Soil compaction can cause non-uniform emergence and poor field stands in soybean (Glycine max L. Merrill). The effect of soil compaction on soybean seedling emergence in the greenhouse environment was evaluated using seed lots with high germination, but of high, medium or low vigor (accelerated aging test) from four cultivars. One or three seeds were planted in soil in 11.1 (diameter) x 13.3 cm (height) plastic containers and compaction was imposed after planting by dropping a 2.5 kg weight on the soil one or more times to provide a range of compactive efforts (CE) (0.0, 4.6, 9.2, 13.7, 18.3, 22.9 kJ m-3). Daily emergence counts of normal seedlings were made for ten days, after which the non-emerged but germinated seedlings and dead seeds were determined. As CE increased, the normal seedlings that emerged when averaged across all seed lots decreased from 92% at 0.0 kJ m-3 to 37% at 22.9 kJ m-3. The number of seedlings that germinated but had not broke through the top soil increased from 3 to 27% at 0.0 kJ m-3 to 22.9 kJ m-3 CE, respectively. When cultivars were averaged across CE treatments, normal seedling emergence for high and low vigor seed lots were 75 and 43%, respectively. Under lower CE levels (4.6 and 9.2 kJ m-3) normal seedling emergence of one seed per container was 28 and 33 percentage points (average of three varieties) less than three seeds per container (3.81 cm spacing). Soil compaction caused greater reductions in seedling emergence of low vigor seed lots compared with high vigor seed lots. When exposed to low levels of soil compaction, three seeds planted in close proximity of each other had greater emergence than one seed per container.
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