Explanation:

1, 2 and 3

• The basic reasons for waterlogging and salinity are primarily related to poor drainage and excessive irrigation.
• Heavy clay soils such as black cotton soils are prone to water logging, as they hold moisture for long periods.
• Also, soils prone to surface sealing cause temporary water logging.
• In waterlogged lands, the water table rises to an extent that the soil pores in the crop root zone are saturated resulting in restriction of the normal circulation of air.
• This causes a decline in the level of oxygen and increase in the level of carbon dioxide.