RESUMO As plantas de cenoura não se desenvolvem bem em solos muito argilosos. Por sua vez, o fino de carvão vegetal (CF) que é um resíduo composto por partículas porosas, tem potencial para ser misturado no solo visando diminuir a densidade do mesmo. Entretanto, não existe evidência de que a aplicação de CF melhora a produção de cenoura em solo argiloso. Assim, foi idealizado um experimento em vasos, composto por 16 tratamentos compostos pela combinação de 5 tamanhos de partículas de CF (1-2 mm, 2-4 mm, 4-8 mm, 8-16 mm, 16-32 mm) com 3 doses (proporções volumétricas) de CF (25%, 50% e 75%), mais um controle (somente solo), visando verificar qual a situação que promove o melhor crescimento e produção das plantas. Foi observado que a mistura de CF no solo diminui a densidade do mesmo e aumenta a retenção de água. Os resultados desta pesquisa também revelaram que a maior produção (peso fresco e seco) de cenouras foi alcançada com CF misturado no solo na proporção de 50%), usando tamanho de partículas de CF de 2-4 mm. O maior comprimento e diâmetro da cenoura foi obtido com dose de CF em torno de 45%. Substratos contendo CF retardaram o crescimento inicial das plantas até 45 DAE, mas aumentaram o desenvolvimento das plantas após 75 DAE e melhoraram o desempenho das plantas e a produção de cenoura, quando avaliados na época da colheita (90 DAE).

ABSTRACT Carrot plants do not develop well in clayey soils. In its turn, the charcoal fine (CF), which is a residue composed of porous particles, has the potential to be mixed in the soil to reduce its density. However, there is no evidence that the application of CF improves carrot production in clayey soil. Thus, an experiment in pots was designed, consisting of 16 treatments composed of the combination of 5 sizes of CF particles (1-2 mm, 2-4 mm, 4-8 mm, 8-16 mm, 16-32 mm) with 3 volumetric rates of CF (25%, 50% and 75%, plus a control (soil alone), aiming to verify which situation promotes the better plant growth and production. It was observed that mixing CF into the soil decreases substrate density and increases substrate water retention. The results of this research also revealed that the highest yield (fresh and dry weight) of carrots was achieved with CF mixed with the soil at a rate of 50%, using a CF particle size of 2-4 mm. The greatest length and diameter of carrots were obtained with a dose of CF of around 45%. CF-containing substrates delayed initial plant growth up to 45 DAE, but increased plant development after 75 DAE and improved plant performance and carrot yield measured at the harvest time (90 DAE).

ABSTRACT The cultivation of grasses in sewage sludge (SS) with aeration has the potential for stabilization of sludge organic matter in the production of organic fertilizer. Thus, the objective of this work was to evaluate the cultivation of Urochloa brizantha and Pennisetum purpureum under aerated system on the chemical and biological attributes of SS to obtain a matured organic fertilizer. The study was conducted in a randomized block design in a 2x2+2 factorial scheme with four replications. Factors consisted of cultivation of P. purpureum or U. brizantha in SS, with or without intermittent aeration. Control treatments were SS without cultivation, with or without aeration. Sewage sludge was collected in layers and the chemical and microbial attributes were evaluated. There was no significant difference between treatments for grass dry matter. The C/N ratio was not matched with organic fertilizer stabilization due to similar losses of C and N (~7%). However, microbial activity was reduced in the presence of plant cultivation demonstrating improvement in the properties of the organic fertilizer produced. Through uni- and multivariate analysis, organic fertilizer produced from SS aerated and cultivated with P. purpureum showed matured organic matter.