Remote Sensing of Soil Moisture in Vineyards Using Airborne and Ground-Based Thermal Inertia Data

Aiman Soliman,Ralph Brown,Alexander Brenning,Stephen Miller,Richard Heck

doi:10.3390/rs5083729

Aiman Soliman, Ralph Brown + Show 3 more

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https://doi.org/10.3390/rs5083729

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Abstract

Thermal remote sensing of soil moisture in vineyards is a challenge. The grass-covered soil, in addition to a standing grape canopy, create complex patterns of heating and cooling and increase the surface temperature variability between vine rows. In this study, we evaluate the strength of relationships between soil moisture, mechanical resistance and thermal inertia calculated from the drop of surface temperature during a clear sky night over a vineyard in the Niagara region. We utilized data from two sensors, an airborne thermal camera (height ≈ 500 m a.g.l.) and a handheld thermal gun (height ≈ 1 m a.g.l.), to explore the effects of different field of views and the high inter-row temperature variability. Spatial patterns of soil moisture correlated more with estimated thermal inertia than with surface temperature recorded at sunrise or sunset. Despite the coarse resolution of airborne thermal inertia images, it performed better than estimates from the handheld thermal gun. Between-row variation was further analyzed using a linear mixed-effects model. Despite the limited spatial variability of soil properties within a single vineyard, the magnitudes of the model coefficients for soil moisture and mechanical resistance are encouraging indicators of the utility of thermal inertia in vineyard management.

Highlights

The quality and quantity of grapevine production is controlled by many factors, such as soil characteristics, climate, management system and the frequency of exposure to pests and diseases.Recent studies [1,2] show that productivity within a single vineyard could vary as much as eight-fold.Precision viticulture takes advantage of remote sensing and geomatics to model this variation and estimate yield quality and quantity at the vineyard level [3].Soil is an important factor in determining the productivity of vineyards
We evaluate a technique for estimating thermal inertia using airborne thermal images acquired over a grass covered soil in a vineyard in the Niagara Region, Ontario, Canada
We further explore the functional relationships between estimated thermal inertia in the presence of grass sod and subsurface soil properties

Summary

Introduction

The quality and quantity of grapevine production is controlled by many factors, such as soil characteristics, climate, management system and the frequency of exposure to pests and diseases.Recent studies [1,2] show that productivity within a single vineyard could vary as much as eight-fold.Precision viticulture takes advantage of remote sensing and geomatics to model this variation and estimate yield quality and quantity at the vineyard level [3].Soil is an important factor in determining the productivity of vineyards. The quality and quantity of grapevine production is controlled by many factors, such as soil characteristics, climate, management system and the frequency of exposure to pests and diseases. Observations show that high and low production regions within a vineyard tend to be stable over a longer time [4], and these patterns relate to soil spatial distribution, micro-climate patterns and topography variations [5]. The common method for calculating thermal inertia depends on the periodic daily heating [29]; in contrast, Equation (2) depends on the non-periodic cooling of the surface under still and clear sky conditions. The absence of turbulent heat fluxes (i.e., sensible heat flux and latent heat) during the night simplify the relation between surface temperature and ground heat flux, which cannot be guaranteed during the day [30]

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