Phytolith-occluded carbon in residues and economic benefits under rice/single-season Zizania latifolia rotation

Zizania latifolia is a wild rice that contains phytoliths (Phyt) that have considerable potential for carbon sequestration. We hypothesized that the capacity of phytolith-occluded carbon (PhytOC) sequestration in residues might increase by 20%, and economic profit would be twice as high under a rice/single-season Z. latifolia rotation as under rice monoculture. To test this hypothesis, we collected rice and Z. latifolia plants and their corresponding soil samples from Zhejiang Province to determine the ability of both crops to fix carbon in the phytoliths. We showed that the soil concentrations of available Si, total carbon (Ctot) and total nitrogen (Ntot) were highly positively correlated with the concentrations of phytoliths and phytolith-occluded carbon in the residues of both crops. The cold waterlogged paddy fields in China have low productivity but their environmental conditions are suitable for planting Z. latifolia. Our model scenario, built on secondary data, demonstrated that, on a national basis, if the cold waterlogged paddy fields (occupying approximately 15% of the total paddy fields) were under rice/single-season Z. latifolia rotation, the contents of phytoliths and PhytOC in rice and Z. latifolia residues would be up to 19.46 × 106 t yr−1 and 8.82 × 104 t yr−1 (0.32 Tg CO2 yr−1), respectively. As a result, the economic benefit would be increased by 1.12 × 1011 USD per year compared to rice monoculture. Therefore, adopting rotational cropping of rice with single-season Z. latifolia will not only increase the content of PhytOC sequestration in residues and improve cold waterlogged paddy fields but also bring economic benefits to farmers.