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

Abstract

-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 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 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.Index terms: Gliricidia sepium, Vigna unguiculata, biological nitrogen fixation, natural abundance, 15 N. Nitrogênio fixado simbioticamente por feijão-caupi e gliricídia em sistemas tradicional e agroflorestal sob condições semiáridasResumo -O objetivo deste trabalho foi estimar as quantidades de N fixadas em feijão-caupi em sistema tradicional e em feijão-caupi e gliricídia em sistema agroflorestal, sob condições semiáridas do Nordeste brasileiro. O experimento foi conduzido em blocos ao acaso, em arranjo em parcelas subdivididas, com quatro repetições, no semiárido da Paraíba. As parcelas consistiram dos sistemas agroflorestal e tradicional (sem árvores), e as subparcelas, dos três cultivos entre as linhas das árvores, no sistema agroflorestal. Para estimar a fixação de N, amostras das plantas foram coletadas no quarto ciclo de crescimento das espécies perenes e no quarto ciclo de cultivo das espécies anuais. No sistema agroflorestal com capim-buffel e palma forrageira, a gliricídia fixa simbioticamente altas proporções de N (>50%) e adiciona quantidades maiores de N (40 kg ha -1 nas folhas) que no sistema tradicional (11 kg ha -1 nos grãos e 18 kg ha -1 na palhada). No sistema agroflorestal com milho e feijão-caupi, a gliricídia não fixa N e a adição de N é limitada à fixação no feijão-caupi (2,7 kg ha -1 ), que é menor que no sistema tradicional em razão da sua baixa produção de biomassa.Termos para indexação: Gliricidia sepium, Vigna unguiculata, fixação biológica do nitrogênio, abundância natural, 15 N.

The damage caused by Callosobruchus maculatus on cowpea grains is dependent on the plant genotype

“…Inoculation of cowpea seeds with commercial inoculants helps to establish plants in the field and can increase grain yield . Recent studies performed in the north‐east region of Brazil, inoculation of cowpeas with efficient nitrogen‐fixing rhizobia strains resulted in yields similar to those observed with nitrogen fertilization, indicating that the use of inoculants is an alternative nitrogen source for cowpea producers of this region …”

Symbiotic efficiency of native rhizobia in legume tree Leucaena leucocephala derived from several soil classes of Brazilian Northeast region

“…In general, in semiarid regions such as those found in the Brazilian Northeast, the soils have low available N. Usually, these agricultural systems do not use mineral fertilizers and predominated N-dependent crops are produced from the mineralization of organic matter and the BNF process (Freitas et al, 2010, Martins et al, 2015. Naturally, after successive agricultural cropping, the soil may become depleted, degraded, and finally abandoned for regenerations of the natural vegetation.…”

“…However, a viable and sustainable alternative for agricultural systems and rehabilitation of degraded areas of the semiarid region is the planting of legumes with the ability to associate symbiotically with nitrogen-fixing bacteria (Yuan et al, 2016). These legumes can be used in the agroforestry systems, mainly in the soils with low nitrogen content, to produce high quality forage for animal feed, wood and firewood, live fences, shade trees for planting crops and green manure (Freitas et al, 2011;Estringana et al, 2013;Martins et al, 2015).…”

Leguminous Alley Cropping Improves the Production, Nutrition, and Yield of Forage Sorghum

“…The leguminous alleys recovered about 20% of N directly from the residues deposited in the soil [11][12][13][14][15][16]. BNF can also represent N inputs relevant to the soil/plant system and reduce the need for N fertilizer application, which is often expensive and most susceptible to losses [8].…”