I Farm a Little Land in the Song Dynasty

[Transmigration to the Song Dynasty + System Missions + Farming and Trade + Fighting off the Jin Invaders + Multiple Heroines + Decisive and Ruthless] The protagonist owes billions on Planet Earth when he is chosen by the System and transmigrates to the Song Dynasty. Using modern technology to buy up land and farm it, he becomes a bona fide super-landlord, so powerful that even the emperor kneels and begs him to send troops to defend the country...