Soybeans are similar to many other legumes although they are tropical plants and very sensitive to cooler temperatures. Plant when soil is thoroughly warmed. They will grow best in warm dry climates where there is little risk of soybean rust, a serious fungal pest. Make sure your soil is fertile and well-drained. Avoid overhead watering, but do keep soil moist to promote best growth.
Soybeans prefer to be planted within the narrow range of one to one-and-a-half inches. If planted too deeply, the seeds may take longer to germinate and emerge. Seed planted too shallowly may also be late in germinating, probably due to inadequate moisture. Shallowly planted seed may also dry out and fail to germinate at all.
The amount of water in the soil is the determining factor in planting soybeans. Soil composition also makes a difference, as clay soils will hold water better, while sandy soils dry more quickly. You can plant more shallowly in clay soils – about one inch. In sandy soil, however, you will probably have better success by planting two inches deep. In either case, make sure the soil is moist, especially the top two inches.
Planting soybeans at the lower end of their preferred range is necessary in some situations for best germination. Soybeans should be planted shallowly in the following conditions:
- When you are planting early in the season.
- When there is still residue from the previous crop.
- When the soil is very finely textured.
- When you have very moist soils.
Just as there are times to plant shallowly, there are also times when planting deeply will increase germination and growth. However, don’t plant more deeply than two inches. Plant deeply when:
- You are planting later than normal or succession planting later in the season.
- When soil is very coarse textured (sandy soils).
- In drought or dryland conditions.
In addition to soil moisture – which is the most important factor in planting depth – other factors can affect your success in planting soybeans. Some varieties of seed emerge more quickly or grown strong sprouts. Called the emergence score, this characteristic is primarily important to commercial growers. Larger seeds should be planted a little more deeply unless the soil is prone to crusting.