EFFECT OF SHADING AND SUBSTRATE ON THE GERMINATION AND SEEDLING GROWTH OF Acacia mangium AND Acacia mearnsii

Abstract

A germina\ue7\ue3o r\ue1pida e uniforme das sementes, seguida por pronta emerg\ueancia das pl\ue2ntulas, s\ue3o caracter\uedsticas altamente desej\ue1veis na forma\ue7\ue3o de mudas. Estudos com a finalidade de viabilizar a utiliza\ue7\ue3o de res\uedduos org\ue2nicos como o lodo de esgoto e a casca de pinus na cadeia produtiva representam uma demanda atual. O objetivo deste trabalho foi identificar condi\ue7\uf5es de sombreamento e substrato favor\ue1veis ao processo de germina\ue7\ue3o das sementes e crescimento de pl\ue2ntulas de Acacia mangium e Acacia mearnsii . Ap\uf3s a supera\ue7\ue3o da dorm\ueancia, por imers\ue3o em \ue1gua quente, as sementes foram semeadas em tr\ueas tipos de substratos: substrato comercial Plantmax florestal (testemunha), casca de pinus e mistura de casca de pinus com bioss\uf3lido (1:1). Os tubetes foram colocados em viveiro, sob duas condi\ue7\uf5es de sombreamento: 50% e 30%, e a pleno sol (0%), como testemunha. Os par\ue2metros avaliados foram: velocidade e porcentagem de germina\ue7\ue3o (diariamente, at\ue9 30 dias) e comprimento da parte a\ue9rea de pl\ue2ntulas (semanalmente, de 75 a 150 dias). O delineamento experimental utilizado foi o inteiramente casualizado com os tratamentos dispostos em um fatorial 3 x 3, os resultados foram submetidos \ue0 an\ue1lise de regress\ue3o e teste T. Maiores porcentagens de germina\ue7\ue3o foram obtidas na semeadura de Acacia mangium em casca de pinus sob 30% de sombreamento, e substrato comercial sob 30 e 50% de sombreamento e para Acacia mearnsii em casca de pinus sob 50% de sombreamento, ou substrato comercial a pleno sol. Para ambas as esp\ue9cies, as pl\ue2ntulas cresceram mais rapidamente e atingiram maior tamanho final no substrato casca de pinus com bioss\uf3lido e em qualquer condi\ue7\ue3o de sombreamento (30 e 50 %) e a pleno sol, antecipando a produ\ue7\ue3o de mudas.The speed and uniform germination of seeds, followed by the prompt seedling emergence, are highly desirable characteristics in seedling production. Studies aiming to enable the use of organic waste such as sewage sludge and pine bark in the supply chain represent a current demand. The aim of this study was to identify conditions of shading and substrate which are more favorable to the process of seed germination and seedling growth of Acacia mangium and Acacia mearnsii . After overcoming dormancy in hot water, the seeds were sown in three substrates: substrate plantmax commercial forest (control), pine bark and pine bark mixed with biosolids (1:1). The tubes were placed in a tree nursery under three shading conditions: 50%, 30% and 0% (full sun). The evaluated parameters were: speed and germination percentage (daily until 30 days) and shoot length of seedlings (weekly from 75 to 150 days). The experiment was a completely randomized design with treatments in a factorial 3 x 3 and the results were submitted to regression analysis. The highest germination was obtained in the sowing of Acacia mangium in pine bark at 30% shading and commercial substrate at 30 and 50% shading for Acacia mearnsii in pine bark under 50% shading or commercial substrate in full sun. For both species, seedlings grew faster and reached larger size in the final substrate of pine bark with biosolids and in any condition of shading (30 e 50 %) and full sun, anticipating the production of seedlings