Ian, the same thing happened in Spain. This year I took a sample, 10 inches deep, 30 samples. I mixed everything in a bag, about 3 kg. I mixed it well and sent 1 kg to each lab. You can't imagine the disaster of results. So I've ruled out the absurd results (for example, one lab gives me 1700 ppm sulfur, and the other two, much less sulfur). Or one lab gives me 5 ppm manganese, and the other two, one 90 and more. It's been the only way to know approximately how my new clay soil is, without organic matter.