Zoneamento agroclimático e relações hídricas no crescimento de mudas de açaí (Euterpe oleracea Mart.) em sistema automático de irrigação de baixo custo

Abstract

Water is an essential resource in the production of plants due to its various functions in the plant organism. At the same time, this production factor is increasingly scarce, especially in some regions of Brazil. Açaí (Euterpe oleracea Mart.), a species whose fruits are used in the composition of juices, sweets and ice creams, is cultivated predominantly in the state of the northern region of the country. The agroclimatic zoning is an important tool to provide information, based on climatic variables, of regions more appropriate for the cultivation of a certain plant species. Defining climatically suitable areas for açai cultivation in Brazilian regions is a way of encouraging new producers to implant the crop. In this context, the present work had some objectives structured through three chapters. In Chapter 1, the objective was to perform an initial growth analysis of two açaí cultivars (BRS Pará and "Várzea") using the simplified low cost irrigation system (ASI) in an automated system based on differences between the location of the pressure switch in relation to the ceramic capsule inserted in the substrate (40 and 80 cm). The regulation height of 40 cm provided a higher frequency of irrigation for the seedlings, as well as a higher total amount of water during the 130 days of plant development. As a consequence, the electrical conductivity characteristics of the substrate, plant height and leaf area were significantly affected. The BRS Pará cultivar showed higher initial growth than the Várzea cultivar for plant height and stem diameter up to 83 days of cultivation. After this period, the cultivars developed in a similar way. In Chapter 2, the objective was to use chopped and non-composted plant species (Arachis pintoi, Crotalaria breviflora, Panicum maximum) in an automatic irrigation system as an alternative in the substrate composition for the production of açaí seedlings. The proposed methodology of using only non-composted plant material as a substrate for the cultivation of açaí seedlings did not provide adequate conditions for the development of seedlings. Problems such as high initial electrical conductivity and physical characteristics of plant substrates were detected during the experiment, causing plant mortality and compromising the achievement of consistent data for statistical analysis. In chapter 3, the objective was to carry out an agroclimatic zoning for the açaí crop in the state of Rio de Janeiro, aiming to promote the production of this species in this state. Using geographic information systems (GIS) tools and through information on temperature, rainfall and water deficit, it was possible to determine the climatically suitable areas for açaí cultivation in the state of Rio de Janeiro. The state presents thermal and pluviometric limitations for the development of açaizeiro in 67.5% of its territory. In 29.3% of the state the crop could be viable provided that the water demand of the plant was attended by water supply in an adequate irrigation system. The regions of the state with the largest climatically suitable areas for the cultivation of açaí were the Baixadas Litorâneas and Metropolitana.