Evaluation of an Energy-Driven Soil Water Model for GOSSYM

Dana O. Porter


 
ABSTRACT

The GOSSYM cotton crop simulation model has been used widely over the last few years as a production management decision tool for irrigation and fertilizer application scheduling, harvest scheduling, and yield prediction. Continued research and development of the GOSSYM system are directed to improve GOSSYM's performance as a plant growth simulator, increase its applicability to different production conditions, and enhance its usefulness as a crop research and production management tool.

A major portion of the GOSSYM model involves the simulation of processes in the soil environment. These processes determine the availability of water and nutrients to support plant growth and development, as well as specific conditions which affect plant roots. Soil water processes addressed in GOSSYM include 1) surface runoff of rainfall and irrigation; 2) infiltration of water into the root zone; 3) capillary flow or redistribution of water within the root zone; 4) leaching or deep percolation losses; 5) transport of dissolved nitrogen; 6) root extraction of soil solution; and 7) evapotranspiration. A change incorporated into the 1993 update of GOSSYM involves a revision of the method for calculating water movement between soil layers. The new method enables the model to take into account soil hydraulic potential gradients in determining the direction of flow across inter-layer boundaries. A sensitivity study was conducted to determine effects of the water flux calculation change on GOSSYM's soil model output parameters. Results of the study affirmed that the effects are greatest in simulations on soils in which the soil moisture characteristic curves of adjacent layers intersect one another.

Among the new developments intended for incorporation into the GOSSYM system in the near future are a new flow-rate runoff and infiltration model and a new energy-driven water flux model. The new runoff model takes into account rainfall intensity and the soils infiltration capacity in estimating effective precipitation rate. Infiltration of effective precipitation is accomplished through Darcy flow.

Features of the new soil water flux model include flexible boundary conditions and an adjustable soil cell grid which will allow the model to facilitate a range of cropping systems and alternative irrigation systems. Water flux is driven by gradients in soil hydraulic potential.

New developments in GOSSYM's soil water model are designed to improve GOSSYM's performance and increase its applicability to a wider range of crop production conditions. These new models include refined prediction and calculation methods that will enhance GOSSYM as a tool for improving cotton crop management, increasing efficiency in use of farm inputs, and addressing water quality issues.



Reprinted from 1993 Proceedings Beltwide Cotton Conferences pg. 556
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified Sunday, Dec 6 1998