2.1.1 Experimental design
Field experiments for rice (Oryza sativa L., cv. Nanjing 46) were conducted at Chongming, Shanghai, China for two years (2019-2020). Basic soil information was collected before the experimentation (Table 1). The meteorological records of the closest weather station from our experimental site (ca. 5.7 km away) were downloaded from the website of the China meteorological data service centre (http://data.cma.cn). The weather variables include daily solar radiation, minimum and maximum temperatures, precipitation, vapour pressure, and wind speed. The mean air temperature and precipitation at the experimental site for the studied years are shown in Fig. S1, illustrating the typical weather conditions for rice cultivation in Yangtze River Delta.
Details about the field experiment were given previously (Wang et al., 2023). There were six treatments with varied N application amounts from 0 to 320 kg N ha-1 per season in a complete randomized block design and three and four blocks in 2019 and 2020, respectively, in which each plot occupied an area of 180 m2. Rice was sown with a row spacing of 20 cm and a within-row seed spacing of 2-3 cm on 14-Jun and 4-Jun in 2019 and 2020, respectively. The application time and amount of N were split according to the schedule in Table 2. Based on the local practice, sufficient phosphate (112.5 kg P2O5 ha-1) and potash (112.5 kg K2O ha-1) fertilizers were applied per season to prevent phosphorus and potassium deficiencies. Other field managements were the same in each plot following local standard practices, including irrigation, and pest, weed and disease control.