Nitrogen symbiotically fixed by cowpea and gliricidia in traditional and agroforestry systems under semiarid conditions

作者：Rodrigues Martins Julio Cesar; Santiago de Freitas Ana Dolores; Cezar Menezes Romulo Simoes; de Sa Barretto Sampaio Everardo Valadares

来源：Pesquisa Agropecuaria Brasileira, 2015, 50(2): 178-184.

DOI：10.1590/S0100-204X2015000200010

• Gliricidia sepium
• Vigna unguiculata
• biological nitrogen fixation
• natural abundance
• N-15

The objective of this work was to estimate the amounts of N fixed by cowpea in a traditional system and by cowpea and gliricidia in an agroforestry system in the Brazilian Northeast semiarid. The experiment was carried out in a randomized complete block design, in a split-plot arrangement, with four replicates, in the semiarid region of the state of Paraiba, 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 the agroforestry system with buffel grass and prickly-pear cactus, gliricidia plants symbiotically fix high proportions of N (>50%) 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.

• 出版日期2015-2