I farm, and when it comes to organic matter, if we look at the farming practices we had in the seventies when we were going 50-50 or 60-40 with summer fallow acres, the organic matter was falling and falling. It wasn't until we were able to go into no-tillage systems that we started to see the organic matter actually reverse itself.
We also found out that if you start spreading manure you would increase that organic matter quickly. So if you went to areas around Lethbridge or southern Alberta where there were many feed lots, their organic matter was growing rapidly because of the use of manure.
The use of manure for growing wheat and barley is great because it's good organic fertilizer and the crops will never touch the manure. But when you're growing lettuce or strawberries, it can create other issues.