Homero Bergamaschi

Deficit hídrico e produtividade na cultura do milho

O objetivo deste trabalho foi avaliar o impacto do deficit hidrico, no rendimento de graos de milho, e a eficacia da irrigacao em todo ciclo e, especificamente, no florescimento. Os dados foram obtidos em dez anos de experimentacao, durante os quais doses variaveis de irrigacao foram aplicadas por um sistema de aspersao, localizado no centro da area experimental. Foram calculados balancos hidricos, tendo como variaveis a agua precipitada (chuva e irrigacao) e a evapotranspiracao maxima do milho. Foram ajustados modelos de regressao para 27 condicoes hidricas, relacionando-se rendimento de graos com deficit hidrico e razao evapotranspiracao real sobre evapotranspiracao maxima (ETr/ETm). A maior reducao na producao ocorre em consequencia do deficit hidrico na polinizacao, formacao do zigoto e desenvolvimento inicial do grao, numa relacao quadratica. Nesse periodo, a razao ETr/ETm explica quase 80% das variacoes na producao de graos, que se estabiliza acima de uma razao de 0,7. A irrigacao aumenta e estabiliza a producao do milho; doses de rega de aproximadamente 60% daquela necessaria para elevar a umidade do solo a capacidade de campo aumentam a eficiencia de uso da irrigacao.

Alterações micrometeorológicas em vinhedos pelo uso de coberturas de plástico

The objective of this work was to evaluate the effects of plastic covering on the microclimate of vineyards (Vitis vinifera L., cultivar Moscato Giallo), in Serra Gaucha region in Rio Grande do Sul State, Brazil. The experiment was performed in Flores da Cunha, RS, during the 2005/2006 growing season. It comprised uncovered and covered rows of vines, using a 160 µm thick plastic film. Photossinthetically active radiation (PAR), air temperature and humidity, and wind velocity were monitored: over the plastic covering; between the film and the canopy; over the uncovered canopy; and close to grapes of both treatments. Reference evapotranspiration was estimated for both treatments. From the incoming PAR, 67.5% reached the covered canopy, 16% reached the covered grapes, and 36% reached the uncovered grapes. The plastic covering increased by 3.4oC the maximum air temperatures close to plants. Diurnal air relative humidity was reduced, while water vapor pressure and vapor pressure deficit were increased because of the plastic covering, which also reduced in 88% the wind velocity in comparison to open air. The reference evapotranspiration on the covered canopy was 35% lower than in open air. Although increasing diurnal air temperatures, the plastic covering may reduce the evaporative demand on vineyards, by reducing the incoming solar radiation and the wind velocity.

Uso da radiação solar pelo milho sob diferentes preparos do solo, espaçamento e disponibilidade hídrica

O objetivo deste trabalho foi avaliar a eficiencia de interceptacao e de uso da radiacao fotossinteticamente ativa (RFA) pela cultura do milho em diferentes sistemas de manejo do solo, arranjos de plantas e disponibilidade hidrica. O milho foi cultivado em plantio direto e preparo convencional, na combinacao com duas disponibilidades hidricas (irrigado e sequeiro) e espacamentos de 40 e 80 cm entre fileiras de plantas. Em cada tratamento, foram instalados sensores para medida da RFA transmitida pela cultura, na superficie do solo, ao passo que a RFA incidente foi medida acima da cultura. A reducao da distância entre fileiras aumentou a eficiencia de interceptacao em todos os tratamentos. Sob plantio direto, a cultura apresentou maior eficiencia de interceptacao em relacao ao preparo convencional. O deficit hidrico diminuiu a eficiencia de interceptacao devido ao enrolamento foliar, e esse efeito foi mais pronunciado em preparo convencional, em ambos espacamentos estudados. Embora a eficiencia de interceptacao tenha sido maior no espacamento de 40 cm, a eficiencia de uso nao diferiu entre espacamentos, mas diminuiu em condicoes de deficit hidrico.

Crescimento de cultivares de alface conduzidas em estufa e a campo

The growth of lettuce cvs. Veronica, Marisa and Regina was analised through an experiment carried out under plastic greenhouse and under field conditions, from April 15th to June 03rd 1999, in Eldorado do Sul, Rio Grande do Sul State, Brazil. Sampling of plants started one week after transplanting and proceeded until the end of the plant cycle on a weekly basis. The lettuce cultivated under greenhouse presented more fresh and dry mass, leaf area, specific leaf area and greater number of leaves. In addition, plants cultivated under greenhouse presented a shorter cycle when compared to the plants cultivated in field conditions. The cvs. did not show any difference when cultivated under greenhouse environment, but, in field conditions, the cv. Regina presented a larger number of leaves and a larger leaf area index than the cultivars Marisa and Veronica.

