Suppression of superphosphate-phosphorus fixation by farmyard manure I. High phosphorus uptake from superphosphate

Pot and field experiments were conducted on alkaline calcareous soils of Pakistan to determine the effect of premixing superphosphate (SUP) with farmyard manure (FYM) on the fraction of plant phosphorus derived from the ³⁰P labelled SUP (y value). Premixing (SUP with FYM) before their addition to soil, markedly increased the uptake of SUP-P by plants. The premixed treatment also increased crop yield on phosphorus deficient soli. Optimum quantity of FYM required was twice that of SUP. Higher quantities of FYM had no additional effect on phosphorus availability from SUP.

The possible mechanism of this effect and the implications of these observations in phosphorus nutrition of plants have been discussed.     

明沟-暗管组合控排下稻田水氮流失特征

准确认识稻田灌溉或降雨引起的排水发生规律及面源污染物排放特征,有助于优化控制灌排措施,实现稻田高效控污减排。该研究通过在稻田暗管和明沟排水出口处设置水位控制装置,组成了稻田明沟-暗管组合控排系统,针对6次典型灌溉引起的排水事件,监测了暗管出口和明沟出口处的排水强度和氮素浓度,开展了水氮流失规律研究。结果表明,在仅明沟控制排水（OD）下,灌溉引起的明沟排水量占总灌水量的44.0 %,灌溉导致的排水占比较大,应引起重视;对于明沟-暗管组合控制排水（CD）,暗管和明沟控排的两级衔接改变了稻田和明沟的排水过程,使CD明沟出口排水峰值、强度及排水持续时间均低于OD,排水量降低了51.6%,CD明沟排水量占灌水量的比例降至24.4%;灌溉伴随施肥的排水事件（F1、F2和F3）中铵氮（NH4+）、硝氮（NO3-）和全氮（TN）的浓度远高于单纯灌溉的排水事件（D1、D2和D3）,应注意施肥关键期的排水管理以减少氮素流失;CD明沟控排对暗管排水中的NH4+、NO3-和TN的消减比例分别为52.2%、54.2%和54.9%,同时CD明沟排水NH4+、NO3-和TN负荷相比OD明沟排水降低了42.6%、70.7%和39.3%,明暗组合控排系统的控污减排效果明显。因此,明暗组合控排措施具有较好的减排控污效果,对提高南方稻作区农田水氮利用效率和减轻面源污染具有一定借鉴意义。     

Diurnal patterns of methane emissions from paddy rice fields in the Philippines

Methane (CH₄) emissions from rice paddies often show significant diurnal variations, most likely driven by diurnal changes of radiation and temperature in air, floodwater, and soil. Field measurements, however, are often scheduled at a fixed time of a given measuring day, thereby neglecting sub‐daily variations of CH₄ emissions. Here we evaluated diurnal patterns of CH₄ emissions from traditional paddy rice production as observed during field measurements in the Philippines. Field emissions were measured during three consecutive cropping seasons using an automated chamber and gas sampling system with fluxes being obtained every 4 h. Methane fluxes were monitored with a total of nine chambers during the dry seasons in 2012 and 2013 and 27 chambers during the wet season in 2012. Significant and consistent diurnal patterns of CH₄ emissions were mainly observed from the start of field flooding until the middle of cropping periods, i.e., periods with low leaf area of the rice crop. Our data show that disregarding the diurnal variability of fluxes results in an average overestimation of seasonal CH₄ emissions of 22% (16–31%) if measurements were conducted only around noon. Scheduling manual sampling either at early morning (7:00–9:00) or evening (17:00–19:00) results in estimations of seasonal emissions within 94–101% of the “true” value as calculated from multiple daily flux measurements. Alternatively, uncertainties of seasonal emissions can be reduced to an average of ≤3% by applying sinus function or Gauss function‐based correction factors. Application of correction factors allows the performance of flux measurements at any time of day. We also investigated N₂O emissions from rice paddies with respect to diurnal variations, but did not find, as in the case of CH₄, any significant and persistent diurnal pattern.     

