Measurements for Functional - Structural Crop Models

The aim of this chapter is to give an overview of the measurements needed for development and parameterization of a functional-structural crop model. Special emphasis will be given to measurements for structural/architectural processes. Size (area, length, width, thickness, volume) of the various organs (e.g., leaves, internodes, flowers, fruits and roots), as well as number of organs, 3D position and time of measurement need to be recorded. Existing methods for full 3D data capture and automatic feature extraction still present many problems. Therefore, human-operated sonic or magnetic trackers are at the moment more suitable to extract and store relevant information. Physiological processes like photosynthesis, transpiration and carbon allocation require measurements of freshand dry-matter weight of the various organs throughout the growing season. For vegetables, fruit and ornamental crops, thermal time to harvest needs to be recorded. In many cases a limited chemical analysis (NPK) is also performed. Depending on the crop, we may assume a common assimilate pool. If this is not feasible, we need estimates of flow and sink/source strength of organs in time. However, adequate measurement methods are currently lacking, hampering development of these models. Environmental measurements are needed to model the interaction of the plant with its environment. In most cases this at least involves measurement of light and temperature near (slightly above) the crop at frequent intervals. Furthermore, a detailed description of the test site, growth system and crop management is needed. Measurements of relative humidity and carbon-dioxide concentration of the air and various attributes of the root system are less frequently used.