Don't over fertilize them because it makes them long and slender. They really like loose soil so you might want to do raised beds if you're in Houston clay.

The raised beds have all been spoken for, I dug a trench in the clay and am going to fill the trench with loose soil, it is angled so water runs off and the soil will not stay waterlogged which would rot the taters I'd think.

I think your plan will work. The trench should be as deep & wide as possible. But if you run the vines up & down the row, then you should be fine, even with a narrow trench.

Here is a link that might be useful: vermicomposting-trench

The don't over fertilize advice is a constant refrain with sweet potatoes, but that depends entirely on what you are starting with in the soil, so it means nothing, really. In florida for example, with it's typically impoverished sand one needs to add just about everything. In average garden soil N is probably adequate or maybe even high for SP, but K is likely not. It is the ratio between the nutrients and percentage of OM that determines the tuber size. If the soil has high OM (or clay content) then N and P are very likely to be present to some degree and equally K is likely to be low in relation. In such a case adding K (wood ash, sul-po-mag, muriate of potash all of which are salts and ideally added with compost) should produce a large yield.

I grow them in pretty rocky, clay soil. I've grown them in sandy loam and in sand. I've never fertilized other than to lay down a light layer of compost before making the hills. They've always done well for me. Here, with our rocky soil, I am growing Oklahoma Red, a variety which handles harder soil. But all our varieties are doing acceptably well.

Here's an article I did on sweet potatoes. Perhaps there might be something in there which would be useful.

George
Tahlequah, OK

Here is a link that might be useful: The Indispensable Sweet Potato

Thank you for the article, it was very good. I'm thinking about ordering from Sand Hill, but don't they ship later than the other companies?

Yes, they shipped very late to me last year. But they have such a selection.

Hey George!

Late might be good. The trench is right next to where I sowed the wildflower patch and apparently as I scattered seed, a bunch of seed got into the trench, all except a 12 foot area that turned a corner. There are hundreds of tiny wildflower seedlings emerging down in the trench and I'm not sure I have the heart to bury them in soil to prepare for the taters (I know, I'm such a wuss).
So maybe by the time I get slips from Sand Hill I can find a few nooks and crannies in the trench where the slips can go, or maybe I will expand on my little 12 foot trench.

Hey Pat! I don't get over here often enough.
Lucille, if you're in or near Houston a later shipment shouldn't hurt you at all. Your season is considerably longer than is mine, and I've planted as late as July 18 with satisfactory results.

George