常年淹水稻田甲烷产生潜力和产生途径的季节变化

甲烷的减排问题已成为各国政府和科研人员关注的焦点。稻田是温室气体甲烷的重要排放源,甲烷产生是排放的前提条件,主要有乙酸发酵和CO₂/H₂还原两条途径。常年淹水稻田甲烷排放量高,减排潜力大,但关于这类稻田甲烷产生途径的季节变化规律尚少见报道。于四川省资阳市的常年淹水稻田,采集水稻4个重要生育期(分蘖期、孕穗期、抽穗期、成熟期)的新鲜土样,通过室内厌氧培养试验观测了甲烷产生潜力,并采用稳定性碳同位素方法和氟甲烷(CH₃F,2%)抑制法,量化CO₂/H₂产甲烷的碳同位素分馏系数(α(CO₂/CH₄)),从而定量评估乙酸产甲烷途径的相对贡献率(?乙酸)。结果表明：添加CH₃F显著降低甲烷产生,甲烷产生潜力在成熟期最大,变化范围为3.22～12.71μg·g^–1·d^–1;产生CH₄的δ¹³C值(δ¹³CH_...     

High-Time Resolution Analysis of Diel Variation in Methane Emission from Flooded Rice Fields

Methane (CH₄) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH₄ emission and to estimate the best time of day for optimum extrapolation of daily CH₄ emission. Our results showed distinct diel variation in CH₄ emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH₄ emitted per day (110–160 mg CH₄ m^?2 d^?1) was released at 14:00–15:00. The diel pattern of CH₄ emission resembled that of air temperature (T_a). The T_a coupled with solar radiation could cause a difference in partial pressure of CH₄ (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH₄ emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH₄ emission is an important mechanism causing diel variation.     

Growth and Iron Uptake of Lowland and Aerobic Rice Genotypes under Flooded and Aerobic Cultivation

With increasing water shortages in China, rice (Oryza sativa L.) cultivation is gradually shifting away from continuously flooded conditions to partly or even completely aerobic conditions. The effects of this shift on the growth and iron (Fe) nutrition of different aerobic and lowland rice genotypes are poorly understood. A field experiment was conducted to determine the effects of cultivation system (aerobic vs. flooded), genotype (five aerobic rice varieties and one lowland rice variety), and Fe fertilization [no Fe and 30 kg ha^?1 ferrous sulfate (FeSO₄·7H₂O] on rice grain yield and Fe nutrition. Plants were sampled at tillering and physiological maturity. In both aerobic and flooded plots, Fe application significantly increased shoot dry weight, shoot Fe concentration, and shoot Fe content at tillering but not physiological maturity. At physiological maturity, grain yield and Fe and grain harvest indices were significantly lower in aerobic than in flooded plots. Shoot dry weight and shoot Fe content differed among genotypes at tillering and at physiological maturity. The grain harvest index of aerobic rice genotype 89B-271-17(hun) was significantly greater than that of the other five genotypes when no Fe was applied. Because soil Fe fertilization did not improve the Fe nutrition of rice in aerobic plots, the results indicate that the shift from flooded to aerobic cultivation will increase Fe deficiency in rice and will increase the problem of Fe deficiency in humans who depend on rice for nutrition.     

Effect of Moisture Conditions in Rice Paddies on Phosphorus Fractionation in Agriculture Soils of Rapidly Developing Regions of China

Moisture conditions in rice paddies play an important role in phosphorus (P) cycling and may affect P loss to nearby water bodies. This study seeks to identify factors that contribute to P-fraction transformations in flooded rice paddies on Cambosols and Anthrosols using Zhangjiagang County of the Yangtze River delta region, China, as a study area. Soil samples preserved under flooded and aerobic conditions (n?=?60) were collected, and P fractions and soil properties were measured. Under flooded conditions, soluble and loosely bound P significantly decreased to half of aerobic levels, aluminum/iron-bound P increased by 66%, and organic-bound P decreased by 64%. Soil organic matter, cation exchange capacity, pH, and active iron were well correlated with soil P fractions under both moisture conditions across two soil orders despite a disparity in soil properties. Further research goals that would aid in specific fertilizer recommendations and management strategies are identified.     

