Soil interactions

Plant survival and crop productivity are strictly dependent on the capability of plants to adapt to different environments. This adaptation is the result of the interaction among roots and biotic and abiotic components of soil. Processes at the basis of the root-soil interaction concern a very limited area surrounding the root tissue. In this particular environment, exchanges of energy, nutrients, and molecular signals take place, rendering the chemistry, biochemistry, and biology of this environment different from the bulk soil. 

Most research on the rhizospherc environment has been forcedly descriptive in the past. Recent advances show that organic compounds present in the rhizo-sphere can have a specific role in plant-micro-organism-soil interactions. Moreover, it starts to be elucidated ... 

Further progress may derive from a more accurate definition of the chemical and physical properties of the humic substances present at the rhizosphere and how they interact with the root-cell apoplast and the plasma membrane. An interaction with the plasma membrane H -ATPase has already been observed however this master enzyme may not be the sole molecular target of humic compounds. Both lipids and proteins (e.g., carriers) could be involved in the regulation of ion uptake. It therefore seems necessary to investigate the action of humic compounds with molecular approaches in order to understand the regulatory aspects of the process and therefore estimate the importance of these molecules as modulators of the root-soil interaction. 

Van Genuchten, M.T., G.F. Pinder and W.P. Saukin (1977). Modeling of leachate and soil interactions in an aquifer. Proceedings of the Third Annual Municipal Solid Waste Research Symposium on Management of Gas and Leachate in Landfills. EPA-600/9-77-026. pp. 95-103. 

Gong WQ, Li LQ, Pan GX (2006) Cd uptake and accumulation in grains by hybrid rice in two paddy soils interactive effect of soil type and cultivars. Huan Jing Ke Xue 8 1647-1653... 

In addition to SOM, clay minerals are another important component that may influence contaminant-soil interactions. Expandable 2 1 type clays are usually more reactive than other clay minerals. Park et al. (2003) used a K-saturated montmorillonite as a sorbent to evaluate the availability of sorbed atrazine to three atrazine-degrading bacteria. K-saturated montmorillonite has a high atrazine sorption capacity with a Freundlich sorption... 

Moreale, A. and Van Bladel, R. Soil interactions of herbicide-derived aniline residues a thermodynamic approach. Soil Sci., 127(l) l-9, 1979. 

Apitz S, Borbridge L, Bracchi K, et al. 1992. Fluorescent response of fuels in soils Insights into fuel-soil interactions. Naval Command, Control and Ocean Surveillance Center, San Diego, CA Jun. 92 9. 

Alkaloids from many plants are considered to be used as biological fertilizers in ecological cultivation. This is very important especially in cases when more attention is given to these plants, which play not only a role in production but also in the cyclical maintenance of a field, garden or forest ecosystems . Plants containing alkaloids, for example lupines, have the ability to establish complexes with the soil and with the rhizosphere. The excretion of many chemicals from roots to soil occurs in this complex. Plant mediation with the soil environment is the result. The alkaloids play a major role in this plant-soil interaction system. 

The use of hairy roots for the production of biopharmaceuticals has been studied extensively and has been discussed in Chapter 1 of this book. To date, over 116 different plant species have been induced to produce hairy roots in culture (Guillon, 2006). Originally, an expression system was developed for protein production based on the natural secretion from roots of intact plants. In order to take up nutrients from the soil, interact with other soil organisms, and defend themselves against numerous pathogens, plant roots have developed sophisticated mechanisms based upon... 

Pagliai, H., Guidi, G., and Petruzzelli, G. (1979). Effect of molecular weight on dextran-soil interactions. In Modifications of Soil Structure, Emerson, W. W., Bond, A. D., and Dexter, A. R., eds., John Wiley Sons, New York, pp. 175-180. 

The mechanism and extent of adsorption are ascertained to depend on several factors, which include (a) the physical and chemical nature and properties of both HS and organic xenobiotic and (b) the conditions of the medium. Organic matter in organic amendments is relatively fresh or little humified, has composition and properties that differ substantially from native soil HS, and affects the composition and structure of native soil HS. Therefore, organic xenobiotics added to soils interact with a complex mixture of applied and native HS, which is expected to affect both quantitative and mechanistic aspects of adsorption phenomena. 

Specific management practices influence triazine runoff and leaching, including fertilizer type, tillage crop residues, and previous crop history, as well as triazine application, formulation, and placement (Baker and Mickelson, 1994). Tillage systems affect various soil properties, such as soil moisture, temperature, pH, organic matter, water flow, and microbial populations, especially at and near the soil surface. These factors can affect transformation, retention, and transport of herbicides in soil. Interactions of and compensations between these processes can influence our prediction of triazine transport in soil. Therefore, triazine movement is usually studied under one management practice at a time. 

Nonsingularity of Pesticide-Soil Interactions 136 Degradation Rates of Pesticides 139 Reaction Rates and Mechanisms of Organic Pollutants 143 Supplementary Reading 144... 

However, when data from many of the kinetics studies on pesticide-soil interactions were plotted according to the parabolic diffusion equation, initial nonlinearity resulted (Fig. 6.4). This suggested that only at longer times did the reaction process conform to PD. The rate-limiting step for this reaction is diffusion into or out of micropores. 

Another aspect of pesticide-soil interactions that is very important in predicting the effect of pesticides on environmental quality is the degradation rate. It is not the purpose of this discussion to give an in-depth discussion of pesticide degradation in soils. Numerous reviews are available on transformations, metabolic pathways, persistence, and tl/2 values of... 

Normally, because of the small size of soil particles and the presence of small capillaries and pores in the soil, the water phase is not totally independent of soil solid matter. Water present in larger spaces in soil is relatively more available to plants and readily drains away. Water held in smaller pores or between the unit layers of clay particles is held much more firmly. Water in soil interacts strongly with organic matter and clay minerals. 

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