D. L. Nofziger
Department of Agronomy,
Oklahoma State Agricultural Experiment Station
Oklahoma State University,
Stillwater, OK 74074
A. G. Hornsby,
Dept. of Soil &Water Science
University of Florida
Gainesville, FL 52611.
User support is available by
CMLS was written to serve as a management tool and a decision aid in the application of organic chemicals to soils. The model estimates the location of the center of mass of non-polar organic chemicals as they move through a soil in response to downward movement of water. The model also estimates the relative amount of each chemical still remaining in the soil at any time. The results may be displayed in graphical and tabular forms. The model was developed so it can be easily used and input parameters are easily obtained. CMLS is an expansion of a simpler model (CMIS) of Nofziger and Hornsby (Nofziger, D.L., and A.G. Hornsby. 1985. Chemical movement in soil: IBM PC user's guide. IFAS, University of Florida. Circular 654.) for organic chemical movement in a uniform (homogeneous) soil. CMLS differs from CMIS in six ways: (1) This model can deal with soils with up to 20 layers or horizons. Thus, soil properties need not be assumed uniform over all depths. (2) This model enables the user to enter partition coefficients for each horizon in the soil. (3) This model enables the user to specify the degradation half-life of the chemical of interest for each horizon in the soil, rather than using one value for all depths. (4) This model enables the user to simulate movement of the chemical for up to 15 years. (5) This software includes graphical displays for the relative amount of the chemical remaining in the soil as a function of time as well as tabular displays of the time required for the selected chemicals to move to user-specified depths in the soil profile. (6) Data management tools are included to enable the user to enter soil and chemical properties for sites of interest.
Details of the computational algorithm and simplifications used in CMLS are given in a published manuscript (Nofziger, D.L., and A.G. Hornsby. 1986. A microcomputer-based management tool for chemical movement in soil. Applied Agricultural Research 1:50-56). They are also included in electronic form in the user's manual provided with the software.
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 (CMLS94b) 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.
Source of the Abstract: Information by the Model developers at http://clay.agr.okstate.edu/software/cmls86a.htm and http://clay.agr.okstate.edu/software/cmls94a.htm