ABSTRACT The collapse of the Fundão Dam in Mariana, MG, in 2015 introduced the challenge of using Technosol, a soil type formed by deposition of iron mining waste along the Doce River banks, for agricultural purposes. This study aimed to determine the optimal water depth for enhancing production of tropical forage, Megathyrsus maximus cv. Mombasa, when grown on iron ore tailings. Additionally, it sought to establish a crop coefficient applicable to the edaphoclimatic conditions of Viçosa, MG, Brazil. The experiment was conducted throughout the summer, fall, and winter of 2022, employing 21 drainage lysimeters. A completely randomized experimental design was adopted, featuring six treatment groups (plants in Technosol receiving water depths ranging from 20 to 120% of the crop’s evapotranspiration, as derived from the control treatment), along with a control group (plants in Latosol with a depth of 100%), each with three repetitions. Our findings showed that irrigation must replace 40% of the crop evapotranspiration. Moreover, cultivating in Technosol resulted in a reduction of productive capacity by 37.39% during the summer/fall and fall seasons. For Mombasa grass grown in Oxisol, crop coefficients of 1.2 during the summer and 1.5 during the fall and winter are advised.

RESUMO O rompimento da Barragem do Fundão em Mariana, MG, ocorrida em 2015, trouxe o desafio de usar o Tecnossolo (tipo de solo) formado pela deposição do rejeito de mineração de ferro nas margens do Rio Doce para agricultura. O objetivo desta pesquisa foi obter a lâmina de água para otimizar a produção da forragem tropical Megathyrsus maximum cv. Mombaça, cultivada em rejeito de mineração de ferro e determinar seu coeficiente de cultura para as condições edafoclimáticas de Viçosa, MG. O experimento foi realizado durante as estações de verão, outono e inverno do ano de 2022, com a utilização de 21 lisímetros de drenagem. O experimento foi distribuído em delineamento inteiramente casualizado com 6 tratamentos (plantas em Tecnossolo com lâminas variando de 20 a 120% da evapotranspiração da cultura, obtida do tratamento-testemunha) e adição de uma testemunha (plantas em Latossolo com lâmina de 100%) com três repetições. Recomenda-se irrigação com reposição de 40% da evapotranspiração da cultura. O cultivo em Tecnossolo diminuiu a capacidade produtiva em 37,39% nos ciclos das estações do verão/outono e outono. Recomenda-se os coeficientes de cultura de 1,2 no verão e 1,5 no outono e no inverno, para o capim-Mombaça cultivado em um Latossolo.

ABSTRACT The collapse of the Fundão dam in Brazil caused one of the biggest environmental disasters. One of the challenges was how to manage the tailings so that affected areas could be reused. This study aimed to verify whether applying different irrigation depths to Xaraés grass grown with iron mining tailings would affect grass shoot and root dry masses. The experiment was set up in a randomized design with five irrigation depths (40%, 60%, 80%, 100%, and 120% of crop evapotranspiration) and two additional treatments (grass grown in tailings with soil conditioner, and grass grown in natural soil), each with three repetitions. The grass was cut four times, and the shoot dry mass was evaluated after each cut, while the root dry mass was evaluated at the end of the experiment. Our results showed that irrigation depths had a positive linear effect on shoot dry mass and an exponentially increasing effect on root dry mass, with the highest averages in the treatment applying 120% of crop evapotranspiration. This study showed that even in adverse conditions, Xaraés grass was able to grow and develop well.

ABSTRACT Iron mining tailings have limitations for plant growth and development due to low fertility, coupled with great restriction of physical characteristics such as low water retention, high density, and lack of structure. This study aimed to evaluate whether different irrigation depths applied to Xaraés grass grown in mining tailings influence its yield and bromatological aspects. The experiment was carried out in a completely randomized design with five irrigation depths (40, 60, 80, 100, and 120% of the crop evapotranspiration), two additional treatments consisting of grass grown in tailings with soil conditioner and in natural soil, and three repetitions. Forage dry mass, plant height, leaf: stem ratio, as well as neutral detergent fibre, acid detergent fibre, crude protein, and mineral matter content, were evaluated during four cutting cycles. Xaraés grass could establish and produce forage despite cultivation limitations in iron mining tailings, which are due to their properties. Irrigation depths showed positive and linear effects on Xaraés grass dry matter yield and heights of plants grown in iron mining tailings. The soil conditioner has potential for use in pasture cultivation in iron mining tailing.

