The atmospherical drought as a decisive factor of yield in the main sour cherry varieties of Hungary

The occurrence of drought during the growing period is a well known phenomenon under Hungarian climatic conditions. The numerical expression of damages caused by drought has been attempted by indices of Antal-Glantz (1988). The indices are aiming to exploit meteorological and hydrological parameters to describe the effects of drought on the development of cultivated plants. Studies of Varga-Haszonits (1989), Nemes (1993), Simon (1993) dealt with the feasibility of drought indices, which show close relation with the decline of yields. Water requirement, water-uptake, water utilisation being species(or even variety-) specifi c properties of plants, we have to apply the individual indices to the right object. An important decision is to actualise the purpose of the index. If we would like to evaluate the last year’s or season’s history by means of the data registered, the only absolute condition is the existence of data for calculating the indices required. However, if the policy of planning interventions to avoid damages is actual, as to secure optimal conditions regarding supply of water, we need indices easily compounded from instantly produced but reliable measurements. Most of the indices designed for the agricultural practice require several parameters, which are diffi cult to be produced. The drought index of Palmer (1965) is widely recognised, but the determination of components necessary to calculate water husbandry (the CAFEC value) is rather complicated as indicated by Faragó et al. (1989). Besides the reliability of the index, the operative prevention of drought damage needs instantaneous accessibility of the operator horticulturist. Nowadays, most fruit and vegetable growers invested to dripping irrigation. The optimal water content of the soil is kept successfully, all the same, symptoms of drought appeared. We are interested to fi nd the reasons of that phenomenon, the way to avoid damages, i.e. decline of yield, caused by atmospheric drought. The atmospherical drought as a decisive factor of yield in the main sour cherry varieties of Hungary