Spatio-temporal dynamics of Sorghum halepense in poplar short-rotation coppice under several vegetation management systems

- S. halepense patches affect poplar growth, especially in the first growing season.
- S. halepense shifting is weak and especially towards drip-irrigation lines.
- S. halepense is not as serious a threat to poplar as it is to other irrigated crops.

Weeds are one of the most important factors reducing productivity in poplar short-rotation coppices. Sorghum halepense is a very harmful perennial weed affecting irrigated crops preceding poplar plantations. The main goal of this study is to assess the potential hazards of residual S. halepense patches in newly established poplar crops and the effects of different vegetation control treatments. Our study objectives were: to describe the spatio-temporal dynamics of this perennial weed during the first rotation coppice of poplar in the presence of different vegetation management strategies and to assess the effect that S. halepense has on poplar growth. Experiments were conducted in an experimental field in central Spain and were repeated over time. S. halepense patches were artificially established in a random block design with four replications. Four types of vegetation management were performed: mechanical (field cultivator and rototiller) and chemical (glyphosate and fluazifop-p-butyl). Patches were monitored throughout all the experiments and poplar productivity parameters (height and biomass) were recorded. Monitoring indicated patch displacement towards crop rows, probably due to higher soil moisture levels in this irrigated area, and a reduction in patch density in the central inter-row area owing to different management strategies. However, displacement was barely detected lengthwise, as was originally expected, at least in mechanical management. Mardia's test (circular statistics) indicated no significant differences in patch displacement between mechanical and chemical strategies. Regarding poplar growth, the mixed linear model indicated no consistent significant differences in terms of vegetation management, differences depending more on the proximity of S. halepense patches. This study has demonstrated that while S. halepense has very limited capacity to spread spatially in poplar short-rotation coppice, its proximity to crop rows may cause important damage in poplar productivity, especially during the first growing season. Therefore, proper management of this weed species is strongly recommended during this period.