Planting Date

The date of planting has more effect on soybean grain yield than any other production practice. The results of a two-year planting date study conducted in Clark County, Ohio are shown in Figure 5-2. Yield loss resulting from delayed planting ranges from 1/4 bushel to more than 1 bushel per acre per day, depending on the row width, date of planting, and plant type. In southern Ohio, soybeans should be planted any time after April 15 when soil conditions are suitable. In northern Ohio, planting should begin the last few days of April if soil conditions are satisfactory. Soybeans should not be planted until soil temperatures reach 50 degrees Fahrenheit and moisture is present at the planting depth of 1 to 1.5 inches. Planting too early (before field conditions are adequate) comes with a risk. Factors such as damping-off and pressure from bean leaf beetles are concerns to keep in mind, as well as the possibility of a late-spring frost. 

Regardless of planting date, row width or plant type, the soybean crop should develop a closed canopy (row middles filled in) prior to flowering or by the end of June, whichever comes first. Generally, when planting in early May, rows must be less than 15 inches apart to form a canopy by late June (Table 5-2). An early canopy results in high yields because more sunlight is intercepted and converted into yield than when row middles do not fill in until late in the growing season. Assuming a half bushel per acre per day yield loss with delayed planting, a 10-day delay in planting 300 acres would decrease total production by 1,500 bushels, which is worth $13,275 (at a price of $8.85 per bushel). 

Figure 5-2. Effect of planting date on soybean grain yield in Clark County, Ohio. 

Table 5-2: Effect of Row Spacing on the Number of Days and (Date) to Complete Canopy Formation*. 

Adequate, vigorous stands are sometimes more difficult to obtain with early planting. Seed treatments, good seed-soil contact, and reduced seeding depths, however, aid in establishing vigorous stands. Herbicide programs must provide weed control for a longer time until the crop is large enough to suppress weed growth through competition. Narrow rows provide the needed competition for weeds sooner than wide rows.