Better techniques: even after 3,000 years of agriculture in China. During which Chinese farmers have constantly improved growing techniques. With two breaks: the Great Leap Forward (1950s) and the Cultural Revolution (1966-76), Marxist socialist experiments with state-directed farming, which did not go well — mass famine, tens of millions dead. Because the State doesn’t know how to do things. China has been successful in the fifty~years since the end of the Cultural Revolution to the exact extent that Beijing has stayed out of it, and allowed market forces free play. (TBF, I note state subsidies played a part, above).
And so, as long as socialism is kept out of the equation, the technological improvements in agriculture will go on. Homo sapiens are smart; we’re good at doing things better and better.
Another factor not mentioned here but has been in other studies: that increased CO2 has given higher yields. Because plants love CO2.Yes, it really is “plant food”!
To state the obvious: this news of China’s record harvest is significant, given the popular narrative predicting disastrous failure of agriculture and mass starvation, due to climate change.