RESUMO A produção de cebola é uma atividade agrícola cujo rendimento está associado a fatores ambientais, de mercado e ao manejo cultural. Objetivou-se com este estudo avaliar o custo de produção de cebola em função do sistema de preparo adotado e do teor de água do solo no momento de realização das operações. Foram avaliados três sistemas de preparo: P1 - uma aração + duas gradagens + duas operações de encanteiramento; P2 - duas gradagens + uma operação de encanteiramento; P3 - uma gradagem + uma operação de encanteiramento; e quatro teores iniciais de água do solo: 12, 15, 23 e 26%, em experimento conduzido no perímetro irrigado Tourão, Juazeiro, BA (9° 24’ 07.3” S; 40° 26’ 08.7” W, e altitude de 376 m), em 2017, em parcelas subdivididas, no delineamento em blocos casualizados, com quatro repetições. Foram determinados os custos referentes às operações mecanizadas, operações manuais, insumos e a irrigação da cultura. A eficiência econômica foi avaliada por meio das variáveis custo total e custo unitário de produção da cebola, receita bruta, receita líquida e taxa interna de retorno. A utilização do sistema de preparo com uma gradagem, um encanteiramento e semeadura, na condição de teor de água do solo a 23%, resultou em maior eficiência econômica.

ABSTRACT Onion production is an agricultural activity whose yield is associated with environmental, market and cultural management factors. The objective of this study was to evaluate the cost of onion production as a function of the tillage system adopted and the soil water content at the moment of the operations. Three tillage systems were evaluated: P1 - one plowing + two harrowings + two seedbed raising operations; P2 - two harrowings + one seedbed raising operation; P3 - one harrowing + one seedbed raising operation; and four soil water contents: 12, 15, 23 and 26%, in experiment conducted at the Tourão irrigated perimeter, Juazeiro, BA, Brazil (9° 24’ 07.3” S; 40° 26’ 08.7” W, and altitude of 376 m), in 2017, in split plots, in a randomized block design, with four repetitions. The costs related to mechanized operations, manual operations, inputs and crop irrigation were determined. The economic efficiency was evaluated through the variables total cost and unit cost of onion production, gross revenue, net revenue and internal rate of return. The use of the tillage system with one harrowing, one seedbed raising operation and seeding, under the condition of 23% soil water content, resulted in higher economic efficiency.

RESUMO O excesso de operações mecanizadas de preparo do solo em condições inadequadas pode elevar o custo da produção agrícola e ocasionar a degradação do solo, sem que sejam obtidas respostas adequadas da cultura. Objetivou-se com este trabalho avaliar a resposta da cultura da cebola em função de teores de água e sistemas de preparo do solo. Foram avaliados três sistemas de preparo: P1 (aração, duas gradagens e duas operações de encanteiramento); P2 (duas gradagens e uma operação de encanteiramento); P3 (uma gradagem e uma operação de encanteiramento); e quatro teores de água do solo, 12, 15, 23 e 26%. O experimento foi conduzido no perímetro irrigado Tourão, Juazeiro, BA (9° 24’ 7.3” S; 40° 26’ 8.7” W e altitude de 368 m), em 2017, sendo instalado em parcelas subdivididas, no delineamento em blocos casualizados, com quatro repetições. Nas parcelas foram dispostos os teores de água e nas subparcelas, os sistemas de preparo. A resposta da cultura aos tratamentos foi avaliada por meio da determinação do índice de velocidade de emergência das plântulas, regularidade da distribuição longitudinal das plântulas, estande final, produtividade total, comercial da cultura e produtividade por classe de diâmetro transversal dos bulbos. A variação do teor de água no solo apresentou efeito quadrático sobre as variáveis velocidade de emergência, estande final e produtividade total de cebola. Os tratamentos não afetaram significativamente a distribuição longitudinal das plântulas e a produtividade comercial. O sistema de preparo composto por uma gradagem e uma operação de encanteiramento se mostrou o mais adequado ao cultivo da cebola por semeadura direta.

