Effects of Equal Nitrogen Replacement of Chemical Fertilizer Organic Resources on N2O Emissions and Rice Yield in No-tillage Field

Climate change and water scarcity threaten the sustainability of rice production systems. Alternate wetting and drying (AWD) is a promising option to reduce methane (CH4) emission from irrigated paddy fields. However, its effect on rice yield remains to be clarified. Organic amendment can increase rice yield but may also increase CH4 emission. We therefore hypothesized that the combination of AWD with organic amendment could both increase rice yield and decrease CH4 emission. We carried out field experiments in six consecutive rice seasons during 2019 − 2022 in Central Java, Indonesia. We examined the effect of water management (continuous flooding [CF] and AWD) with (+M) and without (−M) the amendment of cattle manure as a locally available organic matter on rice growth and yield and the emissions of CH4 and nitrous oxide (N2O). AWD significantly (p < 0.05) decreased CH4 emission by 29% but marginally (p < 0.1) increased N2O emission by 10% relative to CF. There was no significant effect of AWD alone on rice yield. AWD significantly increased water productivity (the ratio of rice yield to irrigated water volume) by 50%. Cattle manure amendment significantly increased CH4 emission by 12% and rice yield by 5% but did not affect N2O emission. The combination effect of AWD+M relative to CF−M (control) was additive and resulted in a 7% increase in rice yield, a 19% decrease in the global warming potential (GWP) of CH4 + N2O emissions during both growing and fallow periods, and a 24% decrease in yield-scaled GWP. Our results indicated that the combination of AWD with cattle manure amendment would be a promising means to increase rice yield while reducing total soil greenhouse gas emission from irrigated rice paddies.

Comprehensive impacts of different integrated rice-animal co-culture systems on rice yield, nitrogen fertilizer partial factor productivity and nitrogen losses: A global meta-analysis

Combination of water-saving irrigation and controlled-release fertilizer application reduced gaseous nitrogen loss in single-crop paddy soil.

Methane (CH4) and nitrous oxide (N2O) are two extremely important greenhouse gases in the atmosphere. Nitrogen fertilizer is an important factor affecting CH4 and N2O emissions in rice fields. Rational application of nitrogen fertilizer can not only promote high yields of rice but also reduce greenhouse gas emissions. Existing studies have shown that nitrogen reduction and optimal application can effectively improve the nitrogen use efficiency of rice on the basis of ensuring the yield and reduce the loss of N2O caused by nitrification and denitrification of excessive nitrogen in soil. Fertilization times and fertilizer types have significant effects on CH4 and N2O emissions in paddy fields. In this study, a field experiment was conducted for two consecutive years (2019-2020) to study the effects of fertilizer application on CH4 and N2O emissions from rice fields by setting up four treatments consisting of no fertilizer (CK), customary fertilizer application by farmers (CF), twice fertilizer (TT), and 20% replacement of chemical fertilizer by organic fertilizer (OF) using static chamber-gas chromatography. Additionally, the effect of integrating rice yield and integrated global warming potential (GWP) on the greenhouse gas emission intensity (GHGI) per unit of rice yield was analyzed to explore fertilizer application for yield increase and emission reduction in a typical rice growing area in the middle and lower reaches of Yangtze River. The results showed that:① compared with those of CK, the fertilizer treatments reduced CH4 emissions by 14.6%-25.1% and increased N2O emissions by 610%-1836% in both years; ② compared with those of CF, both the TT and OF treatments showed a trend of increasing CH4 emissions and reducing N2O emissions. CH4 emissions increased by 1.8% (P>0.05) and 14.0% (P<0.05), respectively. The annual average of N2O emissions decreased by 63.3% (P<0.05) and 49.2% (P<0.05) in both the TT and OF treatments, respectively. ③ Compared with that of CK, both fertilizer applications increased rice yield and reduced GHGI; compared with that of CF, the OF and TT treatments increased the average annual rice yield by 17.0% and 10.7%, respectively, and reduced GHGI by 6.8% and 13.7%, respectively. The OF treatment had a better yield increase than that of the TT treatment, and the TT treatment had a slightly better emission reduction than that of the OF treatment. In terms of combined yield and GHG emission reduction, both twice fertilizer (TT) and 20% replacement of chemical fertilizer by organic fertilizer (OF) could reduce the intensity of GHG emission per unit of rice yield and achieve yield increase and emission reduction while ensuring rice yield.