Soil Phosphorus Tests for Flooded Rice Grown in Contrasting Soils and Cropping History

Soil phosphorus (P) tests for flooded rice (Oryza sativa L.) generally present uncertainties for estimating P availability. Bray 1, 1% citric acid, Mehlich 3, Olsen extractants (dry samples), and Bray 1 extractant after 3 days (BI3) and 7 days (BI7) of anaerobic incubations were evaluated to estimate P availability for rice in 43 Uruguayan soils. Field trials were conduced at each site (0, 13, 26, and 39 kg P applied ha^?1). Relative yield and absolute and relative yield increases were determined. Extracted P was variable for the different tests. For silty soils, P availability was better estimated by citric acid, Mehlich 3, and Bray 1, with similar soil P critical concentrations (6?8 mg P kg^?1). The BI3 and BI7 tests showed greater soil P critical concentration but poorer correlations with yield indexes. This study contributes to the scientific basis of P fertilization for flooded rice, promoting more effective fertilizer use and minimizing environmental P losses.     

三峡库区受淹土壤污染物释放量的试验研究

三峡工程建成蓄水后,受淹耕地将遭到江水浸泡,积蓄在耕地上的有机污染物、N、P以及Cu、Cr等微量重金属将通过溶解、交换、扩散而迁移到江水中,增加江水中相应成份的含量。在调查了解三峡库区受淹土壤数量、类型的基础上,选择采集具有代表性的8个耕作土壤作样本,在实验的条件下模拟江水浸泡,求取单位重量的土壤在固—液相平衡状态下释放污染物的负荷量,进而计算三峡库区受淹土壤在江水浸没处于平衡时污染物释放进入水中污染物的量。结果表明,三峡水库受淹耕地污染物释放总量为181540.9t,其中以CODcr,BCOD5为主,二者合计93.78%,这将成为三峡库区水环境污染的重要污染源。     

Efficient Management of Nitrogen Fertilizers for Flooded Rice in Relation to Nitrogen Transformations in Flooded Soils

Recent progresses in efficient management of nitrogen fertilizers for flooded rice in relation to nitrogen transformations in flooded soil were reviewed.Considerable progress has been achieved in the investigation on the mechanism of ammonia loss and the factors affecting it .However,little progress has been obtained in the investigations on nitrification-denitrification loss owing to the lack of method for estimating the fluxes of gaseous N products.Thus,so far the management practices developed or under investigation primarily for reducing ammonia loss are feasible or promising,while those for reducing nitrification-denitrification loss seem obscure,except the point deep placement. In addition,it was emphasized that the prediction of soil N supply and the recommendation of the optimal rate of N application based on it are only semi-quantitative.The priorities in research for improving the prediction are indicated.     

Arsenic Concentrations in Groundwater,Soils, and Irrigated Rice in Southwestern Bangladesh

Arsenic (As) poisoning of groundwater in Bangladesh has become a major environmental and health issue. The extensive use of groundwater in irrigation of rice has resulted in elevated As in soils and crops. A study was undertaken to determine As concentrations in groundwater, soils, and crops in 16 districts of southwestern Bangladesh. Groundwater samples were collected from shallow-tube and hand-tube wells (STW and HTW) used for irrigation and drinking water. Soil and rice plants were sampled from the command area of the tube wells. Arsenic concentrations were determined using an atomic absorption spectrometer equipped with flow injection hydride generator. Groundwater samples contained <10 to 552 μg As L^?1. Arsenic concentrations in 59% of STW samples exceeded 50 μg As L^?1, the national standard for As in drinking water. Unlike groundwater, most of the surface water samples contained <10 μg As L^?1. Concentrations of As in the soils from the command area of the tube wells ranged from 4.5 to 68 mg kg^?1. More than 85% of the soils contained <20 mg As kg^?1. The mean As concentration in the rice grain samples was 0.23 mg kg^?1, which is much less than the maximum food hygiene standard. A positive relationship was observed between groundwater and soil As, implying that soil As level increases as a result of irrigation with contaminated water. However, irrigation water As did not show any relation with rice grain As. The findings suggest that surface water bodies are a safe source of irrigation water in the As-contaminated areas.     

