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

Document Type: Research Paper


Department of Biology Applied to Agriculture, Faculty of Agricultural and Veterinarian Sciences (FCAV/UNESP), Jaboticabal, Brazil


> Sowing crops following cover crops on forage may cause injuries and
productivity reduction, due reasons as allelopathy or glyphosate residues. The
objective of this study was to evaluate the influence of differing periods between
cover crop (Urochloa ruziziensis) desiccation with glyphosate and sunflower
(Aguará 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 an
application of glyphosate at 1.08 kg ae ha-1) preceding the sowing of no-till
sunflower (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. A
control without cover crop was also included in this assay. Biometric evaluations
were performed at the vegetative stage and at harvest. As the period between
U. ruziziensis desiccation and sunflower sowing was shortened, achene production
in sunflower was exponentially reduced. Glyphosate application at 3 or 0 days
pre sowing diminished sunflower development and achene production by
approximately 30% compared to desiccation periods greater than 7 days.