Soil-Surface Straw Influences Micrometeorological Conditions Affecting Canola Mortality During Nighttime Frosts

Samuel Kovaleski,Elizandro Fochesatto,Genei Antônio Dalmago ,J A De Gouvêa ,Arno Bernardo Heldwein ,G R Da Cunha

doi:10.5539/jas.v12n11p246

Samuel Kovaleski, Elizandro Fochesatto + Show 4 more

Open Access

https://doi.org/10.5539/jas.v12n11p246

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Abstract

Our objective was to measure alterations in the micrometeorological conditions surrounding canola seedlings during frost periods, and to quantify seedling mortality as a function of straw distribution on the ground surface. The data was acquired from 15 frosts in 2014. We used four treatments, comprising ground surface without straw (SWS), ground surface entirely straw-covered (SEC), sowing line without straw (SLW), and soil with preexisting surface straw (SES), over three experiments. Net radiation (NR), soil heat flux (G), air (Ta), leaf (Lf), rosette (Tr), and surface temperature (Ts), and plant mortality were evaluated. NR was higher in the SEC treatment and lower in the SLW treatment, whereas G was higher on straw-covered ground; Ts and Ta were lower in the SEC than in the other treatments during the most intense frosts. On 06/19, Tr in the SEC and SLW treatments was -0.66 &deg;C and 0.42 &deg;C, respectively; on 08/14, Lf was -3.62 &deg;C and -2.88 &deg;C in the SEC and SLW treatments, respectively. Plant mortality due to the frost on 06/19 was 30% in the SEC treatment, but 0% in the SLW treatment; the frost of 08/14 caused 33.8% mortality in the SEC treatment and 1.25% in the SLW treatment. This therefore showed that removing straw from the sowing line improved the microclimate around the plants, thus reducing canola mortality at the beginning of the growth cycle, which is when frost events most frequently occur.

Highlights

Canola (Brassica napus L.) plants are susceptible to frost damage at the beginning of their development cycle (Sovero, 1993; Dalmago et al, 2010; Fiebelkorn & Rahman, 2016; Jan et al, 2017)
Favorable conditions for surface and air cooling occurred on four dates, especially on three of these (06/19, 07/26, and 08/14), when Tdp was below Ta0.27 at the beginning of the night
On the night of 05/24, fog formed when U was above 1 m s-1 (Figure 1), a level that favors the mixing of stratified cold air layers, promoting condensation of excess vapor (Nemitz, 2009)

Summary

Introduction

Canola (Brassica napus L.) plants are susceptible to frost damage at the beginning of their development cycle (Sovero, 1993; Dalmago et al, 2010; Fiebelkorn & Rahman, 2016; Jan et al, 2017). Air temperatures of -2 °C to -6 °C may cause significant harm to plants with one to five leaves, and may even lead to plant death (Sovero, 1993; Wilen, et al, 1994; Thomas, 2003; McClinchey & Kott, 2008; Dalmago et al, 2010; Fiebelkorn & Rahman, 2016; Jan et al, 2017). The thermal conductivity of straw is lower than that of clay soil (Ahn et al, 2009) This may mean that, during frosts, the coldest air temperatures are found immediately above the ground surface (Kaspar & Erbadch, 1998; O’Brien & Daigh, 2019), and that canola seedlings, which are closer to the straw, may exhibit more severe damage. Most of the available information about frost damage in canola and jas.ccsenet.org

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