ABSTRACT Excessive tillage operations under inadequate conditions can raise the cost of agricultural production and lead to soil degradation without adequate crop response. The objective of this study was to evaluate the onion crop response to soil water contents and tillage systems. Three tillage systems were evaluated: P1 (plowing + two harrowings + two seedbed raising operations), P2 (two harrowings + one seedbed raising operation), P3 (one harrowing + one seedbed raising operation); and four soil water contents: 12, 15, 23 and 26%. The experiment was conducted in the irrigated perimeter of Tourão, Juazeiro, BA, Brazil (9° 24’ 7.3” S; 40° 26’ 8.7” W and altitude of 368 m), in 2017, and was installed in split plots, in a randomized block design, with four repetitions. Water contents were arranged in the plots and tillage systems in the subplots. Crop response to the applied treatments was evaluated through the determination of the emergence speed index of the seedlings, regularity of the longitudinal distribution of seedlings, final stand, total and marketable yields of the crop and yield per bulb transverse diameter class. The variation of soil water content had a quadratic effect on the variables emergence speed index, final stand and total onion yield. The treatments did not significantly affect the longitudinal distribution of plants and marketable yield. The tillage system composed of one harrowing and one seedbed raising operation showed to be the most appropriate for onion cultivation by direct seeding.

Com o objetivo de avaliar o efeito de diferentes ambientes sobre a qualidade fisiológica e atividade enzimática de sementes de milho, dois lotes de sementes da cv. ‘BR 106’ foram armazenados em embalagem de papel em três ambientes: câmara fria (12±2°C/60±5%UR), ambiente não controlado (média de 21,6°C/71%UR) e câmara controlada (30±2°C/70±5%UR). A qualidade fisiológica (germinação e vigor) e as atividades da peroxidase, catalase e α-amilase foram avaliadas no inicio e a cada 90 dias de armazenamento. A qualidade fisiológica das sementes foi reduzida ao longo do período de armazenamento, independente dos lotes, com menores reduções nas armazenadas em temperaturas mais baixas. A atividade enzimática da peroxidase, catalase e α-amilase decrescem com o aumento do período e da temperatura de armazenamento das sementes, sendo eficiente na avaliação da qualidade fisiológica de sementes armazenadas.

With the objective of evaluating the effect of different environments on the physiological quality and enzyme activity of maize seed, two seed lots of cv. ‘BR 106’ were stored in paper packing in three environments: cold chamber (12±2°C/60±5%UR), uncontrolled (mean 21.6°C/71%UR) and controlled chamber (30±2°C/70±5%UR). The physiological quality (germination and vigor) and the activities of peroxidase, catalase, and α-amylase were evaluated at the beginning and every 90 days of storage. The seed quality was reduced throughout the storage period, regardless of the lots, with smaller reductions when stored in low temperature. The enzymatic activity of peroxidase, catalase and α-amylase decreases with increasing time and temperature of storage of seeds, being efficient in assessing the physiological quality of stored seeds.

RESUMO A couve-flor é uma brássica bastante produzida e consumida no Brasil, cujo cultivo é dependente do suprimento adequado de água e nutrientes. Portanto, objetivou-se com este estudo, avaliar o efeito da aplicação de lâminas de irrigação e doses de nitrogênio nos componentes de produção e na produtividade da água da cultura da couve-flor híbrida ‘Barcelona CMS’. Foram avaliadas as lâminas de 0, 75, 100, 125 e 150% da evapotranspiração da cultura combinadas com cinco doses de nitrogênio (0, 75, 150, 300 e 450 kg ha-1). O experimento foi conduzido em delineamento inteiramente casualizado com arranjo em parcelas subdivididas. Os efeitos da desses fatores foram avaliados pela metodologia de superfície de resposta. Observou-se que a produtividade da água pela cultura apresenta relação decrescente com a lâmina de água aplicada; portanto, a produtividade é maior quando a reposição de água é menor que o recomendado. A maior produtividade total da couve-flor estimada é de 24.547,80 kg ha-1, com diâmetro médio de 19,60 cm, altura média de 12,25 cm e massa fresca da inflorescência de 858,90 g por planta, obtida com irrigação equivalente a 132,09% da evapotranspiração da cultura e 450 kg ha-1 de nitrogênio. Para obtenção do maior diâmetro e altura de inflorescência é necessária lâminas de irrigação equivalentes a 128,70 e 108,20% da evapotranspiração da cultura, respectivamente, na dose de 450 kg ha-1 de nitrogênio. Portanto, a melhor resposta da produtividade da couve-flor híbrida ‘Barcelona CMS’ pode ser obtida com lâmina de irrigação superior à evapotranspiração da cultura, independentemente da dose de nitrogênio aplicada.

