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| Author(s): |
Adriel Ferreira da Fonseca
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. , tabelas. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2002-01-28 |
| Examining board members: |
Adolpho Jose Melfi;
Luis Reynaldo Ferracciu Alleoni;
Heitor Cantarella
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| Advisor: | Adolpho Jose Melfi |
| Field of knowledge: | Agronomical Sciences - Agronomy |
| Indexed in: | Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP |
| Location: | Universidade de São Paulo. Biblioteca Central da Escola Superior de Agricultura Luiz de Queiroz; t633.15; F676d; 78836 |
| Abstract | |
Normally, sewage effluents are treated in the sewage plants, and they are discharged into rivers. This practice has contributed to environmental impact because of the input of organic matter and nutrients, mainly N and P. On the other hand, several countries have been using this wastewater for crop irrigation with three purposes: complementary treatment, water and nutrients sources to the soil-plant system. Two experiments were carried out at USP/ESALQ, under controlled conditions, in Piracicaba - SP (Brazil) with samples of Red Latosol and secondary-treated sewage effluent (STSE) from Lins (SP), with the aim at evaluating the potential and the impact of this wastewater as nitrogen and water sources. In the first experiment, it was used a randomized complete design with four treatments and four replications, and eleven periods of soil samples incubation (0 to 10 weeks). The rates of effluent application were 0, 100, 150 and 200 mL of STSE (49 mg L-1 of N-total, predominantly N-NH4+) per week per kg of soil. It was similar to a surface irrigation. Seven days after the last effluent application, the samples were collected to analyze the total mineral nitrogen though extraction with KCl 2 mol L-1 and it was measured by molecular absorption spectrometry. It was observed that the mineral N concentration increased with application rate of STSE, mainly N-NO3-. About 36% of N-effluent probably were lost through denitrification or volatilization. The second experiment was carried out to observe corn plants irrigated with STSE in pots, in the greenhouse. The experimental design was randomized blocks with five replications, and five treatments. The treatments were: (i) irrigation with water plus mineral fertilization, but N; (ii) irrigation with water plus the whole fertilization; (iii) irrigation with STSE alone; (iv) irrigation with STSE plus mineral fertilization, but N; (v) irrigation with STSE plus the whole fertilization. The experimental period was 58 days after corn plant emergency. Then, the plants were harvested, and the nutrient concentrations as well as toxic elements, in soil sample and plants were analyzed. It was determined the pH and EC in each soil sample. Lins effluent was poor in heavy metals and these elements were not problematic in the soil-plant system. This effluent substituted completely the irrigation water except for the mineral fertilizer, although it affected the uptake of nutrients. It was observed smaller soil acidification of the treatments that received effluent. There were not differences between the whole fertilization plus irrigation with water or STSE, due to the same production of dry matter by corn plants. The major problem of Lins STSE was the high Na concentration, and the content this of element was greatly increased by plants and the Na accumulated in the soil samples. This high concentration of Na in the Lins effluent could be, in part, due to the fact that the water consumed by the Lins population is naturally rich in this element. (AU) | |