Treated domestic sewage irrigation significantly decreased the CH4, N2O and NH3 emissions from paddy fields with straw incorporation

Urea deep placement (UDP) and the alternate wetting and drying (AWD) irrigation method are two promising rice production technologies. However, studies on the impact of UDP under AWD irrigation on nitrous oxide (N2O) and nitric oxide (NO) emissions are limited. In this study, the effects of UDP with AWD irrigation on these emissions, nitrogen use efficiency (NUE), and rice yields are investigated, compared to conventional broadcast application. N2O and NO emissions from three fertilizer treatments – no nitrogen, UDP, and broadcast application of prilled urea (PU) – were measured. Measurements were taken using an automated gas sampling and analysis system continuously for two consecutive Boro (dry) rice seasons. N2O emission peaks were observed after broadcast application of PU but not after UDP. In contrast, large spikes in N2O emission were observed after UDP, compared to broadcast application, during dry periods. Despite differences in emission peaks, seasonal cumulative N2O emissions from UDP and broadcast treatments were similar. However, NO emissions were minimal and unaffected by UDP or AWD. UDP increased rice yields by 28% and N recovery efficiency by 167%, compared to broadcast urea. This study demonstrates that UDP with AWD irrigation can increase yields and NUE without increasing N2O and NO emissions.

A pot trial and a field experiment were conducted to study the effect of timing of application of nitrification inhibitor dicyandiamide (DCD) on N2O and CH4 emissions from rice paddy soil. Four treatments including Treatment CK1, DCD-1 (application of DCD with basal fertilizer), DCD-2 (DCD with tillering fertilizer) and DCD-3 (DCD with panicle initiation fertilizer), were designed and implemented in pot experiment. Total N2O and CH4 emissions from DCD-treated soils were decreased profoundly when compared with that from urea alone (P < 0.05). Application of DCD together with basal fertilizer, tillering fertilizer and panicle initiation fertilizer reduced N2O emission by 8, 30 and 2%, respectively, while those for CH4 were 21, 8 and 1%. The field experiment with four treatments was carried out subsequently, and a kind of urease inhibitor hydroquinone (HQ) was also incorporated with DCD simultaneously. The combined use of HQ and DCD with basal fertilizer, tillering fertilizer and panicle initiation fertilizer decreased N2O emissions by 24, 56 and 17%, respectively, while those for CH4 were 35, 19 and 12%. N2O emission was effectively reduced by the inhibitor(s) applied with tillering fertilizer before midseason aeration, while CH4 emission was effectively decreased by the combined use of inhibitor(s) with basal fertilizer before rice transplanting. Furthermore, an increase in rice yield and a reduction of total global warming potential (GWP) of CH4 and N2O could be achieved by using inhibitor(s) in rice paddy field.

Biochar application might be a newly agricultural method for improving soil quality and carbon sequestration by its special physical and chemical properties, which has generated great interest for scientists and policy makers. However, the physical structure of biochar and its effect on N2O and CH4 emissions are not yet clear. The effect of bamboo biochar and water‐washed bamboo biochar with or without N fertilization on greenhouse gas emissions, soil properties, and rice yield in a pot experiment were investigated. The results showed that biochar application increased soil pH, total N content, dissolved organic carbon (DOC), and rice plant growth. Although biochar application increased DOC content, N2O and CH4 emissions decreased. The soil and contents were significantly decreased by biochar application, indicating that bamboo biochar has a remarkable ability to absorb and . However, no significant differences in N2O emission were observed between biochar and washed biochar treatment. The CH4 emission in the washed biochar treatment was decreased to a greater extent than in the unwashed biochar, indicating that washed biochar has a greater inhibitory effect on CH4 emission than does unwashed biochar, and that the stable physical structure of biochar might be an important factor for reducing CH4 emissions. Additional studies are needed to investigate the role of functional microorganism in order to better understand the biochar on greenhouse gas emissions from paddy soils.

