Dose ótima econômica de nitrogênio e folha diagnóstica para avaliação do estado nutricional do feijão-caupi

Considering that crop nutrition is essential to obtain high yields, the objective of this study was to determine the optimal economical dose of nitrogen (N) associated with maximum technical and economical yield. Additionally, to correlate cowpea cultivars with N contents and yield. The experiment was conducted under the edaphoclimatic conditions of Teresina, PI, Brazil, in Entisol (Fluvic Neosol), in the second half of 2017, in a randomized block design in a factorial scheme (2x2x5), whose factors were: (i) cowpea genotypes (BRS Imponente and BRS Itaim), (ii) form of application of N fertilization (basal + top-dressing or fully top-dressing) and (iii) N doses (zero, 10, 30, 50 and 70 kg ha-1 - urea as source). The variables measured were the total N content in the plant tissue, with a collection of leaves +1 and +3, and grain yield. When analyzing the effect of the interaction, there was significance only for the factors form of application and N doses. However, when the doses were further analyzed for each form of N fertilization, the best response model was the quadratic, whose point of maximum physical yield was verified with N doses of 34 and 44 kg ha-1 for basal + top-dressing and fully top-dressing applications, respectively. Furthermore, the most economical doses for basal + top-dressing and fully top-dressing N applications were 26.0 and 35.6 kg ha-1, respectively. For N, the leaf that best represents the nutritional status for leaf diagnosis was +3.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

Soil Chemical Quality in Integrated Production Systems with the Presence of Native and Exotic Tree Components in the Brazilian Eastern Amazon

Conservation systems involving trees enhance the sustainability of tropical soils. However, little is known on the effect of integrated systems with native and exotic trees on soil chemical quality in the eastern Amazon. We aimed to measure changes in soil chemical quality in integrated production systems in Pindaré-Mirim, Maranhão, Brazil. This study was carried out in 2017 and 2018, evaluating (i) perennial pasture; (ii) crop–livestock–forest integration-I (CLFI-I)—eucalyptus rows interspersed with maize + Urochloa brizantha intercropping; (iii) CLFI-II—babassu palm trees (Attalea speciosa Mart.) with maize + Megathyrsus maximus intercropping; and (iv) maize + M. maximus intercropping. Soil chemical attributes at depths of 0.00–0.10 m, 0.10–0.20 m, 0.20–0.30 m, and 0.30–0.50 m, forage productivity, and soil cover were evaluated. CLFI-II promoted the highest soil organic matter concentration in topsoil and highest pH, lowest Al3+ levels, and potential acidity (H+Al) at all soil depths. Soil under pasture showed the highest N, K+, Ca2+ concentrations, sum of bases, and cation exchange capacity. Changes in CLFI-II are associated with the babassu palm’s ability to modulate the surrounding environment, giving the species a competitive advantage in anthropic environments. The time of adoption is crucial for improving soil fertility in the Brazilian eastern Amazon. Sustainable production systems in the region must comply with long-term management plans