Timing of Planting Warm Season Annuals
While it may be tempting to get your hands on your warm season seed and put it in the ground early, that could be detrimental to your summer forage…
The Right Time
Warm season annual forages such as forage sorghum, sorghum sudangrass, sudangrass, millet, teff and others are C4 grasses originated in places much warmer than the midwest. Especially warmer than the midwest in May. This is why it is very important for soil temperatures to be a minimum of 60 degrees and rising. Soil temperatures should be taken at 7 am at a depth of 4 inches.
Consequences of the Wrong Time
If the soil temperature requirements are not met, your entire stand of warm seasons could be compromised. An Oklahoma State University study of grain sorghum found a range of 20-35% reduction in germination at 53 degrees compared to germination at 60 degrees. Germination reductions lead to tonnage reductions at harvest time.
The seed size of warm seasons makes this slowed germination even more difficult. Warm season grasses range from 18,000 seeds per pound to 1.3 million seeds per pound. For some perspective, corn is about 1600 seeds per pound. Warm seasons have a much smaller energy reserve to pull from while germinating. The longer it takes that seedling to get started and establish a root system, the more it has to deplete that energy source. Also, the longer that tiny seedling takes to get established, more time is left for pathogens to take over.
This rough start to the beginning of the warm season plant’s life means an overall weaker plant and root system. As the plant grows, a weak root system will also have a hard time stabilizing that plant which can lead to lodging later on in the season.
Overall, incorrect timing of warm season annuals can have effects that the stand cannot come out from. Waiting for correct soil temperatures will give your warm seasons the start they need to produce valuable forage for your livestock.