Efecto del rastrojo de seis cultivos de servicio y dos tecnologías de desecación en la dinámica del enmalezamiento en barbecho y cultivo de soja

During the years 2019 and 2020, a series of tests were established at the “Dr. Mario A. Cassinoni” (E.E.M.A.C.), department of Paysandú, with the purpose of evaluating the effects of six service crops (CS) black oats (Witch hazel), white oats (Avena sativa), centeno (Rye cereal), raigras (A multi-flowered lily), black oats plus vetch (A villous vice) and rye with vetch, combined with two desiccation technologies: herbicide and rolling, in weeding and soybeans. The experimental design was adjusted to a model of plots subdivided into strips, it has a random block structure with 3 repetitions with a plot size of 10 x 10 m. Each plot is subdivided into 2 equal parts, one treated with herbicide and the other with rolo. The determinations made in fallow were: dry matter production prior to desiccation, and prior to sowing soybeans; soil cover by stubble and weeds, the density, structure and composition of the weeds. At the soybean level: soybean implantation and development, stubble and weed coverage, weeding, soybean growth and development, and soybean yield. The estimated variables were processed using the INFOSTAT program, performing ANAVA and multiple comparison testing using the Tukey test (0.05). Effects of the type of CS and technology were found, as well as interactions of these effects on desiccation on weed density and weed composition in fallow and in the cultivation stage. In fallow, all CS determined similar weed densities, regardless of the desiccation technology, except Av. B with rolling, which had higher densities. Av. B and Cent. that determined low coverage of stubble and rolling, had higher percentages of fresh weeds and winter broadleaf species. The CS with low stubble and herbicide coverage anticipated summer grass weeding, behaving the same as the control. In the soybean cultivation stage, the CS that initially determined a lower percentage of stubble had a higher percentage of fresh weeds, a higher density of total weeds, total summer weeds and Echinochloa colona. The CS with low stubble coverage and with rolling had higher weed density. Weed cover was reduced by more than 50% in the CS that achieved 50% stubble coverage compared to the control without previous CS. In soybeans, effects of the previous CS, the desiccation technology and the interaction of both effects were detected. With low stubble coverage, rolling determined less soybean implantation than herbicide application, but without changes in development. Allelopathic effects of Av. N and Rg could have been evident, affecting the emergence and/or development of soybean. Soybean yield was more affected by the combination of high stubble coverage and its allelopathic effect on soybean growth and development, as was the case of Av. N.