Residual action soil, requirements

In broad summary, a reasonable measure of residual effect for uptake by plant roots or control of soil-borne organisms requires moderate adsorption (which expresses the partition between solid and liquid phases) and a small fraction in the air-phase to allow some movement in dry soil conditions and some degree of vapour action. This last property is particularly important in ensuring a robustness of performance under varying climatic conditions which may... 

Toxic Residues Contamination by toxic residues is another possible legacy of practices which are no longer acceptable. Removal and treatment of contaminated soil can seriously retard the construction schedule. It can be expected that environmental authorities will be involved, who will require a complete plan of action prior to excavation of the material and will monitor die site amelioration activity. The length of the delay will depend on the extent to which the owner and authorities are prqiared to deal with the situation and act quickly. 

I hope that it is now clearly evident that the use of laboratory and field bioassays of residues, extracts, or individual compounds without the appropriate range of physicochemical and biotic elements (e.g., concentrations, solute potentials, pH values, nutrition, temperature, etc.) and adequate/realistic controls are no longer acceptable when attempting to identify/characterize the existence of plant-plant allelopathic interactions in nature. In spite of the difficulties a much more holistic approach is now required both in the laboratory and in the field. We need a renewed effort to develop tools and procedures that isolate and then reintegrate the actions of physicochemical and biotic elements of soil solutions, rhizospheres, and rhizoplanes that regulate/modulate allelopathic plant-plant interactions. 

One hectare of land requires up to 150 kg of mulch film. Powder residues and buried fragments represent 0.003% (without taking account of dispersal due to mechanical action). Buried strips which have not decomposed under the effect of light amount to 7% of 0.003% (0.0002% or 2 ppm). These strips (buried and not decomposed) come to the surface the first time the soil is turned over and are destroyed by the same mechanism as the exposed film. After a year the powder particles break down into H2O and CO2. Photoinitiators used in these films contain iron and nickel and are probably iron and nickel dithiocarbamates (cf. section 5.9). 

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