To quantify water stress on coffee trees, leaf water potential (LWP) measurements are commonly performed in a Scholander chamber; however, this methodology is restricted to research activities, due to the difficulty of measurement in the field: sampling hours at predawn and intensive work. A crop water stress index (CWSI) based on leaf temperature has been used as indicative of LWP in several crops, and thermal images can be a precious tool for mapping LWP under intensive drip‐irrigated coffee areas, in order to adjust irrigation requirements according to soil moisture spatial variability. This study aims to define the relationships between the water potential of coffee leaf based on CWSI, calculated by means of a portable infrared sensor and a thermal camera, analysing correlation, precision and accuracy indexes. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species of the Catuaí Red variety IAC 144 that was drip irrigated using tensiometers as matric potential sensors. The observed CWSI and LWP presented good correlations in the linear and cubic models. It was concluded that the CWSI is a good indicator of the water potential of a coffee canopy and can be an alternative to measurements of LWP from the Scholander chamber. © 2020 John Wiley & Sons, Ltd.

The plant water potential and the leaf temperature are physiological responses of the coffee tree that can be used as indicative of the irrigation management of this crop. There is a dependence between the leaf water potential with the potential matrix of the soil solution, however, the water potential levels found for the coffee tree show divergent relationships in the literature regarding the matrix potential. The objective of this study is to verify the water potential and leaf surface temperature in the coffee tree when submitted to different irrigation levels. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species from Red Catuaí IAC 144 variety, the drip irrigation system was adopted and the management done by tensiometry. The relationships among these physiological responses and the treatments of actions presented high determination coefficients (R² of 0.84, 0.90 and 0.65 for the leaf water potential, leaf temperature measured with the portable infrared sensor and the thermal camera respectively). The estimated values for leaf water potential were-0.23,-0.56,-0.89 and-1.22 MPa for irrigation treatments L130%, L100%, L70% and L40%, respectively. The calculated leaf temperature values were 31.7, 32.4, 33.0 and 33.7°C in average, for treatments L130%, L100%, L70% and L40% in proper order.

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The leaf area index (LAI) is relevant in studies of phenomena at different scales, such as for the leaf to canopy scale and the calculation of the extinction coefficient of photosynthetically active radiation (kPAR), providing input for the parameterization of physiological basis models. The objective of this work was to verify the variation of the LAI and the coffee kPAR subjected to different drip irrigation levels (130, 100, 70, and 40%) and to compare the data obtained from radiation bar linear sensors (SunScan) in the plants that received full irrigation with the values found by other LAI estimation methodologies. The study was conducted in Piracicaba, São Paulo State, Brazil, using the species Coffea arabica cv. Red Catuaí IAC 144; a drip irrigation system was adopted, with the irrigation controlled by tensiometry. The mean LAI values were higher in the L130 (irrigation level of 130%) and L100 (irrigation level of 100%) treatments than those with deficit irrigation depths. The mean kPAR values were lower for the L130 and L100 treatments than the values found in the deficit irrigation depth treatments. When comparing SunScan to other methodologies, the mean error (ME) and absolute mean error (AME) were high.

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A evapotranspiração de referência (ETo) é uma variável muito importante, uma vez que é usada no planejamento e manejo dos sistemas de irrigação e demais áreas. Sendo assim, sua determinação deve ser feita cuidadosa e rigorosamente em face aos vários métodos de estimativa existentes. Neste sentido, dado que o método padrão de Penman-Monteith FAO/56 exige muitos elementos meteorológicos de entrada, o estudo de métodos alternativos se mostra necessário pelas inúmeras delimitações existentes nas estações automáticas de diversas regiões. O presente estudo objetivou   comparar a evapotranspiração obtida a partir do método padrão Penman-Monteith FAO/56 com as determinadas por equações empíricas, buscando, identificar métodos mais simples e, portanto, alternativos ao método de referência na Bacia Hidrográfica do Alto Juruá. Para o estudo foram utilizadas três estações automáticas localizadas em Cruzeiro do Sul, Porto Walter e Marechal Thaumaturgo no Acre, com dados pertencentes ao INMET e Xavier, King e Scanlon. Os resultados mostraram que os métodos de Pennan Original e Kimberly Penman foram os que melhor estimaram a ETo em relação ao modelo padrão para as três estações automáticas, enquanto que os métodos de Blaney-Criddle e Hargreaves-Samani apresentaram desempenho inferior. Os métodos de Priestley-Taylor e Kimberly Penman foram escolhidos como alternativos aos métodos de Pennan Original e Kimberly Penman.

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O conhecimento do comportamento espaço temporal da precipitação pluviométrica nesse contexto apresenta um papel relevante quando o objetivo é tomar decisões a respeito do recurso mais importante. O objetivo deste trabalho foi investigar a contribuição da longitude, da latitude e a covariável altitude, como variáveis auxiliares na obtenção de estimativas da distribuição espacial da precipitação anual média no estado de Pernambuco. Dentre os modelos testados o exponencial apresentou melhor ajuste aos dados observados, e as tendências apresentaram forte dependência espacial e estão diretamente correlacionadas com a precipitação pluviométrica média anual. A utilização da ferramenta apresentou-se eficaz na estimativa da precipitação pluviométrica, e pode ser empregada em diversas áreas do conhecimento, principalmente como ferramenta de apoio para tomada decisão.