FeIII-tannic acid-modified waterborne polymer-coated urea has agronomic, environmental and economic benefits in flooded rice paddy

Abstract It has been widely reported that resin polymer-coated urea can increase yield, enhance nitrogen use efficiency, relieve reactive nitrogen (Nr) losses, and improve economic benefits in rice cropping systems. However, nano-FeIII-tannic acid-modified waterborne polymer-coated urea (NWU), a new polymer-coated nitrogen fertiliser (PCNF), has not been fully tested in rice cropping systems. To explore the agronomic, environmental and economic performance of NWU, it was compared with unmodified waterborne polyacrylate-coated urea (WU), polyurethane-coated urea (PU, a typical reactive film-forming resin polymer) and uncoated urea (U). We integrated a 3-year field measurement of rice yield, nitrogen (N) uptake and various Nr losses with net ecosystem economic benefits (NEEB), and examined urea release during more than 100 days of pure water dissolving and soil incubation. (1) A single application of WU generally showed no benefits for improving yield, N use efficiency (NUE), net ecosystem economic benefits (NEEB), or reducing Nr losses due to undesirable initial rapid N release. (2) After simple blending of Nano-FeIII and tannic acid with waterborne polymer, the initial release was markedly delayed, allowing better synchronisation with rice N demand than WU; compared to conventional three split urea applications at equal N dose, NWU increased rice yield by 8.3% and reduced Nr losses by nearly 25%, while concurrently enhancing the NEEB by almost 11%. (3) In terms of agronomic, environmental and ecosystem economic performance, NWU performed as well as the most extensively applied PU. Thus, substituting a basal application of FeIII-tannic acid-modified waterborne polymer-coated fertiliser as basal fertilizer for conventional three split urea applications is a viable alternative for improving N use efficiency and reducing N pollution in intensive rice agroecosystems.