Diversifying rotations for climate change adaptation and mitigation

Jeremy’s latest newsletter summarizes a summary of a roundup of rotation research from northern China. Bottom line: more crops better.

Anthropocene Magazine has a handy summary of recent research into crop diversity on the North China Plain. Bottom line: adding more crops to the current dominant rotation of wheat and maize increases yields and profits, sequesters more carbon in the soil and reduces overall greenhouse gas emissions.

The researchers added sweet potato and a legume, like soybeans or peanuts, to the rotation and at the same time reduced the amount of synthetic fertilisers applied to the field. Sweet potato is a cash crop that increased farmers incomes by about 60%. Soybeans and peanuts have a lower impact on incomes (13–22% increase) but more than compensated for lower fertiliser inputs. Not surprisingly, lower nitrogen fertiliser results in lower emissions of nitrous oxide, a greenhouse gas. What was a surprise was an increase in carbon in the soil, perhaps because diverse crops result in more diverse microbial populations which in turn trap atmospheric methane and carbon dioxide.

[D]eveloping and adopting diversified cropping systems should be a key consideration in agricultural policy setting and a top priority for on-farm decision-making.

Projecting the experimental results to the whole of the North China Plain could, the researchers say, increase cereal production by 32% and reduce the need for fertilisers by 3.6 million tonnes. That alone, they say, would reduce China’s greenhouse gas emissions by 6%. And annual farm incomes would increase by 20%.