Introduction
Establishing grass is often difficult to do in our semi-arid climate, particularly when there is weed pressure. That’s why I often recommend a cover crop be planted prior to seeding dryland grasses. A cover crop is allowed to grow, make cover, and is dead by the time grasses are planted. Here’s how and why this strategy works well in Colorado.
Why take time to plant a cover crop before planting your grass seed?
Cover Crops:
- Provide weed control by shading weeds out;
- Add organic matter to soil by their roots and residue (dead plant material left on the ground);
- Hold moisture at the soil surface which is critical during grass seed germination and early root development;
- Protect soil from wind erosion by holding the soil in place.
How it works
Sterile sorghum may be the best option for a cover crop in our semi-arid climate, because the residue will not decompose quickly and will remain on the soil as mulch. Use sterile seed so the crop won’t reseed itself. Sorghum is a warm season crop, like corn, and can be planted after May 15, or after the last frost has passed. Plant 4-8 pounds of sorghum seed per acre. Use a grass drill to plant sorghum seeds ½” – ¾” deep. Sorghum will begin growing within 7-12 days after planting and will quickly tower over competing weeds. It will out-grow and out-compete weeds over the summer so much of the weed pressure will be reduced. Sorghum will grow over the summer and die off by the first frost in September or October.
The cover crop will be dead prior to planting your grass mix. You may need to mow the sorghum if it is taller than 10”. Or you can take it off for hay, but make sure to leave 8-10 inches of stubble behind.
A dormant grass seeding works well in Colorado. Depending on where you live, there is a window of time for planting grass, generally between November 15 and March 15. Use a no-till drill to plant your grass seed mix right into the sorghum stubble. A no-till drill does not require that the soil be tilled and smoothed like traditional drills do. It has double disc openers that slice through the residue and soil, then the seed is dropped at a set depth. Packer wheels close the gaps and press the seed and soil together.
While the grass seedlings are germinating and growing (some take weeks to years to finally establish), the thick sorghum residue will hold moisture and act as a mulch to reduce weed pressure and wind erosion from occurring. For more assistance on grass establishment, contact your local CSU Extension or USDA-NRCS office.