Influence of irrigation frequency on greenhouse gases emission from a paddy soil

Water management is known to be a key factor on methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) emissions from paddy soils. A field experiment was conducted to study the effect of continuous irrigation (CI) and intermittent irrigation (II) on these emissions. Methane, CO₂, and N₂O emissions from a paddy soil were sampled weekly using a semi-static closed chamber and quantified with the photoacoustic technique from May to November 2011 in Amposta (Ebro Delta, NE Spain). Intermittent irrigation of rice paddies significantly stimulated (N₂O + N₂)–N emission, whereas no substantial N₂O emission was observed when the soil was re-wetted after the dry phase. The cumulative emission of (N₂O + N₂)–N was significantly larger from the II plots (0.73 kg N₂O–N ha^?1 season^–1, P < 0.05) than from the CI plots (?1.40 kg N₂O–N ha^?1 season^?1). Draining prior to harvesting increased N₂O emissions. Draining and flooding cycles controlled CO₂ emission. The cumulative CO₂ emission from II was 8416.35 kg CO₂ ha^?1 season^?1, significantly larger than that from CI (6045.26 kg CO₂ ha^?1 season^?1, P < 0.05). Lower CH₄ emission due to water drainage increased CO₂ emissions. The soil acted as a sink of CH₄ for both types of irrigation. Neither N₂O–N nor CH₄ emissions were affected by soil temperature. Global warming potential was the highest in II (4738.39 kg CO₂ ha^?1) and the lowest in CI (3463.41 kg CO₂ ha^?1). These findings suggest that CI can significantly mitigate the integrative greenhouse effect caused by CH₄ and N₂O from paddy fields while ensuring the highest rice yield.     

Estimation of supplementary water to paddy fields in the lower Mekong River basin during the dry season

Efficient management of water resources in paddy fields requires an understanding of the volume of supplementary water used. However, quantifying the volume is laborious due to the large amount of data that must be collected and analyzed. The purpose of our study was to estimate the volume of supplementary water used in paddy fields, based on several years of available statistical data, and to provide information on how much water can be supplied to paddy fields in each target area. In this study, the lower Mekong River basin of northeast Thailand, Laos, and Cambodia was selected as the study area. In the first step, we used agricultural statistics for each country, rainfall data acquired from the Mekong River Commission Secretariat (MRCS), and the value of virtual water required per unit of rice production. Because several years of data were used for dry season harvested areas and rice production in each country, the supplementary water to paddy fields in each province was calculated using virtual water and rainfall. This method made it possible to estimate changes in supplementary water in each province. Through this study, the supplementary water to paddy fields during the dry season in three countries was approximated from the minimum number of data sets. Moreover, for cases in which it is not possible to procure agricultural water use data for a hydrological model simulation, an alternative solution is proposed.     

Dynamics of dissolved ions in the soil of abandoned terraced paddy fields in Sado Island, Japan

We investigated the soil and soil water chemistry in abandoned terraced paddy fields (reed stand) and a thicket of deciduous broad-leaved trees (thicket stand) on the same slope in Sado Island, Japan. The soils gathered from these plots were incubated under different water conditions to examine the dynamics of dissolved ions. The organic carbon pool in the soil in the reed stand at the lower slope position was greater than the thicket stand at the middle slope position. The high concentration of base cations and an almost neutral pH of the soil water at the reed stand corresponded with the high exchangeable cation concentrations and base saturation in the soil. These results reflect the mineral-rich groundwater percolating down the slope, which may be produced by chemical weathering. An in situ sulfate reduction in the reed stand at deeper soil horizons was identified. The different water conditions in the incubated soils affected the soil pH(H₂O), transformation of Fe, and dominant anions (NO₃ ⁻, HCO₃ ⁻, and SO₄ ²⁻). These biogeochemical processes were more conspicuous in the reed stand at the lower slope position where the concentrations of organic matter and base cations were high. When the abandoned terraced paddy field is developed for the conservation of the Japanese crested ibis (Nipponia nippon) habitat in Sado Island, the reductive subsoil at the lower slope position should be kept waterlogged to limit sulfuric acid generation.     

