scholarly journals Early season N<sub>2</sub>O emissions under variable water management in rice systems: source-partitioning emissions using isotopocule signatures along a depth profile

2018 ◽  
Author(s):  
Elizabeth Verhoeven ◽  
Matti Barthel ◽  
Longfei Yu ◽  
Luisella Celi ◽  
Daniel Said-Pullicino ◽  
...  
Keyword(s):  
Water Management ◽  
Management Practices ◽  
Pore Space ◽  
Site Preference ◽  
N2o Emissions ◽  
Mixing Models ◽  
N2o Reduction ◽  
Wetting And Drying ◽  
Soil Redox Potential ◽  
Alternate Wetting And Drying

Abstract. Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions, but may increase N2O and decrease nitrogen use efficiency. In a field experiment with three water management treatments, we measured N2O isotopocule signatures (δ15N, δ18O and site preference, SP) of emitted and pore air N2O over the course of six weeks in the early rice growing season. Isotopocule measurements were coupled with simultaneous measurements of pore water NO3−, NH4+, dissolved organic carbon (DOC), water filled pore space (WFPS) and soil redox potential (Eh) at three soil depths. We then used the relationship between SP × δ18O-N2O and SP × δ15N-N2O in simple two endmember mixing models to evaluate the contribution of nitrification, denitrification, fungal denitrification to total N2O emissions and to estimate N2O reduction rates. N2O emissions were higher in a dry-seeded + alternate wetting and drying (DS-AWD) treatment relative to water-seeded + alternate wetting and drying (WS-AWD) and water-seeded + conventional flooding (WS-FLD) treatments. In the DS-AWD treatment the highest emissions were associated with a high contribution from denitrification and a decrease in N2O reduction; while in the WS treatments, the highest emissions occurred when contributions from denitrification/nitrifier-denitrification and nitrification/fungal denitrification were more equal. Modeled denitrification rates appeared to be tightly linked to nitrification and NO3− availability in all treatments, thus water management affected the rate of denitrification and N2O reduction by controlling the substrate availability for each process (NO3− and N2O), likely through changes in mineralization and nitrification rates. Our model estimates of mean N2O reduction rates match well those observed in 15N fertilizer labeling studies in rice systems and show promise for the use of dual isotopocule mixing models to estimate N2 losses.

scholarly journals Early season N<sub>2</sub>O emissions under variable water management in rice systems: source-partitioning emissions using isotope ratios along a depth profile

2019 ◽  
Vol 16 (2) ◽  
pp. 383-408 ◽  
Author(s):  
Elizabeth Verhoeven ◽  
Matti Barthel ◽  
Longfei Yu ◽  
Luisella Celi ◽  
Daniel Said-Pullicino ◽  
...  
Keyword(s):  
Water Management ◽  
Isotope Ratio ◽  
Isotope Ratios ◽  
Site Preference ◽  
N2o Emissions ◽  
Mixing Models ◽  
N2o Reduction ◽  
Wetting And Drying ◽  
Soil Redox Potential ◽  
Alternate Wetting And Drying

Abstract. Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions but may increase N2O and decrease nitrogen use efficiency. In a field experiment with three water management treatments, we measured N2O isotope ratios of emitted and pore air N2O (δ15N, δ18O and site preference, SP) over the course of 6 weeks in the early rice growing season. Isotope ratio measurements were coupled with simultaneous measurements of pore water NO3-, NH4+, dissolved organic carbon (DOC), water-filled pore space (WFPS) and soil redox potential (Eh) at three soil depths. We then used the relationship between SP × δ18O-N2O and SP × δ15N-N2O in simple two end-member mixing models to evaluate the contribution of nitrification, denitrification and fungal denitrification to total N2O emissions and to estimate N2O reduction rates. N2O emissions were higher in a dry-seeded + alternate wetting and drying (DS-AWD) treatment relative to water-seeded + alternate wetting and drying (WS-AWD) and water-seeded + conventional flooding (WS-FLD) treatments. In the DS-AWD treatment the highest emissions were associated with a high contribution from denitrification and a decrease in N2O reduction, while in the WS treatments, the highest emissions occurred when contributions from denitrification/nitrifier denitrification and nitrification/fungal denitrification were more equal. Modeled denitrification rates appeared to be tightly linked to nitrification and NO3- availability in all treatments; thus, water management affected the rate of denitrification and N2O reduction by controlling the substrate availability for each process (NO3- and N2O), likely through changes in mineralization and nitrification rates. Our model estimates of mean N2O reduction rates match well those observed in 15N fertilizer labeling studies in rice systems and show promise for the use of dual isotope ratio mixing models to estimate N2 losses.

