Option 1: Plugging gullies refers to the process of filling up the channels formed by erosion in the soil. While this can help prevent soil erosion, it may not directly address desertification, which is the conversion of land into a desert-like environment.

Option 2: Checking over-grazing involves managing and controlling the amount of grazing livestock that is allowed in an area. Over-grazing can lead to the removal of vegetation, which in turn increases soil erosion and contributes to desertification. By controlling grazing practices, it is possible to prevent or minimize the degradation of land and the spread of deserts.

Option 3: Contour ploughing is a farming technique that involves ploughing along the contour lines of a slope to create ridges and furrows. This helps to slow down the flow of water and prevent soil erosion. While contour ploughing can help in sustainable land management, it may not directly address desertification.

Option 4: Forming shelter belts refers to planting rows of trees or shrubs to create a barrier against wind and reduce wind erosion. Although this technique helps with soil conservation, it may not directly control desertification.

Alert - Correct answer should be: Option 2 checking over-grazing