Nitrogen transport and transformation in packed soil columns from paddy fields

Our understanding of nitrogen transformation in paddy fields or wetlands is limited due to the complex interactions between soil, water, and biomass. Therefore, we studied transformation patterns resulting from the oxic level in the soil, and studied saturated (anoxic) and unsaturated (oxic) flow conditions. We present a model designed to predict concentrations of nitrate and ammonium at several soil depths resulting from the processes of nitrification, denitrification, and ammonification. Model equations were obtained that describe NO₃-N and NH₄-N concentrations in terms of position, rate constant, and average flow velocity. Although many parameters were included in the model equations, some were determined from the literature and others were derived from experiments. A sensitivity analysis of the rate coefficients for NO₃-N and NH₄-N revealed that they are extremely sensitive to denitrification and ammonification respectively. Experimental results show that there were large differences in the transformations of NO₃-N and NH₄-N, the water pressure distributions, and the oxygen reduction potentials (ORP) between saturated and unsaturated pore water flow conditions. The performance of the model for sequential transformations during the transport of NO₃-N is well documented under both saturated and unsaturated flow conditions.     

Lasting effects of controlled irrigation during rice-growing season on nitrous oxide emissions from winter wheat croplands in Southeast China

Nitrous oxide (N₂O) emission from croplands in China is a serious environmental concern. Water management is an important factor in regulating N₂O emissions from croplands. In China, controlled irrigation (CI) is one mode of the water-saving irrigation for rice and is widely used. This study aims to assess the lasting effects of CI on N₂O emissions from winter wheat croplands in Southeast China, with traditional irrigation (TI) as the control. CI performed during the rice-growing season had obvious lasting effects on N₂O emissions of the subsequent winter wheat-growing season. Compared with TI, CI significantly increased the cumulative N₂O emission by 129.1 % during the rice-growing season (p < 0.05), but significantly decreased it by 47.7 % during the wheat season (p < 0.05). Continuous flooding of the TI during most of the rice-growing season resulted in an increase in N₂O emissions during the winter wheat-growing season. Over the whole annual cycle, the cumulative N₂O emission from the plots under CI during the rice-growing season was 5.3 kg N₂O–N ha^?1, which was 103.2 % of that under TI (p > 0.05). The results suggest that CI does not significantly increase the cumulative N₂O emission from the rice–winter wheat rotation systems while insuring rice and wheat yields. This study focuses on the lasting effects of water-saving irrigation mode during rice-growing season on N₂O emissions during the following wheat-growing season. Thus, it is a development and complement of the previous researches on the effects of water-saving irrigation on N₂O emissions from rice–winter wheat rotation croplands.     

Effects of application of certain herbicides on soil nematodes and aquatic invertebrates in rice paddy fields in Japan

As representatives of herbicides which are used in rice fields in Japan, paraquat (Pa), chlormethoxynil (Ch), a mixture of thiobencarb and simetryne (BS), and oxadiazon (Ox) were chosen for investigation of their effects on invertebrates in soil and flood water of rice paddies. With regard to nematodes, plant-parasitic species from rice roots, mainly Hirschmaniella oryzae, were the most abundant in B plots. All herbicide plots yielded more plant-parasitic nematodes from the soil than did the hand-weeded control plots. Predaceous mononchids, which mostly live in the surface stratum (oxidation zone) were drastically decreased in B and Ch plots. The vertical distribution of the nematode population showed similar patterns between control plots and those to which Pa was applied 2 months before flooding, and also between Ch and B plots, both of which herbicides were applied after flooding. Measurement of the similarity values of the nematode community confirmed these results. Invertebrates in the flood water were not adversely affected in Pa plots, but other herbicides brought about a ripid decrease in arthropods. However, water fleas (excluding copepods) were restored to their usual population levels within a month. The similarity values of the insect community were high between the Ch and B plots (as found for nematodes). Pond snails increased in herbicide-treated plots, especially in Ox plots which had a dense growth of green algae.     

As contamination alters rhizosphere microbial community composition with soil type dependency during the rice growing season

Rhizosphere microbes play a cardinal role in transformation and crop uptake of arsenic (As), thereby relieving or intensifying the risk of As contamination in the food webs. How rhizosphere microbiomes respond to As contamination in different paddy soils and rice growth stages is still unclear. Here, we conducted a rice pot experiment to address the effects of rice developmental stage and As contamination on the rhizosphere microbial communities in two contrast paddy soils, a yellow clayey paddy soil (YP, pH 5.1, soil organic matter 20.8 g/kg) and red paddy soil (RP, pH 6.2, soil organic matter 46.1 g/kg). The rhizosphere microbial communities were investigated using phospholipid fatty acids analysis at tillering, panicle initiation, and maturity stages. The results showed that rice growing in YP soil accumulated 2-10 times higher contents of As in root than that in RP soil. There was a significant effect of rice growing stage, independent of soil types and As treatment, on rhizosphere microbial community composition in both YP and RP soils as depicted by canonical correspondence analysis. As contamination significantly altered rhizosphere microbial community composition only in YP soil, which showed the soil type dependency of the As contamination effect. In RP soil, the higher content of soil organic matter reduced the impact of As contamination. Soil pH explained more percentage of variation in microbial community composition than soil DOC and DON did. These influences of soil physiochemical properties on heavy metal available and rhizosphere microbial community may lay the foundation for exploration of bioremediation potential.     

