Fertilizer-derived nitrogen use of two varieties of single-crop paddy rice: a free-air carbon dioxide enrichment study using polymer-coated 15N-labeled urea

• Published in: Soil science and plant nutrition (Tokyo) 2022-01, Vol.68 (1), p.41-52
• Main Authors: Hayashi, Kentaro, Tokida, Takeshi, Arai, Miwa, Sakai, Hidemitsu, Nakamura, Hirofumi, Hasegawa, Toshihiro
• Format: Article
• Language: English
• Subjects: Abundance; Agronomic efficiency; Aquatic plants; Biomass; Carbon dioxide; Cereal crops; Coatings; Controlled release; Crop production; Efficiency; Environmental monitoring; FACE; Fertilization; Fertilizers; Mineralization; Nitrogen; nitrogen budgets; Nitrogen isotopes; Oryza sativa indica; Oryza sativa japonica; paddy soil; Plant biomass; Polymer coatings; Polymers; recovery efficiency; Rice; Rice fields; Seedlings; Soil fertility; Sustainable production; Urea
• ISSN: 0038-0768; 1747-0765
• DOI: 10.1080/00380768.2021.2003163

Atmospheric concentrations of carbon dioxide (CO 2 ) have steadily increased over recent decades. The fertilization effect of elevated CO 2 concentrations (E-[CO 2 ]) is known to increase the biomass production and also the nitrogen (N) demand of paddy rice, which affects the rice N use efficiency. This study was conducted to elucidate the fertilizer-derived N use of paddy rice (Oryza sativa L.) for two varieties, japonica cv. Koshihikari and indica cv. Takanari, with and without E-[CO 2 ] using a free-air CO 2 enrichment (FACE) facility in central Japan. To quantify the fate of fertilizer-derived N directly, polymer-coated 15 N-labeled urea was used with a one-shot application rate of 80 kg N ha -1 incorporated into the plowed layer at the basal fertilization before transplanting of rice seedlings. The biomass, total N concentrations, and 15 N abundance in each part of the rice plants were measured at the panicle initiation, heading, and maturing stages. The total N content and 15 N abundance in the soil were measured at the maturing stage to evaluate the N balance of the rice-soil system. While E-[CO 2 ] significantly increased the whole plant biomass and the total N content in panicles, it did not increase the total N and the fertilizer-derived N content in the whole plant. The recovery efficiency (fertilizer-derived N in the whole plant to applied N, RE) ranged between 64.9% and 68.7%, and the agronomic efficiency (fertilizer-derived N in panicles to applied N, AE) ranged between 37.8% and 43.8%. The effect of CO 2 on RE and AE was not significant. The REs, higher in Koshihikari, and the AEs, higher in Takanari indicated that Takanari preferentially allocated fertilizer-derived N to panicles. The REs, 69% at the maximum in this study, implies an upper limit of use efficiency of N fertilizer, even for polymer-coated (controlled-release) fertilizer. E-[CO 2 ] significantly increased the rice N uptake from sources other than fertilizer, of which mineralization was the most-likely source. Monitoring of soil fertility and appropriate fertilization management are, therefore, necessary for sustainable rice production avoiding long-term decline in soil N fertility.