Why did agriculture develop greatly during the Spring and Autumn Period and the Warring States Period?

During the Spring and Autumn Period and the Warring States Period, what major changes have taken place in China's agricultural farming methods?

1. The widespread use of iron farm tools. The appearance of iron changed the way of farming. From slash-and-burn to the use of farm tools: before the Spring and Autumn Period and the Warring States Period, slash-and-burn was the main mode of production, with wood and stone tools as the main production tools, and the productivity was relatively backward.

2. Technology popularization in Niu Geng.

During the Spring and Autumn Period and the Warring States Period, people began to use iron farm tools and Niu Geng. Later, Niu Geng became the main cultivator of traditional agriculture. ...

3. The tradition of intensive cultivation began to take shape. Many agricultural technologies are close to modern times.

4. Dujiangyan, Zheng Guoqu and other large-scale water conservancy projects have started one after another, and the irrigation level of farmland water conservancy has been greatly improved.

5. The emergence of plant ecology and taxonomy of animals and plants.