Over Sowing Existing Warm-Season Lawns
The best time for over-sowing lawns composed of warm-season grasses is between February and July, if possible when rain is forecast.
For best results sowing rates of between 1 to 2 kg per 100 m. Bag size is 25 kg
Mow the lawn as low as you can (scalping). This will allow better seed to soil contact which is important in promoting faster germination of the sown seed.
A more professional approach is to use core aeration, or dethatching machinery. Both will remove lawn thatch and slightly disturb the soil giving improved seed to soil contact. Ask your seed supplier or hardware shop about hiring core aerators or dethatching machinery.
In some cases, due to compaction or shallow tree roots popping up in the lawn the topsoil layer may be too thin. Spread about 50 ml of screened topsoil over the area, and rake it in.
A fertiliser spreader would come in handy now to make the job easier. Otherwise the old fashion way of hand broadcasting is what you will be doing. For best results go over the area broadcasting, from side to side, in a north to south direction then turn and broadcast in an east to west direction. Do this two or three times. This will ensure an even coverage of the seed.
If you have access to a light roller, roll the sown area.
Nothing beats steady rainfall but if that’s a bit light on then the grass seeds must be watered properly, in order to germinate. Use a fine spray, as you don’t want to create a flood! The soil should be kept evenly moist, with daily watering (depending on the weather), for several weeks. Best time to water in of an evening.
For best results a good NPK fertiliser should be applied at sowing. CK88 or GH303 which has high nitrogen content are commonly used. Apply at 1 to 2 kg per 100 m².
Grasses generally are more efficient at photosynthesis than trees. The more grass you grow the more carbon dioxide is converted to oxygen and sequestered into soil organic matter.