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United States Department of Agriculture

Agricultural Research Service

Title: Water and Energy Balances at Soil-Plant-Atmosphere Interfaces

Author
item Evett, Steven

Submitted to: CRC Press
Publication Type: Book / Chapter
Publication Acceptance Date: July 1, 2000
Publication Date: January 30, 2002
Citation: EVETT, S.R. WATER AND ENERGY BALANCES AT SOIL-PLANT-ATMOSPHERE INTERFACES. WARRICK, A.A. EDITOR. CRC PRESS; CHAPTER 5. 2002. P. 127-188 THE SOIL PHYSICS COMPANION.

Interpretive Summary: Understanding of the balances of water and energy at the earth's surface is critical to effective management of earth's resources. This chapter examines in detail the movement of water and energy at, into, and out of soil and plant surfaces. Energy from sunlight is seen to be the principle driving force for evaporation from soil and plants. The chapter explains methods of measurement and current instrumentation and its limitations. Also, it gives methods of calculation or modeling of energy from sunlight, evaporation losses, and heat movement to and from soil, plants, and atmosphere. Detailed information is given on how much sunlight is reflected from soil and plant surfaces. The interactions between water in and entering the soil and the balances of sunlight and heat energies are explored. Methods of measurement of the soil water are given with recommendations. In eight examples, further discussion and/or problem sets are given. These cover i) remote sensing of plant growth, ii) precision farming research, iii) crop water use calculation, iv) soil heating, v) heat movement due to wind, vi) the effects of farming practices on surface water movement and conservation, vii) techniques of soil water measurement, and viii) estimation of movement of water to and from the water table.

Technical Abstract: Understanding of the balances of water and energy at the earth's surface is critical to effective management of earth's resources. This chapter examines in detail the surface energy balance and its components of latent and sensible heat flux, net radiation, and soil heat flux. It explains methods of measurement and current instrumentation and its limitations. Also, it gives methods of estimation or modeling of solar and net radiation, latent heat flux, and sensible and soil heat fluxes. Detailed information is given on surface albedo and emissivity and modeling of soil albedo and sky emissivity. The interactions between the soil water balance and the surface energy balance are explored, and methods of measurement of the soil water balance are given. In eight examples, further discussion and/or problem sets are given. These cover i) spectral reflection and radiation for remote sensing of plant attributes, ii) precision farming research, iii) the Penman approximation and its effect on Penman-Monteith equation estimates of latent heat flux, iv) estimation of soil thermal conductivity, v) convective heat flux from soil to air due to wind, vi) human modification of surface water storage capacity, vii) the neutron scattering technique of soil water measurement, and viii) deep flux estimation in soil water balance calculations.

Last Modified: 8/1/2014
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