Estimativa do balanço de energia e das necessidades termohídricas do açaizeiro irrigado no Leste da Amazônia.

Abstract

The economic appreciation, the growing demand for products from the acai tree and the seeking for reducing pressure on the floodplain ecosystems have been promoting the expansion of acai cultivation to upland areas since the 90's. However, several questions were created during the expansion process of the crop, between which, some stand out: what would be the thermal and water requirements for the crop? As well as what would be the seasonal variability of the energy balance partitioning in a plantation of irrigated acai? In order to approach these questions, an experiment was carried out in the municipality of Capitão Poço, over a 10-hectare acai plantation between 2017 and 2019, where a micrometeorological tower was installed in the center of the experimental area to monitor several meteorological variables. Subsequently, the lower (Tb) and upper (TB) basal temperatures were evaluated through the degree-days method, as well as the thermal durations and requirements for the different phenological stages. The water consumption and the cultivation coefficient (Kc) were obtained by the energy budget through the Bowen ratio method, in which the energy available in heat in the soil (G), the sensitive heat (H), the heat latent (LE) and the heat stored in the plant canopy (Sdv) were partitioned. Basal temperatures varied throughout the cycle, with the flowering stage being the most sensitive with thermal amplitude between Tb and TB of 18.73 ° C. The average duration of the acai tree reproductive cycle was 316 days with a total thermal requirement of 4,545.98 degree-days. In the acai planting, the available energy is divided by an average of 67% for evapotranspiration, 29% for heating the air and 4% for heating the soil. The effect of the heat stored in the acai tree canopy is irrelevant because it represents less than 0.2% of the available energy. Regarding the results, the acai tree presents a variation in water consumption throughout the cycle, with a daily average of 3.48 mm day-1 and a total average consumption of 1064.85 mm, whereas the Kc of acai is maximum during the green fruit stage, when there is the fruit growth, and minimal during the pre-flowering. Therefore, the research results show the importance of the correct irrigation management for the acai trees, as they allow us to design water management protocols more adequately to the water needs of the crop. Thus, increasing the efficient use of water by the crop which consequently leads to economic gains for the producer.