NewAg (Natural Eco-friendly Wood for Agriculture) posts are naturally durable, and preservative treatment is not necessary.

This organic alternative is milled out of Western Juniper trees and has none of the disposal problems associated with treated wood and steel.
Western Juniper has been used for decades as fence posts, poles, corrals... because it is extremely durable and resistant to rot.

In a long term fence post service life study since 1928, Oregon State University reported Western Juniper to last 30+ years, longer than any other untreated western species.
In general,
sapwood, regardless of species, has a low resistance to decay. There is no evidence that heartwood improves the performance of adjacent sapwood, and that also goes for the Redwood and Cedar species. So when we talk about durability we want to talk directly to the heartwood content.