At the heart of mechanistic, process-level, crop simulation models are rate equations that describe the physiological responses of crop plants to environmental variables.In order to develop these rate equations, experiments are conducted under carefully controlled environmental conditions.

Experiments are performed in controlled environment chambers, glasshouses and field plots.

Outdoor, naturally sunlit, plant growth chambers referred to as SPAR (Soil Plant Atmosphere Research) units provide precise control of the major environmental variables influencing crop growth including temperature, humidity and atmospheric carbon dioxide concentration.

The SPAR units are fully automated to measure crop
canopy gas exchange, including photosynthesis, respiration, 
transpiration and water use efficiency.