Nitrogen Management and Methane Emissions in Direct‐Seeded Rice Systems

Abstract

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 (CH 4 ) emissions, eld 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 e ciency (NRE) and rice yield as a ected 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 ood would satisfy both agronomic and environmental goals of N management within each system. Both WS systems resulted in similar growing season CH 4 emissions. However, the DS system reduced CH 4 emissions by 47% compared with the conventional WS system, possibly due to a decreased period of anaerobic soil conditions. is study highlights the importance of assessing bene ts as well as tradeo s when evaluating opportunities for increasing the sustainability of direct-seeded establishment systems with respect to N management and CH 4 emissions.

Greenhouse Gas Emissions and Management Practices that Affect Emissions in US Rice Systems

“…3B; Linquist et al, 2009). These results are similar to those of Pittelkow et al (2014), who reported that when fertilizer N was applied at optimal or suboptimal rates to rice crops, especially those that stay continuously flooded, N 2 O emissions were low and had little relationship to the amount of N applied. However, Pittelkow et al (2014) also reported that when fertilizer N was applied at greater than optimal rates, N 2 O emissions increased rapidly.…”

Seasonal Methane and Nitrous Oxide Emissions of Several Rice Cultivars in Direct-Seeded Systems

“…2). The dual CH 4 peaks observed at CA‐2 and AR‐1 can also be seen in the seasonal CH 4 patterns of other studies (Chidthaisong and Watanabe, 1997; Wassmann et al, 2002; Pittelkow et al, 2014). In a 13 C‐tracer experiment, Chidthaisong and Watanabe (1997) observed two CH 4 peaks.…”

Modeling methane and nitrous oxide emissions from direct‐seeded rice systems

“…In direct‐seeded rice fields with standard fertilizer N application rates and fallow period flooding and straw incorporation, reports on the contribution of fallow period GHG emissions to annual emissions have ranged from 3% [ Pittelkow et al ., ] to 61% [ Fitzgerald et al ., ] for CH 4 and from 57% [ Pittelkow et al ., ] to 76% for N 2 O [ Adviento‐Borbe et al ., ]. When rice fields are flooded during the winter, simulated CH 4 emissions are primarily controlled by (1) substrate concentrations predicted by SOC decomposition (equations and ), (2) allocation of substrates to either CH 4 production or CH 4 oxidation routines (equations ) according to the anaerobic balloon concept, and (3) transport of CH 4 from soil to the atmosphere via diffusion and ebullition (equations and ).…”

“…Detailed management routines, including dates and methods of tillage, irrigation, and fertilizer application, were also obtained. Additional details of the experiments can be found in their respective publications [Lauren et al, 1994;Bossio et al, 1999;Fitzgerald et al, 2000;Adviento-Borbe et al, 2013;Pittelkow et al, 2013Pittelkow et al, , 2014bSimmonds et al, 2015]. Briefly, the data represented a range of N fertilizer rates (i.e., 0 to 260 kg N ha À1 ) and seeding systems (i.e., water seeded or dry seeded), with distinct fallow period straw and water management regimes (i.e., straw burning, straw incorporation, and with and without flooding).…”

“…In direct-seeded rice fields with standard fertilizer N application rates and fallow period flooding and straw incorporation, reports on the contribution of fallow period GHG emissions to annual emissions have ranged from 3% [Pittelkow et al, 2014b] to 61% [Fitzgerald et al, 2000] for CH 4 and from 57% (3) and (4)), (2) allocation of substrates to either CH 4 production or CH 4 oxidation routines (equations (7)-(9)) according to the anaerobic balloon concept, and (3) transport of CH 4 from soil to the atmosphere via diffusion and ebullition (equations (10) and (12)). Overestimation of fallow period CH 4 emissions (Figures 5 and 6) may partly be due to underestimation of the inhibitory effect of clay content on CH 4 diffusion (equation (11)) as well as on rates of decomposition of SOC (equation (3)).…”