Hi Jay,
Nutrien is a solid company and an industry leader. However, its fortunes are tied to the supply and demand dynamics of the price of potash. As the price goes, so too does its share price. If you look at the company's long-term chart, you'll see that investors who bought 10 years ago are in the red, and since the big Nutrien-Potash merger back in 2018, the price has been flat.
This is not to say its a bad company, but since it is reliant on commodity prices (potash) which can be impacted by outside factors, it could make for a less stable core holding. It could certainly rebound quite nicely on strong market dynamics, but those market dynamics can change several times over a 20-year span. That is why it is very difficult to say, yeah its an excellent long-term hold. It may very well be, or it could turn sour quite quickly.
I will say that it is diversifying and is now the largest argricultural retailer in the states, but then again agriculture industry tends to be cyclical with periods of strong and negative returns. Given this, i would not be comfortable coming out and saying that Nutrien is a rock solid bet for the next 20 years.
Mat