不同节水稻作模式对土壤理化特性和土壤酶活性影响研究

针对南方丘陵区季节性干旱现状与目前稻田单一化的连作耕作制度对农田环境造成的不利影响因素,通过4a田间定位试验研究了节水稻作模式下土壤理化性状和土壤酶活性变化规律影响.结果表明,与该区常规稻作模式相比.在试验设计范围内,节水稻作模式下稻田的土壤理化性状明显改善,随着耕种年限增加,土壤容重下降,而孔隙度增加.土壤通透性增强,有效阻止土壤次生潜育化和土壤酸化.提高了土壤pH值;就土壤酶活性而言,节水稻作模式处理酶活性常规稻作模式相比.除转化酶外,其它酶活性均有不同程度的增加,尤其对磷酸酶与脲酶影响最大.     

Use of Single Extraction Methods to Predict Bioavailability of Heavy Metals in Polluted Soils to Rice

Human exposure to toxic heavy metals via dietary intake is of increasing concern. Heavy-metal pollution of a rice production system can pose a threat to human health. Thus, it was necessary to develop a suitable extraction procedure that would represent the content of metal available to rice plants (Oryza sativa L.). The aim of this study was to predict, on the basis of single extraction procedures of soil heavy metals, the accumulation of heavy metals (cadium, lead, copper, and zinc) in rice plants. Six extracting agents [Mehlich 1, Mehlich 3, EDTA (ethylenediaminetetraacetic acid), DTPA–TEA (diethylenetriaminepentaacetic acid–triethanolamine), ammonium acetate (NH₄OAc), and calcium chloride (CaCl₂)] were tested to evaluate the bioavailability of heavy metals from paddy soils contaminated with lead–zinc mine tailings to rice. The extraction capacity of the metals was found to be of the order EDTA > Mehlich 3 > Mehlich 1 > DTPA–TEA > NH₄OAc > CaCl₂. The correlation analysis between metals extracted with different extractants and concentrations of the metals in the grain and stalk of the plant showed positive correlations with all metals. The greatest values of correlation coefficients were determined between the NH₄OAc- and CaCl₂-soluble fractions of soil and contents in plants in all four metals studied. Therefore, NH₄OAc and CaCl₂ were the most suitable extractants for predicting bioavailability of heavy metals in the polluted soils to rice. The results suggested that uptake of heavy metals by rice was mostly from exchangeable and water-soluble fractions of the metals in the soils. Soil-extractable metals were more significantly correlated with metal accumulation in the stalk than in the grain. The pH had more significant influence on availability of heavy metals in the soils than total content of metals and other soil properties. The bioavailability of metals for rice plants would be high in acidic soils.     

不同土培条件下荧蒽在水稻和小麦中的分布特征

通过盆栽试验方法,在荧蒽污染的黄棕壤和潮土上种植水稻和小麦,分别设置空白（CK）、低（L）、中（M）、高（H）4个污染浓度水平,比较荧蒽对作物生长的影响和两种不同土壤中植物体荧蒽的分布情况。结果显示,在试验设置的荧蒽污染浓度下,荧蒽未对两种植物的生长造成抑制,相反还促进了植物某些部位的生长;水稻和小麦各部位的荧蒽含量随土壤荧蒽含量的增加而增大;植物体内荧蒽的传导系数随土壤荧蒽含量的增加而减小,且两种土壤的趋势一致。黄棕壤和潮土有机质、养分、阳离子交换量等性质影响植物体内荧蒽的运移和富集;水稻茎叶对荧蒽的富集能力强于小麦,而小麦籽粒富集荧蒽的能力强于水稻。     

Direct and Residual Effects of Zinc on Zinc-Efficient and Zinc-Inefficient Rice Genotypes Grown under Low-Zinc-Content Submerged Acidic Conditions

