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Rio de Janeiro, Brazil

Scursoni J.A.,Catedra de Produccion Vegetal | Satorre E.H.,Catedra de Cerealicultura
Crop Protection | Year: 2010

From their introduction in 1996, glyphosate resistant (GR) soybean cultivars have been rapidly adopted by farmers in Argentina and in other countries in the world. The high rate of adoption of this technology seems to be based on the simplicity of use provided by a single herbicide (glyphosate), its high efficacy to control many weeds and, the low costs of the technology relative to that used in conventional crops. During 2001-2002, 2002-2003 and 2003-2004 soybean growing seasons, field surveys and field experiments were performed with the aim of studying the effect of different glyphosate management strategies on the diversity of soybean weed communities, weed control, individual survival, fecundity and crop yield. In addition, the emergence pattern of three important weeds, Digitaria sanguinalis, Cyperus rotundus and Anoda cristata, was also studied. Both field surveys and field experiments were carried out on no-till soybean crops sown immediately after wheat or barley harvest (double cropped system). Experiments were set up in commercial soybean crops and consisted of different times of a single glyphosate application, two glyphosate applications and also the application of glyphosate plus a residual herbicide imazethapyr. A. cristata, D. sanguinalis, Stellaria media, Chenopodium album and Cyperus sp. were the most prevalent weeds recorded at pre-harvest of the soybean crops, showing regional constancy higher than 80% in both years. In three out of four field experiments, crop yield was not increased when glyphosate was applied twice compared with a single application of the herbicide. In addition there was a lower negative effect on weed species richness when glyphosate was applied once during the crop cycle than with two applications of glyphosate or glyphosate plus imazethapyr. D. sanguinalis escaped the glyphosate early treatment because of the long weed emergence period, while A. cristata and C. rotundus survived treatments due to their high individual tolerance. The results suggest that it is possible to manage glyphosate application to get high crop yield with a low impact on weed diversity, depending on the weed species and their abundance. © 2010 Elsevier Ltd. Source


De San Celedonio R.P.,Catedra de Cerealicultura | Micheloud J.R.,Catedra de Cerealicultura | Micheloud J.R.,University of Lleida | Abeledo L.G.,Catedra de Cerealicultura | Miralles D.J.,Catedra de Cerealicultura
Ciencia del Suelo | Year: 2014

In Argentina, wheat production is affected with some regularity by waterlogging events, whose frequency depends on each particular year and area. However, there are few information about which is the probability of occurrence of waterlogging in different locations of the Argentinean wheat production area. The objective of this work was to quantify the probability of occurrence of waterlogging during the wheat crop cycle in different locations of the wheat belt. To fulfill the objective, 33 growing seasons of wheat crop were simulated using the CERES-Wheat model v. 3.5, with a combination of five locations (Bordenave, Capitán Sarmiento, Gualeguaychú, Junín y Tandil), two sowing dates (early and late sowing date), and three soil water content at sowing (low, medium and high). The average probability of waterlogging during the crop cycle was from 7 to 24%, depending on the location. However, during the period of more sensitivity to waterlogging (i.e. terminal spikelet (TS) - flowering (Fl)), the probability was, in general, higher than that considered for the whole cycle. Thus, considering an early sowing date and medium soil water availability at sowing, in 50% of the years between 2 and 7 days of waterlogging is expected during TS-Fl period, depending on the location. The number of days of waterlogging can be greater or lesser depending on the soil water content at sowing. Variations in sowing date did not modify the probability of waterlogging. However, for a similar number of days of waterlogging, the negative effect on yield would be higher at a late than at an early sowing date. This is due to an increased environmental demand that crop is exposed during a waterlogging at a late sowing date. Therefore, similar number of days of waterlogging in different locations can produce different grain yield losses, as a consequence of differences in the environmental demand among sites. © 2014, Asociacion Argentina de la Ciencia del Suelo. All rights reserved. Source

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