长期定位试验对水稻田土壤甲烷氧化活性和甲烷排放通量的影响

通过对长期定位施肥的黄松稻田土的甲烷氧化活性和甲烷排放通量的研究表明,长期定位施肥对稻田土壤的好氧甲烷氧化活性和甲烷排放通量有显著性的影响(|t|t0.05,P0.05),而对稻田土壤的厌氧甲烷氧化活性有影响但未达显著性水平(|t|t0.05,P0.05)。施加有机肥能显著增加稻田土壤的甲烷氧化活性和甲烷排放通量;当有机肥和无机肥混合施用时,其促进作用明显大于单施有机肥或无机肥。施加尿素后,稻田土壤的甲烷氧化活性及甲烷排放量都有所下降,但钾肥和磷肥能缓解由尿素引起的抑制作用。施肥后耕作的稻田甲烷氧化活性和甲烷排放通量高于施肥后不耕作的稻田;耕作而不施肥的稻田甲烷氧化活性和甲烷排放通量要低于不施肥也不耕作的稻田。     

Effect of rice variety on methane emission from an Indonesian paddy field

Variations in CH₄ emission from a Sumatra paddy field in which 8 popular modern varieties in Indonesia were grown were compared in the 1994/1995 rainy season. Total amounts of CH₄ emitted during the period of rice growth were in the ranges of 32.6-41.7 and 51.3–64.6 g CH₄ m^-2 for the plots amended with chemical fertilizer only and those amended with both rice straw and chemical fertilizer, respectively. The mean CH₄ emission rate was highest in the plot with the variety Bengawan solo and lowest in the plots with the varieties Atomita-4 and Way seputih among the plots which received chemical fertilizer, while highest in the plot with Way seputih and lowest in the plot with Bengawan solo among the plots amended with both rice straw and chemical fertilizer. The increase in the mean CH₄ emission rates by rice straw application was higher for the plots planted with Way seputih (1.98 times) and Atomita-4 (1.77 times) than for the plots with Bengawan solo (1.23 times) and IR-64 (1.35 times). The plots with Walanai and Cisanggarung recorded intermediate mean emission rates and the increase in CH₄ emission by rice straw application was also intermediate (1.57–1.64 times). It was noteworthy that Way seputih and Atomita-4 were derived from the variety Cisadane, Bengawan solo and IR-64 from the variety IR-54, and Walanai and Cisanggarung from the varieties IR-36 and Pelita 1-1, respectively.

The amounts of CH. emitted for 1 kg grain production ranged from 53 (Atomita-4) to 74 (Kapuas and Walanai) and from 89-93 (IR-64, Bengawan solo, and Atomita-4) to 121 (Kapuas) g CH₄ kg^-1 of grain for the plots amended with chemical fertilizer and those amended with rice straw and chemical fertilizer, respectively.     

Effect of the long-term application of anaerobically digested residual slurry on methane emissions in a rice paddy field

ABSTRACT

The anaerobic digestion of livestock manure is an environmentally compatible technology used for the production of renewable energy. Anaerobically digested residual slurry has been used worldwide as a liquid fertilizer in both upland and paddy fields. However, a controversial question remains as to whether the application of slurry to rice paddy fields increases methane emissions; although methane is one of the most prevalent greenhouse gases, little is known about the effects of the long-term application of residual slurry on methane emission. In this study, we repeatedly applied slurry to a paddy field for six years at different application rates (10, 15, and 20 g N m^?2 based on ammonium-nitrogen content). At the fifth and sixth years of application, we evaluated the effect in terms of methane flux and soil total carbon content. The effect of the long-term application of the slurry (10 g N m^?2) on grain yield was equivalent to that of chemical fertilizer (10 g N m^?2). The application of the residual slurry was likely to increase the cumulative methane emissions during rice growing season in both 2006 and 2007. On the other hand, we observed that soil total carbon did not accumulate significantly in the soil. Thus, we cannot rule out the potential risk of additional methane emissions caused by the application of the residuary slurry to paddy fields.     

