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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Canopy Shading and Irrigation on Soil Water Content and Temperature

Authors
item Fares, A - UNIV. HAWAII-MANOA
item Simunek, Jirka - UC RIVERSIDE, CA
item Parsons, L - UNIV. FLORIDA
item Van Genuchten, Martinus
item Morgan, K - UNIV. FLORIDA

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2005
Publication Date: October 1, 2005
Citation: Fares, A., Simunek, J., Parsons, L.R., Van Genuchten, M.T., Morgan, K.T. 2005. Effects of canopy shading and irrigation on soil water content and temperature. In: S. Torkzaban and S. Majid Hassanizadeh (eds.), Proceedings of Workshop on HYDRUS Applications, p. 6-10, October 19, 2005, ISBN 90-39341125, Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands.

Interpretive Summary: Root systems of trees, such as most citrus crops, are usually exposed to different thermal and hydrologic conditions as a result of tree canopy shading and micro-irrigation below the canopy. Because micro-sprinklers wet only part of the soil surface and are located under the tree, roots under the canopy usually receive more water than those outside the tree canopy. Also, assuming isothermal (constant temperature) conditions in studying water movement and root uptake can result in relatively large errors. We investigated shading and irrigation effects on the spatial distribution of water content and soil temperature at different soil depths. We were especially interested in the combined effects of varying soil temperatures and water input on the redistribution of soil moisture under field conditions in Florida sandy soils. Detailed water content and soil temperature measurements were carried out, while weather parameters were monitored simultaneously at the same location. Two-dimensional unsaturated water flow and heat transport at the site were simulated using the HYDRUS-2D computer software package. The predicted water contents and soil temperatures compared favorably with their corresponding observed parameters. HYDRUS-2D was found to be very helpful for optimal analysis of the field data. Results of studies like this one give insight in the unequal subsurface moisture and temperature distributions below trees. These two variable are key factors determining the chemical, physical and biological functioning of a soil.

Technical Abstract: Citrus root systems are exposed to different thermal and hydrologic conditions as a result of tree canopy shading and under-tree micro-irrigation. Because micro-sprinklers wet only part of the soil surface and are located under the tree, roots under the canopy usually receive more water than those outside the tree canopy. The combined effects of different soil temperature and water input on water redistribution under field conditions have not been fully studied in Florida sandy soils. The objective of this study was to investigate shading and irrigation effects on spatial distribution of water content and soil temperature at different soil depths. Real-time capacitance soil water sensors and thermocouples were used to monitor soil water content and temperature at depths of 0, 10, 20, 40, 80 and 150 cm. Weather parameters were monitored simultaneously at the same location. HYDRUS-2D, a two dimensional computer package for simulating movement of water, heat, and multiple solutes in variably saturated media, was used to simulate water flow and heat transport under such conditions. The predicted water contents and soil temperatures compared favorably with their corresponding observed parameters. In addition to its accuracy in simulating this system, HYDRUS-2D helped to improve the analysis of this research project.

Last Modified: 11/26/2014
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