Abstract
Most of the risk in Hungarian fruit growing is the damage caused by late spring frosts. The frequency of late frosts seems to increase nowadays. The aim of the study was to check this contention: what is the real probability of the damages. Based on earlier experiences, the physiological LT50 function has been elaborated for new fruit varieties, which are eligible to moderate the danger when being threatened by frost. By means of this technique, the probability of freezing is distinguished between frost susceptible, frost resistant and medium frost resistant fruit species and varieties around their blooming time. The degree of frost damage depends on the duration and severity of the low temperature and not at least on the frost tolerance of the plant. For that purpose, the frequencies of frost damages were studied at two Transdanubian and two Trans-Tisza fruit growing sites by means of a meteorological database for the 60-year-long period 1951–2010. Being aware of the LT50 values changing during the phonological phases of the fruit trees from budding, bloom, fruit set and fruit growth, the number and date of critical (frosty) days could be settled. An important role is attributed to the orographic relief and the height above the sea level of the site, as 20–30 m differences and expositions may become decisive within the same plantation. The spatial distribution of damages is also dependent on the air circulations within the Carpathian basin. At the southern and northern borders of the country, especially valley bottoms represent additional risks of frost. Most spring frost damages are experienced in April 20–22, and cause heavy damages by temperature minima between – 3°C and – 6°C. The severity of damage depends largely on the temperature of the preceding few days. The earlier bloom the heavier damage is expected. The study is emphasising the importance of the varieties. Frost tolerance of some varieties may lower the risk of spring frosts by 40–50%, as experienced on the plantations. The quantifi cation of the risks based on data raised during the last years will be suitable to defi ne the security of yields of each growing site successfully.
Highlights
Among the climatic risks of horticultural production, the spring frost damages are the most important, its quantification is highly justified
The severity of the damage claims a physiological approach by the LT50 function
The present study attempts the use of the function to distinguish between frost-susceptible, medium tolerant and frost tolerant apricot and peach varieties
Summary
Among the climatic risks of horticultural production, the spring frost damages are the most important, its quantification is highly justified. The severity of the damage claims a physiological approach by the LT50 function. The present study attempts the use of the function to distinguish between frost-susceptible, medium tolerant and frost tolerant apricot and peach varieties. The tests of measuring the severity of spring frost damages should be extended to other fruit species. Apricot and peach are relatively susceptible fruit species; the experiments are initiated with those. Two Transdanubian and other two TransTisza growing sites have been selected for the meteorological study, how we could calculate the probability of the damage at least on the 50% level. As by knowing the frequency of climatic risks would help to determine the risks of production
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