than that I would presume the rules on burial apply as they would with standard power lines noted on 300.5
Don't forget a garden spade, shovel, or enthusiastic Roto-Tiller. Route of the line should also be marked or photographed while under construction to prevent fun when digging a hole for a new tree...I would say in a field as long as its deeper than a bottom plow, and in a yard at least deeper than a good plugger..
Not Chapter 3, Article 300.No. Chapter 3 only applies where specifically referenced in 725 on up.
-Hal
725.3 ... Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.