Fertigation of agricultural crops using raw domestic sewage (RDS) has proven to be an excellent choice as opposed to conventional treatment. In this context, this work’spurpose was to evaluate the characteristics of the RDS to be applied in elephant grass fertirrigation as to its possible nutrients and pollutants. RDS was submitted to chemical (pH, COD, BOD5, Na, macronutrients and micronutrients) and physical (EC, TS, TFS and TVS) laboratory analyzes. Sodium was the referential chemical element for the definition of the RDS’s sheet to be applied to the ground, which was 215 mm of RDS at 26 cultivation weeks. NTK and P concentrations in RDS were 137 and 19.9 mg L-1, corresponding to the applied load of 296 and 43.9 kg ha-1 respectively, values that can be considered high. Furthermore, the mean concentrations of BOD5 and COD were 433 and 743 mg L-1 respectively, which leads to a COD/BOD5 ratio of 1,7, signaling a high biodegradability of organic matter in the RDS, indicative of good quality for agricultural purposes. Based on the applied sheet, it can be concluded that the RDS provided the availability of sufficient quantities of nutrients, ensuring good conditions for forage grass development.

Considering the significant expenses with fertilizer and irrigation, the use of wastewater in fertirrigation has been studied as an alternative, since it can supply part of the water demand and provide nutrients to the plants. The objective of this work was to evaluate the changes in soil nutrient/pollutant contents, with successive applications of Domestic Sewage. Two treatments were implanted, one of them without alternation and another with alternation in the direction of the flow. Chemical and physicochemical analyzes of soil in the superficial layer were made in samples collected after 10 and 26 weeks from the beginning of application. According to the results, there was an increase in the Total Nitrogen, Sodium content available and in the electrical conductivity values, but a decrease in Potassium, Organic Matter and pH values. Although Total Nitrogen levels increased, they remained below the limit of risk. Potassium reduction can be explained by the high mobility in the soil and the absorption of plants. However, the reduction in the content of organic matter and in the pH value is due to the effect of the nutrient supply, which favored the degradation of the native organic matter of the soil.

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A fertirrigação como alternativa de disposição final de esgoto doméstico é uma solução viável, tendo em vista o baixo custo de sua implantação, o aproveitamento dos nutrientes pelas plantas e a obtenção de melhorias na estruturação do solo. Neste trabalho, será avaliado o potencial do uso de efluente do tratamento preliminar de esgoto doméstico (EDP), a economia de água na irrigação e na adubação, considerando--se sua qualidade química para fertirrigação do capim--elefante (Pennisetum purpureum). Cada parcela experimental foi constituída por 4 linhas plantadas e 3 sulcos de aplicação de água/esgoto doméstico, sendo o espaçamento entre linhas de 0,6 m e o comprimento de 40 m. Foram impostos dois tratamentos: T1 -- aplicação de adubação química convencional e água potável, em irrigação; e T2 --aplicação, em fertirrigação, de EDP, sendo a necessidade hídrica das plantas complementada com água da rede de abastecimento. A dose de aplicação do EDP foi estabelecida considerando--se suas características químicas e as necessidades nutricionais e de água do capim--elefante. Os resultados obtidos demonstraram que o EDP utilizado na fertirrigação do capim--elefante, considerando--se uma lâmina de aplicação para fornecimento de 300 kg ha --1 ano --1 de Na, foi capaz de suprir 100% do P 2 O 5 , 33% do K 2 O e 93% do N demandado na adubação do capim--elefante, gerando uma economia financeira de US$ 445,00 ha --1 , no que se refere à adubação; de US$ 624,00 ha --1 , no que se refere ao custo de produção; e de US$ 6,00 ha --1 , no que se refere ao custo de irrigação, proporcionando uma economia total de US$ 630,00 ha --1 e uma economia hídrica de 58% do total demandado. PALAVRAS--CHAVE:Custo de produção, custo de irrigação, economia hídrica. POTENTIAL, WATER AND FERTILIZATION ECONOMY WITH APPLICATION OF PRELIMINARY TREATMENT EFFLUENT OF DOMESTIC SEWAGE IN FERTIGATION OF ELEPHANT GRASS ABSTRACTFertigation as an alternative of final disposal of domestic sewage is a viable solution, considering the low cost of its implantation, the use of nutrients by the plants and the obtaining of improvements in the soil structure. In this work, the potential of the effluent of the preliminary domestic sewage treatment (PST), the water savings in irrigation and fertilization, will be evaluated, considering its chemical quality for elephant grass (Pennisetum purpureum) fertigation. Each experimental plot consisting of 4 planted lines and 3 water/domestic sewage application grooves, between 0.6 m and 40 m long lines. Two treatments were imposed: T1 --application of conventional chemical fertilization and drinking water, in irrigation; and T2 -- application in PST fertigation, being the water requirement of the plants complemented with water from the supply network. The application rate of EDP was established considering its chemical characteristics and the nutritional and water needs of elephant grass . The results showed that the EDP used in elephant grass fertigation, considering an application sheet for to supply 300 kg ha --1 ano --1 of Na, wa...