Integrated systems (crops, livestock, and forest) are tools to avoid increases in greenhouse gas (GHG) emissions, such as CO2, CH4, and N2O. The objective of this study was to evaluate the GHG emissions and soil biological and chemical characteristics in an integrated system. The experiment was carried out in an area with crop-livestock-forest integration systems (CLFI), in Pindaré-Mirim, state of Maranhão, Brazil. The treatments consisted of maize (Zea mays) intercropped with forage (Urochloa brizantha cv. Marandú) between eucalyptus trees (Eucalyptus urophylla × Eucalyptus tereticornis) (S1); maize intercropped with forage (Megathyrsus maximus cv. Massai) (S2); and degraded pasture areas with no soil or forage management for more than 14 years (S3), which was used as reference treatment. The experiment was conducted with four replications of four trenches for soil collection or four static chambers for gas flow assessments. The GHG emissions were collected by static chambers and analyzed by gas chromatography, and the soil quality was determined by chemical analysis. The interaction between GHG emissions and soil characteristics was assessed for each treatment, using multivariate analysis and PCA. The soil of the degraded pasture presented higher GHG emissions. The integrated systems presented negative methane fluxes, which denote their mitigating effect on GHG emissions. The CLFI system with eucalyptus and maize intercropped with U. brizantha cv. Marandú was the best option to improve the soil biological characteristics and mitigate GHG emissions. Crop-livestock-forest integration with Eucalyptus, maize, and U. brizantha cv. Marandú is indicated to improve soil biological characteristics and mitigate GHG emissions in the Amazonian region of the state of Maranhão, Brazil.
Considerando que a nutrição da cultura é preponderante para obtenção de elevadas produtividades, objetivou-se determinar a dose ótima econômica de N associada à máxima produtividade técnica e econômica. Adicionalmente, realizar correlações entre cultivares de feijão-caupi com os teores de N e a produtividade. O experimento foi conduzido nas condições edafoclimáticas de Teresina, PI, em um Neossolo Flúvico, no segundo semestre de 2017, em delineamento em blocos casualizados em esquema fatorial (2x2x5), cujos fatores foram: (i) genótipos de feijão-caupi (BRS Imponente e BRS Itaim), (ii) época de aplicação da adubação nitrogenada (fundação+cobertura ou totalmente em cobertura) e (iii) doses de N (zero, 10, 30, 50 e 70 kg ha-1 – fonte ureia). As variáveis mensuradas foram a análise do N total do tecido vegetal com a coleta da folha +1 e +3, além da produtividade de grãos. Quando analisamos o efeito da interação houve significância somente para os fatores época de aplicação e doses de N, e quando desdobramos as doses para cada época de adubação nitrogenada o melhor modelo de resposta foi o quadrático, cujo ponto de máxima produtividade física foram verificados com as doses de 34 e 44 kg ha-1 de N para a aplicação na fundação+cobertura e totalmente em cobertura, respectivamente. Ainda, a doses mais econômica para a aplicação de N em fundação+cobertura e totalmente em cobertura foram de 26,0 e 35,6 kg ha-1, respectivamente. Para o N a folha que melhor representa o estado nutricional para a diagnose foliar mostrou-se ser a +3.
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