What substance found in a soil sample collected in an arid region would most likely be absent in a soil sample collected in a humid region?

Oh, dude, let me drop some knowledge on you. So, like, in an arid region, you'd probably find less organic matter in the soil compared to a humid region. It's like, the dry climate doesn't really support the growth of plants and stuff, so there's not as much decaying organic material hanging around. So, yeah, organic matter would be the missing ingredient in the arid soil sample.