ABSTRACT Cauliflower is a brassica produced and consumed in Brazil, whose cultivation depends on the adequate supply of water and nutrients. The objective of this study was to evaluate the effect of irrigation depths and nitrogen doses on the production components and water yield of cauliflower hybrid Barcelona CMS. The treatments consisted of five irrigation water depths (0, 75, 100, 125 and 150% of the crop evapotranspiration) combined with five nitrogen doses (0, 75, 150, 300 and 450 kg ha-1). The experiment was conducted in a completely randomized design with a split-plot arrangement. The effects of these factors were evaluated using the response surface methodology. The water yield of the crop decreases with increasing irrigation water depth; therefore, the yield is higher when water replenishment is lower than the recommended. The highest estimated total inflorescence yield is 24,547.80 kg ha-1, with a inflorescence mean diameter of 19.60 cm, a inflorescence mean height of 12.25 cm, and an inflorescence fresh weight of 858.90 g plant-1, obtained with an irrigation water depth equivalent to 132.09% of the crop evapotranspiration (ETc) and a nitrogen dose of 450 kg ha-1. The highest inflorescence diameter and height are obtained with an irrigation depth equivalent to 128.70 and 108.20% of ETc, respectively, and a nitrogen dose of 450 kg ha-1. Therefore, the best productivity response of the Barcelona CMS cauliflower hybrid can be obtained using an irrigation depth greater than the crop evapotranspiration, regardless of the nitrogen doses.

ABSTRACT This study was conducted with the aim of assessing the effects of different ambient temperature values on the performance of laying birds from one to 42 days of age in order to obtain optimal comfort temperatures. A total of 864 laying hens were distributed in four climatic chambers with different temperature ranges. One of the chambers was maintained within the thermal range recommended by the literature and the others were maintained under temperatures that consisted of mild and moderate cold stress and moderate heat stress. The experiment was conducted according to a completely randomized design in a split-plot arrangement and six replications. The data were analyzed by means of the analysis of variance and regression. The final performance of birds with temperatures of 33, 28, 26, 23, 19, and 19 °C (for the first, second, third, fourth, fifth, and sixth week of age, respectively) presented better productive results, confirming the assertiveness regarding the best thermal comfort and welfare of laying birds during the rearing stage. The results showed that under conditions of cold thermal stress, birds presented a worse performance, thus affecting their development and productive efficiency.

RESUMO O objetivo do trabalho foi avaliar o crescimento do tomateiro cultivar Upiã nos sistemas de cultivo Vertical, Cerca Cruzada e Viçosa, visando obter esclarecimento para os ganhos produtivos alcançados no sistema Viçosa. O experimento foi conduzido em Viçosa-MG, no período de 21 de agosto a 05 de dezembro de 2012, no esquema de parcelas subdivididas, sendo as parcelas representadas pelos sistemas de cultivo: Vertical, tutorado com fitilho em espaçamento 1,0 x 0,5 m; Cerca Cruzada, tutorado com bambu em espaçamento de 1,0 x 0,5 m; e Viçosa, tutorado com fitilho em espaçamento 2,0 x 0,2 m. As subparcelas foram compostas pelas épocas de amostragem das plantas: 15, 30, 45, 60 e 75 dias após o transplantio. O delineamento experimental foi em blocos casualizados, com quatro repetições. Cada parcela foi constituída por três linhas de 10 plantas, perfazendo um total de 30 plantas por parcela, sendo avaliadas as quatro plantas centrais de cada parcela. Avaliou-se matéria seca de folhas (MSF), caule (MSC), inflorescências (MSI), frutos (MSFr) e total (MST). Utilizando-se a área foliar, medida em escâner digital, e as massas secas previamente obtidas, foram determinados os seguintes índices fisiológicos de crescimento: índice de área foliar (IAF), área foliar específica (AFE), taxa de crescimento relativo (TCR) e taxa assimilatória líquida (TAL). O sistema Viçosa alterou o padrão de crescimento do tomateiro, quantificado pela análise de crescimento, em relação ao Cerca Cruzada e Vertical. O prolongamento da segunda fase de crescimento para a matéria seca de frutos, possivelmente, explicaria os ganhos produtivos obtidos no Sistema Viçosa. Estudos adicionais são necessários para esclarecer a relação entre a duração da 2a fase de crescimento da matéria seca de frutos, os índices fisiológicos AFE, IAF e TAL com o tamanho e produção de frutos do tomateiro.

