Soil Plant Atmosphere System Model (SPASMO)


SPASMO models the transport of water, microbes and solutes through soils integrating variables such as climate, soil, water uptake by plants in relation to farm and orchard practices, and any other factors affecting environmental process and plant production.


SPASMO, which has been in continuous development for over 20 years, has been used by six Regional Councils for allocation of irrigation water. It has also been used in a large number of projects within other Regional Councils, commercial clients and researchers.

The SPASMO computer model considers water, solute (e.g. nitrogen and phosphorus), and microbial (e.g. viruses and bacteria) transport through a 1-dimensional soil profile. The soil water balance is calculated by considering the inputs (rainfall and irrigation) and losses (plant uptake, evaporation, runoff and drainage) of water from the soil profile.

The model includes components to predict the carbon, nitrogen and phosphorus budget of the soil. These components allow for a calculation of plant growth and uptake of both N and P, various exchange and transformation processes that occur in the soil and aerial environment, recycling of nutrients and organic material to the soil biomass, and the addition of surface applied fertiliser and/or effluent to the land.

The filtering capacity of the soil with regard to micro-organisms is modelled using an attachment-detachment model with inactivation (i.e. die-off) of microbes. SPASMO is currently used as an 'in house‘ code within Plant and Food Research. Models are tailored according to the individual needs of the end user. End users are councils at regional and district levels as well as consultants, and the model accounts for a range of on-farm and within-orchard practices. For example, consultants may use a SPASMO framework when analysing irrigation to determine the need to irrigate a given crop in the next week, month or period until harvesting, on a particular soil given the weather history at the site and the current weather-cycle conditions.

SPASMO incorporates data from several databases including weather and soil databases and from information such as material safety data sheets for pesticides which record the holding times in soils. Because a unique SPASMO simulation is created for individual client, and their farm and orchard practices, the data sources used are appropriate for the question and for the time period specified. SPASMO is now being used as the software engine for online, real-time irrigation scheduling, and it has also been modified to act as a water footprint calculator for primary products.

Latest Version 2012
State of Development Closed Beta
Current Development Activity As needed

Development Contact

Brent Clothier
+64 6 953 7687
Plant & Food Research
Private Bag 11-600
Palmerston North 4442
New Zealand

Main Developers

  • Plant & Food Research


Outcome Areas Environmental, Economic
Management Domains Land
Subdomains Contaminant Losses, Water Yield, Crop/Farm Systems, Pesticide leaching
Intended End Users In-house only
Spatial Resolutions Point
Spatial Extents Regional
Spatial Dimensions 1D
Temporal Resolutions Days
Temporal Extents Dependent on weather data, Years, Decades, Centuries
Steady State or Dynamic Dynamic
Level of Integration Economic, Environmental

Input & Output Data

Key Input Data Land Use, Rainfall, Temperature, Potential Evaporation
Input Data Formats CSV
Key Output Data Micro-economic data, Runoff, Drainage leaching, gaseous loss
Output Data Formats CSV


Open/Closed Source Closed Source
Licence Type No Licence
Licence Cost
(Non Commercial)
Not available for non-commercial use
Licence Cost
Not available for commercial use

User Information

Operating Systems MS Windows
Software Needed Unknown
User Interface Other (please specify)
Ease of Use Difficult Difficult because of the complex structure and large range input data files required.
Use in Policy Process Plan (Policy Formulation), Do (Policy Implementation), Review (Issue Identification)

N/A but there are several publications with some parts of the model described

Support Meta-model to end-users available
Users Forum Not Available

Technical Considerations

Programming Language Fortran
Methods included for calibration and validation Extensive calibration and validation; see references
Methods included for managing uncertainty Outputs are given as probability distributions.
Analytical Techniques Input/output, GIS, System dynamics
Keywords irrigation, nutrient leaching, soil, climate, plant production
Linkages to other Models
Key References
R. Cichota & V. O. Snow (2010) Estimating nutrient loss to waterways—an overview of models of relevance to New Zealand pastoral farms, New Zealand Journal of Agricultural Research, 52:3, 239-260, DOI: 10.1080/00288230909510509

Rosen MR, Reeves RR, Green SR, Clothier BE, and Ironside N, 2003. Prediction of Groundwater Nitrate Contamination after Closure of an Unlined Sheep Feedlot. Vadose Zone Journal 3, 1990-2006.

Green SR and Clothier BE 1995. Root-water uptake by kiwifruit vines following partial wetting of the rootzone. Plant and Soil 173:317-328.

Green SR, Kirkham MB, and Clothier BE 2006b. Root uptake and transpiration: from measurements and models to sustainable irrigation. Agricultural Water Management 86:165-176

Green, S.R., B.E. Clothier, C. van den Dijssel, M. Deurer and P. Davidson, 2008. Measurement and modelling the stress response of grapevines to soil-water deficits in their rootzones. Chapter 15, In Soil Science Society America Monograph “Modeling the response of crops to limited water: Recent advances in understanding and modeling water stress effects on plant growth processes”, L. Ahuja et al.[Eds] Chapter 12, pp 357-386

Associated Case Studies

SPASMO - Groundwater Nitrate Contamination after Closure of a Feedlot.

Nitrate contamination of groundwater by a sheep feedlot in Hawke's Bay, New Zealand led to closure of the feedlot in 1998.