Origin and properties of humus in the subsoil of irrigated rice paddies

Stability of humus in the plow layer soil is considered to affect the quantity and quality of dissolved organic matter leached from the plow layer soil. Therefore, a model experiment was conducted to analyze the effect of soil reduction under submerged conditions on the stability of humus in the plow layer soil. The changes in the stability of humus in the plow layer soil during submerged incubations with and without rice straw application were evaluated based on the changes in the binding type of humus. Binding type of humus in the plow layer soil was analyzed by successive extractions of organic matter with water, 0.25 M Na₂SO₄, 0.1 M Na₄P₂O₇ (pH 7.0), 0.1 M Na₄P₂O₇ (pH 10.5), and 0.1 M Na₄P₂O₇ (pH 10.5) with NaBH₄. Amounts of Fe, Mn, and Mg in each fraction were also determined to estimate the relationships between humus and metals.

The successive extraction of humus indicated that the amount of organic carbon which was extractable with the (NaBH₄ +0.1 M Na₄P₂O₇) solution decreased while that of the 0.1 M Na₄P₂O₇ (pH 7.0}-extractable organic carbon increased during submerged incubation with rice straw application. The origin of the increase in the amount of organic carbon in the Na₄P₂O₇ (pH 7.0)-extractable fraction during submerged incubation was investigated further by another incubation experiment using ¹³C-glucose as a reducing agent. Atom- 13C% analysis showed that the contribution of organic carbon derived from compounds other than glucose to the increase in the contents of humic acids and fulvic acids in the Na₄P₂O₇ (pH 7.0)-extractable fractions was ca. 80%. Therefore, it was concluded that the binding type of humus changed from (NaBH₄ + Na₄P₂O₇)-extractable to Na₄P₂O₇ (pH 7.0)-extractable humus under reducing conditions. Since the amounts of organic carbon and Fe increased in the Na₄P₂O₇ (pH 7.0)-extractable fraction and decreased in the (NaBH₄ +0.1 M Na₄P₂O₇)-extractable fraction simultaneously, iron reduction was presumably associated with the change in the binding type of humus in submerged paddy soil.     

Incorporation of 14C into methionine as an intermediate for phytosiderophore biosynthesis in barley

In order to verify the precursory role of methionine (Met) in the biosynthesis of the mugineic acid family of phytosiderophores (MAs), feeding experiments of ¹⁴C-Iabeled compounds to barley (Hordeum vulgare L. cv. Minorimugi) roots grown hydroponically were conducted. When both ^l4C-Glucose (Glc) and unlabeled Met were fed to segmented roots, ¹⁴C was incorporated into Met and MAs in the roots. Molar-radioactivity of Met was higher than that of the amino-butanoic-acid unit in MAs in the roots. When ^l4C-Glc and unlabeled homoserine (Hse) were fed to decapitated roots, l4C was incorporated into Met but not into Hse. Therefore, it was considered that Hse might not be a major precursor of MAs. In addition, ¹⁴C was incorporated into Met and MAs in the roots when both ¹⁴C-glycerol (Gol) and unlabeled Met were fed to segmented roots. It is suggested that MAs may be synthesized from Glc via Met, bypassing Hse, and that the MAs biosynthesis may involve an unknown pathway associated with Gol and leading to Met.     

汉江上游铁矿尾矿库区土壤重金属污染分析

应用地累积指数法和生态危害指数法对汉江上游某铁矿尾矿库区周边土壤重金属污染特征和潜在生态环境污染风险进行了研究。结果表明尾矿库区土壤中重金属除Ti外均超出当地土壤背景值,以Cd超标最严重(超标12倍);形态分析表明Fe、Ti、As、Hg的主要存在形态是残渣态,Mn的可交换态和碳酸盐结合态所占比例最高(均值24.07%),Zn的易还原态所占比例最高(均值22.07%),Ni和Co的易氧化态所占比例最高(均值分别为28.99%、25.46%);地累积指数法评价表明尾矿库区土壤Hg和Cd达到中-强污染等级,As和Co属中度污染等级,Fe、Zn、Mn、Ni以无污染-中污染为主,其余金属无污染;生态危害指数法结果显示Cd和Hg的生态风险等级为极强,As生态风险等级为中等,其余元素生态风险等级为轻微,尾矿库采样区域整体处于很强的生态风险等级,尤其需要加强对Cd、Hg、As的污染防治。     

