About captive mines for fertilizers
Here is an article from policy section of economic times. It talks about the global race to control the strategic mines that produce Potash and Phosphate reserves in the world. These two macro nutrients (of the famous NPK trio) form an important part of the plant nutrients supplement in India. Of all the talks about using organic manure, the ground reality is that these supplements are the ones that are actually being used in a big way. For this, see here for the general reasons. The subsidy component varies from 60 to 75% of total cost in India, which adds to the economic reason for high demand of fertilizers over organic manure. For fertilizer consumption in India, see here The imports of DAP and MOP (from which phosphate and potash are obtained, respectively) by India is one of the highest in the world. Close to 70% of the phosphate based fertilizers and 100% of potash-rich fertilizers sold in India are imported. So that makes these two imports vital for our food security.