Is that all the same plant?

It looks like Trichocereus peruvianus. Hard to say how active that cactus will be though. Have you sampled it before?

Two samples tested - inactive

Its a huge old stand of cactus. If this is the cactus from your other post then I would still say that its worth using a big piece and brewing tea. That way at least you would know for sure. It could be active but weak.

There is quite a bit of variation between the different columns on that cactus. Thats not uncommon on large plants. But some of those columns do show characteristics of Cuzcoensis genetics. The wavy look to the ribs, where they go from fat to thin to fat to thin... And the extreme spininess of some of the columns. That shows that there could be some Cuzcoensis DNA. Also the overall thinness of the columns for such an established and healthy looking plant. It could well be what is sometimes referred to as a "Peruzco" which is a Peruvianus with some Cuzcoensis admixture. I have a cactus of this type, and while it is active, the activity level is quite low. For me a normal sized dose leads to some feelings of sedation and a slightly different than normal headspace. Visual perception is somewhat enhanced. But thats about it. No actual trip.

In the end, if you do try using a big piece and it still does not have the activity level that you want, then seeking out Bridgesii as Wolf said would make a lot of sense. Cuttings from a Bridgesii plant of that size would be very very potent.

Yes. That's the one I mentioned in the previous post. Last time I used a bit more than 80cm of cacti! Should I use more for a single dose? How much then would you recommend?

Thats a lot of cactus. I wouldn't brew more than 2 feet (60 cm) of that cactus. The main point would be to do a traditional tea preparation using the entire cutting. That will give you a good idea of the activity level of this cactus. Hopefully it is active enough that it would just be a matter of using enough material to get as high as you want. You certainly have plenty of plant material to work with. If the tea turns out to be inactive or very weak then you know that this cactus is a "dud". But if you get effects from the tea then you will have a better idea of how much cactus to use next time. At least thats what I would do before giving up on that cactus.

30 cactuses from 30 different seeds, 30 times testing. It's gonna be a great amount of bitterness. I wonder is there some kind of test I could do with samples from the cactus? Are there some morphological characteristics that could give me a clue? I see some are bluer than others, some have a V shape over the areols, some have shorter or longer spines, some are thicker or their ribs are thicker, some have a gap between their ribs, some don't.

Oh I see. I didnt realize that there were 30 seed grown plants there. I thought that was all one stand with the same DNA.

Yes there should be variation there. There is an interesting thread on the Shroomery where someone has been growing out various Matucana Trichocereus and bioassaying them. Some of those plants fall within the Pachanoi phenotype range while others have more of a typical Peruvianus phenotype. The link is here:
https://www.shroomery.or...flat.php/Number/26221535

The author found a similar pattern that I have observed. Which is that the less spiny phenotypes are generally more potent in psychedelic effects.

From among your cacti you are most likely to find good activity in the individual plants that are fattest, bluest, and the least spiny. The skinnier, greener, very spiny ones probably hold the least potential, though there could be some outliers there. But in general you want to select from a phenotype that is most similar to true Peruvianus or true Pachanoi. And you want to select from plants that are large and robust.

I would seek out a specimen or specimens similar to what is outlined in these photos. Try to take from the biggest plant that has that phenotype throughout. Hopefully there is some good activity among some of your cacti.

OK. I'll try them and see. Many thanks