Otimização do depósito de pulverização no cafeeiro sob diferentes condições operacionais

Abstract

Air-assisted spraying is widely used in the phytosanitary management of coffee (Coffea arabica L.), but it faces significant limitations. The complex architecture of the plant, the variability in the orientation of branches and leaves, and the dependence on airflow make precise and uniform droplet distribution difficult, potentially compromising the effectiveness of phytosanitary control and generating environmental impacts. Air-assisted spraying deposits part of the droplets in the target application area (reference fraction), while another part passes through the canopy, propelled by the airflow (pass-through fraction). In this context, deepening the knowledge about droplet deposition in tree crops, through the analysis of scientific production and understanding how operational parameters influence deposition, in fractions of the sprayed area and along the canopy, becomes essential to support future studies and the development of more effective and sustainable spraying strategies. Therefore, this work aimed to: (i) to analyze the scientific production on spray deposition in perennial crops using scientometrics; (ii) to determine the deposit in the fractions of the sprayed area using an air-assisted sprayer, considering different application rates and nozzle types; and (iii) to determine the deposit in the fractions of the sprayed area, especially on leaf surfaces (adaxial and abaxial) of coffee plants, under different spray angles on different sides of the application row. The analysis of scientific production was conducted using scientometrics, with the aid of Bibliometrix and VOSviewer software. The Web of Science database was used to search for documents, with prior definition of keywords and application of filters. The retrieved records were exported with complete information and subjected to quantitative analyses, such as number of publications per year, most productive journals, most frequent authors and institutions, number of citations, as well as keywords and co-authorship networks. To determine the deposition in fractions of the sprayed area, both field experiments adopted a 3 x 2 factorial design. In the first trial, the factors were three application rates (200, 400, 600 L ha-1) and two spray nozzle types (hollow cone and flat fan), with four replications. The deposition was quantified on two application sides (left and right of the application row), three thirds of the plant (upper, middle, and lower), and two positions of the plagiotropic branch (inner and outer). In the second trial, the factors were three different spray jet angles (varying angles along the branch 40º-60º-90º, fixed angles of 80º and 90º) and two application sides (left and right of the application row). Deposition was quantified on the three thirds of the plant (upper, middle, and lower) and on the abaxial and adaxial leaf surfaces. The deposition was determined by adding a tracer to the spray solution, with readings taken by spectrophotometry. Measurements on application sides, plant thirds, and branch positions were nested. Due to the experimental complexity, the data were analyzed using linear mixed models, with mean comparisons using Tukey's test (p < 0.05) in RStudio software. The scientometric analysis revealed a growth in studies on deposition in tree crops; however, gaps remain regarding evaluation on natural targets and leaf surfaces, as well as the need for intelligent technologies to optimize spraying in these crops. Deposition tests in fractions of the sprayed area showed that, at an application rate of 200 L ha-1, the hollow cone nozzle provided greater deposition in the reference fraction and reduced deposition in the overlap fraction, while the flat fan nozzle increased deposition in the overlap fraction, indicating greater spray passage through the canopy. A 90º spray angle provided greater deposition and better uniformity, but increased losses due to overlap. In contrast, an 80º angle demonstrated greater retention of the spray solution in the target area, although with reduced uniformity. The combination of angles (40º-90º-60º), although more heterogeneous, showed an alternative for vertically directed applications. The abaxial surface of the leaf receives greater droplet deposition in the upper third of the plant, while on the adaxial surface greater deposition occurs in the lower third. The greater accumulation of droplets in internal positions and the differences between application sides highlight the influence of plant architecture and airflow asymmetry on the spatial distribution of droplets. It is estimated that between 20 and 30% of the tracer exceeded the target area, resulting in losses due to overlap. These results indicate the need to optimize operational parameters and spray direction to increase efficiency and reduce product losses in phytosanitary management.