Fluxos de radiação solar e desempenho fisiológico da amora-preta (Rubus spp) em diferentes épocas de poda

Abstract

Still growing in Brazil, the blackberry (Rubus sp.) stands out among the small fruits with the best prospects in increasing production and supply for commercialization, presenting itself as one of the most promising. The main management in the crop is pruning, which consists of removing the branches that produced in the previous harvest and driving the new branches. The experiment was conducted in the municipality of Morro Redondo - RS in the 2019/20 harvest, with the objective of evaluating the influence of the pruning season and water restriction on the gas exchange of blackberry, to characterize the radiation balance during the phenological phases, the interference of the pruning season on the energy balance and to determine the relationship between the net radiation and the reference evapotranspiration. The experimental design used was in randomized blocks, with ten replications, in which each plot will consist of six plants, the treatments consisted of three pruning seasons: 1st season - 07/19, 2nd season - 08/15 and 3rd season - 09/09. The phenological monitoring was carried out through visual observations, weekly, observing the stages of budbreak, fully open flower, green berry, and ripe berry. The micrometeorological variables were collected using meteorological instruments programmed to independently record each measurement. The gas exchange measurements were made between 10:00 and 14:00, on days with completely clear sky, evaluating the net CO2 assimilation rate, stomatal conductance, transpiration rate, intercellular CO2 concentration, vapor pressure deficit and efficiency of the water usage.The net CO2 assimilation rate, stomatal conductance and transpiration are not influenced by the pruning season, being affected by the number of days after the rain. The number of days after the rain has an effect on the intercellular concentration of CO2, for plants that received conventional pruning. The efficiency of water use differed between the pruning times with the lowest value at nine days after the rain. The anticipation of pruning causes a reduction in the accumulation of energy to complete the phenological cycle. For all pruning seasons, the highest amount of global solar radiation and net radiation available occurred during the green berry to mature berry phase. Cloudiness causes a reduction in the instantaneous values of net radiation, global solar radiation, reflected solar radiation, short wave balance and long wave balance in blackberry cultivation. For the blackberry crop, the albedo should not be assumed to be constant and the net radiation has a positive correlation with evapotranspiration, approximately 27% of the net radiation is destined for evapotranspiration.