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.     

Manure-based biogas fermentation residues – Friend or foe of soil fertility?

Anaerobic digestion of organic residues has the potential to significantly contribute to a shift from fossil to renewable energy. The by-product, anaerobic slurry, does have properties that are different from the undigested material. There are concerns of soil organic matter depletion in soils, enhanced greenhouse gas and odour emissions, and pathogen spread upon production and use of biogas slurries as fertilizer. However, considering the pros and cons, anaerobic digestion of residues does have positive effects for the climate, the environment and for the farmer, compared to the use of undigested matter.     

生物质炭输入减少稻田痕量温室气体排放

为揭示不同水平生物质炭输入对稻田土壤理化性质、水稻产量及温室气体排放的影响,采用自制竹炭在4种不同施用水平下(0、10、20、40 t/hm2)输入稻田土壤,开展了水稻一个生长周期的田间试验。结果表明,生物质炭输入可显著提高土壤p H值和有机碳含量(P0.05),且有机碳含量增幅与生物质炭施用水平呈正比(相关系数为0.78,P0.01)。生物质炭施用可显著降低土壤容重(P0.05),最大降幅为0.25 g/cm3,土壤容重随着生物质炭施用量的增加而降低。不同处理水稻产量无显著性差异(P0.05)。CH4累积排放量与生物质炭施用量呈负相关性(相关系数为-0.24,P0.01),投加生物质炭可显著降低稻田CH4排放通量和累积排放量(P0.05),但过量施用生物质炭(超过20 t/hm2)并不能显著降低CH4累积排放量(P0.05)。相比对照处理(不输入生物质炭),生物质炭输入后一周内可显著性降低N2O排放通量(P0.05),并在排水烤田时升高,最终稳定于9.80 mg/(m2·h)。生物质炭输入可显著性降低N2O累积排放量(P0.05),但不同水平生物质炭输入处理之间差异不显著(P0.05)。该试验条件下,生物质炭施用量为20 t/hm2时可实现稻田稳产和固碳减排目标,该研究可为太湖地区苕溪流域稻田增汇和温室气体减排提供参考。     

Effect of rice straw application on CH4 emission from paddy fields

The effect of rice straw (RS) incorporated at the time of plowing in the previous cr–p season on CH₄ emission from rice paddies was investigated in a pot experiment. Rice straw that incorporated just before transplanting of rice seedlings (June) into a paddy field was collected after the harvest (October) and at the beginning of the next cropping period (May). Methane emission rates from the rice-planted pots with the application of fresh RS, RS collected in October. and RS collected in Mayas well as the pots without RS application were measured using the chamber method. The composition of organic constituents in the three kinds of RS was estimated by the proximate analysis. The cumulative amount of CH₄ emitted during the first 50–d period was lower in the order of the pots with RS collected in May, pots with RS collected in October, and pots with fresh RS. The cumulative amount of CH₄ emitted throughout the rice growth period from the pots with fresh RS and with RS collected in October was significantly larger while that from the pots with RS collected in May did not differ statistically compared with the total CH₄ emission from the pots without RS. These results suggested that there was an overall decrease in the amount of organic constituents in RS based on the large differences in T-C content and similar composition of organic constituents between the fresh RS and RS collected in May. Significant effect of RS continuously applied during the previous cropping period on the increase in CH₄ emission was discussed.     

How do greenhouse gas emissions vary with biofertilizer type and soil temperature and moisture in a tropical grassland?

