Effect of seed-furrow openers on soybean root growth in compacted Oxisol

This study aimed to evaluate the effects of seed-furrow openers and soil compaction on parameters such as sowing quality and root growth of soybean. The experiment was conducted using a randomized blocks experimental design with split plots, with the plots arranged by compaction level (1.16, 1.20, 1.22 and 1.26 Mg m-3) and the subplots by type of furrow opener (double disk and shank type). Root growth was assessed at three depths (0.00-0.10; 0.10-0.20 and 0.20-0.30 m) in the sowing line and interrow. The sowing quality data means were compared using the Tukey test (p≤0.05), while the root growth data means were compared using the LSD test (p≤0.05). Penetration resistance increased with increasing soil compaction to a depth of 0.20 m. The sowing depth and mobilized soil area were not affected by soil compaction levels. The type of furrow opening mechanism only influenced the sowing depth, with greater depth achieved using the double disc. Neither the seed-furrow openers nor the level of soil compaction significantly influenced soybean root growth when evaluated in the sowing line. The type of furrow opening mechanism did not influence any of the evaluated parameters. Soil compaction altered soybean root growth in the interrow, but did not impede rooting. Regardless of the assessment depth in the interrow, there was a reduction in root volume, length, surface area and diameter with increased soil density.   Key words: No-tillage, seeder, soil density, sowing depth, penetrometer resistance.