水稻植株特性对稻田甲烷排放的影响及其机制的研究进展

水稻是我国最主要的口粮作物,稻田是重要温室气体甲烷的主要排放源之一。水稻植株特性既是水稻产量形成的关键因子,也是稻田甲烷排放的主要影响因子。但是,至今关于水稻植株对稻田甲烷排放的调控效应及其机制仍存在许多不一致的认识。为此,本文从形态特征、生理生态特征、植株-环境互作等方面,对现有的相关研究进行了综合论述。水稻地上部形态特征如分蘖数、株高、叶面积等对稻田甲烷排放的影响的研究结果不尽相同,起关键作用的是地下系统。优化光合产物分配在持续淹水的情况下可以减少稻田甲烷排放。提高水稻生物量在低碳土壤增加稻田甲烷排放,但在高碳土壤下降低甲烷排放。本文还明确了相关研究现状和存在的问题。在此基础上,作者认为未来应加强水稻根系形态及其生理特征,以及水稻植株-土壤环境(尤其是水分管理和养分管理)互作对稻田甲烷产生、氧化和排放影响的研究,在方法上应加强微区试验和大田试验的结合,并开展植株和稻田的碳氮互作效应及其机制研究,为高产低碳排放的水稻品种选育和低碳稻作模式创新提供理论参考和技术指导。     

三江平原低湿地水田土壤理化特性及暗管排水效果

低湿土壤渍涝问题是限制农业生产的瓶颈问题,为改良低湿土壤渍涝问题,该文研究低湿地水田草甸沼泽土土壤特性,并探讨利用暗管排水进行低湿地排水及种植水稻的效果。结果表明,草甸沼泽土土壤质地黏重、各层土壤黏粒质量分数在40%以上;有效孔隙低,在6.40%~7.81%之间,通气、透水性差,母质层几乎不透气、透水,土体容气度为5.55%~16.08%;含水率高,自然状态达到40%以上;土壤容重低,耕层为0.93 g/cm3,母质层1.30 g/cm3;硬度低,液性指数在0.38~0.61之间,整体处于可塑状态,机械承载力差;草甸沼泽土上设置暗管可以改善土壤的透水性,随距暗管距离不同,土壤排水效果有差异,距离暗管越近,土壤排水效果越好,水分降低的越明显;同样排水晒田后,暗管处理土壤表层状态呈干裂状态,对照(无暗管排水区)则仍呈湿润状态;从水稻产量看,有暗管的处理水稻产量比无暗管处理增产8.06%。研究可为低湿地水田合理利用及改良提供依据。     

National-scale estimation of methane emission from paddy fields in Japan: Database construction and upscaling using a process-based biogeochemistry model

We have estimated methane (CH₄) emission from total rice (Oryza sativa L.) paddies in Japan by means of a process-based biogeochemistry model, DeNitrification-DeComposition(DNDC)-Rice, combined with a geographic information system (GIS) database of climate, soil and farming practices. In the GIS database, 2 million ha of rice paddies were divided into 17,408 units according to 136 climate areas, 16 soil types, four classes of drainage rate and two classes of groundwater level, to simulate CH₄ flux from each of the units applying the DNDC-Rice model. As a result, the national-scale CH₄ emission in 1990 was estimated to be 216 Gg carbon (C), 13% lower than a previous inventory estimated by the Tier 2 method. By our Tier 3 approach, a relatively higher CH₄ flux was estimated from eastern regions than from western regions of Japan, presumably due to the differences in climate and water management. Sensitivity analysis and uncertainty assessment indicated that it is important to account for the heterogeneity in soil properties such as field water capacity, iron (Fe) concentration and drainage rate, in order to reduce the uncertainty in regional estimates.     

