I am going to be cutting out sod, taking the dirt down a little more, then hauling in new dirt where i cut the sod out for a ladiies flower garden more or less. Some spots will be getting 4inches of dirt, some 6+ inches. My question, should I spray anything on the grass to kill it before I cut it out or not? Just wondering if that makes it easier, or if it will hurt the soil or anything. Let me know. Thanks!