Effect of biochar on CH4 and N2O emission from soils vegetated with paddy

Biochar is believed to have positive impact on soil properties and plant yield. Due to the presence of C, it can also enhance CH₄ emission in paddy soils. On the other hand, ammonium sulphate can decrease CH₄ emission due to negative impacts on methanogenesis. Keeping these points in view, a pot experiment was conducted to determine the effect of biochar along with ammonium sulphate on CH₄ and N₂O emission from paddy soil. Analysis revealed that biochar treated soils released more CH₄ compared to untreated. Ammonium sulphate treated soil emitted the highest N₂O whereas biochar addition decreased its emission significantly. Further, total emission was found to be higher for CH₄ (16.9–34.7 g/m²) in comparison to N₂O (?0.05 to 0.02 g/m²) for all treatments. Biochar application has positive impact on plant variables such as panicle number and weight of panicles. This study suggests that biochar application significantly decrease N₂O emission and increase CH₄ emission possibly due to affecting the availability of organic C in the soil to microbial activity for methanogenesis. Another possibility for enhancing CH₄ emission by following biochar could be attributed to the increase in plant biomass.     

Mechanical insights into the effect of fluctuation in soil moisture on nitrous oxide emissions from paddy soil

Paddy fields are subjected to fluctuating water regimes as a result of the alternate drying and wetting water management, which often incurs a sensitive change in N₂O emissions from paddy soils. However, how the soil moisture regulates the emission of N₂O from paddy soil remains uncertain. In this study, three incubation experiments were designed to study the effects of constant and fluctuating soil moisture on N₂O emission and the sources of N₂O emission from paddy soil. Results showed that the N₂O emission from paddy soil at 100 % WHC (water-holding capacity) was higher than that at 40, 65, 80, 120, and 160 % WHC, indicating that 100 % WHC was the optimum soil moisture content for N₂O emission under the incubation experiment. Small peak of N₂O flux appeared when the soil moisture content from 250 % WHC decreased near to 100 % WHC, lower than that triggered by nitrogen (N) fertilization, which was mainly owing to the low NH₄ ⁺ concentration at this period. Nitrification dominated the emissions of N₂O from paddy soil at 250 % WHC (54.96 %), higher than that of nitrification-coupled denitrification (6.74 %) and denitrification (38.3 %). The contribution of denitrification to N₂O emissions (44.10 %) was equivalent to that of nitrification (44.45 %) in soil at 100 % WHC, which was higher than that of 250 % WHC treatment. In conclusion, the finding suggested that the peak of N₂O in paddy soils during midseason aeration could be attributed to the occurrence of optimum soil moisture under sufficient N availability, favorable for the production and accumulation of N₂O.     

Effects of tillage and irrigation on the occurrence and establishment of native wetland plant species in fallow paddy fields

Traditional weed management, such as tillage and irrigation, has led to an enhanced maintenance of wetland plant species in fallow paddy fields. Recent herbicide usage and improvements in irrigation and drainage systems however have caused habitat loss of these species, especially in fields on open lowlands. We conducted experiments in three fallow paddy fields situated on the alluvial Echigo Plain in central Japan with an aim to restore the habitat of native wetland plant species. The three experimental fields were managed under different irrigation regimes, (1) perennially flooded with water, (2) intermittent irrigation, and (3) temporary irrigation. Half the area of each experimental field was tilled before irrigation. Detrended correspondence analysis revealed obvious floristic differences between experimental and control fields with no irrigation. The proportion of wetland plant species in the experimental fields increased corresponding to the irrigation period, ranging 60–86%, and was relatively greater than that in control fields. In the experimental fields, differences in both tillage and irrigation affected the occurrence of plant species. Tillage restricted the occurrence of many non-wetland plant species, and had a positive effect on the establishment of several annual wetland plant species. In addition, a longer duration of irrigation is not necessarily suitable for the occurrence of all wetland plant species. We concluded that fallow paddy fields provide a possible habitat for the restoration of native wetland plant species through appropriate tillage and irrigation.     

Methane production and nitrogen mineralization in paddy soil treated with sludge from anaerobic digestion enhanced by hyperthermophilic pretreatment

Paddy and Water Environment - Hyperthermophilic pretreatment (80&nbsp;°C, 24&nbsp;h) is a technology that promotes methane yield in the anaerobic digestion of sewage sludge. However,...     