ABSTRACTChanges in weather and management practices such as manure and fertilizer applications have a major effect on nitrous oxide (N2O) and nitric oxide (NO) emissions from soils. N2O and NO emissions exhibit high intra- and inter-annual fluctuations, which are also highly influenced by land-use change. In this study we investigated how land-use change between grassland and cornfield affects soil N2O and NO emissions using long-term field measurements in a mollic andosol soil in Southern Hokkaido, Japan. Soil N2O and NO emissions were monitored for 5 years in a 30-year old grassland (OG), which was then plowed and converted to a cornfield for 3 years and then converted back to grassland (new grassland, NG) for another 3 years. We established four treatment plots: control, without any nitrogen (N) input (CT plot); chemical fertilizer only (F plot); chemical fertilizer and manure (MF plot); and manure only (M plot).Changing land use from OG to cornfield increased annual N2O emissions by 6–7 times, while the change from cornfield to NG resulted in a 0.3–0.6 times reduction in annual N2O emissions. N2O emissions in the newly established grassland were 2–5 times higher than those in the 30-year old grassland. Soil mineral N (NO3− and NH4+) was higher in cornfield, followed by NG and lowest in OG, while water extractable organic carbon (WEOC) did not significantly change with changing land use but tended to be higher in OG and NG than in cornfield. The ratio of WEOC to soil NO3− was the most important explanatory variable for differences in N2O emissions as land use changed. High N input, surplus soil N, and precipitation and low soil pH led to increased N2O emissions. N2O emissions in fertilizer- and/or manure-amended plots were 3–4, 2–5 and 1.4–2 times higher than those in the control treatment in OG, cornfield and NG, respectively. NO emissions were largely influenced by soil mineral N and N addition, and showed less response to changing land use. There were high inter-annual variations in both NO and N2O emissions in all plots, including the control treatment, highlighting the need for long-term measurements when determining local emission rates.

Urea deep placement (UDP) has demonstrated its benefits of saving N fertilizer and increasing nitrogen use efficiency (NUE) and grain yields. However, studies on its environmental impacts, particularly on nitrous oxide (N2O) and nitric oxide (NO), are limited. We conducted multi-location field experiments in Bangladesh to determine the effects of UDP versus broadcast prilled urea (PU) on N2O and NO emissions, NUE, and rice yields. N2O and NO emissions were measured from three N fertilizer treatments—no N, UDP, and PU—using automated gas sampling and analysis systems continuously for two rice-growing seasons—Aus (May–August) and Aman (August–December). Fertilizer-induced peaks in N2O emissions were observed after broadcast application of PU but were rarely observed after UDP. Total seasonal N2O and NO emissions, yield-scaled emissions, and fertilizer-induced emissions were affected by fertilizer treatments and sites. Though nitrogen fertilizer increased emissions significantly over the control, emissions resulting from UDP and PU were similar. Effects of N placement on grain yields and NUE were site- and season-specific. Of the N placement methods, UDP increased grain yields by 13% (p < 0.05) during the Aman season and gave similar yields in spite of lower N application during the Aus season. UDP increased N recovery from 25 and 16% of broadcast PU to 61 and 73% during the Aus and the Aman seasons, respectively in one site, but was similar in another site. On the other hand, alternate wetting and drying irrigation reduced grain yield and N recovery at the BRRI site during the Aman season.

