Evaluation of a Penman–Monteith approach to provide “reference” and crop canopy leaf wetness duration estimates

Sentelhas, Paulo César; Gillespie, T. J.; Gleason, Mark L.; Monteiro, José Eduardo B.M.; Pezzopane, José Ricardo Macedo; Pedro, M.J.

doi:10.1016/j.agrformet.2006.09.010

Cited by 43 publications

(60 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This model was developed to estimate LWD from DPD, U and RH data, using a binary classification tree with knots (categories) and branches to verify if an interval of 20 min presents wetness or not (Figure 1), through equations 1 and 2. PM: as presented by Sentelhas et al (2006), this model eliminates the need of the air temperature measurement at the crop height by assuming that the air temperature measured over turfgrass at the SWS, usually between 1.5 and 2.0 m height, represents the air temperature at the same height on the crop canopy (turfgrass, in this case). For this approach, a new resistance is added to the model, which was assumed as the aerodynamic resistance (ra, s m -1 ), described for Monteith & Unsworth (1990):…”

Section: Methodsmentioning

confidence: 99%

“…In the standard weather station (SWS), LWD was recorded in a reference position, at 30 cm height over turfgrass, at a 30º angle to horizontal and with the sensor surface facing south (Sentelhas et al, 2004). Also, air temperature (T), relative humidity (RH), wind speed at two meters (U), net radiation (Rn) and rainfall (P) were measured with the same frequency of the crop LWD.…”

Section: Methodsmentioning

confidence: 99%

“…Standard weather data were used to estimate LWD by four different models: number of hours with relative humidity above 90% -NHRH > 90% (Sentelhas, 2004), dew point depression -DPD (Gillespie et al, 1993), classification and regression tree -CART (Gleason et al, 1994) and Penman-Monteith -PM (Sentelhas, 2006), as follows: NHRH > 90%: RH = 90% was considered as limit for the beginning of dew deposition (Sentelhas, 2004). The number of intervals of 20 min (during one day) with RH above 90% divided by three was considered as LWD (h).…”

Section: Methodsmentioning

confidence: 99%

“…LWD is a variable of difficult measurement or estimation, because it is governed not only by the atmospheric conditions but also by the structure and composition of the vegetable community (Magarey et al, 2001;Sentelhas et al, 2005). So, LWD is seldom measured in conventional or automatic weather stations.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Estimating leaf wetness duration over turfgrass, and in a 'Niagara Rosada' vineyard, in a subtropical environment

Lulu¹,

Sentelhas

Júnior³

et al. 2008

Sci. agric. (Piracicaba, Braz.)

View full text Add to dashboard Cite

Leaf wetness duration (LWD) is a key parameter in agrometeorology because it is related to plant disease occurrence. As LWD is seldomly measured in a standard weather station it must be estimated to run warning systems for schedule chemical disease control. The objective of the present study was to estimate LWD over turfgrass considering different models with data from a standard weather station, and to evaluate the correlation between estimated LWD over turfgrass and LWD measured in a 'Niagara Rosada' vineyard, cultivated in a hedgerow training system, in Jundiaí, São Paulo State, Brazil. The wetness sensors inside the vineyard were located at the top of the plants, deployed at an inclination angle of 45º and oriented southwest, with three replications. The methods used to estimate LWD were: number of hours with relative humidity above 90% (NHRH > 90%), dew point depression (DPD), classification and regression tree (CART) and Penman-Monteith (PM). The CART model had the best performance to estimate LWD over turfgrass, with a good precision (R 2 = 0.82) and a high accuracy (d = 0.94), resulting in a good confidence index (c = 0.85). The results from this model also presented a good correlation with measured LWD inside the vineyard, with a good precision (R 2 = 0.87) and a high accuracy (d = 0.96), resulting in a high confidence index (c = 0.93), showing that LWD in a 'Niagara Rosada' vineyard can be estimated with data from a standard weather station. Key words: Vitis labrusca, LWD estimate, relative humidity, dew point temperature ESTIMATIVA DA DURAÇÃO DO PERÍODO DE MOLHAMENTO SOBRE O GRAMADO E EM VINHEDO DE 'NIAGARA ROSADA' EM CONDIÇÃO SUBTROPICALRESUMO: A duração do período de molhamento (DPM) é uma variável agrometeorológica chave para a ocorrência de doenças de plantas. Como a DPM é raramente medida nas estações meteorológicas, ela deve ser estimada quando se pretende empregar sistemas de alerta de controle químico. Desse modo, o objetivo do presente estudo foi avaliar a estimativa da DPM sobre gramado por diferentes modelos a partir de dados meteorológicos obtidos em uma estação meteorológica padrão e verificar as relações entre a DPM estimada para o gramado e a medida em um vinhedo de 'Niagara Rosada', conduzido em espaldeira, em Jundiaí, SP, Brasil. Os sensores de molhamento no vinhedo foram instalados no topo das plantas com um ângulo de inclinação de 45º e com a face superior do sensor voltada para sudoeste, com três repetições. Os quatro modelos de estimativa da DPM foram: número de horas com umidade relativa do ar acima de 90% (NHUR > 90%), depressão do ponto de orvalho (DPO), árvore de classificação e regressão (CART) e o de Penman-Monteith (PM). O modelo CART estimou melhor a DPM no gramado, apresentando uma boa precisão (R 2 = 0,82) e uma ótima exatidão (d = 0,94), resultando num bom índice de confiabilidade (c = 0,85). Esta estimativa também apresentou uma boa correlação com a DPM medida no interior do vinhedo, com uma precisão razoável (R 2 = 0,87) e uma ótima exatidão (d = 0,96), resu...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Estimating leaf wetness duration over turfgrass, and in a 'Niagara Rosada' vineyard, in a subtropical environment

Lulu¹,

Sentelhas

Júnior³

et al. 2008

Sci. agric. (Piracicaba, Braz.)

View full text Add to dashboard Cite

show abstract

“…A number of experimental studies were conducted last years to investigate the effect of climatic and environmental conditions on coffee crop development (Carr, 2001;Villa Nova et al, 2002;DaMatta, 2004;Marin et al, 2005;Sentelhas et al, 2006;Lin, 2007;Sato et al, 2007). In this study we used numerical simulation techniques in conjunction with detailed information of soil and crop properties to evaluate the ET process.…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of actual evapotranspiration of a coffee crop

Cesanelli

Guarracino

2011

Sci. agric. (Piracicaba, Braz.)

View full text Add to dashboard Cite

The evapotranspiration estimation has great importance to crop productivity and agricultural water management. In this study, evapotranspiration is analyzed in a coffee (Coffea arabica L.) crop located in Piracicaba, state of São Paulo (Brazil) using a numerical method based on the simulation of both water flow and crop activity in the unsaturated zone of the soil. Actual evapotranspiration is estimated from potential evapotranspiration using water stress functions, meteorological data, soil hydraulic parameters, crop coefficients and leaf area index values. Crop transpiration and soil evaporation are individually quantified improving the analysis of the evapotranspiration process. The numerical procedure can predict periods of crop water stress and becomes an attractive tool to analyze the effect of non-standard conditions on coffee crops and to design efficient irrigation schedules. Simulated evapotranspiration values are in good agreement with experimental values determined in the study site.

show abstract