Greenhouse gases are known to play an important role in global warming. In this study, we determined the effects of selected soil and climate variables on nitrous oxide (N₂O), methane (CH₄), and carbon dioxide (CO₂) emissions from a tropical grassland fertilized with chicken slurry, swine slurry, cattle slurry, and cattle compost. Cumulative N₂O emissions did not differ between treatments and varied from 29.26 to 32.85 mg N m^-2. Similarly, cumulative CH₄ emissions were not significantly different among the treatments and ranged from 6.34 to 57.73 mg CH₄ m^-2. Slurry and compost application induced CO₂ emissions that were significantly different from those in the control treatment. The CH₄ conversion factors measured were 0.21%, 1.39%, 4.39%, and 5.07% for cattle compost, chicken slurry, swine slurry, and cattle slurry, respectively, differing from the recommendations of the Intergovernmental Panel on Climate Change (IPCC). The fraction of added N emitted as N₂O was 0.39%, which was lower than the IPCC default value of 2%. Our findings suggest that N₂O emissions could be mitigated by replacing synthetic fertilizer sources with either biofertilizer or compost. Our results indicate the following:N₂O emission was mainly controlled by soil temperature, followed by soil moisture and then soil NH₄⁺ content; CH₄ fluxes were mainly controlled by soil moisture and chamber headspace temperature; and CO₂ fluxes were mainly controlled by chamber headspace temperature and soil moisture.     

Effects of bamboo biochar application on global warming in paddy fields in Ehime prefecture,Southern Japan

Biochar application can reduce global warming via carbon (C) sequestration in soils. However, there are few studies investigating its effects on greenhouse gases in rice (Oryza sativa L.) paddy fields throughout the year. In this study, a year-round field experiment was performed in rice paddy fields to investigate the effects of biochar application on methane (CH₄) and nitrous oxide (N₂O) emissions and C budget. The study was conducted on three rice paddy fields in Ehime prefecture, Japan, for 2 years. Control (Co) and biochar (B) treatments, in which 2-cm size bamboo biochar (2 Mg ha^?1) was applied, were set up in the first year. CH₄ and N₂O emissions and heterotrophic respiration (Rh) were measured using a closed-chamber method. In the fallow season, the mean N₂O emission during the experimental period was significantly lower in B (67 g N ha^?1) than Co (147 g N ha^?1). However, the mean CH₄ emission was slightly higher in B (2.3 kg C ha^?1) than Co (1.2 kg C ha^?1) in fallow season. The water-filled pore space increased more during the fallow season in B than Co. In B, soil was reduced more than in Co due to increasing soil moisture, which decreased N₂O and increased CH₄ emissions in the fallow season. In the rice-growing season, the mean N₂O emission tended to be lower in B (?104 g N ha^?1) than Co (?13 g N ha^?1), while mean CH₄ emission was similar between B (183 kg C ha^?1) and Co (173 kg C ha^?1). Due to the C release from applied biochar and soil organic C in the first year, Rh in B was higher than that in Co. The net greenhouse gas emission for 2 years considering biochar C, plant residue C, CH₄ and N₂O emissions, and Rh was lower in B (5.53 Mg CO₂eq ha^?1) than Co (11.1 Mg CO₂eq ha^?1). Biochar application worked for C accumulation, increasing plant residue C input, and mitigating N₂O emission by improving soil environmental conditions. This suggests that bamboo biochar application in paddy fields could aid in mitigating global warming.     

耕作措施对双季稻田土壤碳及有机碳储量的影响

针对不同耕作措施对双季稻田的固碳效应和固碳潜力问题,选择湖南省宁乡县的双季稻区试验点进行了有机碳、活性有机碳以及耕层有机碳储量的研究,以期为制定适合于稻田条件下的合理耕作方式提供理论依据。结果表明,耕作措施和秸秆还田对有机碳（SOC）和活性有机碳（AOC）含量均产生不同程度的影响。免耕处理下,有机碳和活性有机碳含量皆随土壤深度的增加而减少,土壤0～5cm的SOC和AOC的含量最高,且与其他层次达到显著性差异水平（P＆lt;0.05）,具有明显的表层富集现象。与免耕相比,旋耕和翻耕则更利于5～10cm和10～20cm土层的有机碳和活性有机碳的积累。比较秸秆还田对SOC和AOC的影响表明,秸秆还田有效地提高了0～10cm有机碳含量,但对10～20cm并未产生显著影响,秸秆的输入并未增加土壤活性有机碳的含量。采用等质量方法计算了耕层土壤有机碳储量,结果显示旋耕秸秆还田使有机碳储量明显增加,而免耕只增加了土壤0～5cm和5～10cm土层有机碳储量,10～20cm有机碳储量有所降低,但耕作措施对有机碳储量的长效作用还有待于进一步研究。     

