Marco Antônio Fonseca Conceição

Reference evapotranspiration based on class A pan evaporation

Estimating reference evapotranspiration (ETo) based on Class A pan evaporation (ECA) is very usual in irrigated areas. For this purpose the ECA values are multiplied by a pan coefficient (Kp) to obtain ETo. Kp values can be estimated in different ways being, however, important to know which method would estimate the best value for a given locality. In the present work estimated values of ETo based on Class A pan evaporation, using Kp values determined by different methods, were compared to Penman-Monteith-FAO (EToPM) values for the northwest region of the Sao Paulo State, Brazil. The annual average Kp, determined dividing EToPM by ECA, was 0.74. For the rainy months (December to March) the average Kp value was 0.80 and for the dry months (April to November) 0.70. The reference evapotranspiration estimated using Kp determined by the Snyder equation presented the best regression coefficients when compared to EToPM.

Deficit irrigation in table grape: eco-physiological basis and potential use to save water and improve quality

Table grapes are one of the most productive and economically relevant fruit crops worldwide. Table grape production characterizes by high water productivity but also by an intensive use of water, which puts pressure on local/regional water resources, particularly in dry regions (e.g. South Mediterranean, Northeast and Southeast of Brazil). Climate change and scarcer water resources make the problem more severe in those areas. Meanwhile, consumer’s demand for quality and sustainable production is increasing and environmental issues are becoming critical for competiveness. In this context, table grape “industry” needs solutions to promote water savings, sustain yield, quality and profit. Deficit irrigation emerged as a tool to mitigate the negative impact of drought on yield and quality and to save water in modern irrigated viticulture. Our aim is to describe the potential benefits of deficit irrigation in table grape production namely in what concerns water savings and berry quality. Previous literature shows that the effect of deficit irrigation on water savings varies with the genotype (scion and rootstock), the environmental conditions as well as the adopted agronomic strategies. This paper provides a comprehensive and up-to-date overview on the eco-physiological basis of deficit irrigation strategies and their role on growth, yield and berry quality (biophysical and biochemical) in table grape. Complementary crop management strategies to guarantee a more sustainable use of water (e.g. higher water use efficiency), improved berry quality and smaller environmental impact of table grape production are presented and discussed.

Evapotranspiração de referência com base na radiação solar global estimada pelo método de Bristow-Campbell

The amount of water used in irrigation systems is usually calculated using the local reference evapotranspiration (ETo) values. Several methods can be used for ETo calculation, and Hargreaves method is one of the most popular. This method uses estimated values of global solar radiation (Rs), based on the difference between the maximum (Tmax) and minimum (Tmin) air temperature. However, the Rs may be calculated by other methods, such as the Bristow-Campbell, which also is based on the difference between Tmax and Tmin. In this study were estimated daily values of ETo by the method of Hargreaves in Jales - SP, Brazil, with and without the use of the Bristow-Campbell equation to calculate the Rs. These values were compared with those from the Penman-Monteith method, which is considered standard for the estimation of ETo. The evaluations had considered the wet and dry periods in the region. The use of the Bristow-Campbell equation improved the performance of the Hargreaves method, in relation to the Penman-Monteith, and the performance during the dry period of the year was higher than that of the wet season.

Microclimate conditions inside an irrigated vineyard covered with a plastic screen

A regiao de Jales e uma das principais produtoras de uvas de mesa do Estado de Sao Paulo. As videiras da regiao sao irrigadas e conduzidas, normalmente, no sistema latada, sendo comum, tambem, a utilizacao de coberturas com telas plasticas para a protecao contra granizo, passaros e morcegos. Entretanto, a irrigacao, o sistema de conducao e a cobertura plastica podem modificar as condicoes microclimaticas no parreiral. O presente trabalho teve como objetivo comparar as condicoes meteorologicas no interior de um parreiral de uvas, na regiao de Jales, com as registradas a ceu aberto. As avaliacoes foram realizadas na Estacao Experimental de Viticultura Tropical da Embrapa Uva e Vinho, em Jales-SP, em uma area conduzida no sistema latada, coberta com tela plastica de polietileno e irrigada por microaspersao. Os dados meteorologicos foram registrados fora e no interior do parreiral, empregando-se dois sistemas automaticos de aquisicao de dados, com registros efetuados a cada 15 minutos. Verificou-se que o uso da cobertura de tela plastica reduziu em 20%, em media, a radiacao solar incidente (Rs) acima do dossel. Os valores de Rs abaixo do dossel, durante o periodo de maior expansao foliar, chegaram a ser inferiores a 20% dos registrados a ceu aberto. A temperatura e a umidade relativa do ar no interior do parreiral nao apresentaram, em geral, diferencas para os valores registrados na estacao meteorologica. Durante a irrigacao, a temperatura do ar foi reduzida em 3%, e a umidade relativa do ar aumentou em 4%, em media, no interior do parreiral.

