Infrared thermometry to schedule irrigation of common bean

Abstract

-The objective of this work was to determine the critical irrigation time for common bean (Phaseolus vulgaris L. cv. Carioca) using infrared thermometry. Five treatments were analyzed. Canopy temperature differences between plants and a well-watered control about 1, 2, 3, 4, and 5±0.5ºC were tested. Physiological variables and plant growth were analyzed to establish the best time to irrigate. There was a significant linear correlation between the index and stomatal resistance, transpiration rate, and leaf water potential. Although significant linear correlation between the index and mean values of total dry matter, absolute growth rate, and leaf area index was found, no correlation was found with other growth index like relative growth rate, net assimilation rate, and leaf area ratio. Plants irrigated when their canopy temperature was 3±0.5ºC above the control had their relative growth rate mean value increased up to 59.7%, yielding 2,260.2 kg ha -1 , with a reduction of 38.0% in the amount of water used. Plants irrigated when their canopy temperature was 4±0.5ºC yielded 1,907.6 kg ha -1 , although their relative growth rate mean value was 4.0% below the control. These results show that the best moment to irrigate common bean is when their canopy temperature is between 3ºC and 4±0.5ºC above the control.Index terms: irrigation scheduling, water use efficiency, growth rate. Termometria ao infravermelho na programação da irrigação de feijoeiroResumo -O objetivo deste trabalho foi determinar o momento crítico para efetuar a irrigação do feijoeiro (Phaseolus vulgaris L. cv. Carioca) utilizando a termometria ao infravermelho. Foram analisados cinco tratamentos. As diferenças entre a temperatura foliar das plantas e a de um controle mantido bem irrigado testadas foram de 1, 2, 3, 4 e 5±0,5ºC. Foram analisadas variáveis fisiológicas e de crescimento para identificar o melhor momento de irrigação. Encontrou-se uma correlação linear significativa entre o índice empregado e a resistência estomática, a taxa transpiratória e o potencial hídrico foliar. Embora tenha-se verificado uma correlação linear significativa entre o índice empregado e os valores médios da matéria seca total, da taxa de crescimento absoluto e do índice de área foliar, não se verificou qualquer correlação significativa com os demais índices de crescimento, como a taxa de crescimento relativo, a taxa assimilatória líquida e a razão de área foliar. As plantas irrigadas a uma temperatura foliar de 3±0,5ºC acima do controle apresentaram um incremento de 59,7% no valor médio da sua taxa de crescimento relativo, produzindo 2.260,2 kg ha -1 de grãos, com uma redução de 38,0% na quantidade de água aplicada. As plantas irrigadas a uma temperatura foliar de 4±0,5ºC acima do controle produziram 1.907,6 kg ha -1 de grãos, contudo o valor médio de sua taxa de crescimento relativo foi de 4,0% inferior ao controle. Estes resultados demonstram que o melhor momento de se irrigar o feijoeiro é quando apresentam temperatura foliar entre 3ºC e 4±0,5ºC acima do cont...

Use of Thermal Imaging to Assess Water Status in Citrus Plants in Greenhouses

“…The decrease in canopy temperature is due to transpiration, which cools off the leaf surface, and as the root zone soil moisture is depleted, it induces a decrease in stomatal conductance and transpiration, and consequently an increase in leaf temperature [6,9,38]. The same was observed in other studies with sugarcane ( [8,39]), maize [10], common bean [12], almond [34], and citrus [19,32].…”

“…The use of well-watered control plants as a reference to assess the plant water status was proposed by Fuchs et al [11], as the temperature difference between plants under different soil water availability and control plants can be used to establish a stress index. Lobo et al [12] studied the performance of irrigated common beans subjected to five levels of water stress and determined the time to irrigate the crop when the temperature difference between control plants and treatments reached values ranging from 1 to 5 • C, with measurements taken with infrared thermometers. Researchers concluded the best time to irrigate the crop was when temperatures were 3-4 • C higher than the control (well-watered plants).…”

Ground-Based Remote Sensing for Assessing Tomato Water-Status

“…The infrared thermometry has been largely used for the study of plant water relations (de Almeida Lobo et al, 2004;Cohen et al, 2005;Guilioni et al, 2008). Increases in leaf temperature remotely detected by thermography reflect stomatal closure as a measure of 'stress'.…”

Thermal imaging to evaluate wheat genotypes under dryland conditions

“…Stomatal closure, on the other hand, causes the reduction of transpiration and increases the Tc (Jones et al, 2009;Zia et al, 2013). Canopy temperature is associated with leaf water potential (Blum et al, 1982;Cohen et al, 2005;Dejonge et al, 2015;Lobo et al, 2004) and is a good indicator of plant water status (Blum et al, 1982;Idso et al, 1982;Jackson et al, 1981). It is negatively associated with grain yield (Mohammadi et al, 2012;Zia et al, 2013).…”