Abstract
ABSTRACT: Weeds constitute the main constraint on the productivity of sugarcane agroecosystems in Argentina. This work aimed to analyze the floristic and phytosociological composition of sugarcane weed communities in different agroecological areas in Tucumán. Fifteen plots from each area were sampled 60 to 90 days after crop shooting, by throwing a 0.5 m x 0.5 m quadrat metallic frame six times in random directions in each of the plots. Species found within the frame were identified. Later, fresh and dry biomass weight were calculated per quadrat sample and species. Frequency, density, dominance, importance value index, Shannon-Wiener and Simpson species diversity index and Jaccard similarity index were calculated. The unweighted pair group method with arithmetic mean (UPGMA) was used to interpret similarity. Overall, 35 species were identified, 24 of which were dicotyledons and 11 monocotyledons. Eighteen of them were annual species, versus 17 which were perennial. Considering IVI, the most outstanding families were Poaceae, Cyperaceae, Euphorbiaceae, Amaranthaceae and Asteraceae. The results obtained in all the areas revealed the importance of the species Panicum maximum, Sorghum halepense, Cyperus rotundus, Cynodon dactylon and Euphorbia hyssopifolia. The areas with greater and less diversity were the Depressed Plain-Non-Saline Depressed Plain Subregion and the Subhumid-Humid Chaco-Pampean Plain, respectively. There was a 53% similarity between the Depressed Plain-Saline Depressed Plain and the Depressed Plain-Non-Saline Depressed Plain, and a 47% similarity between the Humid and Perhumid Foothills and the Subhumid-Humid Chaco-Pampean Plain. Hierarchical clustering and Jaccard index led to similar results.
Highlights
Sugarcane is grown in tropical and subtropical regions, and 80% of the world’s sugar production is based on this crop (OCDE/FAO, 2015)
C. dactylon has been reported as a weed present in all the sugarcane areas in the world, together with C. rotundus, P. maximum and S. halepense
D. sanguinalis is one of the three main weeds found in Brazil and the USA, and the most important one affecting the crop in Australia, Cuba and India
Summary
Sugarcane is grown in tropical and subtropical regions, and 80% of the world’s sugar production is based on this crop (OCDE/FAO, 2015). Eighty-five percent of the agrochemicals used to control them are herbicides (CASAFE, 2012), and they are applied as long as approximately 28% of the duration of the crop cycle. If during this period weeds continue to invade the crop, they cause significant yield decreases, as they compete with the crop for scarce eco-physiological resources (Arévalo et al, 1977). Qualitative descriptions point to the relationships among species present in a certain area, whereas quantitative analyses deal with structure, by considering number of individual weeds and their density (Causton, 1988). In order to find out what species are most prevalent in weed infestations, the importance value index (IVI) is calculated: distribution, number of individual plants and the biomass of weed species present in a given area are estimated (Pitelli, 2000)
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