Soil Conservation

The governing soil-conservation principle is to interrupt the downhill movement of water. In contour ploughing, furrows are made along lines of equal elevation, or across the slope, rather than straight up and down it. These furrows and small ridges slow runoff, give rainwater more time to infiltrate, and reduce the force available to detach and transport topsoil. As a result, erosion is reduced and moisture may be retained more effectively. Ploughing down the slope would accelerate runoff, while increasing slope steepness or rapidly reducing fertility is not the purpose. Hence option A is correct.

The governing concept is integrated watershed management, in which the land area draining to a common outlet is planned as one connected system. Its main objective is to conserve soil and water together by slowing surface runoff, reducing erosion, increasing infiltration, harvesting rainwater and supporting vegetation. These measures can improve groundwater recharge and the reliability of water for local use. Therefore option A is correct. A watershed programme may include small water-harvesting structures, contour treatment and vegetation protection, but it is not limited to dam construction. Removing forests increases erosion, and maximum groundwater extraction is contrary to conservation and sustainability.

Trees and other vegetation slow surface runoff, while their roots help hold soil in place. This reduces soil erosion, making option A correct. Infiltration and groundwater recharge may also improve, depending on local conditions.