Estudo da água de tanques de piscicultura para uso em um sistema integrado de agricultura: um estudo químico e hormono-similar em prol do desenvolvimento agrário no interior da região nordeste

Abstract

The low natural fertility of Brazilian soils is due, in the most part, to their high acidity and nutrient levels below those needed for cropproduction. This problem is more accentuated in the interior of the Brazilian Northeast, due to its edaphoclimatic conditions, characterized by their dry climate and irregular rainfall pattern. In another context, fish farming is becoming moreprominent and growing in the region, as aquaculture demands less water than conventional livestock, with an average of 800 L of water per kg of fish produced. Even in its importance, fish farming is considered an activity that generatespotentially toxic effluents, because it has a high content of organic matter (OM) and nutrients. Taking both issues as a challenge — the problem of poor soil fertility and effluent generation by aquaculture — the implementation of an integrated agriculture-fish farming system would be an interesting alternative as it would aim at reusing water from fish farms through enhancement of OM and nutrient recycling through irrigation, promoting benefits for crop production and agrarian development. Part of these benefits is imputed to the hormone-like activity, attributed to the presence of organic molecules that make up the OM fractions. In this sense, the present work aimed to conduct a chemical study of water from fish ponds for use in irrigation of plants of economic interest, besides evaluating the hormone-like activity of OM present in the analyzed samples. Fish farming water samples (FFW) were collected from the Cooperativa dos Produtores do Vale do Itaparica (COOPVALE), in the municipality of Itacuruba (PE) and their characteristics (pH, EC, turbidity, nutrients and TOC) were determined. To evaluate hormone-like activity, bioassays were performed with cucumber (Cucumis sativus) seeds, with different carbon concentrations, present in the FFW. According to the results obtained in the characterization of pisciculture water, it is considered that its chemical characteristics allow the use in irrigation ofplants of economic interest. In the bioassays it waspossible to observe the biostimulant action of FFW at concentrations from 5.0 mg C L-1. Furthermore, it is considered that the higher the carbon concentration in the FFW sample, the greater the biological response, as observed in the increase of C. sativus root growth index. Thus, it is concluded that it is possible to recycle and reuse the OM and nutrients of fish water in cropproduction,in favor of agrarian development within the NE Region, in an integrated system, agriculture-fish farming, in an organic farming system. agroecological, mimicking a cultivation in a family nucleus system, in the interior of the Northeast, in the Pernambuco hinterland.