RESUMO
The scarcity of drinking water affects various regions of the planet. Although climate change is responsible for the water availability, humanity plays an important role in preserving this precious natural resource. In case of negligence, the likely trend is to increase the demand and the depletion of water resources due to the increasing world population. This paper addresses the development, design and construction of a low cost system for measuring soil volumetric water content (θ), electrical conductivity (σ) and temperature (T), in order to optimize the use of water, energy and fertilizer in food production. Different from the existing measurement instruments commonly deployed in these applications, the proposed system uses an auto-balancing bridge circuit as measurement method. The proposed models to estimate θ and σ and correct them in function of T are compared to the ones reported in literature. The final prototype corresponds to a simple circuit connected to a pair of electrode probes, and presents high accuracy, high signal to noise ratio, fast response, and immunity to stray capacitance. The instrument calibration is based on salt solutions with known dielectric constant and electrical conductivity as reference. Experiments measuring clay and sandy soils demonstrate the satisfactory performance of the instrument.
RESUMO
No âmbito da tecnologia de aplicação de agrotóxicos, a pulverização eletrostática é um sistema disponível comercialmente, no entanto, pouco empregado, devido à existência de algumas divergências quanto à eficiência desse sistema, razão pela qual o entendimento dessa tecnologia e suas interações com a planta tornam-se necessários. Nesse contexto, objetivou-se avaliar a utilização da pulverização eletrostática na cultura do café quanto à eficiência de deposição e a uniformidade de distribuição da calda de aplicação. Utilizou-se um pulverizador eletrostático, marca Electrostatic Spraying Systems, modelo ESS MBP 4.0. O experimento foi instalado no delineamento de parcelas subsubdivididas (2x3x6), com dois sistemas de pulverização (sistema eletrostático ligado e desligado), três partes da planta (superior, médio e inferior) e seis posições de coleta das folhas, com quatro repetições. Quanto à uniformidade de distribuição, observou-se que houve maior variabilidade na deposição, quando o sistema eletrostático permaneceu ligado, com maior deposição na parte externa do dossel. Os valores de coeficiente de variação para o sistema eletrostático ligado e desligado foi de 40,3 e 33,08%, respectivamente. O sistema eletrostático foi eficiente na pulverização em plantas de café e proporcionou aumento de 37% na deposição da calda de aplicação em relação ao sistema eletrostático desligado.
In the scope of the application technology of pesticides, electrostatic spraying is a system commercially available, however, little used because there is some disagreement as to the efficiency of this system, so understanding this technology and its interactions with the plant become necessary. In this context, the aim of this study was to evaluate the electrostatic spraying on coffee as to the deposition efficiency and distribution uniformity of spray. We used an electrostatic sprayer, manufactured by Electrostatic Spraying Systems Co., model ESS MBP 4.0. The experiment was set on split plot design, (2x3x6), with two spraying systems (electrostatic system on and off), three parts of the plant (top, medium and bottom) and six positions of leaves collection, with four replications. As for the distribution uniformity of spray, it was observed there was more variability in the deposition when the electrostatic system remained on, with higher deposition in the outer canopy. The coefficients of variation for the electrostatic system on and off were 40.3 and 33.08%, respectively. The electrostatic spraying system was effective in coffee plants and increased spray deposition of 37% compared to when the electrostatic system was off.