长期垄作免耕对稻田土壤有机碳剖面分布的影响

以稻田免耕长期定位试验为平台,研究长期垄作免耕对稻田土壤有机碳剖面分布的影响。结果表明,垄作免耕(中稻)、垄作免耕(稻油)、常规平作(中稻)和水旱轮作(稻油)4种耕作处理实施20年后,稻田0-60cm土体中各土层有机碳含量最高值和最低值分别出现在垄作免耕(稻油)和水旱轮作(稻油)中,且水旱轮作(稻油)中各土层有机碳含量均显著低于其他耕作处理;垄作免耕(稻油)中0-10cm和40-60cm土层有机碳含量与垄作免耕(中稻)、常规平作(中稻)之间差异不显著,但20-40cm土层有机碳含量则显著高于其他耕作处理(P<0.05),可见同传统耕作相比,长期垄作免耕(稻油)稻田的增碳优势主要体现在20-40cm土层。不同耕作处理连续实施20年后,稻田0-60cm土体有机碳密度的高低顺序为垄作免耕(稻油)>垄作免耕(中稻)>常规平作(中稻)>水旱轮作(稻油),且处理间差异显著(P<0.05)。垄作免耕15～20年期间,稻田0-10cm表层土壤有机碳储量基本稳定,但20-40cm土层有机碳储量仍有增加,其中垄作免耕(稻油)增加最为明显,表明20-40cm土层碳累积是长期垄作免耕下稻田发挥增碳功能的重要机制。     

休闲稻田消解沼液生态效应及其对水稻安全生产影响研究

为研究利用休闲稻田消解沼液生态效应及对后季水稻安全生产、土壤肥力及质量的影响,在浙江省嘉兴市脱潜潴育型水稻土青紫泥田上,进行4年定位田间试验,考察了休闲季灌施不同用量沼液对水稻产量、稻谷、土壤中有害重金属含量差异以及土壤中养分含量的变化,提出休闲稻田沼液消解安全容量。研究结果表明：休闲稻田灌施沼液可有效消解单一水稻轮作制地区沼气工程冬春季产生的沼液,每公顷休闲稻田每年安全消纳沼液3000t,后季水稻可在不施化学氮、钾肥,减半施用磷肥的基础上获得与全化肥处理相近或略高的产量;休闲季灌施沼液对土壤肥力有明显改善作用,土壤有机质、全氮、碱解氮、有效磷、速效钾、缓效钾都明显高于不灌沼液处理,但除土壤速效钾和缓效钾外,各种养分含量年度递增趋势并不明显,没有出现养分过度累积导致的富营养化;与全化肥处理相比,休闲季灌施沼液后土壤及稻谷中有害重金属含量没有明显增加;综合沼液灌溉对产量、土壤质量、稻谷安全品质监测结果,在水稻生产安全、土壤可持续利用的目标下,确定休闲稻田沼液安全消解容量为N1500kg·hm-2。     

Methane uptake by unflooded paddy soils

Abstract

Methane (CH₄) is one of the most abundant organic gases in the atmosphere. Recently the importance of CH₄ as a greenhouse gas has been recognized and studies have been carried out to assess its contribution to global warming. Although the rate of increase has slowed down in the last decade (Steel et al. 1992; Rudolph 1994), the results from some of these studies have shown that the atmospheric concentration of CH₄ is increasing at a rate estimated to be approximately 1% per year (Rowland 1991; Blake and Rowland 1988; Bolle et al. 1986; Graedel and McRae 1980). Clearly it is important to identify sources and sinks of CH₄, in both terrestrial and oceanic ecosystems, in order to estimate global methane budgets (Cicerone and Oremland 1988).     

