Trace elements in Bangladesh paddy soils

Abstract

A study was carried out to investigate the status of four micronutrients, iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn), and five other trace elements, cobalt (Co), chromium (Cr), nickel (Ni), lead (Pb), and strontium (Sr), in paddy soils of Bangladesh. Soil samples were digested by hydrofluoric acid (HF)‐nitric acid (HNO₃)‐perchloric acid (HClO₄) for determination of total contents of the nine elements, while DTPA, ASI and 0.1 Mhydrochloric acid (HC1) methods were used for determination of available Fe, Cu, Mn, and Zn. Total trace element contents were found to vary with physiography on which soils are distributed. In general, Ganges Tidal Floodplain soils had the highest content, whereas terrace soils had the lower content. Among the soil properties examined, clay content had a good relation with total trace element contents in the topsoil, except for Sr. Based on the variation with physiography or clay content, the nine trace elements could be grouped into six groups: Cu, Fe and Zn, Pb, Co and Cr and Ni, Mn, Sr. According to the extractable levels of four micronutrients, Bangladesh paddy soils had the medium to optimum amounts of Fe and Cu, but were deficient sporadically in Mn and extensively in Zn. It was indicated that paddy soils of Bangladesh are yet to be polluted with heavy metals.     

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.     

紫色土发育成的水稻土微团粒结构中有机－无机复合体的性质

This paper deals with characteristics of organo-mineral complexing of microaggregates in the paddy soils developed from purple soils in Sichuan, China. Results show that the contents of organic matter in microaggregates are in the order of 1-0.25 mm > smaller than 0.05 mm > 0.05-0.25 mm. But the organic matter in 1-0.01 mm microaggregates accounts for 68.1%-78.7% of that in soil. The organic matter in < 0.05 mm microaggregates is complexed humus on the whole, of which the degree of organo-mineral complexing varies between 96.1% and 99.5%, which is higher than that of the soil or > 0.05 mm microaggregates. The contents of loosely combined humus and the ratios of loosely and tightly combined humus markedly decline with the size of microaggregates. Flesh soil humus formed from semi-decomposed organic material or organic manure added is combined first with < 0.001 mm clay, and then aggregated with other organic and mineral particles to form larger microaggregates, in which the aging of humus happens at the same time; whereas organic matter of the light fraction is mainly involved in the formation of > 0.05 mm microaggregates.     

中国东南部某些水稻土的矿物学

Limited information is available concerning the mineralogy of paddy soils in the southeastern China. Using chemical methods in conjunction with X-ray diffractometry, we studied the mineral composition of three paddy soils: Jinghua (paddy soil on Quaternary red clay), Fuyang (Hapl-percogenic loamy paddy soil), and Shaoxing (gleyic clayey paddy soil). All the soils contained quartz, mica, vermiculite, chlorite and kaolinite, and the distribution of these minerals varied with soil particle size fractions. The clay fraction of the Fuyang and Shaoxing soils also contained smectite. Although X-ray data did not show the presence of smectite in the Jinghua soil, this mineral was identified by the chemical method, suggesting a transitional property of the mineral in the soil. Hydroxy-Al interlayered minerals were also present in the clay fraction. The amount of smectite in the soils was 31.6 (Shaoxing), 16.5 (Fuyang), and 21.4 (Jinghua) g kg^-1; for vermiculite it was 33.3 (Shaoxing), 16.5 (Fuyang), and 8.5 (Jinghua) g kg^-1. Smectite was only found in the clay fraction. In contrast, amounts of vermiculite in soil particle size fractions were 3.0~11.4 (sand), 2.1~6.0 (coarse silt), 4.6~18.9 (medium silt), 0.9~40.0 (fine silt), and 17.0~108 (clay) g kg^-1. The amount of noncrystalline aluminosilicates in the soils in g kg^-1 decreased in the order: Shaoxing (2.4) > Jinghua (1.9) > Fuyang (1.7). This study has provided useful mineralogical information that is fundamental in future development of management strategies of the soils.     

土地管理方式对盐化水稻土生物地球化学机能的影响

Most lowlands in Northeast Thailand （Isaan region） are cultivated with rice and large areas are affected by salinity, which drastically limits rice production. A field experiment was conducted during the 2003 rainy season to explore the interactions between salinity and land management in two fields representative of two farming practices： an intensively managed plot with organic inputs and efficient water management, and one without organic matter addition. Field measurements, including pH, Eh, electrical conductivity （EC）, and soil solution chemistry, were performed at three depths, with a particular focus on Fe dynamics, inside and outside saline patches.
High reducing conditions appeared after flooding particularly in plots receiving organic matter and reduction processes leading to oxide reduction and to the release of Fe and, to a lesser extend, Mn to the soil solution. Oxide reduction led to the consumption of H^＋ and the more the Fe reduction was, the higher the pH was, up to 6.5. Formation of hydroxy-green rust were likely to be at the origin of the pH stabilization. In the absence of organic amendments, high salinity prevented the establishment of the reduction processes and pH value remained around 4. Even under high reduction conditions, the Fe concentrations in the soil solution were below commonly observed toxic values and the amended plot had better rice production yield.     

