Summary: Rice (Oryza sativa) is a characteristic plant of the tropical and subtropical monsoon or savanna climate. After wheat it is the second most important food plant of mankind. Its original habitat is South-East Asia. In the course of its cultivation varieties of it were developed that could adapt themselves to the climate and came into general use also in areas where none of the optimal climatic requirements can be found.

In Hungary experiments for the acclimatization of rice were conducted as early as the 18th century, yet rice-growing on any considerable level started only after World War II.

Rice production in the 20 years between 1951 and 1970 was greatly influenced by the weather conditions. With the exception of the year 1955 the first 10 years were character ized by the warming which had begun at the end of the last century. Between 1961 and 1970 the weather was more changeable and as a consequence of this the average yields became smaller. In the region of Szeged there were high average yields in the unusually warm years. The sunshine and heat requirements of the plant, were especially great in the months of July and August, which comprise the periods of stem formation, flowering, and panicle formation. But the scarcity of light retards the development of the plant from the very beginning of the vegetative phase. High vapor content of the air favors the development of diseases.

The average yield is in correlation with the mean temperature and the duration of sunshine. The correlation is closer when we examine the weather elements in the various phenophases. It is desirable to extend the investigation to the phenophases.

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