Osmar Alves Carrijo

Fibra da casca do coco verde como substrato agrícola

Commercial seedling production and vegetable soilless cultivation are becoming common techniques among vegetable growers around the world. Several organic materials as peat, wood residue, pine bark, rice husk, or inorganic materials as sand, volcanic rocks, perlite, rockwool have been used alone or in mixture with others. Green coconut shells are becoming a major problem for the litter public service in many cities in Brazil, due to the large amount of material and its slow decomposition process. Recently, fibers extracted from coconut shells are being used as substrate. The coconut shells for the substrate production need to be cut, disintegrated in fibers, washed, dried and ground. For seedling production the manufactured coconut fiber substrate needs to be composted. The composting process is not necessary for flowers and vegetable soilless cultivation, but nutrients should be added in pre-plant or by fertigation. Tomatoes cultivated on coconut fiber substrate produced 13,2 kg m-2 of marketable fruits (three years average). This production was about 7,3% more than the production on sawdust (12,3 kg m-2).

Produtividade do tomateiro em diferentes substratos e modelos de casas de vegetação

The trial was carried out at Embrapa Hortalicas, in Brasilia, Brazil, to evaluate the performance of tomato crop production during two years (2000 and 2001), under three greenhouse models and different types of substrates. The greenhouse models were arch roof; even span and an arch roof with upper convective aperture. The substrates were rice husk, carbonized rice husk, coconut fiber, sawdust, coarsed sawdust, rockwool and a substrate for seedling production used at Embrapa Hortalicas. No significant statistical difference was verified for tomatoes cultivated in coconut fiber (10,4 kg m-2), sawdust (9,9 kg m-2), carbonized rice husk (9,3 kg m-2) and coarse sawdust (9,0 kg m-2). On the other hand, the smallest production was obtained for tomatoes cultivated in rockwool (6,4 kg m-2 ). There was a yield reduction between cultivation years due to the South American tomato moth (Tuta absoluta) in all greenhouses. Coconut fiber and carbonized rice husk yielded the heaviest fruits, 128 g and 123 g respectively.

Estudo preliminar do controle biológico da traça-do-tomateiro com o parasitóide Trichogramma pretiosum em ambientes protegidos

A preliminar survey on the biological control of South American tomato pinworm with the parasitoid Trichogramma pretiosum in greenhouse models

Razão entre radiação fotossinteticamente ativa e radiação global no cultivo do tomateiro em casa-de-vegetação

It was proposed in this study to determine and analyze variations in the ratio between photosynthetically active radiation (PAR) and global solar radiation (GR) during the growth season of tomato (Lycopersicon esculentum Mill., cv. Duradoro) crop in sand substract under protected cultivation. Measurements of GR and PAR were conducted inside of a single layer polyethylene greenhouse during the dry season in Vicosa, Minas Gerais, Brazil. Simultaneously, the GR was measured in an automatic weather station. The PAR/GR ratio decreased from 1.691 to 1.574 mol MJ-1, from the first to the ninth week after transplanting, and was relatively constant, oscillating between 1.571 and 1.587 from the ninth to the thirteenth week. Thereafter, when clear sky conditions changed to cloudy days, the PAR/GR ratio increased considerably (1.93 e 2.07 mol MJ-1), reaching values near to those determined in other Brazilian locations. Based on results it is possible to affirm that little effect of leaf expansion on multiple reflections of solar radiation inside the greenhouse occurred, but a remarkable influence of the clouds in the PAR/GR ratio was verified.

Efeito da solarização e biofumigação na incidência da murcha bacteriana em tomateiro no campo

Effect of soil solarization and biofumigation on tomato bacterial wilt incidence. Soilborne plant pathogens cause heavy losses to many vegetable crops. Solarization and organic residues amendments have been evaluated as disease control strategies with good perspectives for aplication in integrated management. Field experiments were carried out at Embrapa Hortalicas, Brasilia-DF, to evaluate the effects of amending soil with organic residues (biofumigation) and solarization on the incidence of bacterial wilt (Ralstonia solanacearum) on tomato, on soil chemical characteristics, and weed control. Amendments with brassica residues (2%), chicken litter residues (2%), methyl bromide treatments and no soil treatment, with or without soil solarization were evaluated. After solarization and biofumigation, soil samples were collected for chemical analysis and weed seed bank evaluation. The tomato seedlings were transplanted after two months of soil solarization. Soil solarization reduced soil pH and levels of B and Zn. Organic amendments increased levels of Ca, K and Na and reduced levels of Al. Soil solarization reduced the number of weed seeds in the soil, mainly monocotyledons. Methyl bromide treatments and chicken litter amendments significantly reduced bacterial wilt incidence and disease progress.

Avaliação de um circuito eletrônico para medição da condutividade elétrica de soluções nutritivas.

Nos sistemas de cultivo hidroponicos ou que utilizam a fertirrigacao, a quantidade total de sais dissolvidos na solucao nutritiva tem grande impacto na produtividade da cultura. A concentracao adequada ao crescimento e desenvolvimento da cultura sofre variacoes marcantes ao longo do seu ciclo, podendo ser avaliada indiretamente por meio do monitoramento da condutividade eletrica da solucao nutritiva. O objetivo deste trabalho foi avaliar um circuito eletronico de baixo custo para a medicao da condutividade eletrica, cujo principio se baseia na medida de frequencia. O circuito eletronico foi conectado a um computador via porta paralela, sendo calibrado utilizando-se de 16 solucoes de KCl. A temperatura das solucoes foi mantida nos niveis desejados por meio de um equipamento de controle da temperatura. Analises de regressao foram utilizadas para obter relacoes entre frequencia e resistencia, visando a medir a condutividade eletrica e a temperatura da solucao com base na frequencia. Os coeficientes de determinacao obtidos demonstraram excelentes correlacoes (R2 > 0,997). Com base nos resultados, pode-se concluir que o circuito proposto e capaz de medir a condutividade eletrica de solucoes na faixa de 0,10 a 10,15 dS m-1 com grande exatidao, compensando automaticamente as variacoes instantâneas de temperatura.