绰墩埋藏古水稻土中木质素特征研究

利用CuO氧化方法分析了苏州绰墩山埋藏古水稻土中木质素分解酚酸产物及特征,以此了解长期利用条件下水稻土中木质素的来源、保存及变化。通过比较相邻埋藏土壤剖面植稻和非植稻层次中木质素源的酚酸化合物特征,探讨水稻种植对土壤木质素结构特征的影响。结果表明,在埋藏古水稻土中木质素源的总酚酸含量在0.004～0.035 mg kg-1之间,显著低于现代水稻土(0.27～0.34 mg kg-1),而在埋藏土壤中,植稻与非植稻土壤层次中木质素无显著差异。埋藏古土壤中木质素源酚酸的组成(香草基类/紫丁香基类(S/V)及肉桂类/紫丁香基类(C/V)比分别为0.40～1.55、0.15～0.89),可证实此古土壤曾种植非木本被子植物;而S/V和C/V在植稻与非植稻土壤中没有显著差异,表明利用木质素特征难以区分同类(不同草本)有机质的具体来源。在埋藏古土壤中木质素碳占总有机碳比例很小,说明木质素在土壤中并非如通常所预期的容易被保存。     

Nitrification activities and N mineralization in paddy soils are insensitive to oxygen concentration

Oxygen concentration is considered to be the most important factor influencing nitrification and mineralization rates in agricultural soils. However, the sensitivities of nitrification and N mineralization in paddy soils to oxygen concentrations are not well known. We examined nitrification activities and N mineralization rates of six paddy soils with pH ranging from 5.23 to 7.83 and incubated at 25°C and 60% water-holding capacity in laboratory after ammonium was added at concentrations of 10, 30 and 50?mg?N?kg^?1 of soil and the headspace gases were replaced with stock gases whose oxygen concentrations were 20%, 10% and 2%, respectively. The tested paddy soils had a very wide range of nitrification activities so that the nitrate ratio in inorganic N varied from >?95% after 1 day incubation to?相似文献   

低产水稻土改良与管理研究策略

我国耕地后备资源极端缺乏,改良低产田是提高粮食产量的重要途径。低产水稻土作为低产田的重要组成部分,相关肥力特征及其改良技术研究比较零散,缺乏系统科学的调控管理策略。本文从低产水稻土类型、新的改良研究方法角度,探索可能的技术突破。基于农业部统计数据,因环境条件不良或土壤自身存在障碍因素,全国约有7.67×106hm2低产水稻土。按其主导成因,低产水稻土可分为冷潜型、粘结型、沉板型、毒质型四类。土壤质量评价是低产水稻土研究的重要方面,其评价方法主要包括土壤质量动力学法、土壤质量综合评分法、多变量指标克立格法、土壤相对质量评价法,现已发展了基于GIS的区域尺度水稻土质量评价方法,以及基于土壤生物学性状的质量评价方法。低产水稻土改良研究更多关注新技术和新方法,稳定性同位素探针技术、傅里叶变换红外光谱法(FTIR)和固相交叉极化魔角自旋13C核磁共振(CPMS13C-NMR)波谱技术的应用,将土壤有机碳的微团聚体分布、腐殖质的转化及其与土壤矿物结合机制深入到微观水平;同时高通量测序、土壤宏基因组学、宏转录组学等方法将相关研究推向分子水平。低产水稻土改良与管理的技术主要涉及到冷潜型、粘结型、沉板型、毒质型四大类低产水稻土的改良技术,基于产量反应和农学效率的推荐施肥方法是水稻土养分管理方法的重要发展方向。1)在低产水稻土质量评价方面,未来要结合不同低产类型的障碍因素开展个性化的土壤质量评价,如白土的质地和耕层厚度,加强引入土壤生物学指标进行土壤质量评价研究。2)在低产水稻土改良方面,要研究稻田障碍层次的形成机理与调控途径;研究其他低产类型如新垦水稻土、盐渍化水稻土、石灰化水稻土和污染水稻土的改良技术;研究长期改良措施对不同粒级团聚体腐殖质结构、酶类、微生物多样性和功能基因的影响。3)在低产水稻土管理方面,着重研究秸秆还田技术、推荐施肥技术、抗逆品种技术、群体控制技术。     

