Which of the following are the man-made causes of soil erosion?

1. Use of improper ploughing methods
2. Practice of leaving roots of crop in the field after harvest
3. Practicing trash farming
4. Use of heavy machines

Leaving the stubble or crop residue essentially in place on the land as a surface cover during a fallow period prevents soil erosion. Similarly, trash farming is a method of cultivation in which the soil is loosened by subsurface tillage or other methods that leave stubble and other vegetation residues in the field and it prevents soil erosion. However, use of heavy machines leads to soil compaction and reduction in infiltration of rainwater. The rainwater then flows heavily as runoff and washes away the soil.