Determination of the proportions in which different maize hybrids should be grown to reduce yield risks

The investigations were carried out using the data of a long-term polyfacto rial experiment set up on chernozem soil with lime deposits at the experime ntal station of the Department of Agronomy of the Agricultural Centre in De brecen University. The aim was to determine the ratio in which three hybrid s (A, B, C) should be grown in order to achieve a given yield level with th e least risk. The factors were three fertiliser treatments (unfertilised, 1 20 kg N + 90 kg P2O5 + 106 kg K2O/ha, 240 kg N + 180 kg P2O5 + 212 kg K2O/h a), three soil cultivation methods (no tillage, spring ploughing, autumn pl oughing), four plant densities (60-70-80-90 thousand plants/ha) and two irr igation treatments (non-irrigated, irrigated). The randomised experiment wa s carried out in four replications over a period of four years (1990-1993). When planning their production the primary aim of farmers is not to achieve maximum income: they are prepared to accept a slightly smaller income if t hey can reduce income fluctuations due to unpredictable factors to a satisf actory extent. Most farmers attempt to reduce the risks involved in farming as far as possible. Using a mean-variance model applicable for risk-averse decision-makers, plans were prepared which recommended the cultivation of hybrid B on a greater area at lower yield levels and that of hybrid C for t he achievement of higher yields, under both irrigated and non-irrigated pro duction conditions, if the planned yields were to be attained with the Leas t risk. It is demonstrated that if the decision-maker chooses a plan promis ing lower yields in place of that offering the highest yields, the reductio n in the yield risk is far greater than the percentage decrease in yield.