基于同步辐射微CT研究不同利用年限水稻土团聚体微结构特征

同步辐射微CT (SRμ-CT)可以无损获取高分辨率、强对比度的内部结构图像,是研究土壤团聚体三维微结构的有效手段.本研究采集了种植水稻20 a和40 a后表层土壤团聚体样品,应用SRμ-CT扫描获取了9μm分辨率的团聚体内部结构图像,然后应用CT图像处理方法和3DMA-Rock软件观察并定量分析了团聚体微结构特征.随着种植水稻年限的增加,土壤有机质含量和全氮含量显著增加,团聚体孔隙数量和孔隙度显著增加,比表面积显著增大.种植水稻20 a的土壤团聚体呈现致密的黏闭结构,而种植水稻40 a的土壤团聚体具有由团粒状小团聚体构成的复杂多孔微结构.结果表明随着种植年限的增加,团聚体微结构和土壤质量明显改善.     

广东主要母质发育水稻土对硅的吸附特性

Silicate adsorption in eight paddy soils developed from four different parent materials in Guangdong Province, China was examined to obtain fundamental knowledge of silicate adsorption to improve the efficacy of silicate fertilizer use in these areas. A correlation analysis showed that silicate adsorption did not obey the Langmuir equation （r = -0.664- 0.301） but did obey the Freundlich and Temkin equations （P〈0.01, r = 0.885-0.990）. When the equilibrium silicate concentration （Ci） was less than 45 mg SiO2 kg^-1, the adsorption capacity was in the following decreasing order of paddy soils： basalt-derived 〉 Pearl River Delta sediment-derived 〉 granite-derived 〉 sand-shale-derived. Stepwise regression and path analysis showed that for the investigated paddy soils amorphous MnO and Al2O3 were the two most important materials that affected silicate adsorption. Moreover, as Ci increased, amorphous Al2O3 tended to play a more important role in silicate adsorption, while the effects of amorphous MnO on silicate adsorption tended to decrease.     

中国水稻土磷储量及其空间分异

Due to the growing concern about the agricultural phosphorus (P) losses pollution, an in-depth understanding of P in paddy soils of China would be helpful in providing a national perspective of the environmental impact of P cycling and fertility on China’s farms. In this study, we evaluated the P storage and the P density of paddy soils in China, characterized the spatial variations of P among the subgroups of paddy soils and soil regions in China, and evaluated the P data using GIS-based analysis, which included a newly compiled 1:1 M digital soil map of China, and using 1 490 soil profiles. The available and total P densities of paddy soils were 6.7 and 698.5 g m-3, respectively. Overall in China, the total P storage within 1 m of paddy soils was estimated to be 330.1 Tg. The P density of paddy soils varied substantially with subgroups due to the different soil water regimes such as groundwater table and soil drainage. The P availability in paddy soils, especially in surface layer, was higher in high temperature and precipitation areas. Further research is needed to examine more anthropogenic impact factors, such as increasing use of chemical fertilizer.     

不同有机肥对稻田温室气体排放及产量的影响

为研究有机肥施入稻田对温室气体排放的影响,设置猪粪、鸡粪和稻草分别与化肥混施处理,利用静态箱法-气相色谱仪监测稻田甲烷(CH_4)和氧化亚氮(N_2O)排放通量并进行分析。研究结果表明,化肥处理(CF)CH_4季节排放为202.1、279.9和332.5 kg/hm~2,与猪粪(PM)无显性差异,明显低于鸡粪(CM)和稻草(RS)处理;CF处理N_2O排放总量最高,与有机肥处理无显著性差异;CH_4季节排放通量与土壤Eh值呈极显著负相关关系,与土壤温度呈极显著正相关关系;肥料中不同活性有机碳质量分数为18.4~114.5 g/kg,肥料中被167 mmol/L高锰酸钾氧化的有机碳(ROC167)与稻田CH_4排放总量呈显著正相关关系(相关系数为0.872,P0.05);施有机肥第三年水稻平均产量比CF处理增加14.3%(P0.05);不同有机肥中,以PM处理的增温潜势和温室气体排放强度最小,与不施肥和CF处理无显著性差异,猪粪的ROC167含量低,能较好的协调环境与产量之间关系,是值得推荐的有机肥种类。     

