Impermeabilização de canais de terra com substâncias químicas para fins de irrigação

Resumo

These experiments were conducted in the hyraulics laboratory of the Federal University of Vicosa and on the Fazenda Paraiso near Vigosa, Minas Gerais, in terrace-fase soil classified as «Podz6lico Vermelho Amarelo Cambico».

The objectives of this research were to first test various channel impermeabilization agents, then select, in the laboratory, the most efficient concentrations of these agents when used on dry soil and on soil previously wetted, and finally to determine the reductions in water loss by infiltration in natural earth channels treated chemically with the selected substances.

The following agents, in concentrations of 10/00, 30/00, 50/00 and 70/0o, were tested in the laboratory: sodium hydroxide (NaOH), sodium carbonate (NazCO3), and sodium («metasilicate») (Na2SiO3). For use in the field, the two concentrations of each substance judged to be the most efficient as treatment agents were selected.

In the field, NaOH and NagCO3, both in concentrations of 10/oo and 30/00, and NagSiOg, in concentrations of 30/00 and 50/00 were used.

Based on the results obtained, the following conclusions were reached:

1. From the laboratory data, it was found that NaOH in all four concentrations, NagCO3 in concentrations of 30/00 and 70/00 and NaSiOg in concentrations of 30/00 and 50/00 may be used with similar results, independent of the moisture content of the soil.

2. Between the agents NaOH and NagSiO3, Na SiO3, Na OH is recommended for use in impermeabilization.

3. In all the channels trated chemically there was a considerable reduction in water loss by infiltration, a result which permits recommendation of treatment of irrigation channels and furrows with the agents employed in this study.

4. When considering the use of any of these substances, it is permissible to select the weakest concentration; for no significant diferrences with respect to water loss by infiltration were noted between concentrations of the same chemical substance.

5. Related and more specific research projects should be initiated, with the objective of determining the period of durability of these and other chemical substances used in the impermeabilization of irrigation channels.

6. Studies should be done with the aim of establishing the toxicity to plants of the chemicals soben used to treat the channels. )

7. Future studies should take into consideration the percentage of sodium contained in the substance to be employed.