中国稻田土壤有机碳汇特征与影响因素的研究进展

稻田是中国面积最大的耕地之一,稻田土壤有机碳（SOC）是重要的农业碳库,被认为在减缓大气二氧化碳（CO2）浓度上升和全球变暖中起着重要作用。明确中国稻田SOC汇特征与影响因素,有助于制定合理的农业管理措施,科学地增强稻田土壤固碳减排潜力。研究发现,在空间分布上,中国稻田SOC含量具有地域性差异,总体表现为华南、西南高于华北、西北,长江中游高于长江下游;且稻田SOC含量沿海拔升高而增加,随土壤深度增加而减少。在组成上,稻田土壤活性碳比例不超过5.3%,惰性碳比例远大于活性碳,高达60%以上,稻田固碳重点在于惰性组分。在影响因素上,人为管理措施是导致稻田碳汇变化的主要原因,并与自然因素密切相关。为充分发挥稻田土壤碳汇功能,未来研究应加强稻田SOC稳定机制研究,制定因地制宜的农业管理推广方案,为中国“双碳”目标的实现提供科学依据。     

南方低产黄泥田与高产灰泥田基础地力的差异

【目的】黄泥田为南方红黄壤区广泛分布的低产田。定量评价黄泥田基础地力,明确与高产灰泥田水稻氮磷钾养分吸收利用的差异,可为黄泥田改良及水稻施肥提供依据。【方法】采集福建省20个县的典型黄泥田0—20cm土壤,同时采集与其邻近且由同一微地貌单元发育的高产灰泥田土壤,进行了水稻盆栽试验。试验设施肥(每盆N0.60g、P2O50.24g、K2O0.42g)和不施肥两个处理。氮肥采用15N丰度10%的尿素,磷肥用磷酸二氢钙,钾肥用氯化钾。水稻品种为‘中浙优1号’,采用移栽种植,每盆种植两穴。收获后,调查籽粒产量,采集土壤和植株样品,植株分地上部和根部,分析了生物量、氮磷钾含量,土壤分析了全氮含量。植株与土壤同位素氮用ZHT-03质谱仪测定15N%丰度。计算了土壤基础地力与水稻养分吸收、累积及肥料利用率。【结果】黄泥田的基础地力经济产量、基础地力地上部生物产量较灰泥田分别低26.9%与23.5%,相应的基础地力贡献率分别低14.1与9.7个百分点。基础地力贡献率(经济产量)与土壤有机质含量呈极显著正相关,与土壤容重呈极显著负相关。不论施肥与否,黄泥田水稻有效穗数均显著低于灰泥田,且不施肥水稻有效穗数与土壤有机质含量呈极显著正相关,而与土壤容重呈极显著负相关。施肥条件下,黄泥田水稻成熟期籽粒、茎叶和根系氮、磷、钾素含量均低于灰泥田,其中3个部位磷素含量较灰泥田分别低9.6%、38.4%和46.3%,差异均显著,黄泥田水稻籽粒和茎叶的钾素含量较灰泥田分别低10.8%和18.5%,差异均显著。施肥下黄泥田水稻成熟期籽粒、茎叶的氮素吸收量较灰泥田分别低10.8%和17.3%,磷素吸收量分别低12.5%和46.2%,钾素吸收量分别低16.6%和28.5%,差异均显著。等量施肥条件下,黄泥田的水稻氮肥利用率较灰泥田低4.6个百分点,但土壤氮肥残留率增加3.0个百分点。【结论】以高产灰泥田为标准,黄泥田基础地力具有20%以上的产量提升潜力。土壤有机质与容重是影响基础地力贡献率与有效穗的重要肥力因子。黄泥田水稻氮肥利用率显著低于灰泥田,但土壤氮素残留率较高。提高有机质、降低土壤容重是提升基础地力的主攻方向。     

