Seeding furrow opening mechanisms and the soybean planting in lowland areas/Mecanismos sulcadores da semeadora e a implantacao de soja em area de terras baixas

The objective of this research was to evaluate the effect of seeder furrow opening mechanisms on soil physical characteristics, plant growth, and soybean yield in lowland areas with the presence of compacted layer near the surface. An experiment was conducted in the lowland experimental area of the Federal University of Santa Maria-RS, Brazil, during the 2015/16 and 2016/17 growing season. The experimental design was a randomized block with five replications and four treatments: Planter using shank (S) at 0.23 m depth; S at 0.13 m; Planter using double disk at 0.07 m depth and Raised-bed + S at 0.12 m depth. The use of S at 0.23 m depth allowed reduction of penetration resistance and increase of soil macroporosity in the layers 0-0.1 and 0.1-0.2 m depth in the seeding row. Sowing with S at 0.23 m depth and Raised-bed + S at 0.12 m depth allowed a better development of soybean plants in compacted irrigated rice area (higher nodulation, leaf area index and root growth), as well as higher grain yield. Key words: shank, soil compaction, raised bed, Albaqualf soil, Glycine max. O trabalho teve como objetivo avaliar o efeito de mecanismos sulcadores da semeadora sobre caracteristicas fisicas do solo, crescimento de plantas e produtividade de soja em area de terras baixas com presenca de camada compactada. Para isso, foi conduzido um experimento na area de varzea da Universidade Federal de Santa Maria, durante as safras agricolas 2015/16 e 2016/17. O delineamento experimental utilizado foi o de blocos ao acaso, com cinco repeticoes e quatro tratamentos, sendo eles: Haste sulcadora (HS) a 0.23 m de profundidade; HS a 0.13 m; Disco duplo a 0.07 m e Microcamalhao+HS a 0.12 m. A utilizacao da HS a 0.23 m possibilitou o aumento da macroporosidade e a reducao da resistencia a penetracao mecanica do solo nas camadas de 0-0.1 e 0.1-0.2 m de profundidade na linha de semeadura. A semeadura com HS a 0.23 m e Microcamalhao+HS a 0.12 m viabilizam melhor desenvolvimento das plantas de soja em area de terras baixas compactada (maior nodulacao, indice de area foliar e crescimento radicular), bem como maior produtividade de graos. Palavras-chave: haste sulcadora, compactacao do solo, microcamalhao, Planossolo, Glycine max.