All the farms and all the water on both sides of the dividing line deteriorate in quality. If the detrimental effects were the result of the redistribution of land, then we should see a disproportionate decline in the green farms on the right.
Since all the farms declined in fertility and water containment, it appears to me that there was another factor affecting the deterioration than just new owners.
Before:http://img714.yfrog.com/i/beforem.png/
After:http://img185.yfrog.com/i/afterq.png/
It shows up the use of the clone tool around the bottom of the images more clearly.