Germination and vigor tests are essential components of seed quality control programs adopted by seed industries. We studied different procedures to perform the controlled deterioration test to identify differences in vigor among okra seed lots. Four seed lots of Colhe Bem cultivar and five seed lots of Santa Cruz 47 cultivar were submitted to the following tests: germination, seedling emergence, controlled deterioration (seeds with moisture contents of 18, 21 and 24% at 45°C for 24 and 48 hours) and moisture content. The controlled deterioration test is efficient to evaluate the physiological potential of okra seeds, and the combination of 24% water, 45°C during 24 hours is recommended.

RESUMO Os testes de germinação e de vigor são componentes essenciais do processo de controle de qualidade das empresas produtoras de sementes, e o teste de envelhecimento acelerado

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Compaction modifies the structural arrangement and essential functions of soil pores. In this context, the objective of this study was to evaluate the impact of different compaction levels in an Argissolo Amarelo (Ultisol) on the physical-hydraulic attributes that indicate the functionality of soil pores. The experiment was conducted using 0.05 x 0.05 m soil cylinders with 4 compaction levels (CL): 61, 71, 82 and 92%, and at each CL, the pore-size distribution, intrinsic soil air permeability (Kair), pore continuity index N, soil water characteristic curve and cumulative pore-size frequency were quantified under a completely randomized design. The increase in CL did not impact the amount of micropores, but reduced the amount of macropores to values lower than the minimum required from the CL of 82%. The increase in CL caused reductions in N index, Kair and aeration porosity, but with different amplitude depending on the CL and the water tension in the soil. CL above 61% reduced the water content at the tension range between 0 and 6 kPa and, as a consequence, increased the percentage of aeration pores, besides promoting greater water retention within the range between 10 and 1500 kPa. The evaluation of the physical-hydraulic attributes of the Argissolo Amarelo (Ultisol) revealed that the increase in the compaction level altered soil structure, reduced and formed pores that were poorly continuous and less permeable to air flow and, despite the higher water retention at the higher tensions, promoted lower available moisture content.

RESUMO: O uso de substratos é um fator de extrema importância na produção de mudas de espécies florestais, sobretudo por proporcionar o seu rápido desenvolvimento. A presente pesquisa teve o objetivo de avaliar o efeito de diferentes substratos na produção de mudas de Pithecellobium dulce (Roxb.) Benth. Os tratamentos foram constituídos de subtratos obtidos de cinco misturas, nas seguintes proporções: S1 (solo + areia-2:1); S2 (solo + esterco-2:1); S3 (esterco + solo-2:1); S4 (esterco + areia-2:1) e S5 (solo). Os parâmetros analisados foram emergência, altura da parte aérea, comprimento do sistema radicular, diâmetro do coleto, número de folhas, índice de clorofila, massa seca de caule, folhas e raiz, e massa seca total. O substrato mais indicado para produção de mudas de Pithecellobium dulce foi o S4 resultante da mistura de esterco bovino com areia na proporção 2:1.

Due to their physical characteristics, cohesive soils of either low or high aeration porosity can intensify limitations on plant cultivation. With the hypothesis that moist cohesive horizons where the soil has not yet reached a hard to extremely hard consistency may present a level of aeration porosity that affects gas exchange in maize plants, the aim of this study was to understand the influence of a cohesive horizon at different levels of aeration porosity on gas exchange in maize. The experiment was conducted in Fortaleza in the state of Ceará in a screened and covered environment, in a completely randomised block design with five levels of aeration porosity (AP) (0.04, 0.06, 0.09, 0.11 and 0.13 m 3 m -3 ) and six replications, giving a total of 30 experimental units. The variables under analysis were intrinsic permeability (K air ) and gas exchange. Increases in AP afforded an increase in K air . The AP of 0.04 and 0.13 m 3 m -3 reflected in lower values for the photosynthetic rate (A) (24.54 and 25.50 μmol CO 2 m 2 s -1 respectively) and internal CO 2 concentration (140.72 and 118.66 µmol mol -1 respectively). With the increase in AP, stomatal conductance and transpiration were reduced by 18% and 13.6% respectively, while the increase in instantaneous carboxylation efficiency was 19%, and intrinsic water use efficiency, 21%. It was concluded that variations in aeration porosity in cohesive soils affected gas exchange in maize plants. The AP of 0.04 and 0.13 m 3 m -3 reduced the value of A due to non-stomatal and stomatal limitations respectively.

RESUMOA friabilidade do solo é considerada uma importante propriedade física dos solos agrícolas, uma vez que a condição friável é desejada para a germinação das sementes, crescimento das plantas e o estabelecimento das culturas. O objetivo foi estimar os valores de resistência tênsil de agregados do solo em formas naturais com o equipamento TS-Soil portátil, e estimar a friabilidade do solo associando-a à dispersão dos dados de resistência tênsil. Para isso, a coleta dos dados de resistência tênsil foi realizada em agregados coletados nos horizontes A, Bi, Bt com caráter coeso, Bt e Bw. Os agregados foram postos ao ar por 36 horas, para secagem e homogeneização do teor de água. Foram selecionados 30 agregados na forma natural, dos quais tiveram a resistência tênsil em solo seco medida no equipamento portátil TS-Soil. Os maiores valores de resistência tênsil entre os horizontes foram observados nos horizontes Bt e Bt com caráter coeso -como também, os maiores valores de desvios-padrão. Os horizontes diagnósticos de superfície e subsuperficiais foram classificados desde friáveis a muito friáveis. A estimativa da friabilidade com dados de resistência tênsil de agregados obtida com o equipamento portátil TS-Soil, resulta em resultados similares e condizentes com o descritivo morfológico obtido em campo na avaliação do pedólogo.Palavras-chave: estrutura do solo, física do solo, instrumentação na agricultura.