Evaluation of corn crop phenology cycle in Guarapuava, South of Brazil based on the thermal sum

Abstract

The thermal availability has a direct influence on the phonological development of plants, so that local or warmer periods provide more rapid development of them. The objective was to evaluate the climate behavior in order to establish the probable duration of phenological phases and the full cycle of development of the corn crop for the region of Guarapuava-PR, based on thermal sum. The study was developed based on a historical series of average daily meteorological data for the period from 1984 to 2008 compiled from the collection of the meteorological station of the Universidade Estadual do Centro Oeste - UNICENTRO in Guarapuava-PR. In the study, it was used the agricultural zoning of the State of Paraná, recommended by the Agronomic Institute of Paraná - IAPAR, where it considers suitable for the sowing of the corn crop sowing of the period of September 21 to 10 of November. The treatments consisted of estimates of the sowing dates of 1) Sept 21, 2) Oct 01, 3) Oct 11, 4) Oct 21, 5) Oct 31 and 6) Nov 10. The calculation of the thermal sum in degree-days (DD) was performed from the mean air temperature minus the base temperature. It was assumed that the development of the plants was constant between the base temperature below 10°C and temperatures above 32° as base. The use of the thermal method is a practice that can be used to estimate the duration of phenological phases and the cycle of development of the corn crop. When the cultivation of corn is held within the period recommended as agricultural zoning of Paraná, the cycle of cultural development between sowing and physiological maturity varies between approximately 114 and 122 days.