Paddy soils are widely considered a main source of methane (CH4) and nitrous oxide (N2O). Comprehensively evaluating CH4 and N2O emissions from double-rice systems in tropical regions with different water irrigation and fertilizer applications is of great significance for addressing greenhouse gas emissions from such systems in China. In this study, eight treatments were evaluated:conventional irrigation-PK fertilizer (D-PK), conventional irrigation-NPK fertilizer (D-NPK), conventional irrigation-NPK+organic fertilizer (D-NPK+M), conventional irrigation-organic fertilizer (D-M), continuous flooding-PK fertilizer (F-PK), continuous flooding-NPK fertilizer (F-NPK), continuous flooding-NPK+organic fertilizer (F-NPK+M), and continuous flooding-organic fertilizer (F-M). CH4 and N2O emissions in double-rice fields in tropical region of china were monitored in situ by closed static chamber-chromatography method and crop yields as well as global warming potential (GWP) and greenhouse gas intensity (GHGI) were determined. The results show that:① The cumulative CH4 emissions from early rice and late rice are 10.3-78.9 kg·hm-2and 84.6-185.5 kg·hm-2, respectively. Compared with F-PK and F-NPK treatments, F-NPK+M and F-M treatments significantly increased the cumulative emissions of CH4 from early rice season. Under the same fertilizer conditions, the cumulative CH4 emissions under continuous flooding condition were significantly higher than that under conventional irrigation condition. Irrigation and fertilization had extremely significant effects on CH4 emission in the early rice season. ② The cumulative N2O emissions across all treatments were 0.18-0.76 kg·hm-2 in early rice season and 0.15-0.58 kg·hm-2in late rice season, respectively. During early rice season, compared with F-PK, F-NPK significantly increased the cumulative N2O emission; however, compared with D-PK, D-NPK, D-NPK+M, and D-M treatments significantly increased the cumulative N2O emissions. Compared with F-PK, other three treatments under continuous flooding condition significantly increased N2O cumulative emission in late rice season; compared with D-PK, D-NPK, and D-M treatment significantly increased the cumulative N2O emission. Irrigation and fertilization had significant impacts on N2O emissions in late rice season, and fertilization had significant impacts on N2O emission in early rice season. ③ Early and late rice yields were 7310.7-9402.4 kg·hm-2 and 3902.8-7354.6 kg·hm-2, respectively. Early rice yields in both F-NPK and F-M treatments were significantly higher than those in F-PK, D-PK, and D-NPK treatments. Compared with PK, the other three fertilization treatments under the same irrigation condition significantly increased late rice yield. The GWP and GHGI in early rice season were 580.8-2818.5 kg·hm-2and 0.08-0.30 kg·kg-1, respectively. There was no significant difference in GWP among four fertilizer treatments under conventional irrigation condition in the early rice season. However, F-NPK+M and F-M treatments had a significant increase in GWP compared with F-PK. The GHGI in F-NPK+M and F-M treatments were significantly higher than that in other treatments. The GWP and GHGI in late rice season were 3091.6-6334.2 kg·hm-2 and 0.50-1.23 kg·kg-1, respectively. Irrigation significantly affected GWP and GHGI in both early and late rice seasons but fertilization had no significant impact on GWP and GHGI in late rice season. ④ Correlation analysis results showed that soil NH4+-N content and soil temperature below 5 cm soil layer had an extremely significant negative correlation with CH4 emissions. Soil pH was extremely significant positive correlated with CH4 emissions but significantly negatively correlated with N2O emission. Soil NH4+-N and NO3--N concentrations were extremely significantly negatively correlated with N2O emission. Given crop yield, GWP, GHGI, and D-NPK+M can be recommended for local water and fertilizer management to reduce greenhouse gas emissions while maintaining rice yields.

Straw return, as an important measure for soil fertility improvement in farmland, significantly affects the emissions of greenhouse gases N2O and CO2. Thus, the collected soil samples from five long-term (30-year) fertilization treatments (no fertilization, CK; recommended chemical fertilizer, F; 200 % of recommended chemical fertilizer, 2F; pig manure, M; and chemical fertilizer combined with pig manure, FM) were amended with and without straw and incubated under constant temperature and humidity conditions (25 ℃ and 65 % maximum field water holding capacity) for 20 days so as to investigate the key factors influencing N2O and CO2 emissions in response to straw addition in long-term fertilization treatments. The results showed that fertilization significantly increased N2O emissions. Compared to those under the unfertilized treatment[(22.05 ±2.09) μg·kg-1, calculated as nitrogen, the same as below], cumulative N2O emissions from the chemical fertilizer treatments significantly increased by 119 %-195 %[(48.38 ±20.81) μg·kg-1 and (65.13 ±12.55) μg·kg-1 from the F and 2F treatments, respectively], and those from the manure treatments increased by 275 %-399 %[(82.72 ±12.73) μg·kg-1 and (1 101.99 ±425.71) μg·kg-1 from the M and FM treatments, respectively]. Soil NO3--N, DOC, and DTN were the main factors influencing N2O emissions from fertilized treatments in the absence of straw addition. Straw addition significantly increased cumulative N2O emissions by 345 % and 247 % in the 2F and M treatments, respectively, compared to those in the corresponding fertilized treatments without straw addition, with no significant effect on N2O emissions in the CK, F, and FM treatments. Straw addition increased DOC content and microbial activity and decreased soil NO3--N and DTN contents, thereby increasing N2O emissions. Fertilization also significantly increased CO2 emissions. Compared to those from the unfertilized treatment, cumulative CO2 emissions from the manure treatments significantly increased by 120 %-130 %[(122.11 ±4.3) mg·kg-1 (calculated as carbon, the same as below) and (116.47 ±4.55) mg·kg-1 from the M and FM treatments, respectively], and those in the 2F treatment increased by 28 %[(65.13 ±12.55) mg·kg-1]. In the absence of straw addition, soil MBC, DOC, and DTN were the main factors influencing CO2 emissions. Compared to those in the treatments without straw addition, straw addition significantly increased cumulative CO2 emissions by 660 %-1132 % among fertilization treatments, due to increased DOC and MBC contents and enhanced microbial activity. In conclusion, straw addition significantly increased N2O and CO2 emissions through increased soil DTN consumption and DOC content among fertilization treatments. In soils treated with manure amendment, straw return should be rationally considered for the purpose of balancing the comprehensive trade-offs between fertility improvement and greenhouse gas emissions.