灌排调控的稻田排水中氮素浓度变化规律

基于农田排水氮素浓度及湿地进出口断面总氮（TN）、氨态氮（NH4+-N）、硝态氮（NO3--N）浓度的监测,研究了灌溉排水措施以及沟塘湿地对农田排水中氮素浓度变化的影响。结果表明,控制灌溉的水稻全生育期稻田排水中TN、NH4+-N和NO3--N浓度分别较常规灌溉处理低12.08%、20.33%和13.51%;控制排水处理下稻田排水中TN、NH4+-N和NO3--N浓度分别较常规排水处理低2.21%、7.08%和20.92%;湿地出口水体中TN、NH4+-N和NO3--N浓度分别比入口降低了16.8%、14.4%和50.9%,湿地水体中TN、NH4+-N、NO3--N浓度随时间近似服从指数函数衰减趋势。控制灌溉、控制排水及沟渠塘湿地系统的调控措施对农田排水中氮素的净化效果比较显著。     

Influences of indigenous phototrophs on methane emissions from a straw-amended paddy soil

A pot experiment was conducted to investigate the influences of indigenous phototrophs on methane (CH₄) emissions from a paddy soil where rice straw was incorporated or was surface-applied. During the cultivation, half of the pots were covered with aluminum foil, except for the minimum space for rice plants, to prevent ambient light reaching the floodwater or the soil surface. Growth of oxygen-producing phototrophs was hardly observed in the unilluminated plots, whereas intensive growth of algae, duckweed and hydrophytes was found in the illuminated ones. Plant growth was not affected by the different treatments. Seasonal changes in CH₄ emission determined by a closed chamber method indicated that illumination had no or only minor effects on CH₄ emissions when rice straw was incorporated or was not applied, but significantly reduced CH₄ emissions when rice straw was surface-applied. Methanogenesis occurring in the soil-floodwater interface was further investigated in two lab-scale model experiments measuring methanogenic activity. As a result, more activated methanogenesis was found in the surface-applied rice straw and the soil around the straw compared with the soil incubated without rice straw. The magnitude of the methanogenic activity in the rice straw incubated under illuminated conditions was significantly lower than that incubated in the dark. Consequently, this study demonstrates that methanogenesis in paddy soil occurs even in the soil-floodwater interface if plant residues like rice straw exist, and such methanogenesis is likely to be suppressed by growth of indigenous phototrophs under illumination.     

基于无线传感网络的改碱暗管排盐监控系统

针对目前盐碱地暗管改碱技术应用过程中存在的有效评测数据缺乏、无法准确对实施效果进行科学评价的问题,设计了一种基于无线传感网络的改碱暗管排盐监控系统,以实现对管道内地下水的水质监测、流量统计以及蓄水池水位控制等。监测节点实时采集各路暗管的p H值、电导率和流量信息传输到中心节点,监控中心计算机通过RS232接口获取各采集信息并进行处理显示;同时,液位传感器实时获取蓄水池的水位信息并通过无线传输模块将水位信息发送至中心节点,中心计算机根据实际水位和设定水位信息进行控制决策,并通过中心节点向水位控制节点发送控制指令,实现蓄水池的水位远程自动控制。为验证系统整体性能,对监控系统开展了水位控制、传感器检测精度、通讯距离与丢包率试验测试。试验结果表明:系统p H值和电导率的平均测量误差分别为1.81%、1.89%,各节点的最大丢包率为2.6%,整体运行稳定,数据传输可靠,能够满足实际生产需要。该系统能够准确获取改碱暗管内的水质信息及迁移变化情况,为暗管改碱技术的效果评价提供有利的数据支撑。     

封闭系统水稻土甲烷氧化的模拟

Methane oxidation by paddy soils in a closed system could be simulated by the equation x=k1xo/(k1 k2x0)exp(k2t)-k2x0 where x0 and x are the CH4 concentrations at time zero and t,respectively;k1 and k2 are constants related to the constant of first-order-kinetics.According to the equation the change of soil ability to oxidize CH4 could be estimated by the equation Ac=k2/k1(x0-x)x0k2/k1-1.The results showed that the soil ability to oxidize CH4 varied,depending on the initial CH4 concentration.High initial CH4 concentration stimulated soil ability to consume CH4,while low concentration depressed the ablility.This characteristic of paddy soil seemed to be of considerable significance to self-adjusting CH4 emission from flooded rice fields if there exist oxic microsites in the soil.     