ABSTRACT The objective of this work was to analyze the growth of the Upiã tomato cultivar in the Vertical, Crossed Fence and Viçosa cultivation systems, in order to obtain explanations for the productive gains achieved in the Viçosa system. The experiment was conducted in Viçosa, Minas Gerais State, Brazil, from August 21st to December 5th, 2012, in the scheme of subdivided plots, being the plots represented by the cultivation systems: Vertical, using tape, 1.0×0.5 m spacing; Crossed Fence, staked with bamboo, 1.0x0.5 m spacing; and Viçosa, using tape, 2.0x0.2 m spacing. The subplots were composed by the sampling times of the plants: 15, 30, 45, 60 and 75 days after transplanting. The experimental design was in randomized blocks, with four replications. Each plot was composed by three lines of 10 plants, making a total of 30 plants per plot, being evaluated the four central plants of each plot. We evaluated the dry matter of leaves (MSF), stem (MSC), inflorescences (MSI), fruits (MSFr) and total (MST). Using the foliar area index, measured by digital scanners and the previously obtained dry masses, we determined the physiological growth indices: foliar area index (IAF), specific foliar area (AFE), relative growth rate (TCR), and net assimilation rate (TAL). The Viçosa system altered the growth pattern of the tomato, quantified by the growth analysis, in comparison to Crossed and Vertical Fences. The prolongation of the second growth phase for the dry matter of fruits could possibly explain the productive gains obtained in the Viçosa system. Additional studies are required in order to clarify the relationship between the duration of the second phase of fruit dry matter growth, the physiological indexes AFE, IAF and TAL with the size and fruit yield of the tomato.

ABSTRACT The implementation of the ozonation process in the milling industry to control insect pests and improve wheat flour qualities requires understanding the behavior of ozone during ozonation. Therefore, this study aimed to investigate the reaction kinetics of ozone gas in wheat flour. Wheat flour ozonation at concentrations of 0.54, 1.07, 1.61 and 2.14 mg L−1 was used in a prototype consisting of a cylinder and a mixing system with a helical thread. The iodometric titration method was used to quantify the ozone concentration in the air stream. The reaction kinetics were characterized by determining the saturation time and the decomposition kinetics (decay rate and half-life time). With increasing ozone concentration, less time was required to saturate the wheat flour. The saturation times were 812, 434, 370 and 342 min for ozone concentrations of 0.54, 1.07, 1.61 and 2.14 mg L−1, respectively. Increasing the ozone concentration did not influence the constant decay rate and half-life time. The ozone decomposition kinetics could be represented by a first-order model, with a decay rate constant of 0.23±0.008 min−1 and a half-life time of 3.02±0.081 min.

ABSTRACT The objective of this study was to evaluate and model the traction performance parameters of a tractor 4x2 FWD, according to the tractor speed, the internal pressure and the type of tires construction. For each type of tire construction was assembled an experiment in which we evaluated the influence of internal pressures of the front and rear tires and the speed of the mechanical assembly. It was found that the sliding of the diagonal run, presented significant effect in all variables analyzed, since the radial showed no influence of the factors evaluated. The power available in the drawbar was higher when the tractor was equipped for radial tires. The response variables, fuel consumption schedule and specific fuel consumption were more sensitive to the speed of the internal tire pressure. The fuel consumption per area worked, did not affect the analyzed variables. As for the effort prediction models in the tractor drawbar, it was only possible for diagonal run, which are influenced by speed and internal pressure levels of the front and rear tires.

