TY - JOUR
T1 - Optimum N rate for grain yield coincides with minimum greenhouse gas intensity in flooded rice fields
AU - Kim, Gil Won
AU - Gutierrez-Suson, Jessie
AU - Kim, Pil Joo
PY - 2019
Y1 - 2019
N2 - Excessive application of N fertilizer to rice results in water and atmospheric pollution including greenhouse gas (GHG) emissions. Therefore, N fertilizer management needs to be optimized taking into account grain yield, global warming potential (GWP, Mg CO 2 eq. haˉ1) and GHG intensity (GHGI, kg CO 2 eq. kgˉ1 grain). However, the tradeoffs between the effects of N rate on rice grain yield, GWP and GHGI have not been adequately evaluated. Therefore, field experiments to determine the effect of N rate (as urea) on yield, GWP and GHGI were conducted in a typical flooded, transplanted rice paddy in a temperate environment. Methane (CH₄) and nitrous oxide (N₂O) emission rates were determined throughout the entire year (both during growing and fallow seasons) over two years. Rice grain yield showed a quadratic response to N rate, and the maximum yield (6.7–6.8 t haˉ1) was achieved at 112–119 kg N haˉ1, 50% higher than the yield of the control (0 kg N haˉ1). Increasing N rate increased the seasonal N₂O flux by 4.56–7.11 g N₂O kgˉ1 N, but N₂O flux contributed less than 7% of the total GWP. The GWP was mainly determined by the CH₄ flux, which showed a relatively flat quadratic response to N rate, peaking at 124–138 kg N haˉ1. Thus, GWP also showed a quadratic response to N rate, peaking at 122–130 kg N haˉ1. The GHGI decreased as N rate increased and was the lowest (1.10–1.28 kg CO 2 -eq. kg −1 grain yield) at 104–112 kg N haˉ1, approximately 20% lower than GHGI in the 0 N treatment. In conclusion, the N rate for maximum yield was similar to the N rate for minimum GHGI, mainly because of the small effect of N rate on CH₄ emissions and the low magnitude of N₂O emissions. Thus, GHGI was largely driven by grain yield, so the N rate for maximum grain yield was similar to the N rate for maximum GHGI. Proper N fertilization is essential in rice farming systems to increase crop productivity and reduce the global warming impact (GWP and GHGI).
AB - Excessive application of N fertilizer to rice results in water and atmospheric pollution including greenhouse gas (GHG) emissions. Therefore, N fertilizer management needs to be optimized taking into account grain yield, global warming potential (GWP, Mg CO 2 eq. haˉ1) and GHG intensity (GHGI, kg CO 2 eq. kgˉ1 grain). However, the tradeoffs between the effects of N rate on rice grain yield, GWP and GHGI have not been adequately evaluated. Therefore, field experiments to determine the effect of N rate (as urea) on yield, GWP and GHGI were conducted in a typical flooded, transplanted rice paddy in a temperate environment. Methane (CH₄) and nitrous oxide (N₂O) emission rates were determined throughout the entire year (both during growing and fallow seasons) over two years. Rice grain yield showed a quadratic response to N rate, and the maximum yield (6.7–6.8 t haˉ1) was achieved at 112–119 kg N haˉ1, 50% higher than the yield of the control (0 kg N haˉ1). Increasing N rate increased the seasonal N₂O flux by 4.56–7.11 g N₂O kgˉ1 N, but N₂O flux contributed less than 7% of the total GWP. The GWP was mainly determined by the CH₄ flux, which showed a relatively flat quadratic response to N rate, peaking at 124–138 kg N haˉ1. Thus, GWP also showed a quadratic response to N rate, peaking at 122–130 kg N haˉ1. The GHGI decreased as N rate increased and was the lowest (1.10–1.28 kg CO 2 -eq. kg −1 grain yield) at 104–112 kg N haˉ1, approximately 20% lower than GHGI in the 0 N treatment. In conclusion, the N rate for maximum yield was similar to the N rate for minimum GHGI, mainly because of the small effect of N rate on CH₄ emissions and the low magnitude of N₂O emissions. Thus, GHGI was largely driven by grain yield, so the N rate for maximum grain yield was similar to the N rate for maximum GHGI. Proper N fertilization is essential in rice farming systems to increase crop productivity and reduce the global warming impact (GWP and GHGI).
KW - global warming
KW - methane
KW - nitrous oxide
KW - urea
UR - http://handle.westernsydney.edu.au:8081/1959.7/uws:51804
U2 - 10.1016/j.fcr.2019.04.011
DO - 10.1016/j.fcr.2019.04.011
M3 - Article
SN - 0378-4290
VL - 237
SP - 23
EP - 31
JO - Field Crops Research
JF - Field Crops Research
ER -