创新南疆地区“两年三熟”种植制度，挖掘棉花冬闲田粮食生产能力

粮食安全是“国之大者”,牢牢把住粮食安全的根本在耕地。南疆地区现有植棉面积约146.67万hm²（约2 200万亩）,多为棉花单作的“一年一熟”种植制度,将其创新为棉花-小麦-棉花轮作的“两年三熟”种植制度,具有年增种66.67万hm²（1 000万亩）冬小麦的潜力,是保障国家粮食安全的重要创新技术。当前“两年三熟”种植制度在南疆地区已具备发展条件,初步形成了“接茬明确、效益显著、适应性强”的配套技术体系。后续将围绕“两年三熟”种植制度发展目标,在种植制度区划、品种筛选与技术研发、节水技术创新集成、全程机械化生产体系创建等方面持续攻关,扩大“两年三熟”种植面积和影响力。总之,“两年三熟”种植制度是优化调整南疆地区种植结构的科学尝试,是落实“藏粮于地、藏粮于技”战略的重要举措。     

湘中地区冬油菜全生育期碳通量变化特征分析

为探讨冬油菜的净碳交换特征及其固碳能力,采用涡度相关法对湘中地区油菜生态系统（2019年10月-2020年5月）的碳通量进行连续观测,分析了油菜全生育期内碳通量变化特征。结果表明：油菜生育期内碳通量具有明显的日变化和季节变化动态,碳通量月平均日变化以及不同生育期日变化均呈现为夜间高、白天低、正午达到最低谷的“U”型单峰曲线变化,不同月份和不同生育期的差异主要体现在曲线变化的幅度上;油菜不同生育时期的固碳能力有所不同,固碳能力由大到小依次为：花期、角果期、抽薹期、苗期,固碳能力总体随生育进程推进不断提升;油菜生育期内的净碳交换量总和为-101.62 gC·m^-2、总初级生产力为461.67 gC·m^-2、总呼吸为360.05 gC·m^-2,即净CO₂吸收量为1.02 t·hm^-2,说明油菜生态系统表现出一定的碳汇功能。     

Variance of microbial composition and structure and relation with soil properties in rhizospheric and non-rhizospheric soil of a flooded paddy

Paddy and Water Environment - Soil microbial structure and nutrient properties varied with fertilization and plant growth simultaneously in the rhizosphere. However, the relationships between...     

铁岭地区稻田土壤养分肥力状况调查报告

为掌握铁岭地区稻田土壤肥力变化情况,提高水稻产量及品质,特采集土样进行检测。结果表明,铁岭地区稻田土壤中有效磷、有效钾含量丰富;碱解氮、有机质和全氮含量处于中等水平;有效硅、交换性钙和交换性镁含量很丰富;有效铜、有效锌和有效锰含量很丰富;有效铁含量丰富;有效硼含量处于中等水平;土壤酸碱度差异很大。     

2005年早季稻田一代二化螟重发原因分析及防治对策

2005年一代二化螟在福建沙县早季稻田危害严重,据沙县植保植检站5月份在部分防治失当的田块调查,前期田间平均枯鞘率达32.67%,后期田间枯心株率达10.27%。收割期回访农户,因一代二化螟危害,该地段早季稻谷平均产量损失近四成。1 2005年沙县早季稻田一代二化螟重发原因分析1.1一     

Controlled-release fertilizer,floating duckweed,and biochar affect ammonia volatilization and nitrous oxide emission from rice paddy fields irrigated with nitrogen-rich wastewater

It is of great concern that nitrogen-rich (N-rich) wastewater irrigation increases ammonia (NH₃) volatilization from rice (Oryza sativa L.) paddy fields. A pilot-scale field trial was conducted to study the impact of different management practices on reducing NH₃ volatilization and their subsequent impacts on nitrous oxide (N₂O) emission from a paddy field irrigated with N-rich wastewater generated by livestock production and supplemented with urea N fertilizer. A total of 225 kg N ha^?1 combined with urea and N-rich wastewater was split into basal, the first, and second supplementary applications for the following five treatments: urea N mixed with controlled-release N fertilizer (BBF), floating duckweed (FDW), biochar alone (BC), biochar mixed with calcium superphosphate (BCP), and control with no amendment (CK). Results showed that each treatment had similar pattern of NH₃ volatilization and N₂O emission after N application. Treatments of BBF, FDW, and BCP effectively reduced NH₃ losses by 22.8, 55.2, and 39.2 %, respectively, compared with the CK. BBF treatment decreased NH₃ volatilization after the first supplementary N fertilization; BCP treatment reduced NH₃ volatilization after the basal fertilization; and FDW treatment reduced NH₃ volatilization after both the basal and first supplementary fertilization. Besides controlling the NH₃ volatilization, BCP treatment also reduced 19.5 % of N₂O loss. However, BC alone suppressed N₂O emission by 24.3 %, but did not reduce NH₃ loss. The findings can practically guide farmers to choose the appropriate management practices in improving N use efficiency and minimizing the impact of fertilization on environmental quality.     

