Recent rains across much of Oklahoma have been timely for producers looking to plant another crop in their fields after harvesting wheat.
“The success of double cropping depends highly on initial soil moisture at planting, continued rainfall though the season and severity of heat stress when the crop is at the reproductive growth stage,” said Josh Bushong, Oklahoma State University Extension area agronomy specialist for western Oklahoma.
Soybeans and grain sorghum are the most common double-crops planted following wheat, though sesame, sunflowers and forage crops such as crabgrass, teff or any of the sorghum haygrazer types are popular with some producers. Farmers using no-till systems may want to review an OSU Extension fact sheet on no-till cropping systems in Oklahoma.
Crop maturity will depend on the specific crop being grown, but OSU experts shared the following guidelines:
- The later the crop is planted the less growth can be expected, so narrower row-spacing with a bit more seed is suitable.
- Planting rates typically will increase by 15-30% because of less germination and less plant growth.
- Higher pest pressure is to be expected in crops planted later.
- Early freezes tend to be more devastating on double-cropped plants because they have less maturity when temperatures drop.
“We will typically see less yield drag with double-cropped soybeans in western portions of Oklahoma because the delayed maturity will result in the plant reaching reproductive stages in more favorable conditions during August and September as opposed to June and July,” said Josh Lofton, OSU Extension cropping systems specialist.
The new OSU Extension fact sheet PSS-2197 about management strategies for double-cropped soybeans is available online and through all OSU Extension county offices.
Many Oklahoma producers have experienced strong double-crop yields in the last few years. However, with those yields come nutrient demands and nutrient needs. Now that fields have softened up with recent rains, it is a great time to go out amidst the wheat stubble and take soil samples, send them to a laboratory for testing and take the guesswork out of nutrient management decisions.
Precision Crop Nutrient Management Specialist Brian Arnall recently stressed the importance of soil testing on OSU Extension’s agricultural television program SUNUP, saying producers may want to do more site-specific soil sampling this year, perhaps breaking up a field into high and low areas or sandy and clay areas and sampling each.
“Pay attention to the soil tests,” he said. “If the wheat needed potassium or phosphorus so will the double-crop soybeans or sorghum. It’s okay to get a crop in the ground and then fertilize. There is a real opportunity to have excellent yields when soil moisture is in good condition.”
Remember that a nutrient management program in terms of nitrogen, phosphorus, potassium and micronutrients can be top notch but crop growth and production will suffer without having soil pH in the correct range. It is one of the most important numbers on a soil test. Soil acidity influences the availability of all nutrients, the activity of soil macro and microorganisms, the severity of soil-borne disease organisms and the effectiveness of herbicides.
“Lime is an investment that will need to be applied in most fields sooner or later, but it can take 200-300 days to get the desired level of change in soil acidity,” Arnall said. “The sooner lime can be applied to fields – conventional and no-till alike – the more time it has to react to the soil and make conditions better for the next crop.”
Double cropping is not a true crop rotation if the same crop is being grown during the same time period year-after-year. Switching warm season crops or winter small grain crops can be beneficial.
“In order to break pest cycles and especially diseases, a third crop or fallow period will need to be included,” Bushong said. “For most crop producers in western Oklahoma, there will be less risk in a system that is based on three crops every two years rather than two crops every year. The main risk is typically going to be attributable to a lack of soil moisture.”
OSU Extension is one of two state agencies administered by the university’s Division of Agricultural Sciences and Natural Resources and is a key part of OSU’s state and federally mandated teaching, research and Extension land-grant mission.