Simulating wind effect on microsprinkler water distribution

Wind incidence can affect microsprinkler water distribution. Evaluations of those conditions can be facilitated using simulations by computational models. The present work evaluates the performance of a ballistic model on simulating the wind effect on microsprinkler water distribution. Experimental tests were carried out using self-compensating microsprinklers, nozzle sizes 1.00 mm (gray), 1.10 mm (brown), 1.48 mm (orange), and 1.75 mm (yellow). The gray and brown nozzles used black swivels and the orange and yellow nozzles used blue swivels. The wind effect was artificially caused by fourteen 200 W fans. Computational simulations were realized using SIRIAS software, based on a ballistic model originally developed for sprinkler systems. The correlation coefficients (r) varied from 0.619 to 0.880, while the exactness coefficients (d) varied from 0.842 to 0.944. Swivels internal geometry influenced results. Tested models presented performances classified as very good for the black swivel nozzles and regular for the blue swivel nozzles.

Uso da temperatura para cálculo do índice de seca de regiões produtoras de uva

O Sistema de Classificacao Climatica Multicriterios Geoviticola (CCM), empregado na caracterizacao climatica de regioes produtoras de uvas, e composto pelos indices Heliotermico (IH), de Frio Noturno (IF) e de Seca (IS) sendo que este se baseia no balanco hidrico potencial do solo. Para se calcular os valores de IS, sao necessarios dados da precipitacao pluvial e da evapotranspiracao potencial (ETP), estimados pelo metodo-padrao de Penman-Monteith. Nem todas as regioes viticolas, no entanto, apresentam as variaveis meteorologicas necessarias para o uso desse metodo. Dai a importância de metodos que permitem estimar a ETP com base apenas em dados da temperatura do ar, como o de Hargreaves. No presente trabalho, foram comparados os Indices de Seca calculados com base nos valores de ETP estimados, empregando-se os metodos de Penman-Monteith e Hargreaves, para diferentes regioes viticolas do mundo. Foram utilizados dados climaticos de 83 estacoes meteorologicas, representativas de regioes viticolas localizadas em 18 paises. A equacao de Hargreaves obteve um desempenho classificado como muito bom, podendo ser adotada no sistema CCM, quando nao se dispoe de dados para o uso do metodo de Penman-Monteith.

Modelo balístico para estimar a distribuição de gotículas aplicadas por microaspersores

Experimental determination of microsprinkler droplets is difficult and time-consuming. This determination, however, could be achieved using ballistic models. The present study aimed to compare simulated and measured values of microsprinkler droplet diameters. Experimental measurements were made using the flour method, and simulations using a ballistic model adopted by the SIRIAS computational software. Drop diameters quantified in the experiment varied between 0.30 mm and 1.30 mm, while the simulated between 0.28 mm and 1.06 mm. The greatest differences between simulated and measured values were registered at the highest radial distance from the emitter. The model presented a performance classified as excellent for simulating microsprinkler drop distribution.

Frequency of fungicide application for controlling downy mildew in seedless grape plant ‘BRS Vitória’

Different application frequencies of metalaxyl + mancozeb were evaluated to control downy mildew in vine plants ?BRS Vitoria? in two experiments conducted in Jales, Sao Paulo, one in the production cycle and another in branches formation cycle. In experimental design of randomized blocks, five treatments were compared (1- two weekly applications; 2- one weekly application; 3- one application every 14 days; 4- one application every 21 days; 5- applications after sporulation) with four replications, each plot with three plants.