Zinc (Zn) deficiency has been identified as a major cause of poor yield in rice. Flooding and submergence bring about a decline in available Zn due to pH changes and the formation of insoluble Zn compounds. A field experiment (undisturbed randomized complete block design with three replications) was conducted in farmers’ fields of Kedah state during 2008 and 2009 to determine the direct and residual response of Zn on rice genotypes at the rates of 0 and 15 kg Zn ha^?1 in low-Zn-content acidic submerged soil. The genotypes differed significantly in grain yield and its components. Single application of Zn significantly increased the growth and yield of the crop for two seasons. Based on the grain yield efficiency index, the most Zn-efficient genotypes were MR 106 and Seri Malaysia Dua. Two genotypes, MR 220 and MR 219, were moderately efficient, but MR 211 and Bahagia were classified as inefficient.     

西南地区冬水田剖面的微生物空间分异规律

为研究冬水田土壤基本理化性质对微生物多样性和冬水田生态系统功能与结构的作用,以西南地区3个不同样地的冬水田为研究对象,采用烘干法、电位法、静态室内培养法、稀释涂布平板法和氯仿熏蒸法对土壤理化和生物学指标进行检测。结果表明:(1)各样地含水量均沿垂直深度逐渐降低,pH为6.3～7.1,呈微酸—中性生境,铵态氮(NH4+—N)含量总体呈现为合川区冬水田沙坪坝区冬水田北碚区紫色土基地,且表层(0—10cm)亚表层(10—20cm)底层(20—40cm),整体为36.97～52.02mg/kg,3种冬水田各土层硝态氮(NO3-—N)含量差异不显著(2.13～2.61mg/kg)。(2)微生物量碳(MBC)和微生物量氮(MBN)含量呈现为北碚区紫色土基地合川区冬水田沙坪坝区冬水田,不同层次表现为表层(0—10cm)亚表层(10—20cm)底层(20—40cm)。(3)各样地间微生物丰度表现为细菌放线菌真菌,微生物数量沿土层垂直深度降低,各土层细菌、放线菌和真菌数量均呈极显著负相关(p0.01),不同样地间表现为合川区冬水田沙坪坝区冬水田北碚区紫色土基地。     

Chemistry of Lowland Rice Soils and Nutrient Availability

Rice is the staple food crop for about 50% of the world's population. It is grown mainly under two ecosystems, known as upland and lowland. Lowland rice contributes about 76% of the global rice production. The anaerobic soil environment created by flood irrigation of lowland rice brings several chemical changes in the rice rhizosphere that may influence growth and development and consequently yield. The main changes that occur in flooded or waterlogged rice soils are decreases in oxidation–reduction or redox potential and increases in iron (Fe²⁺) and manganese (Mn²⁺) concentrations because of the reductions of Fe³⁺ to Fe²⁺ and Mn⁴⁺ to Mn²⁺. The pH of acidic soils increased and alkaline soils decreased because of flooding. Other results are the reduction of nitrate (NO₃ ^?) and nitrogen dioxide (NO₂ ^?) to dinitrogen (N₂) and nitrous oxide (N₂O); reduction of sulfate (SO₄ ^2?) to sulfide (S^2?); reduction of carbon dioxide (CO₂) to methane (CH₄); improvement in the concentration and availability of phosphorus (P), calcium (Ca), magnesium (Mg), Fe, Mn, molybdenum (Mo), and silicon (Si); and decrease in concentration and availability of zinc (Zn), copper (Cu), and sulfur (S). Uptake of nitrogen (N) may increase if properly managed or applied in the reduced soil layer. The chemical changes occur because of physical reactions between the soil and water and also because of biological activities of anaerobic microorganisms. The magnitude of these chemical changes is determined by soil type, soil organic-matter content, soil fertility, cultivars, and microbial activities. The exclusion of oxygen (O₂) from the flooded soils is accompanied by an increase of other gases (CO₂, CH₄, and H₂), produced largely through processes of microbial respiration. The knowledge of the chemistry of lowland rice soils is important for fertility management and maximizing rice yield. This review discusses physical, biological, and chemical changes in flooded or lowland rice soils.     

