Tipos de recipientes, substratos e doses de fertilizante de liberação controlada na produção de mudas açaí-solteiro (Euterpe precatoria Mart.)

Abstract

Açai is a superfood derived from Amazonian sociobiodiversity that has been gaining prominence on a large scale in various sectors of both national and international markets. Two Amazonian species are exploited for acai production: Euterpe oleracea (more than 90% of production) and E. precatoria (less than 10% of production), with the latter having a smaller share in overall production but significant importance for the state of Amazonas, as most of the state's acai production comes from this species. Despite the economic and social importance of E. precatoria and its potential contribution to the acai production chain, few investments have been made to develop technologies for cultivating this species. Among the necessary technologies are recommendations that enable the production of high-quality seedlings. The aim of this study was to evaluate the effects of recipient type, substrate, and controlled-release fertilizer on the formation of E. precatoria seedlings. Three experiments were conducted, each in a different type of recipient: black polyethylene bags with dimensions of 15 cm x 28 cm (BB) and 20 cm x 30 cm (SB), and 900 cm³ tubes (TB). The experiments followed a completely randomized design in a factorial scheme, with two substrates (3 parts topsoil : 1 part sand (T+SAN) and 3 parts topsoil : 1 part sawdust (T+SAW)) and six fertilizer doses (0g, 3g, 6g, 9g, 12g, and 15g L-1 of substrate) of the controlled-release fertilizer Basacote® (15-08-12 12M), with six repetitions and one seedling per plot. Biometric evaluations were performed monthly, starting from the second month after transplanting the seedlings, measuring the following variables: plant height (PH), collar diameter (CD) and leaf number (LN). At 11 months of age, a destructive sampling was conducted to analyze the dry matter of the aerial part and the root system. The relative growth rate of the seedlings was calculated using bimonthly evaluations. The experimental data were subjected to individual and combined ANOVA, a mean comparison test for independent qualitative variables and regression analysis to assess the effect of fertilizer doses. The variance analyses revealed significant interactions between the three sources of variation assessed in the experiments. Considering all the evaluated variables, the greatest growth of seedlings was observed when using containers SB and BB. In the absence of fertilizer, the highest growth occurred with the substrate T+SAN, while with fertilizer application, the highest growth was observed with the substrate T+SAW. The controlled-release fertilizer dose of Basacote (15-08-12 12M) that promotes optimal growth, considering all the evaluated variables, ranged from approximately 12 to 15 g L⁻¹ of substrate, depending on the cultivation container used.