1. General Model Information

Name: OZCOT - A simulation model for cotton crop management.

Acronym: OZCOT

Main medium: terrestrial
Main subject: agriculture, hydrology
Organization level: ecosystem
Type of model: compartment model
Main application:
Keywords: crop, nitrogen, water-balance, cotton


Dr. A.B. Hearn(1) and Mr. M.P. Bange(2)
(1)CSIRO, Division of Plant Industry, Cotton Research Unit, P.O.Box 59, Narrabri, NSW 2390 AUSTRALIA.

(2)CSIRO, Australian Cotton Research Institute, P.O.Box 59, Narrabri, NSW 2390 AUSTRALIA.
Phone: (1)+61.67.991500 and (2)+61.67.991500
Fax: (1)+61.67.931186 and (2)+61.67.931186



A simple temperature driven model of the fruiting dynamics (Hearn & Da Rosa, 1985) was linked to the widely used Ritchie (1972) soil water balance model. The function describing the processes in the fruiting model were made sensitive to solar radiation, water and nitrogen stress and water logging, and a leaf area generator, a boll growth model and an elementary nitrogen model were included. The model can be used for dryland and irrigated crops, and for specific historical crops with given sowing and irrigation dates, or the model can simulate the sowing and irrigation date decisions. Output at the end of the season consists of yield and yield components, nitrogen uptake, seasonal evapotranspiration and the number of irrigations and amount of irrigation water. Within season, either daily or at selected intervals, output consists of numbers of squares, bolls and open bolls, leaf area index and soil water content. OZCOT is applied throughout cotton growing areas in Australia. OZCOT assumes that the soil is one of the vertisols on which cotton is usually grown in Australia, and that there is negligible deep drainage, so that any rainfall or irrigation in excess of that needed to restore the soil to the upper limit runs off. Soil water balance is too simplistic in respect to drainage and run off. The soil nitrogen model is rudimentary and not process based. The ability of OZCOT to differentiate between varieties is limited. The model does not simulate fibre quality and can only partially simulate skip-row planting configurations. Target use/user group: On-farm, consultants, extension workers, planning, research, water allocation policy.

Purpose of the model: : Management and economic decision making for cotton production at strategic and tactical levels; regional climatic analysis. Tactical use includes pest management, therefore fruiting is simulated in sufficient detail interface with insect feeding models.

Model parentage:

Source of the AbstractCAMASE Register of Agro-ecosystems Models

II. Technical Information

II.1 Executables:

Operating System(s):

II.2 Source-code:

Programming Language(s):

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

Weather data: rainfall, maximum and minimum temperature, solar radiation, optionally wet and dry bulb. Agronomic data: variety, plant population and row spacing, sowing date or sowing window, irrigation dates or parameters for irrigation, expected seasonal uptake of non-fertilizer N (previous crop or soil test), date and amount of N fertilizer. Soil data: plant available soil water capacity and initial content by layers.

III.2.2 Output

IV. References

Hearn, A.B. & G.D. da Roza, 1985. A simple model for crop management applications for cotton (Gossypium hirsutum L.). Field Crops Research 12: 49-69
Hearn, A.B., 1994. OZCOT: A simulation model for cotton crop management. Agricultural Systems 44: 257-299
Talpaz, H., G.D. da Roza & A.B. Hearn, 1987. Parameter estimation and calibration of simulation models as a non-linear optimization problem. Agricultural Systems 23: 107-116

Bryant, M. et al., 1989. A study of reliability of water supply for irrigated cotton in the Namoi Valley. Centre for Water Policy Research.
Cox, P.G. & A.B. Hearn, 1990. A simple spreadsheet model of the area of irrigated cotton to plant. Fifth Australian Cotton Conference, Broadbeach, 8-9 August, 1990. ACGRA, Wee Waa. 123-127
Dudley, N.J. & A.B. Hearn, 1993. El Nino effects hurt Namoi cotton growers, but they can do little to ease the pain. Agricultural Systems 42: 103-126
Dudley, N.J. & A.B. Hearn, 1993. Systems modelling to integrate river valley water supply and irrigation decision making under uncertainty. Agricultural Systems 42: 3-23
Hearn, A.B., 1988. Water use - an update on strategies. The Australian Cotton Grower 9: 4-7
Hearn, A.B., 1990. Climatic risk in Australian cotton production. Models and management in the semi-arid tropics and subtropics. In: Muchow, R.C. & J.A. Bellamy (Ed.). Poster papers from the International Symposium, Brisbane, 2-6 July, 1990. CSIRO Division of Tropical Crops and Pastures, Brisbane. 48-49
Hearn, A.B., 1990. Prospects for rain-fed cotton. Fifth Australian Cotton Conference, Broadbeach, 8-9 August, 1990. ACGRA, Wee Waa. 135-144
Hearn, A.B., 1992. Risk and reduced water allocations. The Australian Cotton Grower 13(5): 50-55
Hearn, A.B., 1995. High prices and low rainfall: calculating the risk. The Australian Cotton Grower 16(5): 20-28
Routley, S.A. & C.A. Constable, 1994. Sensitivity of Australian raingrown cotton yield to soil and climate. In: Gonstable, G.A. & N.W. Forrester (Ed.). World Cotton Research Conference - 1: Challenging the future. Brisbane, Australia 14-17 February 1994. CSIRO, Melbourne.
Sharpley, A.N., & J.R. Williams (Eds.), 1990. EPIC - Erosion/Productivity Impact Calculator. 1. Model Documentation. U.S. Department of Agriculture Technical Bulletin No. 1768. 235 pp.
Aslyng, H.C. & S. Hansen, 1985. Radiation, water and nitrogen balance in crop production. Field experiments and simulation models WATCROS and NITCROS. Hydrotechnical Laboratory. The Royal Veterinary and Agricultural University, Copenhagen. 146 pp.
Hansen, S., H.E. Jensen, N.E. Nielsen & H. Svendsen, 1991. Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model Daisy. Fertilizer Research 27: 245-259

V. Further information in the World-Wide-Web

VI. Additional remarks

Parentage: Actual Evaporation Model according to RITCHIE 1972
Last review of this document by: T. Gabele: Dec 10 1997
Status of the document:
last modified by Joachim Benz Mon Jul 2 18:31:37 CEST 2007

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