Monday, 10 July 2006

Two-Dimensional Soil Water and Temperature Dynamics Under Row Crops: Modeling Approaches.

Dennis Timlin1, Rose M. Shillito2, Yakov A. Pachepsky3, Soo-Hyung Kim4, David Fleisher5, and Bruno Quebedeaux2. (1) USDA-ARS Crop Systems and Global Change Lab, Bldg 001, Rm 342 BARC-W, 10300 Baltimore Ave, Beltsville, MD 20705-2350, (2) Univ of Maryland, Dept of Natural Resource Sciences and Landscape Architecture, College Park, MD 20742, (3) USDA/ARS/BA/ANRI/ESML, Bldg.173, Rm. 203, Powder Mill Road, Beltsville, MD 20705, (4) USDA-ARS, Bldg 001 Rm 342, BARC-W, Beltsville, MD 20705-2350, (5) USDA, ARS, Crop Systems and Global Change Lab., Bldg 001, Rm 342 BARC-W, 10300 Baltimore Avenue, Beltsville, MD 20705

Water movement and heat transport in soil under row crops varies both vertically and laterally. This is partially due to the presence and spatial distribution of the plant canopy and roots. The spatial variation in water and heat fluxes around the plant can affect solute transport, and water and temperature dependent soil processes. Physically-based crop/soil models can be used to make management decisions that take two dimensional processes into account. The objective of the research presented here is to model root activity and soil infiltration in and around a corn plant with contrasting canopy development. Data were collected from two plots planted to maize, one in a no nitrate treatment and one in a high nitrate treatment. In each plot, a total of 24 soil moisture probes were placed beneath and between corn plants and at depths of 20, 40, and 60 cm. Thermocouples were also placed at each location. The maize simulation model, MAIZE-SIM, was used to simulate water movement and heat transport. This is a mechanistic model of maize growth and development model that uses, 2DSOIL, a two dimensional finite element model to simulate soil processes. Temperature and water dynamics varied with spatial location and canopy development. The model simulated surface water contents better than subsurface water contents. Canopy interception of rainfall and radiation need to be accounted for in order to modify boundary conditions for heat transfer and infiltration of water. The spatial and temporal distribution of soil moisture as a function of nitrogen plant stress is discussed. Along with data from an evapotranspiration sensor located in the field, water uptake in the corn plants is evaluated.

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