ABSTRACT In the correct pasture management, nutritional factors such as nitrogen and potassium fertilization play an important role in the forage production and quality. The aim was to evaluate the effects of the application of water levels, nitrogen and potassium doses in the Xaraés grass in the south of the State of Tocantins. For this, Xaraés grass was cultivated in the experimental field of the Federal University of Tocantins, municipality of Gurupi, TO. We used a mixture of fertilizer, combinations of N and K2O following the 1 N: 0.8 K2O ratio. To evaluate the effect of irrigation water levels and combinations of N and K2O doses in Xaraés grass, the plant height, the crude protein content and neutral detergent fiber were determined. The greatest height observed in the grass was 61.6 cm, with the dose application of 700 kg ha-1 yr-1 of N: 0.8 K2O and a water level of 120% of the ETc. The highest protein content was 11.7%, with the highest dose application of fertilizer and absence of irrigation. The highest fiber content in neutral detergent was 64%, with the estimated amount of 385.5 kg ha-1 yr-1 of N: 0.8 K2O and a water level of 120% of ETc. The conclusion was that the plant height, fiber detergent and crude protein content were influenced by the change in water level of irrigation and fertilizer doses. The values of plant height and crude protein increased with the increase of water levels and manure dose, while the fiber content of neutral detergent decreased with the increase of irrigation and varied little with the increase of fertilizer dose.

An experiment was carried out to assess the performance of steers on Brachiaria brizantha and Cynodon dactylon cv. Coast cross pastures by the continuous stocking method with a variable stocking rate. A completely randomized experimental design was used with two pastures representing the treatments, each containing 10 replicates. The results of t-tests demonstrated that the steers grazed for less time (7:19 h) on the B. brizantha grass pasture than the on Coast-cross grass pasture (8:13 h). There was no difference in rumination time from 6:46 and 6:89 h for the B. brizantha and Coast-cross pastures, respectively. There was a significant difference for the values regarding the time that the steers remained idle, and the animals were more frequently idle on the B. brizantha pasture, which was associated with less grazing time because there was no significant difference in the total rumination time. The lowest bite rates were observed in the Coast-cross pasture compared with B. brizantha during the daytime and nighttime. Nonetheless, the total number of bites were significantly higher in the Coast cross pasture; however, the lowest bite rate overall was recorded in the B. brizantha pasture. These results suggested that there was a compensation mechanism between the grazing times and the bite rates so that the animals could regulate the quantity of forage ingested.

Se realizó un experimento para evaluar el comportamiento de novillos en pasturas de Brachiaria brizantha y Cynodon dactylon, en pastoreo continuo con carga animal variable. El diseño experimental fue completamente al azar con las dos pasturas como tratamientos, cada uno con diez repeticiones. La prueba T demostró que los novillos pastaban en menos tiempo la pastura de Brachiaria, con el tiempo 7:19 horas, mientras que el tiempo en la pastura Coast-cross era 8:13 horas. No hubo diferencias en el tiempo rumia, lo cual fue 6:46 y 6:89 horas para pastos de hierba Brachiaria y Coast-cross, respectivamente. Para las cantidades relacionadas con el momento en que los novillos se quedaron inactivos, hubo diferencias significativas, con más tiempo para los animales que permanecieron en la pradera de Brachiaria; este hecho se asocia con el menor tiempo pastoreo, ya que no hubo diferencias significativas en el tiempo total de la rumia. Las tasas de mordeduras más bajos fueron significativamente inferiores en Coast-cross en comparación con Brachiaria, ya sea en el día o la noche. No obstante, el número total de mordeduras fueron significativamente más altos para en Coast-cross pastos, sin embargo, la tasa de picadura más bajo sobre el tiempo total se registró en Bracharia pastos. Los resultados sugieren que existe un mecanismo de compensación entre los tiempos de pastoreo y la tasa de mordeduras, de modo que los animales podían regular la cantidad de forraje consumido.