Investigations on the effect of traditional food processing,preservation and storage methods on vegetable nutrients: A case study in Tanzania

The effect of traditional food proceesing, preservation and storage methods on vegetable nutrients was studied using cassava, pumpkin and mwage leaves. Traditional cooking method for 90 min for cassava, 50 min for pumpkin and mwage leaves resulted in significant losses in protein, fats and vitamins. Sundrying using traditional mats caused losses of vitamin A of 36.3%, 38.0% and 50.3% for cassava pumpkin and mwage leaves respectively. Storage using earthenware pots for six weeks resulted in significant losses of vitamin C. In general, traditional methods for processing, preservation and storage of vegetables cause significant losses of nutrients, an effect that could account for poor, nutritional status in Morogoro region (Tanzania).     

甜菜铁素吸收特点及其对光合性能的影响

[目的]揭示甜菜吸收铁素的规律和铁素对甜菜的生理作用,为甜菜合理利用铁素提供科学依据.[方法]在田间试验条件下,研究了甜菜不同生育时期植株吸收铁素的规律和特点,以及叶面喷施铁素对其光合生理指标和相关酶活性的影响.[结果]甜菜植株中铁素含量随生育进程先升后降,最高时期在块根及糖分增长期;随生育进程铁素积累量逐渐增加;甜菜对铁素吸收性能最强的时期在叶丛快速生长期至块根及糖分增长期,在该时期叶面喷施1～5 g·L-1硫酸亚铁溶液,甜菜产量增加5.05％～ 8.87％,含糖率提高0.42％～0.67％,产糖量增加7.74％ ～ 13.29％,且铁素含量、叶绿素含量、光合生产率、CO2同化率及气孔导度均有所增加,核酮糖二磷酸羧化酶和蔗糖磷酸合成酶活性增强.[结论]铁素改善了甜菜光合性能,为块根生长和糖分积累奠定了物质基础.     

A Preliminary Study on Physiological and Molecular Effects of Iron Deficiency in Fuji/Chistock 1

In order to get experimental data on apple rootstock with iron-efficient genotypes capable of improving scion resistance to iron deficiency, this experiment was conducted on the physiological and molecular characteristics of Fuji/ Chistock 1 (F/C) under different iron conditions and compared it to Fuji/ M. Baccata (F/B). F/C was less sensitive to iron deficiency than F/B. F/B showed chlorosis after 25 days under iron-deficient conditions, but F/C showed no phenotypic changes, even after 40 days. The shoot and leaf area growth of F/C were respectively 5cm and 1000 mm² higher than those of F/B, regardless of the iron-deficient or iron-efficient conditions. The young leaf chlorophyll and active iron of F/C were 5 SPAD and 5 mg kg^?1 higher than those of F/B, either in iron-deficient or iron-efficient conditions. The expression of YSL5 and CS1 showed the same pattern. The enhancement expression of iron transport genes may be one explanation for these findings.     

运用简单线性水库模型计算Pothwar黄土平原（巴基斯坦）磷灰石损失情况

Apatite is the dominant phosphorus （P） mineral in early stages of soil development, and its redistribution as labile forms under pedogenesis controls terrestrial bioavailability. Quantitative distribution of labile forms of P and apatite-P was examined in Pothwar Loess Plain, Pakistan where the degree of pedogenesis varied with relief. Four soil types, Typic Ustorthents （Rajar）, Typic Calciustepts （Missa）, Udic Calciustepts （Basal）, and Udic Haplustalfs （Guliana）, were sampled from three replicated locations at genetic horizon level. With the exception of total P value at surface, the mean total and apatite-P decreased towards the surface in Udic Haplustalfs and Udic Calciustepts where dicalcium and octacalcium phosphate increased toward surface. Iron （oxides and oxyhydroxides） adsorbed and occluded P forms were also in greater quantities in Udic Haplustalfs and increased toward the surface, whereas they were lowest and uniform in the Typic Ustorthents. Aluminum- and organic P correlated with soil organic matter. Apatite-P decreased exponentially with an increase in the sum of iron adsorbed and occluded P fractions, and fitted the equation M（x） =M0[1 - exp（-wx）] with r^2=0.996, where M（x） is the mean apatite-P concentration in solum, M0 is the apatite-P content in the loess sediments, x is the cumulative iron adsorbed and occluded P, and w is an empirical factor indicating the change rate of apatite-P in the loess. From the calculated apatite-P of 740 mg kg^-1 at the time of deposition, mean apatite-P loss was 60% in Udic Haplustalfs, 33% in Udic Calciustepts, 23% in Typic Calciustepts, and 8% in Typic Ustorthents. The transformation of soil P to labile forms was faster and deeper in level or slight depressions followed by gently sloping areas in wide plains, and was the least in the gullied land.     

