The objective of this research was to study the variability of individual tracer deposits (simulating herbicides applied in post-emergence) on Brachiaria plantaginea and Commelina benghalensis infesting soybeans crop. The tracer deposits were evaluated also on the crop. A boom sprayer was used, equipped with 110-SF-03 nozzles and 250 L ha-1 of a solution was applied containing 0.18% of each of the following dyes: FDC-1 and Satur-Yellow; 150 soybean plants; 141 and 150 Brachiaria plantaginea plants were used as targets located in the rows and between the rows of the crop, respectively; 50 Commelina benghalensis plants located between the rows and 125 glass plates of 19.76 cm² (25 in the rows; 50 and 50 at 12.25 cm and 22.5 from the rows). The spray deposits (mL per plant or plate and mL cm-2) were individually estimated in each of the 566 targets by washing them in de-ionized water and measuring the concentration of dye FDC-1 in the solutions by spectrophotometry. The results for each target type and position were expressed in an increasing order and associated to accumulated frequencies from 0 to 100%. Regression analysis was performed according to the Gompertz model and using the individual deposits and the accumulated frequencies as independent and dependent variables, respectively. The values for ratio maximum deposit/minimum deposit were 7, 4, 10 and 6 for soybean, Commelina benghalensis and Bachiaria plantaginea in the rows and between the rows, respectively. The average deposits were 34% superior in the plants of Brachiaria plantaginea located in the rows, compared to the plants between the rows.
B. plantaginea; deposition; soyben; spray; tracers
