Fertilization management and greenhouse gases emissions from paddy fields in China: A meta-analysis

Abstract

ContextThe contribution of rice paddy soils to greenhouse gases (GHGs) emissions and global warming has attracted widespread attention. ObjectivesThere are studies on the local effects of fertilizers on soil GHGs emissions, but few have looked at the comprehensive and comparative effects of fertilization management, considering soil and environmental characteristics. MethodsOur meta-analysis used data from 83 Chinese paddy fields to investigate the effects of NPK (nitrogen, phosphorus and potassium), NPKS (NPK with straw return), NPKM (NPK with manure), and NPKB (NPK with biochar) on CO2, CH4 and N2O emissions compared to the unfertilized fields (control) under single rice in the south (SRS), single rice in the north (SRN) and double rice (DR). ResultsThe order of increased global warming potential (GWP) was NPKB (10 %) < NPK (20 %) < NPKM (70 %) < NPKS (140 %). The highest GHG increases were 60 % for CO2 and 270 % for N2O under NPKM, and 180 % for CH4 under NPKS, while the lowest were 25 % for CO2, 2 % for CH4, and 5 % for N2O under NPKB compared to control. The NPKB positively increased CH4 by 38 % in SRN, while NPK resulted in a 285 % increase in N2O emission in SRS. The CO2, CH4, and N2O reached the highest increased values of 18×103, 500, and 2 kg ha−1, respectively when the N input under NPKM and NPKS was 200–300 kg ha−1. Such a relatively high N input only increased the yield by 1–4 t ha−1. In contrast, a 30 %-50 % reduction in N input (equivalent to 130–260 kg C kg−1), with a yield increase of about 4–5 t ha−1, decreased CO2, CH4, and N2O emissions by 86 %, 66 %, 75 % respectively (GWP by 12 %) under NPK and NPKB. The soil properties are also the main controllers of GHGs from paddy soils, where the highest GHGs were associated with soils with clay loam, pH=5–6, and C/N=10. The estimated cumulative emissions of CO2, CH4, and N2O under NPK in China in 2021 were 430, 7.5, and 0.038 Tg, respectively, while the addition of NPKB led to a reduction of the mentioned GHGs by 23 %, 43 %, and 47 % (GWP by 30 %), respectively. ConclusionReducing inorganic nitrogen inputs and incorporating biochar, but cautiously applying manure and straw in fertilization management are win-win strategies in paddy fields to reduce GHGs and ensure rice yield. Implications/significanceOur study highlights the importance of proper fertilization management according to rice zones and soil properties, which could decrease the GHGs emissions and bring yield and environmental benefits.