Potencial da água na folha como um indicador de déficit hídrico em milho

RESUMO - Este trabalho foi desenvolvido na Estacao Experimental Agronomica da UniversidadeFederal do Rio Grande do Sul, localizada no municipio de Eldorado do Sul, nos anos agricolas de1993/94 e 1994/95. O objetivo foi avaliar o potencial da agua na folha como indicador do deficit hidrico,em milho (Zea mays L.), relacionando-o ao potencial da agua no solo. O experimento constou de tresniveis de irrigacao, desde a capacidade de campo ate a ausencia de irrigacao. Os valores do potencialminimo da agua na folha foram desde -1,2 a -1,5 MPa em plantas irrigadas (na capacidade de campo) ede -1,6 a -2,0 MPa em plantas nao irrigadas. O potencial minimo da agua na folha correlacionou-se como potencial matricial da agua no solo a 45 cm de profundidade (r

Soil quality assessed by carbon management index in a subtropical Acrisol subjected to tillage systems and irrigation

The combined influence of no-till and irrigation on soil quality in tropical and subtropical regions is still to be better clarified. The objective of this study was to evaluate the influence of sprinkler irrigation on soil quality of a southern Brazilian sandy loam Paleudult subjected to conventional tillage and no-till for 8 years. The soil quality indicator was the carbon management index (CMI), based on variations in the total C stock (expressed by the C pool index, CPI) and in the C lability (expressed by the C lability index, LI) related to the reference native grassland soil. The C lability was given by the ratio between the concentration of labile C, separated with NaI solution (1.8 Mg/m3), and non-labile C, obtained from the difference between total C and labile C. The total C stock, and thus the CPI, in the 0–200 mm layer were affected neither by tillage system nor by irrigation. On the other hand, the concentration of labile C, and thus the C lability and LI, were lower in conventional tillage than in no-till, and in irrigated than in non-irrigated systems. The effect of irrigation in decreasing the C lability was more pronounced in no-till than in conventional tillage soil. A combination of residue accumulation and greater water availability on the no-till soil surface probably provided suitable conditions to increase microbial mineralisation activity on the light fraction of the organic matter. The results of CMI, whose variations were caused mainly by LI, indicate that soil quality was improved with adoption of no-till in substitution of conventional tillage, but not with adoption of irrigation. No-till soils subjected to irrigation require a higher phytomass addition than non-irrigated soils.

Microclima de vinhedos sob cultivo protegido

Microclimate alterations promoted by plastic covering over vineyards interfere in the plant physiology and fungal diseases incidence on grapevines. The aim of this research was to evaluate the influence of the plastic covering on the microclimate of vineyards, in particular on the quality of the incoming solar radiation. The experiment was carried out in 2005/06 and 2006/07 seasons in Flores da Cunha-RS, in a vineyard of Moscato Giallo cultivar shaped in Y, with impermeable plastic (160μm) over 12 rows of 35m length and five rows without covering (control). In both treatments the air temperature and humidity, incoming photosynthetically radiation and wind speed were measured at the level of the canopy and clusters. Continuing measurements were taken through sensors and automatic acquisition systems (datalogger). Influences of the covering on quality of the incoming solar radiation, from 300 to 750nm, were evaluated through a spectroradiometer. The impermeable plastic covering above the plant rows increased the air temperature and decreased the photosynthetically radiation and wind speed. The covering interfered on the quality of the incoming solar radiation, by reducing mainly the irradiance in the ultraviolet band and reducing also the ratio between the irradiance in the red and far-red bands.

Maize yield and rainfall on different spatial and temporal scales in Southern Brazil

This study aimed to establish relationships between maize yield and rainfall on different temporal and spatial scales, in order to provide a basis for crop monitoring and modelling. A 16-year series of maize yield and daily rainfall from 11 municipalities and micro-regions of Rio Grande do Sul State was used. Correlation and regression analyses were used to determine associations between crop yield and rainfall for the entire crop cycle, from tasseling to 30 days after, and from 5 days before tasseling to 40 days after. Close relationships between maize yield and rainfall were found, particularly during the reproductive period (45-day period comprising the flowering and grain filling). Relationships were closer on a regional scale than at smaller scales. Implications of the crop-rainfall relationships for crop modelling are discussed.

Potencial produtivo de videiras cultivadas sob cobertura de plástico

The objective of this work was to evaluate the effect of plastic cover on the yield components of grapevine (Vitis vinifera L.) cultivar Moscato Giallo. The experiment was carried out in 2005/2006 and 2006/2007 crop seasons, in Flores da Cunha, RS, Brazil, in two vineyard areas, one covered with an impermeable plastic film and other without covering (control). The microclimate was evaluated in terms of air temperature, air relative humidity, photosynthetically active radiation and wind speed above canopy and close to clusters. The yield components were evaluated in a completely randomized design, in ten plants randomly selected in each area. Measures were made for production per plant, yield per hectare, clusters per vine, clusters per square meter, twigs per square meter, weight and length of clusters, weight of rachis, number of berries per cluster, diameter of berries, and skim/pulp ratio. Plastic cover promotes yield increases, does not affect pulp/skin ratio, and promotes production stability, independently of climate conditions in each season.

Retenção e disponibilidade de água às plantas, em solo sob plantio direto e preparo convencional

This work had the objective of evaluating the soil water storage and availability to plants, when comparing the no-tillage (NT) and conventional tillage (CT) systems. The study was conducted in Eldorado do Sul, Brazil, in 2002. Soil density, total porosity, macroporosity, mesoporosity, microporosity, distribution of mesopores size, curves of water retention, field capacity (FC), and permanent wilting point (PWP) were analyzed in seven depths, into the soil profile. The highest differences occurred close to the soil surface. At 2.5 cm deep, the soil density was 7% lower while the total soil porosity was about 15% higher in NT than in CT. The mesoporosity showed an exponential distribution in NT, with highest values for largest mesopores, but it tended to a normal curve in CT. Considering the entire soil profile, the soil water storage was about 53% higher in CT than in NT. However, close to the soil surface (at 2.5 cm deep) it was 80% higher in NT than in CT. From the soil surface to 15 cm deep, 70% of the available water was retained above the limit of -80 kPa in NT, in comparison to 50% in CT. The no-tillage system increases the water availability to plants and reduces the energy of retention in the upper soil layers, in comparison to the conventional tillage.