Written Paper

Conséquences de l'apport de verre pilé à la surface du champ et de son incorporation dans la couche travaillée  [2001]

de Louvigny , Nathalie (INRA , Avignon (France). UR 0403 Unité de science du sol)

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Eco-Emballages and BSN-Glasspack have envisaged the possibility to incorporate into the soil the unrecycled part of the glass collects. This incorporation can influence the physical, chemical and biological characteristics of the soil. We have carried out experiments to evaluate the effects of glass wastes and we used models to generalise our results.Concerning changes in the chemical characteristics of the soil layers, the experiments in aerobic and anaerobic conditions showed that only the reducing conditions induced by organic matter easily fermentescible brought the solute of Pb and Mn.On a clay-silty soil, a 3 cm thick mulch and a mixture of soil with 40% glass, decreased the evaporation and increased the temperature of soil profile. The effects of glass in mixtures with 10 to 80% were measured on transfer properties. Relations were made in order to describe these properties. They were the sum of the property of soil and the property due to the mixture porosity. The simulations were made with a mechanistic model of heat and mass flows. They well reproduced the in situ observations, and allowed to estimate the mulch effect according to its thickness, the type of soil and the climate.We have also studied the consequences of glass waste deposition on soil on sugarbeet emergence in laboratory experiments and used a model simulating emergence. We examined the effects glass fragments used as a 2 cm thick mulch, or incorporated into a glass-soil mixture, or
into clods. The glass used as mulch or in the glass-soil mixture did not reduce the percentage emergence. Glass incorporated into clods reduced emergence of seedlings because of the increase in clod roughness. But the simulations indicated that the emergence rate is hardly changed in a seedbed with such clods. Emergence is faster because of the increase in soil temperature.Our work shows that experiments in controlled conditions and the use of models were an efficient way to specify the range of changes induced by glass waste, and to determine the conditions avoiding unfavorable effects.