Was Russia's original territory unfavorable for agriculture?
The area outlined covers several climatic zones. The northeastern part was, and to some extent still is, permafrost at shallow depth, so obviously this was not good for agriculture. Further south most of the area outlined is covered in podzols, which are generally sandy and nutrient poor. Therefore, where water availability is not a limiting constraint (and we have no rainfall records for the 1500s), and where it is not too cold, the soils could have supported agriculture- but only just. They would most likely not have been high yielding. Even today, such soils need a lot of extra nutrients and additional organic carbon to give good results. Politics apart, maybe this is why much of Russia has remained so poor for so long?