两步法高效水解水稻秸秆制取木糖和葡萄糖

在序批式高压反应釜反应器中,采用两步法研究了水稻秸秆在稀硫酸水溶液中水解为木糖和葡萄糖,系统考察了反应温度、反应时间、水稻秸秆用量和稀酸浓度对水稻秸秆水解反应的影响。实验结果表明:与传统一步法酸水解相比,采用两步法酸水解水稻秸秆,既可以得到很高的木糖产率,又可以得到较高的葡萄糖产率;反应温度、反应时间和酸浓度对水稻秸秆酸水解产物的分布和产率有着重要影响。第一步水解反应中,当底物用量为1.5 g,酸浓度为0.5%wt时,140℃反应120 min,木糖产率高达162.6 g·kg-1;第二步水解反应中,当底物用量为0.5 g,酸浓度为1.0%wt时,180℃反应120 min,葡萄糖产率高达216.5 g·kg-1。本研究为农业废弃物水稻秸秆的高效和高值资源化利用提供了新的策略。     

Immobilization of Zinc Fertilizer in Flooded Soils Monitored by Adapted DTPA Soil Test

Zinc (Zn) deficiency is a persistent problem in flooded rice (Oryza sativa L.). Severe Zn deficiency causes loss of grain yield, and rice grains with low Zn content contribute to human nutritional Zn deficiencies. The objectives of this study were to evaluate the diethylenetriaminepentaacetic acid (DTPA) extraction method for use with reduced soils and to assess differences in plant availability of native and fertilizer Zn from oxidized and reduced soils. The DTPA‐extractable Zn decreased by 60% through time after flooding when the extraction was done on field‐moist soil but remained at original levels when air‐dried prior to extraction. In a pot experiment with one calcareous and one noncalcareous soil, moist‐soil DTPA‐extractable Zn and plant Zn uptake both decreased after flooding compared with the oxidized soil treatment for both soils. In the flooded treatment of the calcareous soil, both plant and soil Zn concentrations were equal to or less than critical deficiency levels even after fertilization with 50 kg Zn ha^?1. We concluded that Zn availability measurements for rice at low redox potentials should be made on reduced soil rather than air‐dry soil and that applied Zn fertilizer may become unavailable to plants after flooding.     

水稻土镉污染与水稻镉含量相关性研究

采用盆栽试验的方法,考察了水稻土中重金属镉（Cd）的浓度对水稻生长及Cd富集的影响以及Cd在水稻植株的分布情况,并进一步研究了糙米（可食部位）对Cd的富集量与土壤中Cd总量的关系。结果表明,在各个浓度Cd胁迫下,根、茎叶、稻壳、糙米相比,2个品种水稻都是根累积的Cd含量要高于茎叶和稻壳、糙米,即根〉茎叶〉稻壳〉糙米;在水稻的茎叶细胞中,Cd主要分布在细胞壁,细胞可溶性成分,细胞器Cd的分布量较少,即细胞壁〉可溶性部分〉细胞器及膜部分;随Cd浓度增加,茎叶中的Cd积累量极显著增加,各细胞组分中的Cd含量均显著增加;根据国标GB 2762—2005对大米中Cd的限量标准（≤0.2 mg.kg^-1）,水稻土土壤总Cd临界值分别为2.0 mg.kg^-（1博优225）、3.1 mg.kg^-（1矮糯）。因此,在污染土壤上宜选种食用部位重金属积累低的水稻品种,以减少人类吸收重金属的风险。     

Identification of Minimum Data Set Under Balanced Fertilization for Sustainable Rice Production and Maintaining Soil Quality in Alluvial Soils of Eastern India

