Question

how can the problem of land degradation be solved in hilly&desert area

Answer 1

In hilly area:

terrace farmingploughing in contour linesplanting trees on sloped to prevent land erosion

In desert area:

stabilizing sand dunes management of grazing

Answer 2

Land Degradation can be tackled in hilly areas by terrace farming and dividing the river into various channels.
In desert areas by growing small plants or shrubs to stop relocation of Sand dunes.
Creating shelter belts.