Rice straw application improves yield marginally and increases carbon footprint of double cropping paddy rice (Oryza sativa L.)

Sustainable production of paddy rice is essential in supplying staple food worldwide. In the present study, we determined annual yield, greenhouse gas emissions (GHGs) and carbon footprint of double cropping paddy rice (Oryza sativa L.) as impacted by organic and inorganic amendments in a 38-year study from central China. A balanced synthetic fertilizer of nitrogen (N), phosphorus (P) and potassium (K) combined with rice straw application (NPK_RS) consistently produced higher annual grain yield by 5%, 11% and 64%, respectively, compared with NPK, anaerobically digested manure (NKM) and NK. Average GHGs associated with both early -and late-season rice production were 47,300 kg CO2eq ha-1 yr-1 for the NPK_RS, 24,100 kg CO2eq ha-1 yr-1 for the NPK, 27,700 kg CO2eq ha-1 yr-1 for the NKM, 24,300 kg CO2eq ha-1 yr-1 for the NK, and 20,400 kg CO2eq ha-1 yr-1 for the non-fertilized control (CK). Of the total GHGs, approximately from 80% to 95% of the emissions resulted from methane fluxes, and from 3% to 7% emitted as soil nitrous oxide while only from 2% to 15% of the total emissions derived from other sources such as fertilizer, herbicide and pesticide production and field operation. As a result, carbon footprint of paddy rice varied from 2.1 to 3.9 kg CO2eq kg-1 grain. Straw addition with the NPK improved rice yield only marginally, but increased methane emissions and carbon footprint significantly, compared with the NPK. On the other hand, the NKM increased rice yield by 48% and GHGs by 10% and lowered carbon footprint by 23%, compared with the NK. Timing of straw application and manure amendments are critical for improving yield of paddy rice, reducing GHGs, and lowering carbon footprint.

Automated summary

This study found that the balanced synthetic fertilizer of nitrogen, phosphorus, and potassium, combined with rice straw, can increase rice yield and reduce greenhouse gas emissions and carbon footprint.