Chlorophyll index for real-time prediction of nutritional status of 'Prata' banana

Abstract

This study aimed to select regression equations based on the correlation between chlorophyll index and leaf nutrient contents, for real-time prediction of the nutritional status of 'Prata' banana. Six cultivars of 'Prata' banana were used as treatments, with five replicates and four plants per plot, arranged in a completely randomized design. Nutrient levels were evaluated based on laboratorial analysis and chlorophyll indices using a portable chlorophyll meter, in the third leaf from the apex to the base. Data were subjected to analysis of variance, calculating the correlations between leaf nutrient contents and chlorophyll indices, and the regression equations were adjusted to the associations that were significant and with greater magnitude. The selected models estimate leaf nutrient contents and allow a real-time, low-cost reliable prediction of the nutritional status of 'Prata' banana. It is an auxiliary technique that, combined with leaf and soil analysis, contributes to a more precise and secure nutritional evaluation.

Gas exchange and yield of Prata-type banana plants with fertilizer sources for organic management

“…Under seasons with more weather stress, such as September and October, the maximum ambient temperature over the period reached up to 39.2°C, relative humidity, from 30 to 35%, which characterizes a condition of high VDP, with recorded values above 2.5 kPa (Figure 2) and the incident radiation on the leaf reached up to 1.998 µmol photons m -2 s -1 . These weather conditions are above what is considered to be optimum for the photosynthesis of the banana plant (Robison and Galán Saúco, 2012), and the decrease in photosynthetic rates might occur because of the stomatal closure or enzymatic problems, leading to decreases in carboxylation efficiency (Arantes et al, 2016). Conversely, under milder conditions, potassium accumulates in cell guards; as a result, their osmotic potential increases, and in addition to water, their turgidity is also increased, which favors the stomatal opening; therefore, the positive quadratic behavior at 8:00 am is explained.…”

“…This is probably due to the high soil fertility at the beginning of the experiment, whose average P and K contents before planting were 468.33 and 493 mg dm -3 , respectively. Also, doing the physiological readings at specific times contributed to this outcome as these readings vary with the atmospheric conditions and soil moisture at the time of measurement, which might not reflect the conditions imposed by the treatments (Santos et al, 2013;Arantes et al, 2016). The 'Dwarf-Prata' cultivar, at 8:00 am exhibited a decreasing quadratic behavior for g s rates (Figure 2 The amounts of N and K 2 O supplied by cattle manure and rock powder contributed toward explaining the g s rates at both reading times.…”

“…Always, 3 rd or 4 th leaf was measured, in case the 3 rd leaf is of difficult access or damaged by the wind, from tip to base (Arantes et al, 2016) . These measurements were performed by anLcpro+® Portable Photosynthesis System (ADC BioScientific Limited, UK) infrared gas analyzer (IRGA), always with the radiation shield facing the sun, with ambient temperature and irradiance, and airflow of 200 ml min -1 .…”

“…According to Silva et al (2011), a safe recommendation of a new cultivar requires its evaluation in different environments, regions, and repetitions of production cycles, aiming at the identification of cultivars, as it allows establishing a genotypic variation of physiologic responses under local conditions (Turner et al, 2007). These variations allow extrapolation of these results to be used in the management of specific production systems and to properly manage cultivars under similar conditions (Arantes et al, 2016).…”

“…however, studies on physiological characteristics in fertilizer-related trials are needed as the aforementioned studies are predominantly on Cavendish cultivars (Robinson and Gálan Saúco, 2012) even though there are some available results for Prata-type cultivars (Arantes et al, 2016), where cultivars and irrigation systems were studied.…”