scholarly journals Effect of Fertilizer and Manure on the Growth, Yield and Grain Nutrient Concentration of Boro Rice (Oryza sativa L.) under Different Water Management Practices

2013 ◽  
Vol 11 (2) ◽  
pp. 44-51 ◽  
Author(s):  
MM AL Fakhrul Islam ◽  
Md Asaduzzaman Khan ◽  
ASM Fazle Bari ◽  
MT Hosain ◽  
M Sabikunnaher
Keyword(s):  
Water Management ◽  
Nutrient Concentration ◽  
Management Practices ◽  
Poultry Manure ◽  
Growth Yield ◽  
Control Treatment ◽  
Fertilizer Treatment ◽  
Wetting And Drying ◽  
Alternate Wetting And Drying ◽  
Continuous Flooding

The experiment was conducted in the Sher-e-Bangla Agricultural University research farm, Dhaka, Bangladesh during December 2010 to April 2011 to study the effect of fertilizer and manure with different water management on the growth, yield and nutrient concentration of BRRI dhan28. The experiment consisted of 2 factors i.e. irrigation and fertilizer plus manure. There were 2 irrigation levels (I0= Alternate wetting and drying, I1= Continuous flooding) and 8 fertilizer treatment (T0: control, T1: 100% RDCF, (N100P15K45S20Zn2), T2: 10 ton cowdung/ha, T3: 50% RDCF + 5 ton cowdung/ha, T4: 8 ton poultry manure/ha, T5: 50% RDCF + 4 ton poultry manure/ha, T6: 10 ton vermicompost/ha, T7: 50% RDCF + 5 ton vermicompost/ha). There were 16 treatment combinations and 3 replications. Irrigation had no significant effect on the yield and yield parameters of BRRI dhan 28. The yield contributing characters and yields were significantly influenced by applied fertilizer and manure. The T5 (50% RDCF + 4 ton poultry manure/ha) showed the highest effective tillers/hill, plant height, panicle length, 1000 grain wt., grain yield (5.92 kg/plot) and straw yield (5.91 kg/plot). The higher grain and straw yields were obtained organic manure plus inorganic fertilizers than full dose of chemical fertilizer and manure. The highest grain (5.93 kg/plot) and straw yields (6.42 kg/plot) were recorded from I0T5 (Alternate wetting and drying + 50% RDCF plus 4 ton poultry manure/ha) and the lowest was found in I1T0 (Continuous flooding + control treatment) treatment combination. The highest concentrations of grain and straw N, P, K, S were recorded in T5 treatment. The levels of organic matter and nutrient concentration were increased in the post harvest soils due to added manure plus inorganic fertilizer. DOI: http://dx.doi.org/10.3329/agric.v11i2.17486 The Agriculturists 2013; 11(2) 44-51

scholarly journals Arsenic Accumulation in Rice Grain as Influenced by Water Management: Human Health Risk Assessment

Agronomy ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1741
Author(s):  
Israt Jahan Harine ◽  
Mohammad Rafiqul Islam ◽  
Mahmud Hossain ◽  
Hasina Afroz ◽  
Rounok Jahan ◽  
...  
Keyword(s):  
Water Management ◽  
Health Risk ◽  
Management Practices ◽  
Human Health Risk ◽  
Rice Grain ◽  
Wetting And Drying ◽  
Straw Yield ◽  
Alternate Wetting And Drying ◽  
Drying Condition ◽  
1000 Grain Weight

Rice is a staple food for humans and a key source of soil arsenic (As) transfer to the human food chain. As a result, it is critical to develop ways for reducing As accumulation in rice. A pot experiment with seven different water management practices was done to examine the impacts of water management on rice (cv. BRRI dhan28) growth, yield, and As accumulation in rice grain. Any health risk due to As accumulation in rice grain was also determined. The soil used in the experiment was artificially contaminated with As and the source of As was sodium arsenate (Na2HAsO4 7H2O). Water management practices affect different plant growth and yield parameters including filled grains per panicle, unfilled grains per panicle, 1000-grain weight, grain yield and straw yield of rice. The number of filled grains per panicle and 1000-grain weight were found to be at their highest in the T7 (alternate wetting and drying) condition, whereas the number of unfilled grains per panicle was at its lowest in the same treatment. The T7 also demonstrated the highest grain yield (21.08 g/pot) and straw yield (22.02 g/pot), whereas the lowest values were noted in T1 (flooding throughout the growth period). The highest As concentration in rice grain (0.52 mg kg−1) was found in T1 and the lowest As concentration in grain (0.27 mg kg−1) was found in T7. Estimation of the human health risk revealed that the non-carcinogenic risks (HQ > 1) and carcinogenic risks (CR > 1.0 × 10−4) were greatly affected by different water regimes. The rice plant grown under alternate wetting and drying condition (T7) showed the lowest health risks compared to other water management practices. Thus, alternate wetting and drying conditions are a good water management strategy for increasing rice output while reducing arsenic buildup in rice grain.

