Afarmer buys a horse to replace his oxen but notices the horse is having problems pulling the plow. what does he need to make the horse’s job easier

Since the horse has less pulling power then an oxen, then the farmer has two wise options to make. 
1. To make the plow smaller, thus making less pressure on the horse because of it will turn and pull lesser amount of ground.
2. To buy another horse, so that the plow is not reduced and the job to be done quicker, and the horses will share the effort so they will have no problem in pulling the plow.