Estimation of soybean leaf wetness from meteorological variables

Wagner Teigi Igarashi,José Alexandre De França,Marcelo Augusto De Aguiar E Silva,Otávio Jorge Grigoli Abi Saab,Seiji Igarashi

doi:10.1590/s0100-204x2018001000001

Wagner Teigi Igarashi, José Alexandre De França + Show 3 more

Open Access

https://doi.org/10.1590/s0100-204x2018001000001

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Abstract

Abstract: The objective of this work was to determine models for the estimation of leaf wetness percentage at three heights in the soybean (Glycine max) canopy, using meteorological variables from stations installed at the crop site and at an agrometeorological station. The experiment was conducted in three harvest seasons, in an area cropped with soybean, in the municipality of Londrina, in the state of Paraná, Brazil. To collect the meteorological variables, electronic trees were installed at four heights (0.3, 0.6, 0.9, and 1.7 m) in the crop and a station was installed in an agrometeorological station. The data were separated according to days with and without rain, and the analyses of correlation and of simple and multiple regressions were carried out, in order to obtain models with equations for leaf wetness estimation. Most of the equations that did not use the data of the sensors installed at 1.7 m, especially those of the models based on variables only from the agrometeorological station, presented low reliability. The models obtained with meteorological data only from the soybean crop show high reliability and use a lower amount of variables, which makes them a good alternative for wetness estimation.

Highlights

The objective of this work was to determine models for the estimation of leaf wetness percentage at three heights in the soybean canopy, using meteorological variables from stations installed at the crop site and at an agrometeorological station
The equations from models 1, 3, 4, 7, 9, and 10 for dry and rainy days did not use leaf wetness percentage (LWP) data obtained at 1.7 m in the soybean crop
R2 was greater in the equations for the lower and middle thirds of the plant, i.e., at 0.3 and 0.6 m, respectively, in the models that did not use LWP data obtained at 1.7 m

Summary

Introduction

Asian rust intensity on crops depends on several factors, including agrometeorological variables, which affect all fungus biological processes. Among these factors, Vale et al (2004) highlight leaf wetness measured as leaf wetness duration (LWD), which is a requirement for the occurrence of infection processes and fungi reproduction. According to Igarashi et al (2014), another method used to quantify leaf wetness is leaf wetness percentage (LWP). These authors pointed out that LWP is important, since, in days when wetting takes place for a long period, but in

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