Shortwave Radiation Affected by Agricultural Practices

Jerzy Cierniewski,Sławomir Królewicz,Eyal Ben-Dor,Arnon Karnieli,Cezary Kaźmierowski,Jakub Ceglarek

doi:10.3390/rs10030419

Jerzy Cierniewski, Sławomir Królewicz + Show 4 more

Open Access

https://doi.org/10.3390/rs10030419

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Abstract

The albedo of bare soil depends on its organic matter, iron oxide, carbonate contents, and reflectance geometry, features considered stable over time, and also depends on salinity, moisture and roughness, which change dynamically due to agricultural practices. This paper deals with the quantitative estimation of the amount of shortwave radiation that could be reflected by air-dried bare soils in clear-sky conditions within arable lands in Israel throughout the year, assuming that they were shaped by a plough, a disk harrow, or a smoothing harrow. An area of bare soils was extracted from Landsat 8 images, within the contours of arable lands. The radiation reflected from the bare soils was calculated by equations predicting variations in their half-diurnal albedo as the solar zenith angle function. Accordingly, laboratory reflectance data of Israeli soil samples were used. The results clearly showed annual variation in the amount of short-wave radiation reflected from all bare soils within arable lands. The minimum radiation occurred in the winter, between the 1st and 70th day of the year (DOY), and the maximum was identified in the summer between 200th and 250th DOY. This could reach about 3–5 PJ/day and 16–23 PJ/day, respectively.

Highlights

The broadband albedo of bare soils depends on their brightness, which is affected mainly by the soil’s content of organic matter, iron oxides, and carbonates and by their reflectance geometry
The goal of the current paper is to estimate the highest possible amount of shortwave radiation that could be reflected from bare soils within arable lands in Israel throughout the year, depending on the roughness of the soil surfaces caused by the use of selected agricultural tools
The arable lands of Israel were very attractive for this research due to the high stability of sunny days, making it very useful for collecting the half-diurnal albedo of soils in various roughness states, as well as due to the different distributions of the radiation maximum in Israel compared to Poland

Summary

Introduction

The broadband albedo of bare soils depends on their brightness, which is affected mainly by the soil’s content of organic matter, iron oxides, and carbonates and by their reflectance geometry (slope aspect and the sun angle). These properties are considered to be stable with time or corrected, in contrast to soil surface roughness, salinity and moisture content, which change dynamically, especially due to agricultural practices in arable lands. The range of albedo (on a scale of 0–1) of dark-coloured, wet, and rough soils, is about 0.05–0.15, while that of light-coloured, dry, and smooth ones is usually 0.35–0.4 [1,2]. Matthias et al [8] reported that the ploughing of soils decreased their reflectance by about 25%

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