Ideal desiccation periods of Urochloa ruziziensis for a no-till sunflower crop

Abstract

> Sowing crops following cover crops on forage may cause injuries andproductivity reduction, due reasons as allelopathy or glyphosate residues. Theobjective of this study was to evaluate the influence of differing periods betweencover crop (Urochloa ruziziensis) desiccation with glyphosate and sunflower(Aguara 4) sowing in a no-tillage system on crop development and productivity.Two assays were performed in two seasons, one in pots and the other in a field.Treatments in field assay consisted on 5 desiccation times of U. ruziziensis (with anapplication of glyphosate at 1.08 kg ae ha-1) preceding the sowing of no-tillsunflower (0, 3, 7, 10 and 30 days). At the pot assays, 6 times were studied: 0, 3, 7,10, 15 and 20 days between cover crop desiccation and sunflower sowing. Acontrol without cover crop was also included in this assay. Biometric evaluationswere performed at the vegetative stage and at harvest. As the period betweenU. ruziziensis desiccation and sunflower sowing was shortened, achene productionin sunflower was exponentially reduced. Glyphosate application at 3 or 0 dayspre sowing diminished sunflower development and achene production byapproximately 30% compared to desiccation periods greater than 7 days.