http://www.tulsamastergardeners.org/veggies/spring_veggies.shtml
See if this has anything ehlpful in it.

Thanks OKC1. I just discovered there is a tomatoe forum. I didn't know they were that popular. I also read the thread about cantaloupe that has some information about growing them. I never even thought about the OSU extension fact sheets.

You've come to the right place.
Manure and compost are good standard amendments, but what I learned last year about gardening in OK is...mulch mulch mulch!!!

Yup. and with a dought predicted, you'd better get it now if you buy cedar mulch. The last drought year you couldn't find cedar mulch by July.

I've got some pine straw and cedar mulch waiting to be spread out. I went out and started digging and discovered that the soil where I'm planning to plant is clay about 6 inches below the surface and full of grubs. Oh boy, what fun. I need a jackhammer or maybe a backhoe to dig the clay out and replace it with nice rich, loose soil with manure and compost mixed in, ready for planting. It's kinda cold and cloudy today so I have to stay inside and dream.

There are a couple of ways to approach your planting concerns. The first way is to ammend the soil specifically in the area you are planting in. Don't try to add compost or rich mix to a 50' x 50' bed (or whatever size you'll have). Work with the soil directly where the plants roots will be affected. If it were me, I'd dig a hole about 12" deep and equally wide, then ammend the soil in that hole. Most of a plant's roots are within the top 6" of soil, so you don't have to expand that area by much to ensure that the nutrients the plant needs will be available to it.

The second way is much like the first, only instead of digging down, you build your soil "up" using raised beds. You can use nearly anything to hold the "good" soil in place, be it concrete blocks, landscape timbers or sturdy plastic edging. In some areas, I have put down landscape fabric, then added my rich mix on top of that. In other areas, I've cleared the weeds/grasses (two applications of Roundup two weeks apart), then added rich mix or compost and worked it in.

Don't forget that tomatoes can be grown in containers, too, just remember that they'll need watering more frequently.

I hope this helps.

~Carla

I agree with digging holes and amending just in the area you are going to plant for right now, since you have so little time to really build the soil and especially if you can't afford to build raised beds right away.
However, IMO, it would be wise this year to dig the holes a bit wider and deeper, since a drought is predicted.
You might consider digging a trench about 2 feet deep and 2 feet wide and amending the clay with compost in the trench. Don't try to plant in straight compost, mix it with the clay.
Plant in the trench and weave soaker hose around your plants.
Or, you can also plant 2.5 foot lengths of six inch perforated PVC pipe upright between each pair of plants. If you use these to water and feed your plants deeply, you'll get the nutrients down to the bottom of the trench and that's where the bulk of the rots will develop.
In a drought, the key to survival is helping the roots grow deeper by getting the water and nutrients deeper in the soil. Plan to water less frequently but more deeply.
If you water frequently and only water the surface lightly, all the plants' roots will develop on the surface and that means they won't anchor the plants well.
You really don't want your plants knocked down in a southerly, dry wind!
Really, deep watering and feeding is the key.
Mulch them well to conserve moisture once the weather heats up. Keep the mulch a few inches from the stems of the plants so fungus and bug problems don't develop there, and whala, healthy tomatoes.