CHEMICAL MOVEMENT IN LAYERED SOILS: CMLS94

Developers
Description
Water Quality Applications
Features
Limitations
Support
Latest Release
Resource Requirements
Downloading Information
Batch Version of CMLS
Supplemental Information
Installation Instructions

Developers: D. L. Nofziger, Department of Agronomy, Oklahoma State Agricultural Experiment Station, Oklahoma State University, Stillwater, OK 74074 and A. G. Hornsby, Dept. of Soil & Water Science, University of Florida, Gainesville, FL 52611.

Description: CMLS94 is an update to the original CMLS model of Nofziger and Hornsby written to serve as a management tool and a decision aid for the application of organic chemicals. CMLS can be used to estimate the movement of chemicals in soils in response to downward movement of water. The model also estimates the degradation of the chemical and the amount remaining in the soil profile. CMLS was specifically formulated for ease of use. All of the parameters required by the model are relatively easily obtained. CMLS94 includes routines to estimate daily infiltration and evapotranspiration values from historical weather records.

A new feature of CMLS94 is the ability to assess uncertainty in leaching estimates due to unknown future weather at a site, spatial variability of soils, and uncertainty in chemical properties. This additional capability provides the decision-maker with insight into the range of leaching expected or the probability of leaching more than a specified amount of chemical past some critical depth. Sixteen types of graphs and various forms of tables are provided to view results. Extensive data entry and editing capabilities are also provided. The model is written for MS-DOS computers and is available on the Internet.

Water Quality Applications: Examine the position and amount of pesticide in the vadose zone as a function of time for specific soils, application dates, application depths, weather and irrigation regimes, and other site-specific conditions.

Obtain probability distributions for the amount of chemical leaching beyond a critical depth, the depth of chemical at a specific time, and the time required for a chemical to reach a specified depth.

Compare the leaching potential of different pesticides for a specific soil-management system.

Rank pesticide leaching for different pest management systems.

Estimate the current depth of an applied pesticide to determine if an additional application is needed.

Demonstrate the impact of specific soil properties, chemical properties, weather, and management practices upon pesticide leaching.

Features: CMLS94 is an interactive model in which the user defines the soil - chemical - management system using pull-down menus and interactive screens. Context-sensitive help messages are available to aid the user. A batch version of the software is available for large studies and GIS work.

The effect of unknown future weather at a site upon leaching estimates can be determined using a built-in Monte Carlo simulator and the WGEN weather generator of Richardson and Wright.

Soil and chemical properties required in the model are easily obtained.

Sixteen types of graphs and numerous types of tables are provided so the user can easily examine the results of simulations. These include histograms and probability distributions for examining the range of behaviors resulting from uncertainties in future weather at the site as well as naturally variable soil and chemical properties.

A soil profile can be made up of up to 20 layers with different soil properties. Sorption coefficients and degradation rates of chemicals can change from layer to layer.

Supplemental irrigation can be read from a file, applied on a periodic basis, or scheduled by depletion of water in the root zone.

The impact of tillage upon leaching can be estimated by simulating transport using different curve numbers appropriate for each practice.

Extensive database management capabilities are built into the software to enable the user to enter and reuse soil and chemical properties for their sites.

Daily infiltration amounts can be provided by the user or estimated from daily weather records. Daily evapotranspiration can be read from user-provided input files or estimated from daily weather data using one of several built-in estimators.

English or metric units can be used.

Limitations: The CMLS94 user's manual describes in detail all of the processes incorporated into the model and the assumptions made in it. In some applications the assumptions may be limitations, but in many cases they represent useful simplifications based on comparisons with research models.

CMLS94 does not attempt to estimate pesticide concentration profiles, only the location of the center of mass and total amount of pesticide.

CMLS94 does not track the production, transport and fate of chemicals produced during degradation of the applied pesticide.

Upward movement of pesticide in the profile is ignored. This may lead to overestimating leaching in very dry regions.

The degradation rate is not adjusted for temporal changes in temperature or soil water content.

CMLS94 does not attempt to estimate preferential pesticide movement through large soil pores and cracks.

Support: CMLS94 software, manuals, and sample databases are available free of charge via Internet. The software with printed manual is also available for $50 from the Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK 74078. User support is available by e-mail to david.nofziger@okstate.edu.

Latest Release: September, 1995. This release fixes a problem in graphical and tabular output of evapotranspiration (ET). Although the depth and amount of chemical were calculated correctly in the previous version, the daily ET saved in the output file was incorrect for days when the available soil moisture was greater than zero but less than the ET demand.

Resource Requirements: CMLS94 requires an MS-DOS compatible computer with at least 640 K bytes of random access memory, a graphics monitor (VGA or better preferred), and 3-10 MB of disk space. A 386, 486 or pentium processor is desirable for Monte Carlo simulations, but slower processors can be used. CMLS94b, the batch version of the software, can be used on any platform supporting ANSI C, such as MS-DOS PCs, and Sun workstations. Click here to download a self-extracting installation of CMLS94 (approximately 1144140 bytes).

Batch Version of CMLS: A batch version of the CMLS software useful in processing many soil - chemical - management systems at one time is available for downloading here. The manual explaining its use is online and can be printed locally. An executable version of the program for DOS/Windows is included. CMLS is written in C. The source code is included so the batch version can be compiled for different platforms. The latest version includes provision for adjusting the degradation rate for changes in temperature with time and soil depth.

Supplemental Material: - WGEN Documentation: CMLS94 contains the WGEN computational algorithms developed and tested by Richardson and Wright (Richardson, C.W., and D.A. Wright. 1984. WGEN: A model for generating daily weather variables. USDA, Agricultural Research Service, ARS-8. 83p.). This tool enables CMLS94 to carry out Monte Carlo simulations for weather at a site. The manual prepared by the authors is out of print, so it cannot be obtained from them. However, it is available in electronic form here (approximately 1187154 bytes) so it can be downloaded and printed on your system. The authors of CMLS94 recommend that you download this manual along with the CMLS94 software and databases.