The dataset of global methane emissions from rice paddies as affected by N fertilization

We conducted a meta-analysis to assess the N effects on CH4 emissions from rice paddies. We used the Web of Science to search journal articles published before November 2023 using search terms “rice OR paddy” and “methane OR CH4”, and “nitrogen OR N OR fertilizer OR fertilization”. To prevent selection bias, we only included papers that met the following criteria: (i) the continuous, multi-season fertilization experiments were conducted under field conditions with random design and replicates because N fertilization is typically a long-term practice, (ii) experiments adhered to cropping systems which are widely used by local farmers in the study area, (iii) the management practices (e.g. P and K rate, N type, N placement, organic amendment, tillage, irrigation) need to be the same between controls (zero N fertilizer input) and treatments (N fertilizer input), and (IV) we excluded data from the initial season of each study, because the plant residues from previous crop season are the same between zero N fertilizer input and N fertilizer input treatments, thereby focusing instead on the effect of sustained N fertilizer use. Finally, a total of 153 observations from 41 studies were included in our analysis.

For each observation, we tabulated the means of seasonal CH4 emissions and rice growth data (that is, total aboveground biomass or yield), and their standard deviation (SD) and replicates for both control and treatments. Missing SDs were estimated according to the mean coefficient of variation across our dataset. Climate, soil properties and experimental management may affect CH4 emissions from rice paddies, in turn regulating the impact of N additions. Thus, we also tabulated the corresponding factors from collected papers, i.e., mean annual temperature (°C), annual precipitation (mm), cropping system (single rice, rice-upland or double rice), experimental duration (yr), soil pH, soil organic carbon content (g kg-1), soil total N content (g kg-1), water regimes (continuous flooding or intermittent irrigation), rice cultivar (Indica or Japonica), organic management (i.e. organic matter input, yes or no), N fertilizer rate (kg N ha-1 season-1) and type (e.g. urea, controlled-released or ammonium N fertilizer).