Spring frosts in Santa Catarina - a contribution to a recional agricultural calendar

Abstract

In the present work minimum temperature data obtained from the Meteorological Institute "Coussirat de Araújo" were utilized to determine the probability of freeze occurrence in the Spring in several localities of the State of Santa Catarina. These freezes represent a danger for the crops which are grown in that season, particularly those which are less resistant even to the less severe temperatures. The extent of damage caused to plants by freezing temperatures depends upon the resistance of the plant and to its stage of development. Thus, the intensity of the freeze is the principal factor to be taken into account in determining the extent of the damage. Also, the duration of the freezing condition, the rapidity of falling temperature and conditions prior to the freeze are other important factors to be considered. Thus, in the present work the freezes were classified as; weak, moderate, mildly strong, strong, very strong, extremely strong and exceptionally strong, according to the temperatures which occurred. In this way, a weak freeze will damage only tender plants and a strong freeze will kill or injure most crops. Maps were elaborated, based on the results obtained, indicating three levels of hazard: 50, 20, and 10 percent, for each frost intensity after a given date in Spring. Such maps can be used as a base for the establishment of the planting time for different crops in the various localities of Santa Catarina. The use of the mape depends upon the critical temperature for the crop to be grown and the magnitude of the hazard the farmer is willing to accept.