Produtividade de biomassa em sistemas agroflorestais e tradicionais no Cariri Paraibano

Abstract

As produtividades de biomassa de sistemas tradicionais (cultivos de milho e feijão, capim buffel ou palma) e agroflorestais (cultivos entre fileiras de gliricídia ou maniçoba) foram comparadas em experimento em parcelas subdivididas, de 2006 a 2009, em Taperoá, Paraíba. A precipitação média é de 600 mm. Nas parcelas agroflorestais as fileiras de árvores distavam 6 m, com 1 m entre árvores. No sistema tradicional, os cultivos produziram 33% mais biomassa e a biomassa de milho e feijão foi o dobro da produzida nos sistemas agroflorestais. O capim buffel foi o cultivo que mais produziu no sistema agroflorestal. No sistema tradicional os cultivos que mais produziram foram buffel e consórcio milho e feijão. A gliricídia produziu nove vezes mais biomassa de folhas, galhos finos e lenha que a maniçoba. Incluindo essas biomassas, a produtividade total nos sistemas agroflorestais foi 260% maior que nos sistemas tradicionais. Os coeficientes de variação da produtividade anual de biomassa foram menores nos sistemas agroflorestais. Portanto, a presença de árvores não só aumentou a produtividade total como conferiu maior estabilidade aos sistemas.

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

“…Another possibility would be an inhibition of fixation due to the accumulation of N by the gliricidia plants in previous years. The intercropping of gliricidia, maize, and cowpea produced the highest amounts of aboveground biomass in the previous years (Martins et al, 2013) and probably also the highest amounts of belowground biomass. The decomposition of this biomass could increase the availability of mineral N, and it has been shown that high N availability reduces N fixation (Schipanski et al, 2010).…”

“…Nitrogen concentrations in the legume plants (Table 2) were high in all systems, close to 4%, and the contents of N reflected the predominant effect of biomass production (Martins et al, 2013). Quantification of N in the straw is important, although seldom done in the region (Sampaio et al, 2004), because of its use as forage or because it is incorporated into the soil where it constitutes a net input to soil organic matter.…”

“…(2) Tips include leaves plus twigs less than 1.5 cm in stem diameter; wood consists of branches larger than 1.5 cm in diameter; and straw comprises leaves, stems, and pods (Martins et al, 2013 in the other associations. Considering the harvest index of 0.37, obtained by Freitas et al (2012) for local cowpea varieties in the Brazilian Northeast, the straw biomass (leaves, stems, and legume pods) was estimated at 61 kg ha -1 in the agroforestry system and at 698 kg ha -1 in the traditional system.…”

“…In recent years, agroforestry systems that combine rows of trees and maize and cowpea have been introduced, in which tree pruning is done shortly after sowing of the annual crops to increase fodder production, while maintaining some grain production (Pérez Marin et al, 2006. In the long run, this system could be more stable than the itinerant system, considering frequent crop failure due to low and erratic rainfall and the pressure to reduce fallow periods (Martins et al, 2013).…”

“…Martins et al (2013) evaluated the productivities of maize, cowpea, and gliricidia trees and found that the agroforestry system produced the largest amounts of biomass, indicating that it can be a viable system in the region. However, a proper management of the system requires the knowledge of the amounts of N introduced by symbiotic fixation of trees and cowpea, and this information is not available for agroforestry systems tested in the semiarid area of Northeast Brazil.…”