How to Kill Nut Grass
Corn gluten also works for this, and it can be found at seed and feed stores along with directions for application.
Nut grass, also called nutsedge, is a pesky grass that is very hard to get rid of since the roots are very tenacious. They have nodules on them that look like small nuts. If you try to uproot nut grass, the roots tend to break off and the nuts will simply produce a new plant. The best way to get rid of nut grass permanently is to kill it with a pesticide, but this can kill your lawn as well. Fortunately, there is a way to kill nut grass organically that will not harm your lawn in the process.
Water your lawn. This will prepare it for your organic sugar treatment. Do not saturate the lawn, but be sure that the soil is moist and that the grass is wet.
Sift the sugar onto your lawn. Walk in regular, straight lines just as if you were mowing. Turn the handle on the sifter so that the sugar falls onto the grass evenly. Continue turning the handle the entire time that you are walking. The sugar will nourish microbes that benefit your lawn grass and eat the nutsedge or nut grass.
Water down the sugar. Spray your lawn again with the garden hose. Do not saturate it to the point that water is running off or you will lose all of the sugar that you just deposited on the lawn.
Do this in the spring when you would first seed and feed your grass as well as one or two more times throughout the growing season. By the end of the season, the nut grass should all be dead.