RESUMO -Planting trees is an important way to promote the recovery of degraded areas in the Caatinga region. Experiments (E1, E2, and E3) were conducted in a randomized blocks design, with three, three, and five replicates, respectively. The objectives were to evaluate biomass of the shoots of: a) gliricidia (G) and sabiá (S), as a response to planting density; b) G, S, and neem (N) in competition; c) G, and S in agroforestry. E1 was conducted in split-plots, and planting densities (400, 600, 800, 1000, and 1200 plants ha -1 ) as subplots. E2 consisted of a factorial comprising the following plots: GGG, NGN, SGS, NNN, GNG, SNS, SSS, GSG, NSN (each letter represents a row of plants). E3 was conducted with G and S in agroforestry experiment. The trees were harvested after 54, 42, and 27 months old, in E1, E2 and E3, respectively. In E1, G presented higher green biomass of the stems and leaf at smaller densities than S, but lower green biomass of branches at most densities. The species did not differ for mean stem dry biomass and leaf dry biomass, but G showed higher branch dry biomass at most densities. Higher planting densities increased green and dry biomass of stems, branches, and leaves in S, but decreased those characteristics in G, with the exception of leaf dry mass, which was not influenced by density. In E2, the behavior of each species was identical in plots containing the same or different species. Griricidia showed the highest green biomass of stems and branches, and the highest values for geren biomass of the leaf were observed for gliricidia and neem. The highest stem, branch, and leaf dry biomass values were obtained for G, S, and N, respectively. In E3, G was superior for stem and leaf green biomass, and for stem and branch dry biomass. There were no differences between species for the other biomass values. Palavras-chave: Azadirachta indica; Gliricidia sepium; Mimosa caesalpiniifolia. BIOMASSAS DE ESPÉCIES ARBÓREAS EM RESPOSTA A DENSIDADES DE PLANTIO E À COMPETIÇÃO INTERESPECÍFICA ABSTRACT -Existe interesse na recuperação de áreas degradadas da Caatinga com o plantio de árvores. Experimentos (E1, E2 e E3) foram realizados, em blocos ao acaso com três, três e cinco repetições, respectivamente, para avaliar as biomassas da parte aérea: a) da gliricidia (G) e sabiá (S), em resposta à densidade de plantio; b) da G, S e nim (N) em competição; e c) da G e S em experimento agroflorestal. E1 foi realizado com

Cowpea varieties that are more competitive against weeds are, by themselves, not enough to control the weeds. However, the adoption of more-competitive varieties, together with other cropping practices, including planting density and weeding, can provide greater weed control in addition to affording the farmer more time to carry out this control. This study had the following objectives: a) to identify, in a preliminary evaluation (E-1), varieties that are the most competitive against weeds, based on dry grain yield; b) among the most-competitive varieties, identify the most productive in terms of green and dry grain yield (E-2). The seeds used for E-1 were obtained from producers chosen at random from each of 48 districts in the State of Rio Grande do Norte. A randomized block design with five replications was used. In E-2, the twelve varieties presenting the highest grain yield in E-1 were evaluated in a randomized block design with five replications. In both evaluations, only one weeding was carried out, 30 days after sowing. In E-1, the Umarizal, Itaú, Upanema, Lagoa de Pedras, José da Penha and São Tomé varieties were superior. The second experiment demonstrated that Umarizal is the most productive variety in terms of pod yield and green grain. There is no difference between the varieties for dry grain yield. The Umarizal variety has potential for use in the production of green pods and grains, and of dry grains. The preliminary evaluation is effective in identifying superior varieties.

-In agroforestry systems, annual plants closest to trees may behave differently from plants in rows that are more distant. This study evaluated the proximity effects of Mimosa caesalpiniifolia (sabiá) and Gliricidia sepium (gliricidia) on corn yield under the taungya and alley cropping systems. The two species were evaluated, in randomised blocks with five replications, in 2010 and 2011, under taungya and alley cropping, respectively. Three rows of corn (left, middle, and right) were grown between two rows of trees. Sabiá trees grew higher than gliricidia trees. The difference in crown diameter between species depended on plant age. There was a linear relationship between plant age and plant height and between plant age and crown diameter for both sabiá and gliricidia trees. In the taungya system, left rows produced more green ears than middle and right rows, but grain yield was higher in middle rows. In the alley system, green ear yield was also higher in left rows than in middle and right rows, but grain yield was unaffected by row position. In both agroforestry systems, there were no differences in corn yield for corn grown between sabiá or gliricidia trees.Keywords: Mimosa caesalpiniifolia. Gliricidia sepium. Zea mays. Taungya. Alleys. EFEITOS DE PROXIMIDADE MILHO -ESPÉCIES ARBÓREAS EM EXPERIMENTOS AGROFLORESTAISRESUMO -Nos sistemas agroflorestais as plantas anuais mais próximas às árvores podem apresentar comportamento diferente das plantas das fileiras mais distantes. O objetivo do trabalho foi avaliar os efeitos de proximidade das leguminosas Mimosa caesalpiniifolia (sabiá, S) e Gliricidia sepium (gliricídia, G) sobre os rendimentos do milho nos sistemas taungya e aléias. Em 2010 e 2011, as espécies foram avaliadas em blocos ao acaso com cinco repetições nos sistemas taungya e aleias, respectivamente. Três fileiras de milho (esquerda, central e direita) foram cultivadas entre cada duas fileiras de árvores. A sabiá foi superior à gliricídia quanto à altura de planta (AP). A sabiá foi superior à gliricídia, quanto ao diâmetro da copa (DC) nas últimas cinco avaliações, exceto na avaliação feita aos 240 dias após o plantio, em que as espécies não diferiram. As espécies não diferiram quanto ao DC nas demais avaliações. A resposta das duas espécies à idade da planta, em termos de AP e DC, foi linear. No sistema taungya, a fileira esquerda produziu mais massa de espigas verdes do que as outras fileiras, mas o rendimento de grãos foi maior na fileira central. Em aléias, a fileira esquerda apresentou maior rendimento de espigas verdes do que as outras fileiras, mas o rendimento de grãos não foi influenciado pela posição da fileira. Nos dois sistemas não existiram diferenças entre espécies quanto aos rendimentos de espigas verdes e de grãos do milho.Palavras-chave: Mimosa caesalpiniifolia. Gliricidia sepium. Zea mays. Taungya. Aléias.

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