Methane emission from irrigated rice ecosystem: relationship with carbon fixation,partitioning and soil carbon storage

Rice is a major agricultural crop and accounts for 40 % of the total food grain production of India. A field experiment was conducted for two successive seasons (December–June, 2012–13 and December–June, 2013–14) to assess the efficiency of rice varieties for methane (CH₄) emission in relation to atmospheric carbon fixation, partitioning of carbon, and storage in the soil. Six high yielding rice varieties, Bahadur, Cauvery, Dinanath, Joymoti, Kanaklata, and Swarnabh were grown under irrigated condition. Results of the present investigation depicted differences in photosynthetic rate among the varieties accompanied by differential ability for plant biomass partitioning between the shoots and the roots. Stomatal frequency of flag leaf at panicle initiation stage was found to have strong influence on photosynthesis. Low CH₄-emitting rice varieties, Bahadur and Dinanath, were found to have lower size of the xylem vessels than the high CH₄-emitting rice varieties, Joymoti and Kanaklata, and found to influence the CH₄ flux. Soil organic carbon storage of 0.505 Mg C ha^?1 y^?1 in the plough layer of soil (0–15 cm) confirmed that irrigated rice ecosystem is an effective sink of carbon. These findings suggest that selection of suitable rice varieties with higher photosynthetic efficiency and lower emission of CH₄ can be a suitable biological mitigation of this greenhouse gas. Although an inverse relationship of CH₄ with carbon dioxide (CO₂) efflux was observed, irrigated rice ecosystem has a good potential to store substantial amount of carbon in the soil.     

Rice-related greenhouse gases in Japan, variations in scale and time and significance for the Kyoto Protocol

The contribution of rice production to the three major greenhouse gases CO₂, CH₄ and N₂O in 1990, the base year of the Kyoto protocol is investigated for Japan. For the CO₂ assessment, we use a top-down life cycle approach, CH₄ is assessed using the Japanese GHG emission inventory and N₂O is assessed according to the ratio of rice area divided by the total area of agricultural soils. In total, 1.6% of greenhouse gas (GHG) emissions in 1990 originated from rice production. Next, we assess regional variations in nine rice-producing regions, based on the CO₂ data of 1990. General trends in rice production from 1960 to 2000 and data from the Japanese GHG emission inventory since 1990 are used to assess variations in time. The rice-related GHG emissions decreased to 1.05% of the total GHG emissions in 2001 and will be less than half the 1990 level in 2012, mainly due to the decrease in rice production. Contrary to the trend in GHG emissions of rice, overall GHG emissions increased as rice production fulfils important roles, in mitigating global warming and in adapting to changing climates. The protection of rice production is required to counter the increase of GHG emissions in transportation, waste and domestic sectors and to minimize problems related to landscape, water and natural hazard management.     

Irrigation of paddy soil with industrial landfill leachate: impacts in rice productivity,plant nutrition,and chemical characteristics of soil

Treated industrial effluents have high levels of nutrients and dissolved organic matter. The irrigation of rice by flooding can increase nutrient uptake and grain yield. Therefore, this study evaluated the nutrient contents in the shoots and grain of the rice crop and also the chemical of the soil after irrigation of the crop with leachate of the treated industrial effluent. A greenhouse experiment was conducted using pots filled with 20 kg of soil in a randomized block design with three replications. The treatments consisted of control (irrigation with distilled water) and four concentrations of the leachate (25, 50, 75, and 100 %) for irrigation. At the end of the experiment, the nutrient contents in tissues of rice plants, sterility of spikelets, and grain mass were evaluated. Results showed that irrigation with the leachate at 25 % content increased the macro- and micronutrients’ concentrations in the shoot biomass and grain, except for potassium and iron. Irrigation with the industrial leachate decreased tillering and grain yield; however, it increased chlorophyll content, sterility of spikelets, and sodium intake at this leachate concentration. The potassium and sodium levels and the electrical conductivity values of soils irrigated with treated industrial leachate were increased. The use of the treated leachate from industrial effluents is an alternative that reuses the nutritional load, but the volume of leachate should be limited and monitored to prevent the sodicity in the soil and problemsdue to eutrophication.