Growth and production of ornamental sunflower irrigated with dilutions of treated domestic sewage / Crescimento e produção de girassol ornamental irrigado com diluições de efluente doméstico tratado

ABSTRACT

The water and nutritional potential of wastewater has been frequently exploited as an alternative water source for the irrigation of crops, especially in regions affected by the scarcity of water resources. Thus, this study aimed to evaluate growth and production of ornamental sunflower (Helianthus annuus L.) cv. Anão de Jardim irrigated with different dilutions of treated domestic sewage in public-supply water. The experiment was conducted in completely randomized design with five treatments and four replicates, in a greenhouse, in the Experimental Area of the Agricultural Engineering Graduate Program of the Federal University of Recôncavo of Bahia, located in the municipality of Cruz das Almas - BA, Brazil. Treatments started seven days after transplanting of the seedlings and consisted of five dilutions of treated domestic sewage (TDS) in public-supply water (PSW) (100% PSW ­ control; 25% TDS + 75% PSW; 50% TDS + 50% PSW; 75% TDS + 25% PSW and 100% TDS). In the control treatment, plants were fertilized with 100% of the mineral fertilization recommendation, whereas plants in treatments with effluent received 50% of the nitrogen (N) and potassium (K) recommendation. Biometric (plant height, stem diameter, number of leaves, shoot fresh and dry matter and leaf area) and production (capitulum internal and external diameter, capitulum fresh and dry matter, beginning of flowering and full capitulum opening) indicators evaluated at harvest demonstrated that ornamental sunflower plants irrigated with 100% TDS showed similar performance to those irrigated with PSW, which makes it possible to infer on the possibility of replacing PSW by TDS in irrigation, along with the 50% reduction in the recommendation of N and K fertilization, with no damage to the growth and production of ornamental sunflower, cv. Anão de Jardim, thus leading to the saving of good-quality water and fertilizers. KEYWORDSHelianthus annuus L.. Wastewater. Water resources. INTRODUCTION In agriculture, water is essential for crop development and production. Therefore, in areas where rainfall is scarce, it is of fundamental importance to complement irrigation. In some regions, such as the Northeast semi-arid region, where weather conditions establish a situation of scarcity of water resources due to the low rainfall levels and high evapotranspiration rates, domestic and industrial purposes are the priority in the use of water, which limits the use and expansion of irrigated agriculture. In addition to such limitation, most regions also face sanitary problems, with poor sanitation systems and sewage effluents dumped in watercourses, causing contamination of water bodies and environment. Given this environmental degradation, especially water pollution, many studies have been carried out in Brazil to establish a sustainable management for water resources. Since irrigated agriculture is one of the most water-consuming activities and water resources are becoming increasingly scarce, wastewater utilization in agriculture and studies on defining techniques for the treatment of these waters and their subsequent use have been stimulated (CUBA et al., 2015). The reuse of water in agriculture has increased significantly due to factors such as the increasing difficulty in identifying alternative sources of water for irrigation, the high cost of fertilizers and the treatment systems required before its discharge into receiving bodies, in addition to the guarantee of being used with minimum risks to public health and soil contamination. Therefore, water reuse represents a tool for the sustainability of water resources, applied mainly for non-potable Received 08/04/19 Accepted 30/12/19

RESUMO

O potencial hídrico e nutricional da água residuária vem sendo frequentemente explorado como fonte hídrica alternativa para irrigação de culturas, principalmente em regiões acometidas pela escassez de recursos hídricos. Desse modo, o objetivo deste trabalho foi avaliar o crescimento e a produção do girassol ornamental (Helianthuns annuus L.) cv. Anão de Jardim irrigado com diferentes diluições de efluente doméstico tratado em água de abastecimento. O experimento foi conduzido em delineamento experimental inteiramente casualizado com cinco tratamentos e quatro repetições, em casa de vegetação na área experimental do Programa de Pós-Graduação em Engenharia Agrícola, da Universidade Federal do Recôncavo da Bahia, localizada no munícipio de Cruz das Almas (BA). Os tratamentos foram iniciados sete dias após o transplantio das mudas e constituíram-se de cinco diluições de efluente doméstico tratado (EDT) com água de abastecimento (AA) (100% AA ­ testemunha; 25% EDT + 75% AA; 50% EDT + 50% AA; 75% EDT + 25% AA e 100% EDT). No tratamento testemunha as plantas foram adubadas com 100% da recomendação de fertilizante mineral e nos tratamentos com efluente utilizou-se 50% da recomendação de nitrogênio e de potássio. Os indicadores biométricos (altura, diâmetro do caule, número de folhas, massa fresca e seca da parte aérea, área foliar) e de produção (diâmetro interno e externo do capítulo e massa fresca e seca do capítulo, início da floração e abertura total do capítulo) avaliados na colheita mostraram que as plantas de girassol ornamental irrigadas com 100% do efluente apresentaram desempenho semelhante ao das plantas irrigadas com água de abastecimento, o que permite inferir sobre a possibilidade de substituição da água de abastecimento por efluente doméstico tratado para a irrigação juntamente com a redução de 50% da recomendação de adubação com nitrogênio e potássio sem prejuízos ao crescimento e produção das plantas de girassol ornamental cv. Anão de Jardim, resultando assim a economia de água de boa qualidade e de fertilizantes.