  
Shaista Nazir Bhat ◽  
Rajnish Yadav ◽  
Mushtaq Ahmad Wani
Keyword(s):  
Electrical Conductivity ◽  
Organic Carbon ◽  
Spatial Variability ◽  
Management Practices ◽  
Particle Density ◽  
Chemical Properties ◽  
Soil Management ◽  
Physical And Chemical Properties ◽  
Physical And Chemical ◽  
And Chemical Properties

Due to geological and pedological soil-forming factors, spatial variability of soil physical and chemical properties across the agricultural fields is intrinsic by its nature, however variability may arise from tillage and other soil management practices. The main aim of this survey was to investigate the spatial variability of soil physical along with chemical properties and the preparation of thematic maps across the study area. The physico-chemical properties determined were Particle size distribution, Bulk density, Particle density, total porosity, soil resistance, soil pH, Electrical conductivity (EC), Organic carbon (OC), Nitrogen(N), Phosphorus (P), Potassium(K). Soil samples were collected from 45 sites using Geographical Positioning System (GPS) under different land-use systems. The results showed normal distribution for Sand, silt, particle density, electrical conductivity, and soil pH. Organic carbon recorded the maximum coefficient of variation (82.2%) and soil particle density (5.66%) the minimum. Soil macronutrients were medium in range excluding phosphorus which was found inadequate in the watershed. Employing such analytic work, it is feasible to devise accurate soil management practices and an unerring soil sampling system for taking efficient management judgments that result in sustainable agricultural production.

scholarly journals Soil Physico-chemical Properties of Organic Grapes Farms with Different Culture Facilities and Soil Management Practices

2013 ◽  
Vol 46 (5) ◽  
pp. 399-407
Author(s):  
Sun-Kook Kim ◽  
Byeong-Sam Kim ◽  
Beom-Ryong Kang ◽  
Seung-Koo Yang ◽  
Byeong-Ho Kim ◽  
...  
Keyword(s):  
Management Practices ◽  
Chemical Properties ◽  
Soil Management ◽  
Physico Chemical
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