Annual nitrous oxide (N₂O) emissions from arable soil have gradually increased due to intensive nitrogen (N) fertilization. Nitrous oxide is emitted from arable soil through microbial processes such as nitrification and denitrification. Metals including copper (Cu), iron (Fe), and zinc (Zn) are rela...
Annual nitrous oxide (N₂O) emissions from arable soil have gradually increased due to intensive nitrogen (N) fertilization. Nitrous oxide is emitted from arable soil through microbial processes such as nitrification and denitrification. Metals including copper (Cu), iron (Fe), and zinc (Zn) are related to these processes and play an important role in crop growth as a micro-nutrient. Therefore, this study was conducted to examine the effect of metals on N₂O emission and maize yield from upland soil. Maize (Zea mays L.) was transplanted into upland soil on May 22, 2018 and May 11, 2019, respectively, and harvested on October 4, 2018 and July 23, 2019, respectively. Urea as N fertilizer was applied immediately after transplanting. The zero-valent metals including Cu, Fe, and Zn were added at the rate of 0 and 187 kg ha-1 a week before transplanting. To examine N₂O emissions from the soil gas samples once a week were collected using a closed chamber method. The N₂O flux with metals increased dramatically immediately after the urea application. Cumulative N₂O emissions during the growing season were 3.74, 2.77, and 5.45 kg N₂O ha-1 184 days-1 with Cu, Fe, and Zn in 2018 and 2.21, 1.54, and 3.42 kg N₂O ha-1 184 days-1 in 2019, respectively. The order of these from the highest to the lowest was Fe > Cu > Zn in both years. This was similar to the order of remaining ammonium (NH₄+) concentrations in soil with metals. Ammonium concentration in soil was significantly greater with Fe than control, but nitrate (NO₃-) concentration was lower. Copy number of amoA genes related to NH₄+ oxidation appeared lowest with Fe implying that the nitrification process was inhibited by this metal. That of the nosZ gene associated with the reduction process of N₂O to N₂ was highest with Cu. The addition of metals did not significantly affect maize ear yield in both years. Maize ear yields were 5.17, 5.76, 5.18, and 5.99 Mg ha-1 with control, Cu, Fe, and Zn in 2018 and 5.77, 5.85, 5.06, and 5.87 Mg ha-1 in 2019. As for the yield-scaled N₂O emission it appeared that 1, 0.6, 0.5, 0.9 g kg-1 with control, Cu, Fe, and Zn in 2018 and 0.7, 0.4, 0.3, 0.6 g kg-1 in 2019. Compared with control, metals were statistically effective to reduce it in both years. Conclusively, Fe was the most effective to reduce N₂O emission without a decrease of maize yield.
Annual nitrous oxide (N₂O) emissions from arable soil have gradually increased due to intensive nitrogen (N) fertilization. Nitrous oxide is emitted from arable soil through microbial processes such as nitrification and denitrification. Metals including copper (Cu), iron (Fe), and zinc (Zn) are related to these processes and play an important role in crop growth as a micro-nutrient. Therefore, this study was conducted to examine the effect of metals on N₂O emission and maize yield from upland soil. Maize (Zea mays L.) was transplanted into upland soil on May 22, 2018 and May 11, 2019, respectively, and harvested on October 4, 2018 and July 23, 2019, respectively. Urea as N fertilizer was applied immediately after transplanting. The zero-valent metals including Cu, Fe, and Zn were added at the rate of 0 and 187 kg ha-1 a week before transplanting. To examine N₂O emissions from the soil gas samples once a week were collected using a closed chamber method. The N₂O flux with metals increased dramatically immediately after the urea application. Cumulative N₂O emissions during the growing season were 3.74, 2.77, and 5.45 kg N₂O ha-1 184 days-1 with Cu, Fe, and Zn in 2018 and 2.21, 1.54, and 3.42 kg N₂O ha-1 184 days-1 in 2019, respectively. The order of these from the highest to the lowest was Fe > Cu > Zn in both years. This was similar to the order of remaining ammonium (NH₄+) concentrations in soil with metals. Ammonium concentration in soil was significantly greater with Fe than control, but nitrate (NO₃-) concentration was lower. Copy number of amoA genes related to NH₄+ oxidation appeared lowest with Fe implying that the nitrification process was inhibited by this metal. That of the nosZ gene associated with the reduction process of N₂O to N₂ was highest with Cu. The addition of metals did not significantly affect maize ear yield in both years. Maize ear yields were 5.17, 5.76, 5.18, and 5.99 Mg ha-1 with control, Cu, Fe, and Zn in 2018 and 5.77, 5.85, 5.06, and 5.87 Mg ha-1 in 2019. As for the yield-scaled N₂O emission it appeared that 1, 0.6, 0.5, 0.9 g kg-1 with control, Cu, Fe, and Zn in 2018 and 0.7, 0.4, 0.3, 0.6 g kg-1 in 2019. Compared with control, metals were statistically effective to reduce it in both years. Conclusively, Fe was the most effective to reduce N₂O emission without a decrease of maize yield.
Keyword
#greenhouse gas nitrous oxide metal upland soil nitrification denitrification
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