RESUMO A atividade fungiostática pode, principalmente durante o armazenamento, levar à rápida deterioração na qualidade nutricional dos grãos e reduzir seu aproveitamento e inutilização em processo industrial pela contaminação com toxinas (aflatoxinas entre outras). Dentre as tecnologias apontadas como promissoras no controle desses microrganismos se destaca a ozonização. Objetivou-se, com este estudo, determinar a concentração e o tempo de saturação do gás ozônio em grãos de arroz e definir o tempo de ozonização eficaz na desinfecção de fungos e leveduras. Grãos de arroz (14,3% b.u.) foram inoculados com Penicillium spp. e Aspergillus spp. e posteriormente sua ozonização foi realizada na concentração de 10,13 mg L-1, em fluxo contínuo de 1,0 L min -1, em cinco períodos de exposição (12, 24, 36, 48 e 60 h). A concentração e o tempo de saturação do gás ozônio nos grãos de arroz foram de 5 mg L-1 e 13,97 min, respectivamente. Observou-se redução em 3,8 ciclos log (100%) na contagem de leveduras e completa inibição para os fungos dos gêneros Aspergillus e Penicillium nos grãos ozonizados.

ABSTRACT The fungistatic activity, especially during storage, can lead to rapid deterioration in the nutritional quality of grains, and reduce their use and disposal in industrial process due to contamination with toxins (aflatoxins and others). Among the technologies identified as promising in controlling these microorganisms, there is ozonation. The objective of this study was to determine the concentration and the saturation time of ozone gas in rice grains and set the effective ozonation disinfection time in filamentous fungi and yeast. Rice grains (14.3% w.b.) were inoculated with Penicillium spp. and Aspergillus spp. and, subsequently, ozonized at the concentration of 10.13 mg L-1, under continuous flow of 1.0 L min-1, in five periods of exposure (12, 24, 36, 48 and 60 h). Ozone gas concentration and saturation time in rice grains were 5.00 mg L-1 and 13.97 min, respectively. There was a reduction of 3.8 log cycles (100%) in the count of yeasts and complete inhibition of fungal from the genera Aspergillus and Penicillium in ozonized grains.

O sistema de preparo mecanizado do solo influencia diretamente sobre as propriedades físicas e biológicas do solo, além de propiciar ambiente adequado para o estabelecimento das culturas. O preparo do solo pode interferir na atividade microbiológica. Dessa forma, objetivou-se com o presente trabalho avaliar como os sistemas de preparo mecanizado do solo podem afetar sua atividade microbiológica. Os tratamentos foram os seguintes tipos de preparo do solo: plantio direto (PD), plantio convencional (PC) e cultivo mínimo (CM). Todas as análises foram feitas em três instantes: antes do preparo do solo, depois do preparo e 14 dias após o preparo do solo. Os tratamentos foram dispostos no delineamento em blocos casualizados, com quatro blocos. As coletas foram realizadas em triplicata, em duas faixas: 0,0 a 0,10 m e de 0,10 a 0,20 m de profundidade. Foram determinados o carbono orgânico total (COT), o carbono da biomassa microbiana (CBM), a respiração basal do solo (RBS), o quociente metabólico (qCO2) e o quociente microbiano (qMic). O plantio direto apresentou maiores índices de carbono da biomassa microbiana e da respiração basal do solo, na faixa de 0,0 - 0,10 m de profundidade. O plantio direto foi o sistema que apresentou menor interferência da atividade microbiológica do solo.

In addition to provide appropriate environment for crops, mechanized tillage directly affects physical and biological soil properties; besides influencing microbial activity. Therefore, we aimed at assessing how different mechanized tillage systems may affect soil microbiological activities. Treatments consisted of the following soil tillage types: No-tillage (PD), conventional tillage (PC) and minimum tillage (CM). Treatments were arranged in a randomized block design. All analyses were performed at three moments: before and after soil preparation and 14 days after tillage. Collections were made in triplicate at two soil depths (0-0.10 m and 0.10 – 0.20 m). It was determined values of total organic carbon (COT), microbial biomass carbon (CBM), basal soil respiration (RBS), metabolic quotient (qCO2) and microbial quotient (qMic). No-tillage system showed higher ratios of microbial biomass carbon and soil basal respiration at 0.0 – 0.10 m depth. Therefore, no till was the system that had greater microbial activity in the soil.