The scarcity of non-renewable fertilizers resources and the consequences of climate change can dramatically influence the food security of future generation. Introduction of high yielding varieties, intensive cropping sequence and increasing demand of food grains day-by-day, application of recommended dose of fertilizers could not fulfill our targets due to outdated fertilizers recommendations are yet in practice. It not only alters soil quality, nutrient balance, microbial and enzymatic ecology but also affected productivity and sustainability of rice in Gangetic alluvial soils of India. The effect of fertilizers application based on “fertilizing the soil versus fertilizing the crop” which insure real balance between the applied and available soil nutrient is urgently needed. Hence, the present study was conducted during three consecutive crop seasons (2010, 2011, and 2012) to assess the effect of imbalance and balance fertilization based on initial soil test values and targeted yields, and to determine the effect of farmyard manure (FYM) when superimposed with balanced fertilizers on identification of minimum data set for the development soil quality, nutrient acquisition, and grain yield of rice. The six fertilizer treatments were laid out in a randomized block design with three replications. The treatments were: T₁-control (no fertilization), T₂-farmyard manure @ 5 t ha^?1, T₃-farmers practice (60:30:30 kg N:P₂O₅:K₂O ha^?1), T₄-precise application of mineral fertilizers based on initial soil test values (77:24:46 kg N:P₂O₅:K₂O ha^?1) for targeted grain yield of 4.0 t ha^?1, T₅-precise application of mineral fertilizers based on initial soil test values (74:23:43 kg N:P₂O₅:K₂O ha^?1) plus FYM (5 t ha^?1) for targeted grain yield of 4.0 t ha^?1 and T₆-precise application of mineral fertilizers based on initial soil test values (135:34:65 kg N:P₂O₅:K₂O ha^?1) for targeted rice grain yield of 5.0 t ha^?1. Result revealed that the targeted rice grain yield of 4.0 and 5.0 t ha^?1 was achieved in T₄ and T₆ treatments with 1.59% (4.06 t ha^?1) and –3.40% (4.83 t ha^?1) deviations, respectively. T₄, T_5, and T₆ significantly increased crop growth, nutrient uptake, available P (P_a) and K (K_a) and augmented rice grain yield by 10.6, 20.2 and 31.6%, respectively, over T₃. Microbial biomass carbon, soil respiration and enzymatic activity were enhanced significantly in T₅ as compared to T₆. Highest soil quality index was found in T₅ (0.95) followed by T₆ (0.90) and, lowest was in T₁ (0.63). The contribution of minimum data set (MDS) toward the SQI was in the descending order of ALP (30.6%) > SOC (21.5%) > K_a (11.3%) > PSM (9.68%) > N_a (8.51%). Overall, rice yield and soil quality was improved by using balance fertilization based on fertilizing the crop Vs fertilizing the soil in alluvial soils of India.     

秸秆还田地不同水氮条件对水稻产量及土壤肥力的影响

[目的]研究秸秆还田地不同水氮管理对水稻产量、土壤养分以及土壤酶活性的影响,为发展优质、高效生态农业提供理论支持。[方法]通过田间小区试验,设计了3种灌溉方式共9个处理,并设置3个麦秆不还田处理为对照。[结果]施氮量为225kg/hm2时,浅湿调控灌溉模式有利于控制水稻茎蘖量,降低水稻株高,形成合理的群体结构;不同水氮管理对水稻产量构成因素中的每穗总粒数、结实率无显著影响,水稻有效穗数受灌溉措施及施氮量的影响较大,浅湿调控灌溉可以显著提高水稻有效穗数和千粒重,从而提高水稻产量;施氮量为225kg/hm2时,浅湿调控灌溉可以有效提高土壤有机质、全氮、有效磷、有效钾的含量。秸秆还田可以显著提高土壤蔗糖酶活性,降低土壤脲酶活性,而对土壤过氧化氢酶活性无显著影响。秸秆还田地施氮量为225kg/hm2时,浅湿调控灌溉对土壤蔗糖酶活性的提高最为显著,而不同水氮条件对土壤脲酶活性的影响并不显著。[结论]在秸秆还田地,当施氮量为225kg/hm2时,浅湿调控灌溉可以有效提高水稻产量及土壤肥力。