TEORES DE NUTRIENTES EM POVOAMENTOS MONOESPEC\ucdFICOS E MISTOS DE Eucalyptus urograndis e Acacia mearnsii em SISTEMA AGROSSILVICULTURAL

The study had as objective compare the nutrients content in the different species involved in monospecific and mixed stands of Eucalyptus urograndis and Acacia mearnsii and in a consortium with Zea mays . The determination for forest species nutrients concentration, the treatments 100E (100 % eucalyptus + maize); 100A (100 % black-wattle + maize) and 50E:50A (50 % eucalyptus + 50 % black-wattle + maize), and in the maize were done in treatments 100E; 100A, 50E:50A; 75E:25A (75 % eucalyptus + 25 % black-wattle + maize) and 25E:75A (25 % eucalyptus + 75 % black-wattle + maize). The experimental design was a randomized block design with three replications. Forests species sampling was made in average tree in each plot, based on diameter at breast height (DBH), in three trees six month-old per treatment. Within all treatments and your replicates, installed one subplot with long 3.0 m by three corn-rows as wide, where the plants were harvested in stem, leaf, grain, cob and straw. With the exception of Ca, which was more concentrated in the bark fraction and Mg and B in the bark and leaves, the other nutrients in Eucalyptus urograndis, so in monoculture much in mixed stands, contained higher concentration just in leaves. The grain component has the highest concentrations of nitrogen and phosphorus, as straw and cob have the highest potassium concentration and the leaf component has the largest concentrations of other nutrients. The forest species did not influence significantly the levels of nutrients in components of aboveground biomass of maize.O estudo teve por objetivo comparar o teor de nutrientes das diferentes esp\ue9cies envolvidas em plantios monoespec\uedficos e mistos de Eucalyptus urograndis e Acacia mearnsii em cons\uf3rcio com Zea mays no munic\uedpio de Bag\ue9, RS. A determina\ue7\ue3o dos teores de nutrientes das esp\ue9cies florestais foi realizada nos tratamentos: 100E (100 % de eucalipto + milho); 100A (100 % de ac\ue1cia-negra + milho) e 50E:50A (50 % de eucalipto + 50 % de ac\ue1cia-negra + milho), e do milho nos tratamentos 100E; 100A; 50E:50A; 75E:25A (75 % de eucalipto + 25 % de ac\ue1cia-negra + milho) e 25E:75A (25 % de eucalipto + 75 % de ac\ue1cia-negra + milho). O delineamento adotado foi de blocos ao acaso com tr\ueas repeti\ue7\uf5es. A amostragem das esp\ue9cies florestais foi realizada tendo como refer\ueancia a \ue1rvore m\ue9dia de cada parcela, baseada no di\ue2metro a altura do peito (DAP), amostrando-se tr\ueas \ue1rvores por tratamento, aos seis meses de idade. No interior de todos os tratamentos e suas repeti\ue7\uf5es, alocou-se uma subparcela, com 3,0 m de comprimento por tr\ueas fileiras de milho como largura, onde se fracionou as plantas em colmo, folha, gr\ue3os, sabugo e palha. Com exce\ue7\ue3o do Ca, que est\ue1 mais concentrado na fra\ue7\ue3o casca e do Mg e B na casca e folhas, os demais nutrientes no Eucalyptus urograndis, tanto em monocultivo como em plantio misto, apresentam maior teor apenas nas folhas. J\ue1 na Acacia mearnsii, todos os teores de nutrientes s\ue3o superiores nas folhas. O componente gr\ue3o do milho possui os maiores teores de nitrog\ueanio e f\uf3sforo, j\ue1 a palha e o sabugo registram as maiores teores de pot\ue1ssio e o componente folha possui os maiores teores dos demais nutrientes. As esp\ue9cies florestais n\ue3o influenciam nitidamente nos teores de nutrientes nos componentes da biomassa a\ue9rea do milho