江苏沿海垦区暗管排水农田轮作对土壤有机碳的影响模拟

针对江苏沿海垦区地势平坦、降雨量大,农业生产易受涝渍灾害影响,而新开垦农田土壤贫瘠、有机质含量极低的问题,该研究基于江苏省东台市内省水科院农田暗管排水试验基地的气象、土壤、作物等数据,联合运用田间水文模型-DRAINMOD和土壤有机碳模型-DNDC（Denitrification-Decomposition Model）,研究了轮作和秸秆还田方式对暗管排水农田土壤有机碳（Soil Organic Carbon,SOC）累积过程的影响。结果显示：对于地下水位埋深较浅的沿海垦区,在DRAINMOD准确预测暗管排水农田地下水位动态的基础上,运用DNDC模型可以更好地预测土壤有机碳的累积过程;以2021年土壤有机碳含量（2.95 g/kg）为初始值,DNDC模型32 a长序列模拟发现,冬小麦-玉米轮作配施全量秸秆还田措施效果最佳,可提升耕层土壤有机碳含量至17.85 g/kg;冬小麦-玉米-冬小麦-绿肥（紫花苜蓿）轮作配施全量秸秆还田措施可提升耕层土壤有机碳含量至16.12 g/kg,具有很好的固碳效果。与研究区现有明沟排水系统相比,暗管排水可快速降低地下水位,减少涝渍胁迫,作物产量提升3.90%,耕层固碳速率提升39.39%。暗管排水条件下,湿润年频繁降雨造成了土壤干湿交替变化,由此激发了高强度土壤的呼吸作用,导致了一定程度的SOC损失;建议采用农田控制排水措施来抑制过度排水,减少高强度土壤呼吸对SOC累积过程的不利影响。研究成果可为沿海垦区农田地力提升和农业碳中和提供参考。     

中国稻田CH4排放量估算研究综述

稻田是大气CH4的重要排放源,对中国稻田CH4排放量做出准确估算是中国CH4研究的主要目的之一。估算稻田CH4排放的方法主要有四种:根据田间测定结果或特定的排放系数和该值代表的稻田面积外推计算;将水稻的净初级生产力(NPP)的折算系数与模型相结合进行估算;根据新投入到土壤的有机碳量或原有土壤有机质碳折算;机理模型计算。其次,还有模型与GIS技术、其他方法相结合估算。稻田CH4排放在空间和时间尺度上的变异性是估算结果不确定性的主要驱动因素。统计分析显示中国稻田CH4排放量为8.4(7.2～9.5)Tga-1。     

Effect of intermittent drainage in reduction of methane emission from paddy soils in Hokkaido,northern Japan

ABSTRACT

Emission of methane (CH₄), a major greenhouse gas, from submerged paddy soils is generally reduced by introducing intermittent drainage in summer, which is a common water management in Japan. However, such a practice is not widely conducted in Hokkaido, a northern region in Japan, to prevent a possible reduction in rice grain yield caused by cold weather. Therefore, the effects of intermittent drainage on CH₄ emission and rice grain yield have not been investigated comprehensively in Hokkaido. In this study, we conducted a three-year field experiment in Hokkaido and measured CH₄ and nitrous oxide (N₂O) fluxes and rice grain yield to elucidate whether the reduction in CH₄ emission can be achieved in Hokkaido as well as other regions in Japan. Four experimental treatments, namely, two soil types [soils of light clay (LiC) and heavy clay (HC) textures] and two water management [continuous flood irrigation (CF), and intermittent drainage (ID)], were used, and CH₄ and N₂O fluxes were measured throughout the rice cultivation periods from 2016 to 2018. Cumulative CH₄ emissions in 2016 were markedly low, suggesting an initially low population of methanogens in the soils presumably due to no soil submergence or crop cultivation in the preceding years, which indicates a possible reduction in CH₄ emission by introducing paddy-upland crop rotation. Cumulative CH₄ emissions in the ID-LiC and ID-HC plots were 21–91% lower than those in the CF-LiC and CF-HC plots, respectively, whereas the cumulative N₂O emissions did not significantly differ between the different water managements. The amount of CH₄ emission reduction by the intermittent drainage was largest in 2018, with a comparatively long period of the first drainage for 12 days in summer. Rice grain yields did not significantly differ between the different water managements for the entire 3 years, although the percentage of well-formed rice grains was reduced by the intermittent drainage in 2018. These results suggest that CH₄ emission from paddy fields can be reduced with no decrease in rice grain yield by the intermittent drainage in Hokkaido. In particular, the first drainage for a long period in summer is expected to reduce CH₄ emission markedly.     

