Seasonality in the reproductive cycles of the coconut palm: an analysis of basal temperatures, duration and harvest estimates in the Northeast of Pará, Brazil.

The green dwarf coconut (Cocos nucifera L.) has an extreme economic importance in Brazil, especially in the state of Pará, the third largest national producer. The phenological aspects of these plants can undergo changes according to the environment to which they are subjected, so the objective was to determine the basal temperatures, quantify the duration of the reproductive phase and verify the effect of climatic seasonality on the thermal accumulation of the green dwarf coconut tree, in the northeast region of Pará, Brazil. The experiment was conducted at the Fazenda Reunidas Sococo, considering two different areas, one with irrigation and the other without water exchange. The experiment was carried out between September 2020 and February 2022, with phenological observations every 2 days, for a total of about 60 reproductive cycles in each area. The lower and upper basal temperatures for coconut cultivation corresponded to 10 °C and 33 °C, respectively, the average thermal demand found for the commercial reproductive cycle was 3866.2 °C day for the irrigated condition and 3696.3 °C day when rainfed. In a non-irrigated condition, the coconut tree has a well-defined seasonality of cycle length, indicating that greater accumulated rainfall guarantees longer cycles, both in days and degree-days, with their shortening associated with lower water availability. The crop prediction model using thermal units performed well. The results obtained facilitate the understanding of the impact of meteorological conditions on coconut production and assist in the management of the crop in the region.