RESUMOO reuso da água na agricultura é uma alternativa de minimização da degradação dos corpos hídricos receptores, além da possibilidade de fornecimento de água e nutrientes a produção vegetal. No entanto, a irrigação por gotejamento, sistema mais indicado ambientalmente, tem como maior vulnerabilidade a susceptibilidade ao entupimento dos emissores. Este trabalho objetivou analisar a qualidade do efluente de laticínios diluído, em relação ao risco de obstrução de emissores, bem como verificar a alteração de indicadores de desempenho hidráulico como vazão (Q) e coeficiente de variação da vazão (CVQ). O experimento foi conduzido no Laboratório de Poluição e Degradação do Solo da Universidade Federal Rural do Semi-Árido, em Mossoró-RN; a partir da montagem de uma bancada experimental com cinco subunidades gotejadoras tendo os emissores Netafim Streamline, Netafim Tiran, Netafim PCJ CNJ, NaanDanJain TalDrip e Netafim Super Typhoon; onde Q e CVQ foram determinados e avaliados a cada 40 h, até completar o tempo de funcionamento total de 200 h. Os resultados indicaram, conforme diretrizes internacionais, que os sólidos suspensos e pH foram os principais agentes ocasionadores de obstrução de gotejadores que operam com efluente de laticínios diluído. O entupimento dos gotejadores com biofilme acarretou redução de Q e aumento do CVQ, ao longo do tempo. Os menores níveis de obstrução ocorreram nas subunidades gotejadoras dotadas dos emissores Netafim Streamline e Netafim Super Typhoon.Palavras-chave: reuso da água; entupimento; variação da vazão; emissores. CLOGGING OF DRIPPERS OPERATING WITH DILUTED DAIRY WASTEWATER ABSTRACTThe reuse of water in agriculture is an alternative of minimizing the degradation of the water body, besides the possibility of supplying water and nutrients to the vegetal production.

The unregulated use and increased demand in face of the demographic and economic growth of society caused reduction in the availability of water resources in quantity and quality. In this context, this work was carried out to verify the possibility of producing ornamental sunflower (Helianthus annuus L.) fertirrigated with wastewater from fish culture and its mixtures with tap water. Two experiments were conducted in 2017 in a greenhouse at Federal Rural do University of the Semiarid, in Mossoró, RN, Brazil, according to a completely randomized design with 12 replicates. The treatments consisted of dilutions of the fish's wastewater in tap water (0, 25, 50, 75 and 100%). Determinations of plant biomass and flower characteristics were performed. The statistical analysis of the data consisted of analysis of variance by the F test and regression analysis. The biomass of ornamental sunflower showed significant effect of the fish’s effluent dilutions, but, in general, characteristics of flowers were not influenced. The higher values of the variables of the ornamental sunflower evaluated in the first experiment, which received fertilization, indicate that the effluent did not supply the nutritional needs of the plants. The irrigation of the ornamental sunflower can be carried out with effluent from fish farming when there is another source of nutrients for the crop to produce flowers with satisfactory characteristics.

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Emitter clogging is the major problem of drip irrigation systems operating with wastewater. The objective of this study was to evaluate the alteration of the flow rate variation coefficient (FVC) and to identify the biological agents that cause obstruction in drip units operating with swine effluent and public water supply. The experiment was set up in a split-plot scheme, with the times of application of swine effluent and public water supply in the main plots and dripper types in the secondary parcels, evaluating times of FVC in the tertiary parcels, using a completely randomized design (CRD) with three repetitions. The FVC of the drip subunits was calculated on every 40 hours as well as the microscopic analysis of the biological agents of clogging, until 160 h. At the end of the tests, biofilm samples were collected in each drip unit to identify the groups of predominant bacteria. The results indicated that the FVC was effective in detecting the clogging of the emitters, evidencing that the construction characteristics and the times of application of swine effluent and of the public water supply interfere in this process. Microscopic analyzes of the biofilm indicated that the main biological agents that caused obstruction were algae, bacteria, fungi and protozoa.

The study of the soil characterization and the relation of its attributes allows a systematic proposal of the local particularities, leading to adequate practices for maintenance and/or preservation of its productive capacity. In this sense, the aim of this study was to evaluate the influence of structural attributes in association with physical and chemical soil classes, using the multivariate statistical techniques to differentiate environments. The research was carried out in the Moacir Lucena Project, located in the municipality of Apodi, RN, Brazil. Three representative environments were chosen as follows: Profile 1 (P1)-Red-yellow Latosol-Area in recovery (1AR), P2-Haplic Cambisol-Lake Area, (2AL) and P3-Eutrophic Yellow Latosol-Cashew Tree Area (3AC). The soil samples were collected in the horizons of the studied areas. Ten (10) samples were collected per horizons in volumetric rings and in soil blocks (aggregate analysis), which resulted in triplicates in the laboratory. Structural, physical and chemical attributes were evaluated. The data were analyzed using multivariate statistical techniques, with correlation matrix, clustering analysis and factorial analysis performed by the extraction of the factors into principal components. The use of clustering analysis allowed the formation of four groups for soil classes and attributes; the inorganic fractions were determinant for environmental differentiation, where the sand was discriminant for the Red-yellow Latosol and the Eutrophic Yellow Latosol, and the clay and silt for the Haplic Cambisol. Higher similarity was observed in the transition horizons of the Latosols Class. The physical and structural attributes were determinant in the dissimilarity for the Haplic Cambisol, reflecting in physical restrictions to the plant growth. The factor analysis revealed that the variables particle density (Dp), Ca2+, Mg2+, sum of bases (SB) and cation exchange capacity (CEC) for factor 1, followed by pH, P, K+, total Sand, Clay and soil density (Ds) for factor 2 are important soil attributes to distinguish the studied environments.