Rice (Oryza sativa L.) establishment systems based on resource-conserving production practices are gaining popularity globally. To investigate the potential for improved N management and mitigation of methane (CH4) emissions, field experiments were conducted in California on three crop establishment systems: water-seeded (WS) conventional, WS stale seedbed, and drill-seeded (DS) stale seedbed. Fertilizer nitrogen recovery efficiency (NRE) and rice yield as affected by N rate, source, and application timing were evaluated for 2 yr in each system. Methane emissions were monitored over a full annual rice production cycle (growing season plus fallow period). Results indicated that neither split N applications nor ammonium sulfate increased yields or NRE compared with a single application of urea, regardless of system. However, the economic optimum N rate increased by approximately 30 kg N ha-1 in WS stale seedbed compared with the conventional system. Since NRE generally remained similar across N treatments that maximized yields, applying the appropriate N rate as a single dose before the permanent flood would satisfy both agronomic and environmental goals of N management within each system. Both WS systems resulted in similar growing season CH4 emissions. However, the DS system reduced CH4 emissions by 47% compared with the conventional WS system, possibly due to a decreased period of anaerobic soil conditions. this study highlights the importance of assessing benefits as well as tradeoffs when evaluating opportunities for increasing the sustainability of direct-seeded establishment systems with respect to N management and CH4 emissions.
ASJC Scopus subject areas
- Agronomy and Crop Science