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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Plant Physiology and Genetics Research » Research » Publications at this Location » Publication #234828
Title: Issues of Spatial and Temporal Scale in Modeling the Effects of Field Operatiions on Soil Properties

Author
item White, Jeffrey
item JONES, JIM - U OF FL, GAINESVILLE, FL
item PORTER, CHERYL - U OF FL, GAINESVILLE, FL
item McMaster, Gregory
item SOMMER, ROLF - ICARDA, ALEPPO, SYRIA

Submitted to: Operational Research: An International Journal (ORIJ)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2009
Publication Date: 10/14/2009
Citation: White, J.W., Jones, J.W., Porter, C., Mcmaster, G.S., Sommer, R., 2009. Issues of Spatial and Temporal Scale in Modeling the Effects of Field Operatiions on Soil Properties. Operational Research International Journal (ORIJ). DOI:10.1007/s12351-009-0067-1.

Interpretive Summary: Farmers till fields in order to enhance crop growth and conserve soil and water resources. Computer-based models of crops production are used to guide a wide range of decisions relating to agricultural production, but few such models directly predict effects of tillage. The Cropping Systems Model (CSM) was modified to simulate tillage and related field operations for typical farm situations. This paper describes how the model was modified, including what new data are required to describe tillage. The paper also discusses how the relatively simple descriptions of spatial variation in soils and the use of a daily time step in the model affect the suitability of the model for certain applications. Each tillage event is described by the date and implement used, such as a plow or harrow. The implement is characterized by its effects on soil properties, including mixing of soil layers and crop residues and its effect on soil density. The modeled responses are illustrated with a hypothetical case comparing effects of four implements (mold board plow, tandem disk, tine harrow, and planking) and a field experiment in Colorado where winter wheat was grown with different tillage and residue management practices. The new routines for field operations produced results that were similar to basic expectations on how tillage affects soil moisture and density, traits that are very important in determining crop yields. The new tillage routines thus appear suitable for applications where different tillage and residue management practices are considered, but they are perhaps best viewed as providing a framework for future work that might consider effects of residue type, soil type and soil moisture on tillage effects or deal with effects of rainfall more effectively. With further refinement, these routines should allow researchers to predict how tillage practices might be improved. Applications include to conserve water, to reduce fertilizer inputs, and to predict the possible impacts of global change on US agriculture. Improved predictions should ultimately lead to enhance yields and reduce production costs while helping farmers make decisions that conserve natural resources.

Technical Abstract: Tillage is an important procedure for modifying the soil environment in order to enhance crop growth and conserve soil and water resources. Process-based models of crop production are widely used in decision support, but few explicitly simulate tillage. The Cropping Systems Model (CSM) was modified to simulate tillage and related field operations for single seasons or multiple years. This paper provides an overview of how the new routines were implemented and discusses issues of spatial and temporal scaling that influenced the underlying strategy. The processes considered included effects of crop residues on the soil surface and on chemical and physical properties that vary with soil depth. Each event is described by date and implement used. The implement is characterized by its effects on soil properties, including mixing of soil layers and crop residues and changes in soil bulk density. The modeled responses are illustrated with a hypothetical case comparing effects of four implements (mold board plow, tandem disk, tine harrow, and planking) and a field experiment where winter wheat (Triticum aestivum L.) was grown with different tillage and residue management practices. From a programming viewpoint, a key issue was how to manage different spatial and time scales. The soil nominally is assumed to vary only with depth, but the thickness of the soil is affected by tillage. This poses challenges for ensuring that the masses for water, nutrients, residues and the soil per se are conserved, as soils layers are mixed and the density of each layer is altered. The model runs on a daily time step, but events such as tillage, application of residue, and irrigation can all happen within a single day. The new routines for field operations appears suitable for applications where different strategies for tillage and residue management are considered, but they are perhaps best viewed as providing a framework for future work that might consider effects of residue type, soil type and soil moisture on tillage effects and that dealt with effects of rainfall kinetic energy in more detail. [GRACEnet Publication]