Presented paper deals with the topic of preventive maintenance. A decision support system was designed, incorporating historical as well as forecast information to calculate the time remaining to preventive maintenance. The designed system optimizes maintenance costs without any further investment and running costs. An algorithm of the designed system is introduced and a case study of its implementation is described in the paper.

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Kavka M., Mimra M., Kumhála F. (2016): Sensitivity analysis of key operating parameters of combine harvesters. Res. Agr. Eng., 62: 113-121.The sensitivity analysis of key operating parameters on the average annual sub-profit in a group of three combine harvesters operating in companies providing agricultural services were analysed. Based on the results of the cost analysis, the following key operating parameters with the greatest influence on the costs were identified: the purchase price of the machine, the price of fuel, maintenance costs, personnel costs and annual performance. These parameters were used in the sensitivity analysis to investigate their effect on unit costs. Changing the above-mentioned parameters is calculated within ± 30% from their mean value. To perform a sensitivity analysis of the average annual sub-profit of combine harvesters, the unit price of mechanized work was additionally used. The results showed that greatest impact on both the average annual earnings of combines operation and on the changes in unit cost was those of the annual performance of the combine harvester, combine harvester purchase price and the cost of fuel. On the other hand, maintenance and personnel costs had a smaller influence concerning these changes of parameters.Keywords: annual performance; costs optimization; unit costs; cost analysis; average annual sub-profitThe aim of the sensitivity analysis is to evaluate the impact of changes in key operational parameters for the planned result. Appropriate choice of key parameters has a great impact on achieving successful results. Sensitivity analysis aims at assessing the average annual sub-profit of harvesters as a result of changes in the values of key operating parameters or as a result of others factors, e.g. fuel prices on world markets. It is advisable to perform a sensitivity analysis already in the design stage of the project. Its implementation will identify potential risks and identify key operational parameters influencing profitability.According to Rataj (2005), the implementation of sensitivity analysis is necessary to determine the most probable size of the deviations for both optimistic and pessimistic trends. The estimates are based on the development of these parameters in the past. It identifies the impact of parameter changes on the size of the output (or a project result). As reported by Fotr and Kislingerova (2009), the experience of business practice and empirical research findings show that optimistic distortions dominate strategic financial plans and the resulting values of cash flow.

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Abstract:The hitherto development of agricultural production shows that one of the characteristic attributes of the present period is great economic instability. Monitoring of the development of prices of inputs and outputs as well as climatic conditions reveals that similar problems are not limited to the Central European countries. Prosperity and competitiveness of the production is a function of mutual relations of costs, prices and yields. For the sound managerial decision-making, it is necessary to continually analyse and evaluate the rate of risk -soundness of the planned results (Rataj, Kavka 1999;Rataj 2001). For that reason, this contribution concerns the analysis of economic risks of the hop growing that takes into account statistical data in the time horizon of the last 15 years for the "Žatec poloranný červeňák" of traditional planting (further only ŽPČT) and 7 years for ŽPČ virus free (farther only ŽPČV) and the hybrid sorts (farther only HYBR). Key words: hop, risk, costs, gross profit, gross marginAbstrakt: Z dosavadního vývoje zemědělské výroby je zřejmé, že se současné období vyznačuje kromě jiného velkou ekonomickou nestabilitou. Ze sledování vývoje cen vstupů a výstupů, jakož i povětrnostních podmínek vyplývá, že podobné problémy mají ne jen země střední Evropy. Od vzájemného vztahu nákladů, cen a výnosů v tržním prostředí se odvíjí prosperita a konkurenceschopnost výroby. Pro manažerské rozhodování je proto nevyhnutné dostupné informace neustále analyzovat a hodnotit míru rizik -reálnost plánovaných výsledků (Rataj, Kavka 1999;Rataj 2001). Proto je v pří-spěvku zpracována analýza ekonomických rizik pěstování chmele, vycházející ze statistických údajů v časovém horizontu posledních 15 let u Žateckého poloraného červeňáku tradiční výsadby (dále jen ŽPČT) a 7 let u ŽPČ viruprostého (dále jen ŽPČM) a u hybridních odrůd (dále jen HYBR).