Diploma thesis: "Modelling of plant-relevant processes

of organic farming using the model CANDY

including the plant module SIWAPFLAN

at the example of Bad Lauchstädt"

Janine Krüger (Dipl. Geogr.)


The processes of plant growth are one of the most important agroecosystem functions. All are essentially determined by fluctuations of the environmental factors under natural conditions. Changes in environmental conditions influence e.g. soil moisture availability and the plant root uptake of soil nutrients and water. It also affects the onto-genesis and depends on the growth stage of a plant which can result in large losses of plant biomass (VLEK et al. 2007). Knowing the interactions of all factors on a specific site facilitates statements of plant-relevant processes due to environmental factors.
With the help of agroecosystem models it has been attempted to cope with complex natural processes and interactions for more than four decades. Those models abstract and quantify the natural processes and factors of influence using mathematical equations which are subsequently used to reveal the interactions. Based on the quantification, the effects of environmental and agronomic management factors on plant growth processes can be determined and analysed.
CANDY (Carbon and Nitrogen dynamics) (FRANKO 1995a) represents one model in a pool of various agroecosystem models. Its modelling is based on the results of an intensive monitoring and the long term experiments in Bad Lauchstädt. Until now, the model CANDY includes plant dynamics as a simple empirical approach without considering environmental factors. To improve this lack, the plant module SIWAPFLAN (based on SIMWASER (STENITZER 1988)) was implemented in the model CANDY with the aim to model extensive plant processes. The generic module for different plants reacts on the base of environmental influences and simulates plant-relevant variables and processes on the same basis.
Thus, the present study is understood as applicability assessment and improvement of the plant module SIWAPFLAN to describe plant dynamics. The assessment and improvement of the module are based on plant variables which represent and quantify the plant growth processes in an agroecosystem. A detailed observation and measurement time series of crop variables (e.g. leaf area index) are required.