02177naa a2200253 a 450000100080000000500110000800800410001910000220006024501250008226000090020750001630021652012090037965000220158865000220161065300080163265300240164065300330166465300400169765300220173770000250175970000220178470000280180677300890183420109422017-05-25       2015    bl uuuu     u00u1 u    #d1 aMARTINS, J. C. R.  aNitrogen symbiotically fixed by cowpea and gliricidia in traditional and agroforestry systems under semiarid conditions.  c2015  aTítulo em português: Nitrogênio fixado simbioticamente por feijão?caupi e gliricídia em sistemas tradicional e agroflorestal sob condições semiáridas.  aThe objective of this work was to estimate them amounts of N fixed by cowpea in a traditional system and by cowpea and gliricidia in an agroforestry system in he Brazilian Northeast semiarid. The experiment was carried out in a randomized complete block design, in a split?plotb arrangement, with four replicates, in he semiarid egion of the state of Paraíba, Brazil. Plots consisted of agroforestry and traditional systems (no trees), and split?plots of the three crops planted between the tree rows in the agroforestry system. To estimate N fixation, plant samples were collected in the fourth growth cycle of the perennial species and in the fourth planting cycle of the annual species. In he agroforestry system with buffel grass and prickly?pear cactus, gliricidia plants symbiotically fix high proportions of N (&gt50%) and contribute with higher N amounts (40 kg ha?1 in leaves) than in the traditional system (11 kg ha ?1 in grain and 18 kg ha ?1 in straw). In the agroforestry system with maize and cowpea, gliricidia plants do not fix nitrogen, and N input is limited to the fixation by cowpea (2.7 kg ha ?1 ), which is lower than in the traditional system due to its lower biomass production.  aGliricidia sepium  aVigna Unguiculata  a15N  aAbundância natural  aBiological nitrogen fixation  aFixação biológica do nitrogênio  aNatural abundance1 aFREITAS, A. D. S. de1 aMENEZES, R. S. C.1 aSAMPAIO, E. V. de S. B.  tPesquisa Agropecuária Brasileira, Brasília, DFgv. 50, n. 2, p. 178-184. fev. 2015