Double cropping is the establishment and harvest of a second crop (usually soybean) the same season that a first crop is harvested (usually a small grain). There are two primary requirements for profitable double cropping:
- Adequate time to produce the soybean crop.
- Adequate water to produce both crops from stored soil moisture, rainfall, or irrigation.
Double-crop soybean management differs from traditional, full-season soybean management. Following are the differences in management practices.
Planting Date. The date of planting has more effect on soybean grain yield than any other production practice. Early planting of double-crop soybean is essential for success and can be accomplished in two ways:
- Harvest wheat when grain moisture is 18% to 20%. Wheat grain is sometimes accepted at a higher moisture content. If needed, grain can be dried using air with or without supplemental heat. Wheat harvested at a higher moisture generally has greater yield and quality. When dry grain is re-wet in the field, grain may sprout, yield and test weight will be reduced, and vomitoxin levels may increase. Grain will be significantly discounted or rejected for low test weight and high vomitoxin.
- Planting double-crop soybean after winter barley. Winter barley is harvested approximately two weeks earlier than winter wheat, allowing for an earlier soybean planting date.
Relative Maturity. Relative maturity (RM) has little effect on yield when soybeans are planted during the first three weeks of May. However, the effect of RM can be greater for late planting. When planting soybeans late, the latest maturing variety that will reach physiological maturity before the first killing frost is recommended (Table 1). This selection allows the soybean plants to grow vegetatively as long as possible to produce nodes where pods can form before vegetative growth is slowed due to flowering and pod formation.
|Northern Ohio||June 1-15||3.2-3.8|
|Central Ohio||June 1-15||3.4-4.0|
|Southern Ohio||June 1-15||3.6-4.2|
Row Spacing. Double-crop soybeans should be produced in narrow rows- -with 7.5- to 15-inch row spacing. The later in the growing season soybeans are planted, the greater the yield increase due to narrow rows. Soybeans grown in narrow rows produce more grain because they capture more sunlight energy, which drives photosynthesis
Seeding Rate. Harvest population for mid- to late-June plantings should be between 130,000 to 150,000 plants per acre. Harvest population for early-July plantings should be greater than 180,000 plants per acre. Harvest plant population is a function of seeding rate, quality of the planter operation, and seed germination percentage and depends on such things as soil moisture conditions, seed-soil contact, and disease pressure.
Figure 1 shows the partial economic return by seeding rate (grain price of $9.44 per bushel and seed cost of $0.43 per 1,000 seeds) for double-crop soybeans planted in Clark County, Ohio. In 2016, double crop soybeans were planted in July, and the optimum seeding rate was 213,000 seeds per acre. In 2017, double crop soybeans were planted in June, and the optimum seeding rate was >250,000 seeds per acre. Even though the double crop soybeans were planted earlier in 2017, the optimum seeding rate was greater due to heavy rainfall after planting that reduced the soybean plant population. At a rate of 250,000 seeds per acre, the final stand was only 143,000 plants per acre (57% of the seeding rate) in 2017. In 2016, at 250,000 seeds per acre, the final stand was 204,000 plants per acre (82% of the seeding rate).
Figure 1. Partial economic return by seeding rate for double-crop soybeans planted in Clark County, Ohio in 2016 and 2017.
This fact sheet, originally published in 2001, was originally titled, “Double-Cropping Soybeans Following Wheat” and was written by Dr. Jim Beuerlein, Ohio State University Extension.