That may be a bit deep, but 12 inches deep should be acceptable. One of the problems with disk incorporation is that the label states that you should double disk the field at right angles which we cannot do due to our field ditches. A second pass across the field in the same direction but offset a bit from the first pass would be a worthwhile investment, if you are going to use a disk. Speed of disking and field cultivating is important for good mixing. Speed with a rototiller takes the opposite approach, you must go slow enough to thoroughly work the herbicide into the soil.
Soil moisture is very important.
Although the label states apply to dry soil, our experience has been just the opposite. A dry sand tends to be warmer than a moist one and this is a very volatile product. The speed of volatilization will increase with increasing temperature. Some of the worst performance we have obtained was when Tillam was applied to a soil that was on the dry side and the cultivator fluffed it up and allowed it to dry even more. Bed formation was delayed by 2 days in order to bring the moisture back up so firm beds could be formed and the resultant nutsedge control was greatly reduced.