Produção e qualidade de alho sob regimes de água no solo e doses de nitrogênio

The study was carried out at Embrapa Hortalicas, Brasilia, Brazil, in order to evaluate the effects of three soil water tensions (15; 35 and 70 kPa) and three nitrogen (N) levels (20; 100 and 500 kg.ha-1) on yield and quality of garlic bulbs of a secondary growth susceptible cultivar. Greater vegetative growth, total yield and average bulb weight were obtained under tensions between 15 and 19 kPa and N levels between 52 and 97 kg.ha-1. The marketable yield was maximized for 15 kPa tension, and it was linearly reduced with increasing N levels. The percentage of bulbs with secondary growth was affected by the water tension, N and the interaction of both factors, with minimum value obtained for the combination of 70 kPa tension and 20 kg.ha-1 of N. The percentages of dry bulbs and mass loss between 60 and 120 days after harvest increased linearly with N, however, they were not affected by water tension treatments. Hence, to maximize marketable yield of cvs. susceptible to secondary growth both high frequency irrigation regime is recommended, despite favoring secondary growth, and minimum N application.

Spatial variability of tomato rooting system and implications on irrigation management in soiless cropping with substrates

Avaliou-se a distribuicao de raizes do tomateiro e a variabilidade horizontal do potencial matricial (Ym) e da condutividade eletrica da solucao em substratos, de fibra de coco verde, casca de arroz carbonizada, maravalha carbonizada e comercial, acondicionados em sacos de plastico do tipo bisnaga. Cada planta foi irrigada por um unico gotejador, posicionado a 7 cm da mesma. Maior concentracao de raizes e menores valores de Ym, sob condicoes de deficit hidrico temporario, ocorreram junto as plantas, nos substratos de fibra de coco e casca de arroz, e junto aos gotejadores, nos de maravalha e comercial. A baixa concentracao de raizes entre um gotejador e a planta subsequente, irrigada por outro emissor, ocorreu, provavelmente, pela alta condutividade eletrica da solucao do substrato nessa regiao (ate 8,3 dS m-1). As correlacoes entre concentracao de raizes versus Ym e concentracao de raizes versus condutividade foram significativas para todos os substratos. A avaliacao da variabilidade do Ym nos substratos, em plantas submetidas a deficit hidrico, permitiu avaliar qualitativamente a distribuicao do sistema radicular do tomateiro, de forma mais pratica que pelo metodo direto. Para fins de manejo da agua, recomenda-se instalar os sensores de umidade entre a planta e seu respectivo gotejador.

Formas de aplicação de cálcio na cultura do melão rendilhado sob cultivo protegido

An experiment was carried out at Embrapa Hortalicas in Brasilia, Brazil, from April to August 2001 to evaluate calcium application methods on muskmelon (Cucumis melo var. reticulatus), hybrid Galileo, Galia type, on greenhouse cultivation. The experimental design was of randomized blocks, with six treatments and four replications. There were five calcium applications: liming and 30; 80; 130; 180 kg ha-1 Ca rates in fertigation with calcium nitrate and a control treatment with no Ca. The calcium application increased the marketable yield by 35% and the number of fruits by 27% compared to control. These results suggest that even for soils with relatively high Ca content, there is a need for calcium application either in pre-plant or in fertigation. The fertigation treatments average (4.7 kg m-2) did not differ (p>0,05) from liming (4.2 kg m-2). Therefore, the application of calcium in fertigation was as efficient as in liming. The maximum yield of 5.1 kg m-2 was obtained at 115 kg ha-1 Ca rate. Calcium fertigation with 80 and 130 kg ha-1 of Ca presented the highest profitability. No effects were observed on the average fruit weight and nutrient concentration in leaves.

Mini sensor Irrigas® na determinação da curva de retenção de água em substratos para hortaliças

In Brazil, no reliable standard method exists to determine the water retention curve in all available types of substrates for the cultivation of vegetables, mainly for substrates with long and short fibers, such as those of green coconut shell. In this work, the objective was to obtain the substrate water retention curve for the cultivation of vegetables, using a mini Irrigas® sensor. Green coconut substrate was used without composting and with composting during 45; 90; 135 and 180 days while the Plantmax® substrate was used as control in a complete block experimental design with 6 substrates, 11 water tension levels and three replications. For the substrates S0, S45, S90, S135 and S180 the obtained average were: total porosity; 85%; aeration space: 72%; easily available water: 4%; available water: 9%; buffering water: 5% and remaining water: 4%. The aeration space (72%) was indicative that it is convenient to improve the particle size distribution of this substrate, in order to reduce the aeration space to gain water retention capacity. Water tension in the samples was slowly increased by evaporation as the substrate air interface and mini Irrigas® sensors enabled the required water tension measurements, continuously, in three parallel substrate samples for water tensions ranging from zero to 11 kPa. These results make evident the possibility of using the mini Irrigas® sensor for the determination of water retention curves in substrates for growing vegetables, and also opens the possibility of future studies, aiming at comparative tests for other methods.