ABSTRACT A common scenario in the developing countries is the low income and less education of producers. Thus, the tools used for irrigation management must be cheap and easy to handle. In this work, an autonomous and low-cost network of micro-weather stations has been developed for irrigation management. Simulations were performed to evaluate the ability of intelligent systems to compute evapotranspiration with noisy and insufficient data. The network of micro-weather stations was then applied to autonomous irrigation management of a crop of bell peppers. Statistical analysis was performed on data from the developed system and a standard weather station. The results show no statistical difference between the values of evapotranspiration calculated with data from these two sources. The developed system performed with a coefficient of determination of 0.968, mean absolute error of 0.055 mm day−1, and root mean square error of 0.063 mm day−1. The study shows that low-cost intelligent systems can be used as viable tools for efficient irrigation management.

RESUMO Conhecer a umidade de solo disponível para as plantas é preponderante para o manejo adequado do uso da água nas propriedades agrícolas, sendo os métodos automatizados os mais precisos. Entretanto, os custos de aquisição são elevados e a maioria dos controladores de irrigação ainda trabalha com tempos pré-definidos. Assim, o estudo teve por objetivo desenvolver e calibrar um tensiômetro automatizado de baixo custo e alta eficiência no controle da irrigação, baseado em monitoramento em tempo real. A pesquisa foi conduzida nos Laboratórios de Hidráulica e Relação Água-Solo-Planta-Atmosfera pertencentes à Universidade Federal da Grande Dourados (UFGD), em Dourados, MS, com solo classificado como Oxisol. Foram utilizados transdutores de pressão e um microcrontrolador capazes de assimilar a pressão no interior dos tensiômetros e transformá-la em leituras de potencial matricial de água no solo - Ψm. Desta forma, realizou-se a calibração comparando as diferentes leituras do transdutor e do tensímetro digital de agulha. Foram aplicadas diferentes tensões para obtenção da curva de umidade do solo, partindo do ponto mais úmido (saturado) para o mais seco (solo seco em estufa), coletando 20 pontos válidos. Posteriormente, os dados foram submetidos ao teste de normalidade, com posterior análise estatística e modelos de curva de regressão. Foram verificados ajustes lineares com altos valores de coeficiente de determinação (R2 = 0,99), sendo o sistema automatizado construído, capaz de monitorar a tensão de água do solo em tempo real.

ABSTRACT Knowing the soil moisture available to plants is important for adequate management of water use in agricultural farms, with automated methods being the most accurate. However, acquisition costs are high and most of the commercially available irrigation controllers still work using pre-set times. This study aimed to develop and calibrate a low-cost automated tensiometer with high efficiency in irrigation control, based on real-time monitoring. The research was conducted at the Laboratories of Hydraulics and of Water Soil Plant and Atmosphere Relationship, which belong to the Federal University of Grande Dourados (UFGD), in Dourados, MS, Brazil, with soil classified as an Oxisol. Pressure transducers and a microcontroller were used to assimilate the pressure inside tensiometers and transform it into readings of soil water matric potential (Ψm). Thus, the calibration was carried out by comparing the different readings of the transducer and digital tension meter. Different tensions were applied to obtain a soil moisture curve, starting from the most humid point (saturated) to the driest one (oven-dried soil), collecting 20 valid points. Subsequently, the data were subjected to the normality test, with subsequent statistical analysis and regression curve models. Linear adjustments with a high coefficient of determination (R2 = 0.99) were observed, with the automated system built in this study being capable of monitoring soil water tension in real-time.

Resumo Introdução: A proteinúria pós-transplante renal tem incidência variável, sendo um fator de risco cardiovascular e para a sobrevida do enxerto. Objetivo: Avaliar a prevalência de PTN pós-Tx em receptores de um único centro e fatores associados. Métodos: A prevalência de PTN foi avaliada segundo a definição ≥ 500 mg/24 hs. Os pacientes foram divididos em 3 grupos: grupo A, < 500 mg, B, 500-1000 mg e C, > 1000 mg. Foi testada a associação entre PTN pós-Tx e: idade/gênero do doador e receptor, tipo de doador, função retardada do enxerto, rejeição aguda, HAS e creatinina. As variáveis com valor de p < 0,20 na analise bivariada foram incluídas em modelo de regressão logística multivariado. Resultados: Foram avaliados 173 receptores, idade média 39 anos, 57,2% sexo masculino e 60,7% doador falecido. A prevalência de PTN pós-Tx foi de 24,3%. A distribuição dos pacientes foi de 75,7% para o grupo A, 15,6% para o grupo B e 8,7% para o grupo C. Foram associados a uma maior chance de PTN ≥ 500 mg/24hs: o sexo masculino do receptor, o doador falecido e a HAS pós-Tx. A creatinina aos 12 meses foi significativamente maior nos pacientes com PTN. 62% dos pacientes com PTN ≥ 500 mg/24 hs receberam tratamento com IECA/BRA. Conclusão: A prevalência de PTN pós-Tx renal foi 24,3% segundo a definição utilizada. O sexo masculino do receptor, o doador vivo e a HAS estiveram associadas à maior chance de PTN pós-Tx. O bloqueio do sistema renina-angiotensina deve ser intensificado.

Abstract Introduction: Proteinuria after kidney transplantation (Tx) has variable incidence and is associated with cardiovascular risk and graft survival. Objective: To evaluate the prevalence of proteinuria after kidney Tx and its associated factors. Methods: The prevalence of PTN was evaluated according to definition ≥ 500 mg/24 hours. Patients were divided into 3 groups: group A, < 500 mg, B, 500-1000 mg and C, > 1000 mg. We tested the association between PTN and: age/gender of the donor and recipient, type of donor, delayed graft function, acute rejection, hypertension and creatinine. The variables with a p value < 0.20 in the bivariate analysis were included in a multivariate logistic regression analysis. Results: 173 recipients were evaluated, mean age 39 years, 57.2% male and 60.7% deceased donor. The prevalence of PTN after kidney Tx was 24.3%. The distribution of patients according to PTN was 75.7% for group A, 15.6% for group B and 8.7% for group C. The following factors were associated with higher risk of PTN: male recipients, living donor and hypertension. Creatinine at month 12 moths post-Tx was higher among patients with proteinuria. 60% of patients with PTN ≥ 500 mg/24 hours were treated with ACEI/ARB. Conclusion: The prevalence of PTN after kidney Tx varied between 24.3%, according to the definition used. The male gender of the recipient, living donor and hypertension were associated with the occurrence of PTN after kidney Tx. Blockade of the renin-angiotensin system must be prescribed to more patients.