Answer:
- "early ripening rice"
- new irrigation techniques and systems
- planting new crops (cotton, tea)
Explanation:
Song Dynasty was a famous Chinese dinasty ruling from 10th till 13th century.
Among other things, this period is famous for massive agricultural improvements which increased crop production. Subsequently, that led to the increase in China's population.
Probably the most famous improvement was the development and use of "early ripening rice". This rice had a shorter life cycle which meant that it could grow 2 - 3 times per year, making more crops.
Also, new irrigation systems and techniques were invented which allowed the crops to be watered more efficiently and preventing drought.
We must not forget that China started farming other crops at that time including tea and cotton.
All of this improved farming making it one of the most notable legacy of the Song Dynasty.