西南地区紫色水稻土颗粒有机质的季节动态

以西南大学试验农场的紫色水稻土试验田为研究对象,探讨颗粒有机质的季节变化。结果表明,在油菜生长季内,颗粒态土质量分数呈现先升高后降低趋势,变化范围为27.38%～32.15%,具有明显的季节变化。颗粒有机碳(POC)与颗粒有机氮(PON)含量具有相同的季节变化趋势,为"U"字形,主要影响因子为TOC、TN及pH值。POC与PON分配比例的季节变化特征大体相似且均较明显,POC分配比例变化范围为24.96%～42.39%,平均值为35.73%,PON分配比例变化范围为17.19%～30.98%,平均值为22.59%。有机质的输入及其矿化分解是造成POC、PON含量及其分配比例变化的主要原因。生长季内POC/PON介于13.96～17.28之间,极显著高于全土碳氮比,表明颗粒有机质更容易被分解和转化。     

吉林西部盐碱地区稻田土壤有机碳矿化特征

以吉林西部盐碱地区(前郭灌区)土壤为研究对象,选取不同盐碱程度的4块水田(P1、P2、P3和P4),采用野外实地调研采样与室内模拟试验相结合的方法,分别在培养期的第1,4,7,10,14,21,28,35,70天测定土壤CO_2气体的排放通量,结合土壤基本理化性质,分析盐碱稻田矿化模拟培养过程中CO_2通量的动态变化,研究土壤盐碱化程度对有机碳矿化过程的影响。结果表明:P1、P2、P3为弱碱化土,P4为强碱化土;各样地土壤有机碳(SOC)含量差异显著,并存在表层富集现象,与碱化度(ESP)呈显著负相关关系(r=-0.945);SOC矿化量累积过程与培养时间符合一级动力学模型C_t=C_0(1-e^-kt),各样地土壤在矿化培养初期CO_2释放量较大,释放强度降低较快,矿化速率随时间延长呈缓慢平稳下降,在培养期结束时降至最低。SOC矿化过程受多种因子共同作用,ESP是该过程的主要影响因子。土壤的盐碱化抑制了土壤碳循环的速度,相对于碳源过程而言,对碳汇的影响更大。伴随SOC含量增加,SOC矿化反应强度和矿化反应的完全程度加强,矿化反应累积量增加,反之,随ESP程度增加而减弱。     

水热预处理对猪粪厌氧消化及沼液生态安全性的影响

为进一步提高猪粪在厌氧消化过程中水解性和产甲烷性能,同时增加猪粪沼液还田利用途径的生态安全性,该研究采用水热的方式对猪粪进行预处理,探究了不同温度（70、90、120、150和170 ℃）水热预处理对猪粪的理化特性和厌氧消化产甲烷性能的影响,并对其沼液的生态安全性进行评估。结果表明,不同温度水热处理30 min条件下,猪粪SCOD（Soluble Chemical Oxygen Demand,溶解性化学需氧量）增加了3.9%～43.6%;经150 ℃水热处理后的猪粪获得最高的产甲烷量(398±40) mL/g（以VS计算,Volatile Solid,挥发性固体）,相对于未经处理猪粪的产甲烷量显著提高了5.6%（P<0.05）。猪粪经150 ℃水热预处理和厌氧消化后的沼液中重金属Hg、As、Pb、Cr和Cd含量均满足《农用沼液（GB/T 40750-2021）》的限量要求;粪大肠杆菌的含量满足《粪便无害化卫生要求（GB7959-2012）》;土霉素大幅度降低,恩诺沙星、磺胺嘧啶和诺氟沙星的含量均低于检测限。因此,适当的水热预处理（150 ℃）不仅能够提高猪粪的厌氧消化产甲烷性能,并且能够进一步加强粪污无害化处理和降低沼液还田利用的环境风险。