Water management practices in rice paddies, particularly alternate wetting and drying and midseason drainage followed by intermittent irrigation, are widely recognized for reducing methane (CH4) emissions and irrigation water use compared to continuous flooding (CF). However, these practices also increase nitrous oxide (N2O) emissions and their effect on rice yield remains unclear, especially in the context of technology dissemination to farmers. This study (1) reviews 11 recent meta-analyses on CH4 and N2O emissions and rice yield and (2) synthesizes their reported effects on rice growth and yield. Aggregated data show that CH4 emissions decreased by 31–62% (n = 10), while N2O emissions increased by 37–445% (n = 7), relative to CF. Rice yield change ranged from − 5.4% to + 11% with a mean of + 1.3% (n = 8). The impact of water management on rice yield varied depending on the timing and intensity of drainage events, with excessive water stress—particularly during the heading stage—and prolonged reductive soil conditions being key risk factors. Results indicate that mild-intensity drainage practices, such as ‘safe AWD,’ not only avoid yield penalties but can significantly enhance rice productivity when tailored to favorable environmental and agronomic conditions. For effective dissemination of these practices, leveraging yield improvement as an incentive for farmers is essential. Optimizing drainage schedules in accordance with rice physiological stages and local conditions is critical. With appropriate localization, water management can serve as a climate-smart strategy that simultaneously improves water efficiency, reduces greenhouse gas emissions, and maintains or increases rice productivity.

N2O and NOx emissions from a winter wheat-summer maize rotation system in purple soil were measured on a long-term fertilization platform of purple soil for two consecutive cropping years (from November 2014 to September 2016) by using a closed-chamber and gas chromatography-based system. Chemical fertilizer (NPK), pig manure (OM), incorporation of crop residues plus synthetic NPK fertilizer (RSDNPK), pig manure plus synthetic NPK fertilizer (OMNPK), and nitrification inhibitor with NPK fertilizer (DCDNPK) under the same rate of total nitrogen were involved in monitoring N2O and NOx emissions. Short-term fertilizer-free treatment (CK) was used as a control for emission coefficient calculation. The results showed that N2O emission peaks appeared in the early stage of fertilization and in the period of heavy rainfall for all fertilization regimes. The NOx emission process was similar to that of N2O, in that emission peaks appeared at the early stage of fertilization, yet no obvious emission peaks were observed during heavy rainfall. The annual cumulative emissions of N2O from NPK, OM, RSDNPK, OMNPK, and DCDNPK were 1.35, 4.38, 1.43, 2.46, and 0.92 kg·hm-2, respectively, and the emission coefficients were 0.33%, 1.41%, 0.36% 0.73%, and 0.18%. The annual emissions of NOx from NPK, OM, RSDNPK, OMNPK, and DCDNPK were 0.11, 0.38, 0.10, 0.27, and 0.04 kg·hm-2, respectively, and the cumulative emission coefficients were 0.03%, 0.13%, 0.03%, 0.09%, and 0.01%. Amendment of organic material was the main stimulator for N2O and NOx emissions, as they significantly increased 226% and 262% (for OM) and 83% and 157% (for OMNPK), respectively (P<0.01), compared with conventional synthetic fertilizers. The application of synthetic fertilizers combined with nitrification inhibitor (DCDNPK) significantly reduced N2O emissions 32% and NOx emissions 62% (P<0.01), whereas straw returning with NPK application increased N2O emissions 6% and reduced NOx emissions 5% (P>0.05). Furthermore, statistical analyses showed that soil inorganic N content was the main regulating factor of N2O and NOx emissions together, whereas soil water-filled pore space (WFPS) and temperature were the respective main regulating factors of N2O and NOx emissions individually.

Biochar improved rice yield and mitigated CH4 and N2O emissions from paddy field under controlled irrigation in the Taihu Lake Region of China