scholarly journals Revisiting the relationship between soil moisture and N<sub>2</sub>O production pathways by measuring <sup>15</sup>N<sub>2</sub>O isotopomers

2019 ◽  
Author(s):  
Kate A. Congreves ◽  
Trang Phan ◽  
Richard E. Farrell
Keyword(s):  
Soil Moisture ◽  
Pore Space ◽  
Mitigation Strategies ◽  
Soil Conditions ◽  
Site Preference ◽  
N2o Emissions ◽  
Spectroscopic Techniques ◽  
N2o Production ◽  
Nitrification And Denitrification ◽  
The Relationship

Abstract. Understanding the production pathways of potent greenhouse gases, such as nitrous oxide (N2O), is essential for accurate flux prediction and for developing effective adaptation and mitigation strategies in response to climate change. Yet, there remain surprising gaps in our understanding and precise quantification of the underlying production pathways – such as the relationship between soil moisture and N2O production pathways. A powerful, but arguably underutilized, approach for quantifying the relative contribution of nitrification and denitrification to N2O production involves determining 15N2O isotopomers and 15N site preference (SP) via spectroscopic techniques. Using one such technique we conducted a short-term incubation to precisely quantify the relationship between soil moisture and N2O production pathways. For each of three soils, microcosms were arranged in a complete random design with four replicates; each microcosm consisted of air-dried soil packed into plastic petri dishes wherein moisture treatments were established for water contents equivalent to 45 to 105 % water-filled pore space (WFPS). The microcosms were placed in 1-L jars and sealed; headspace samples were collected after 24-h and analyzed for total N2O concentrations using gas chromatography, and for 15N2O isotopomers using cavity ring-down spectroscopy. Relatively low N2O fluxes and high SP values indicted nitrification during dry soil conditions, whereas at higher soil moisture, peak N2O emissions coincided with a sharp decline in SP indicating denitrification. This pattern supports the classic N2O production curves from nitrification and denitrification as inferred by earlier research; however, our isotopomer data enabled the quantification of source partitioning for either pathway thereby providing clarity on N2O sources during the transition from nitrification to denitrification. At soil moisture levels  78 %, denitrification completely dominated. Clearly, the soil moisture levels during transition is a key regulation of N2O production pathways.

scholarly journals Potential of Alternate Wetting and Drying Irrigation Practices for the Mitigation of GHG Emissions from Rice Fields: Two Cases in Central Luzon (Philippines)

Agriculture ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 350 ◽  
Author(s):  
Björn Ole Sander ◽  
Pia Schneider ◽  
Ryan Romasanta ◽  
Kristine Samoy-Pascual ◽  
Evangeline B. Sibayan ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Paddy Rice ◽  
Management Technique ◽  
N2o Emissions ◽  
Tier 2 ◽  
Ch4 Emission ◽  
Ghg Emission ◽  
Wetting And Drying ◽  
Alternate Wetting And Drying ◽  
Ch4 Emissions

Reducing methane (CH4) emission from paddy rice production is an important target for many Asian countries in order to comply with their climate policy commitments. National greenhouse gas (GHG) inventory approaches like the Tier-2 approach of the Intergovernmental Panel on Climate Change (IPCC) are useful to assess country-scale emissions from the agricultural sector. In paddy rice, alternate wetting and drying (AWD) is a promising and well-studied water management technique which, as shown in experimental studies, can effectively reduce CH4 emissions. However, so far little is known about GHG emission rates under AWD when the technique is fully controlled by farmers. This study assesses CH4 and nitrous oxide (N2O) fluxes under continuous flooded (CF) and AWD treatments for seven subsequent seasons on farmers’ fields in a pumped irrigation system in Central Luzon, Philippines. Under AWD management, CH4 emissions were substantially reduced (73% in dry season (DS), 21% in wet season (WS)). In all treatments, CH4 is the major contributor to the total GHG emission and is, thus, identified as the driving force to the global warming potential (GWP). The contribution of N2O emissions to the GWP was higher in CF than in AWD, however, these only offset 15% of the decrease in CH4 emission and, therefore, did not jeopardize the strong reduction in the GWP. The study proves the feasibility of AWD under farmers’ management as well as the intended mitigation effect. Resulting from this study, it is recommended to incentivize dissemination strategies in order to improve the effectiveness of mitigation initiatives. A comparison of single CH4 emissions to calculated emissions with the IPCC Tier-2 inventory approach identified that, although averaged values showed a sufficient degree of accuracy, fluctuations for single measurement points have high variation which limit the use of the method for field-level assessments.

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