WATER AVAILABILITY AND RISK OF DRY SPELLS FOR SOYBEAN IN THE WEST OF PARANÁ STATE, BRAZIL

The water availability is the factor that most affects the production of soybean crops in the state of Paraná. Dry spells are extremely damaging to agricultural production and, therefore, studies that identify the frequency and intensity of these events are relevant to the planning of operations. Thus, the objective of this study was to evaluate the rainfall availability and to determine the frequency of dry spells in the Meso-region of Parana state. Precipitation data were collected from 48 stations distributed throughout the mesoregion between 1976 and 2018. Rainfall variability was analyzed in the annual, monthly and 10-days scales, and the frequencies of dry periods of 10 days from September to March and ≥ 20 days during the year. It was verified that the mesoregion showed differences in the amount of precipitation, but with enough rainfall for soybean cultivation. The relief favors the distribution of rainfall in the region. The southern portion has the highest mean precipitation, while the northern portion has the lowest. The dry spells frequencies per moving 10-day periods showed a maximum of 35% between the months of September and March in the region. The periods with the lowest risk are throughout the month of October, followed by December 10 to January 5. The biggest risks of dry spells are concentrated in the month of September, due to the irregular start of the rainy season. The results of this study help to choose the best sowing times such that the most sensitive phases of soybean cycle occur in the lowest risk periods