Often times people report there is a significant difference between front and back soil. This could be due to excavation from the home being piled in one or the other and then spread or topsoil turcked in for the front but not the back, or in larger yards it could be natural occuring differences from historic deposits. Use observations to help you decide. If you do not see significant soil type differences and you have not seen differences in the same turf grass between the yards (for instance yellowing KBG in the front but not the back), one test should be fine from samples from both yards mixed together. Next year, if you are seeing significant differences in the front and back turf, you can get separrate tests. I initially used only one test and it worked fine for me. If I had seen differences between my turf after the first year, I had planned on going to two tests.
There is a government geological site that maps soil types and in some instances mapping them to allotment level. Sorry but I can't seem to find the link in my bookmarks, but I'm sure if you google soil profile mapping you'll find it. Soil type is only one variable to consider though.

This post was edited by grass1950 on Thu, Feb 7, 13 at 11:03

Appreciate it, that's exactly the info I was looking for. I was actually looking at that site yesterday, if we're talking about the same site at TAMU - http://soildata.tamu.edu/county.htm

Charateristics of soil and grass are pretty much the same front and back ... not much area in the first place. At least initially, I'll send them a healthy mix of both.

Thanks!
Matt

If you live inside Loop 410 in an area with the big houses (King William, Alamo Heights, etc.), then I would get separate tests. Why? Because those areas have long histories of ownership where someone might have neglected the back yard but kept the front looking pristine with lots of chemicals. You could have a build up of P or K in the front which would throw off the plan for the rear. In other areas of town you can almost expect the back to have been neglected some time in the past, but I would not expect that much extra effort in the front. If you have a home less than 10 years old, then the front and back are likely the same.

What part of town are you in? Soils don't vary much until you get towards the south of town or up the escarpment.

Mr. Hall, I'm on the west side, near 1604 & 90. Soil is pretty similar throughout the neighborhood. I wanted to be sure separate tests wasn't standard practice. I'm pretty new to organics, but after reading around in here, I'm pretty excited about the idea. After seeing how compacted and sparse parts of the yard is, plus the fact that a friend found the "wonder fertilizer" that he applied to my front yard which immediately burned and killed it in random patches, I'm pretty much done with synthetics that are supposed to work "anywhere, anytime, on any grass". Now I have to fix the mange, lol.
Matt

dchall makes an excellent point about the lawn's history and possible neglect of the back yard. That's what I was trying to drive at when I suggested you base your decission on observations of differences (like color) as a new owner is unlikely to know what care or lack thereof the previous owner may have done.

Fortunately it was a new construction. No telling where they got the base and topsoil from though. Most of the soil on this side of town is that light brown Texas topsoil. And, of course, a healthy mix of dense caliche. Not sure why, but my front and back both are considerably darker than the typical light brown of the neighborhood. I need to go take a soil science course; a lot more to healthy yards than I thought.