In the 1970s why was foodgrain import discontinued in India?

Due to the success of the Green revolution.

India faced serious food shortages during the 1950s and 1960s. The major item of import at that time was food grain, capital goods, machinery and equipment. The balance of payment was adverse as imports were more than export in spite of all the efforts of import substitution. After the 1970s, foodgrain import was discontinued due to the success of the Green revolution.