Phosphorus status of some paddy soils in Bangladesh

Abstract

Phosphorus status of Bangladesh paddy soils covering the major paddy soil types was assessed in terms of parent materials and physiography. Total P concentration ranged from 172 to 604 mg kg^?1 in the topsoil and from 126 to 688 mg kg^?1 in the subsoil, and varied with the physiography to which the soils belonged. In most soils, the available P concentration was much higher for the topsoil than for the subsoil. The inorganic P concentration was higher than the organic P concentration, except for one soil series from the Old Himalayan Piedmont Plain, and was significantly and positively correlated with the total P concentration. Among the inorganic forms, only the concentration of Al-bound P showed a significant correlation with that of available P based on the Bray P-2 method in both topsoil and subsoil. In general, the P status was critically low in paddy soils of the terrace area. Normal growth of paddy rice in this area is expected to be difficult without application of P fertilizer.     

Movement of ammonium in paddy soils in Taiwan

The movement of ammonium due to diffusion in paddy soils in Taiwan was investigated in the laboratory. The movement of ammonium in flooded soils was inversely proportional to the concentration of ammonium in the soil solution, which was a function of the quantity of ammonium present, the content of solid matter in a unit volume of soil (bulk density), and the adsorptive property of soil. Although there was a considerable variation in the value of both the ammonium adsorption and bulk density of soils, the adsorptive property was more variable. Therefore, the adsorptive property seemed to be the most influencial factor on the movement of ammonium in flooded soils, where the property had a close relation to the cationexchange capacity.

The bulk density of flooded soils in the field could be reproduced in glass tubes under percolating condition in the laboratory. The values of bulk density determined on paddy soils after harvesting or on air-dry soils were considerably different from those in the flooded soils in the field. A simple determination method of bulk density was proposed for paddy soils.     

Effect of rice straw on the composition of volatile soil gas and micro flora in the tropical paddy field

The effect of rice straw on the composition of volatile soil gas and microflora in the tropical paddy field was studied with and without fertilizer application.

The volatile soil gas most abundantly found in plots with rice straw was methane followed by other gases, nitrogen, oxygen and carbon dioxide during the early stage of rice growth, while nitrogen predominated in later stages.

The loss of soil nitrogen through volatilization increased following phosphorus application as well as rice straw application as compared with that in the control plot. In the former case, the enhancement of decomposition of organic-N was assumed to be due to the increase in population of cellulose decomposer.

Rice straw application with or without N-fertilizer increased methane gas formation by 27 to 63 times as compared with the phosphorus plot and the peak of its formation was found 5 to 7 weeks after rice straw application. However methane formation in the control plot was very low and was found only 5 to 9 weeks after flooding.

Rice straw application usually increased the number of various groups of microorganisms along with contributing to the transformation of organic-N to N₂ gas. But the stimulating effect was chiefly observed in the population of Azotobacter.     

中国太湖流域水稻土中的反硝化细菌

This study attempted to determine the characteristics of the communities, the ecological factors, and the denitrifying enzyme activity for denitrifying bacteria found in the paddy soils of the Taihu Lake Basin, China. Samples of the six main soil types of the basin were taken from paddy fields with different fertilities. The total numbers of bacteria and denitrifying bacteria in the high fertility soils were much more than those in low fertility soils, and the number of denitrifying bacteria accounted for 49% to 80% of the total number of bacteria. The O2 content was an important ecological factor that affected denitrification. Of test the strains isolated from the paddy soils in the Taihu Lake Basin, some (e.g., Pseudomonas spp.) grew well under low oxygen partial pressure, while others (e.g., Bacillus spp.) had no strict predilection with O2 content. Another critical ecological factor was the nitrogen concentration. Three selected denitrifying bacteria grew better in aculture medium with 135 instead of 276mg L^-1 nitrogen. At the same time 67% of the test strains were able to reduce NO3^- to NO2^- and 56% had N2O reductase.     

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).     

Nitrification and nitrifying potential of tropical and subtropical soils

Summary Nitrification was measured in five different soils (slate alluvial soil, sandstone shale alluvial soil, sandstone shale and slate alluvial soil, red soil, and Taiwan clay). In these soils different lag periods were recorded before the onset of nitrification. Nitrifying activity was highest in sandstone shale alluvial soil and the lowest in acidic red soil. A part from those in the red soil, the numbers of nitrifying bacteria detected were all higher than numbers reported in temperate soils. However, there were no clear relationships between the numbers of nitrifying bacteria and the rate of nitrification in these soils. When soil cores were incubated for 3 weeks, no NO _inf2 ^sup- or NO _inf3 ^sup- was defected in the slate alluvial soil. This was ascribed to denitrification.