A soil conservation method commonly practiced in Nagaland is:

The correct answer is: d) All of the above.

Contour bunding, strip cropping, and agroforestry are all soil conservation methods that are commonly practiced in Nagaland.

• Contour bunding is a method of soil conservation that involves creating a series of low, earthen walls across the slope of a field. These walls help to slow down the flow of water, which reduces erosion.
• Strip cropping is a method of soil conservation that involves planting different crops in alternating strips across the slope of a field. This helps to prevent soil erosion by breaking up the flow of water.
• Agroforestry is a method of soil conservation that involves planting trees and crops together. The trees help to protect the soil from erosion and provide shade for the crops, which helps to reduce water loss.

All of these methods are effective in preventing soil erosion and maintaining soil fertility.