Spatial variability of leaf wetness duration in a 'Niagara Rosada' vineyard

Abstract

Despite considerable efforts to develop accurate electronic sensors to measure leaf wetness duration (LWD), little attention has been given to studies about how is LWD variability in different positions of the crop canopy. In order to evaluate the influence of 'Niagara Rosada' (Vitis labrusca) grapevine structure on the spatial variability of LWD, the objective of this study was to determine the canopy position of the 'Niagara Rosada' table grape with longer LWD and its correlation with measured standard LWD over turfgrass. LWD was measured in four different canopy positions of the vineyard (sensors deployed at 45º with the horizontal): at the top of the plants, with sensors facing southwest and northeast (Top-SW and Top-NE), and at the grape bunches height, with sensors facing southwest and northeast (Bottom-SW and Bottom-NE). No significant difference was observed between the top (1.6 m) and the bottom (1.0 m) of the canopy and also between the southwest and northeast face of the plants. The relationship between standard LWD over turfgrass and crop LWD in different positions of the grape canopy showed a define correlation, with R 2 ranging from 0.86 to 0.89 for all period, from 0.72 to 0.77 for days without rain, and from 0.89 to 0.91 for days with rain.KEYWORDS: dew, rain, flat plate wetness sensor. VARIABILIDADE ESPACIAL DA DURAÇÃO DO PERÍODO DE MOLHAMENTO EM VINHEDO DE 'NIAGARA ROSADA'RESUMO: Apesar dos esforços consideráveis para se desenvolverem sensores eletrônicos acurados para medir a duração do período de molhamento (DPM), pouca atenção tem sido dada às pesquisas sobre a variabilidade da DPM no interior do dossel das culturas. A fim de avaliar a influência da estrutura da cobertura vegetal da videira 'Niagara Rosada' (Vitis labrusca) na variabilidade espacial da DPM, o objetivo do presente estudo foi determinar a posição da videira com a maior DPM e sua relação com a DPM medida em condição-padrão (no gramado). Para tanto, a DPM foi medida em quatro diferentes posições da planta, com os sensores inclinados em 45º em relação à horizontal: topo da planta com a face superior do sensor voltada para sudoeste e nordeste (Topo-SW e Topo-NE) e altura dos cachos de uva com a face superior do sensor voltada para sudoeste e nordeste (Dossel-SW e Dossel-NE). Não houve diferença significativa da DPM tanto entre a parte mais alta (1,6 m) e a parte mais baixa (1,0 m) da planta, como entre as faces sudoeste e nordeste das plantas. As relações entre os dados de DPM sobre o gramado e nas diversas posições da cobertura vegetal, obtidas por meio de regressão linear simples, apresentaram correlações bem definidas, com valores de R 2 variando de 0,86 a 0,89 para todo o período, de 0,72 a 0,77 para os dias sem chuva e de 0,89 a 0,91 para os dias com chuva. PALAVRAS-CHAVE:orvalho, chuva, sensor de molhamento de placa plana.

Spatial variability of leaf wetness under different soil water conditions in rainfed jujube (Ziziphus jujuba Mill.) in the loess hilly region, China

“…5). This observation is consistent with those of previous studies on LWD for rainforest, apple, soybean, grape and corn plantations (Sentelhas et al, 2005;Batzer et al, 2008;Lulu et al, 2008;Schmitz and Grant, 2009;Binks et al, 2021). Our results are, however, different from those obtained for the studies on coffee, cotton and banana plantations (Sentelhas et al, 2005;Santos et al, 2008).…”

“…Different directions of the instrument affects the result of leaf wetness. For example, grape leaves growing in southwest usually start to wet earlier and dry later than those growing in northeast (Lulu et al, 2008). Also, tomato leaves growing in east dried 20 min later than those growing in north, south and west (Lau et al, 2000).…”

“…Leaf wetness has more ecological effect than the total amount of water stored in leaves (Lulu et al, 2008;Kidron and Starinsky, 2019). When leaves are wet, the thin water layer or water droplets will be formed on the surfaces of wet leaves, these water can serve as a supplementary water source for plants and be absorbed by leaves (Dawson and Goldsmith, 2018).…”