pistachio nut shells
The soil in my yard is very heavy clay - in the good areas. In some areas, just a few inches below the surface, the soil is gray or white and has the consistency of putty or modeling clay, but when dry it is like cement. Could I use well-rinsed pistachio nut shells in planting holes (along with other amendments) to loosen the soil? If so, would I put the shells in the bottom of the planting hole or mix them into the soil? Also, could the shells be used in planting containers?
The white/gray putty-like soil is problematic and suggests a soil that will hold water beneath your plants. It also is indicative of anerobic conditions, that is, a lack of oxygen able to get to plant roots.
We would suggest either trying to avoid these soils as planting areas, or make an effort to break up the area (you may need a pick axe or fork) and amend the entire eventual root area with lots of organic material like compost or Leaf Gro. This would need to be between 8" (grass) to 18" deep (trees).
We don't have any research on the use of pistachio nut shells, and would leave them out.
Same for your pots. This page suggests the best media/soil mix for your containers: https://extension.umd.edu/hgic/topics/soil-containers
Thank you for your response and checking out the use of pistachio nut shells.