上海地区水稻土氮素矿化模拟

Three types of paddy soils, derived from granite, Quaternary red clay and basalt, respectively, were selected to study the effects of Fe and Mn in paddy soils on methane production and emission through pot and incubation experiments. The results indicated that the difference of Fe and Mn in paddy soils was one of the important factors causing obvious differences in methane emission from different soil types. Soil Fe and Mn affecting methane emission from the paddy soils was likely through affecting soil Eh and forming Fe and Mn plaques on rice roots. Different rates and valences of added Fe and Mn significantly affected methane production from paddy soils. Therefore, this study enhanced understanding of processes controlling methane emission from paddy soils and may help to improve modeling and estimating regional and global methane emission from paddy soils.     

江苏沿海垦区暗管排水对冬小麦产量的影响模拟

江苏沿海垦区农田地下水位埋深较浅,冬小麦生长易受到渍害的影响;为探究不同暗管排水条件影响下冬小麦产量的变化,该研究根据在江苏东台试验站实测的气象、土壤、地下水埋深等数据,联合运用田间水文模型DRAINMOD和作物模型AquaCrop模拟不同暗管排水条件对冬小麦产量的影响。结果显示：DRAINMOD模型可准确模拟研究区地下水埋深变化,与作物模型 AquaCrop联合使用,可以更好地预测不同水文年排水条件对冬小麦生长情况的影响;一般年份及湿润年内,涝渍胁迫是影响研究区冬小麦产量的主要因素;在冬小麦生长季降渍保证率达到85%的条件下,排水暗管的最优布局为埋深1.5 m、间距20 m左右,以此可实现研究区较为理想的小麦生产目标。研究可为当地暗管排水系统建设及农业生产提供理论依据和技术支持。     

水肥管理对稻田CH4排放及其全球增温潜势影响的评估

甲烷(CH_4)是主要温室气体之一,对全球增温的作用仅次于二氧化碳(CO_2)。稻田是CH_4的重要排放源,减少稻田CH_4排放对减缓气候变暖具有直接效应。为此,掌握稻田CH_4排放的规律和特征对控制和减少稻田CH_4排放尤为重要。为了解稻田温室气体排放的主要影响因子及影响程度,估算稻田温室气体全球增温潜势,寻求农田减排措施,我们通过收集已发表的文献建立了稻田CH_4排放的数据库,采用析因分析与回归分析方法对稻田CH_4日排放量和全球增温潜势特征和可能的影响因子进行了分析。结果表明,稻田CH_4日排放量和增温潜势均随土壤有机质背景含量的升高而增加,不同类型稻田CH_4日排放量大小依次为:双季稻晚稻双季稻早稻单季稻稻麦轮作晚稻;晚稻田CH_4的增温潜势大于早稻田。不同肥料处理条件下,稻田CH_4日排放量表现为:秸秆还田配施有机肥化学氮肥≈生物炭。控制灌溉水量可降低稻田CH_4的综合增温潜势,表现为:持续淹水晒田干湿交替控制灌溉。研究结果说明,稻田CH_4的产生与排放过程受土壤有机质含量、肥料管理和水分管理以及轮作制度等多种因素的共同影响,应依据不同土壤条件和种植制度,适当调整肥水管理,以减少稻田温室气体排放,降低其增温潜势。