The correct answer is option 3: Potash Fertilizer. Potash fertilizer is the type of fertilizer for which India is fully dependent on imports. Potash is a concentrated source of potassium which is an essential nutrient for plant growth. India does not have adequate natural reserves of potash, therefore it relies heavily on importing this fertilizer from other countries to meet its agricultural needs.

Option 1: Nitrogen fertilizer is not the correct answer. While India does import nitrogen fertilizers, it also has domestic production capabilities.

Option 2: Phosphatic fertilizer is also not the correct answer. India has both domestic production and imports of phosphatic fertilizers.

Option 4: None of these is not the correct answer, as option 3 (Potash Fertilizer) is the correct choice for India`s full dependence on imports.