This master thesis is conducted in a co-operation between the Plant Production Systems Group of Wageningen University and Farm Frites, the third largest potato processing company in Europe. In various countries, potatoes are produced for Farm Frites, and the company management would like to assess the performance of potato supplying farms within and between the various production regions with respect to yield. This master thesis has two aims: 1) to perform a yield gap analysis by investigating the difference between potential and actual yields and 2) to suggest a way to implement the yield gap analysis in the design of an auditing system.
On a Polish farm of Farm Frites, a yield gap analysis was performed using the simulation model LINTUL3p, which consists of modules to simulate potential and water limited potato yield. A nitrogen module was included as well, based on the rice-nitrogen model by Shibu et al. (in prep.). The model parameters were obtained from Scottish nitrogen and water experiments specifically done for model testing. The parameterization process of the nitrogen module led to promising results. However, further testing of the corresponding LINTUL3p module is necessary, and its result of nitrogen were not used in the yield gap analysis. Finally, LINTUL3p was applied to simulate potential yield, yield reductions due to a shortened growing season and water limitations.
The most important defining factors on the Polish farm were found to be the temperature in early spring and the amount of incoming radiation during the growing season. According results reported in the literature, the potential yield on the Polish farm is comparable to important potato growing areas around to world.
The simulation results were implemented into an auditing system breaking down the yield gap analysis performed by LINTUL3p into further limiting and reducing production factors. The contribution of each factor was estimated using scientific literature. Furthermore, opportunities to decrease the yield gap, related to these limiting factors, are discussed. These opportunities are meant to start a technical discussion. Possible constraints, for instance financial restrictions, were not considered.
The crucial elements of the auditing system are the simulation of the potential yield and the relative yield gap, which enables comparison between different production regions of Farm Frites, identification and explanation of limiting and reducing production factors and the opportunities to decrease the yield gap. This whole set serves to identify improvement of farm performance.
The main opportunities to decrease the yield gap found for the Polish farm are 1) expansion of the capacity for field work in spring and autumn, 2) pre-sprouting of seed tubers, 3) the use of latest technical innovations, like precision agriculture, and 4) decreased frequency of potatoes in the crop rotation, e. g. by exchanging land with neighbouring farmers.