Straw crossing by pre- or post-emergence herbicide application determines its effectiveness, dynamics and environmental impact. The trial was carried out at NuPAM - FCA/UNESP, Botucatu Campus, São Paulo, Brazil, to evaluate the performance of different nozzle models in crossing increasing amounts of black oat (Avena strigosa) straw. The treatments consisted of monitoring Brilliant Blue (FDC-1) tracer dye at 3.000 ppm, sprayed with nozzles XR11002-VS; TJ60-11002VS; FL-5VS; DG11002-VS; TXVK-8; TT11002-VP and AI11002-VS, at work pressures 19.9; 28.4; 21.3; 28.4; 69.7; 42.7 and 42.7 PSI, respectively; and mix volumes 200; 200; 428; 200; 213 and 270 L ha-1; on 0, 1, 2, 4, 6, 8, 10 and 12 t ha-1 of black oat straw. The experimental design was entirely randomized with seven treatments and five replications, constituted by plastic boxes packed with straw over a fake bottom of known area, washed after the applications, for posterior tracer quantification by spectrophotometry. The Simplified Mitscherlich model (Y = 10 ^ (2 - (C*X))) showed a satisfactory adjustment for the tracer original data crossing the straw, presenting high determination coefficients (R²) between 0.9782 and 0.9971. The nozzle models were similar in relation to straw crossing by the tracer. The mean crossing percentages were 43.00; 18.77; 3.73; 0.78; 0.17; 0.04 and 0.01% for the amounts 1, 2, 4, 6, 8, 10 and 12 t ha¹ of black oat straw, respectively.
nozzle; Avena strigosa; mulch; FDC-1 tracer