Effect of P fertilizer reduction regime on soil Olsen-P, root Fe-plaque P, and rice P uptake in rice-wheat rotation paddy fields

In agricultural systems, it is vital to use limited yet optimal phosphorus(P) resources, because excessive P fertilizer application leads to the accumulation of P in soil, increasing the risk of environmental pollution and causing the waste and exhaustion of P resources. In a rice-wheat rotation system, omitting P fertilizer application in the rice-growing season is a good alternative;however, how this P fertilization reduction influences changes in P in the soil-root-aboveground system is unclear. In this study, after a seven-year rice-wheat rotation at the Yixing(YX) and Changshu(CS) sampling sites, China, compared with P fertilization in rice-and wheat-growing seasons(PR+W), reduced P fertilization(no P fertilizer application in either season, P0;P fertilization only in wheat-growing seasons, PW;and P fertilization only in rice-growing seasons, PR) did not result in substantial variation in crop biomass. The PW treatment did not reduce crop total P, root iron(Fe)-plaque P, and soil Olsen-P at three stages of rice growth(seedling, booting, and harvesting stages) at the YX and CS sites. In contrast, concentrations of soil Olsen-P, aboveground crop total P, and root Fe-plaque P decreased in the P0 treatment by 45.8%–81.0%,24.6%–30.9%, and 45.6%–73.4%, respectively. In addition, a significant negative correlation was observed between the root Fe-plaque P and crop biomass at the two sites. Significant positive correlations were also observed between root Fe-plaque P and root total P, crop total P, and soil Olsen-P. In addition, the results of a redundancy analysis revealed that soil alkaline phosphatase(ALP) played a major role in the supply of P in soil, and was closely associated with root Fe-plaque P. The results of this study will enhance the understanding of the changes in P in the soil-root-aboveground system, particularly under P fertilizer reduction regimes.     

波兰喀尔巴阡山麓漂白淋溶土中铁锰结核的分布、形态和化学组成研究

Iron and manganese oxides are common components of soils. They frequently occur in nodules constituting important soil sorbents and play a crucial role in a number of chemical reactions in the soil environment. In addition, the oxides are very sensitive to environmental changes (moisture, pH, Eh) constituting important indicators of soil-forming processes and water movement in the landscape. The objectives of the study were: i) to examine the distribution and size of Fe-Mn nodules in Albeluvisols containing a fragipan horizon; ii) to determine the morphology and chemical composition of the nodules, and iii) to estimate the effect of the fragipan horizon on water movement within the soil profile. An investigation was carried out on five soil profiles containing a fragipan horizon and classified as Fragic Albeluvisols within the Carpathian Foothills in Poland. In the Albeluvisols studied, the maximum concentration of Fe-Mn nodules occurred in the horizon lying directly on the fragipan horizon. This suggests that the pan acts as a natural barrier restricting water infiltration and leads to the seasonal development of a perched water table promoting redox processes. The most common are coarse (1--0.5 mm) and medium (0.5--0.25 mm) irregular Fe-Mn nodules showing a gradual boundary and undifferentiated internal fabric. Eluvial horizons contained also larger amounts of round and dense nodules with a sharp boundary, suggesting frequent oxidation and reduction. The fragipan horizon contained mainly irregular and soft nodules, suggesting longer saturation with water during the year. Concentrations of trace elements (Cu, Zn) and P were higher within Fe-Mn nodules than in the surrounding soil materials, showing that iron and manganese oxides adsorbed and immobilised these elements.     

苹果砧木新品种中砧1号

铁是植物生长的必需微量元素,缺铁导致苹果发生失绿症,生长结果受到影响.我国苹果主产区恰在缺铁区域范围内,因此,从丰富的苹果种质资源中筛选出铁高效型资源,通过育种手段选育出耐缺铁苹果砧木新品种,是解决苹果生产上因缺铁造成生长发育受影响、产量品质受损的根本性途径.1984年开始,本项目组从苹果属40个苹果树砧木种质资源中筛选铁高效基因型,发现小金海棠在Fe含量极低的条件下仍然能够正常生长,未表现出缺铁失绿症状,为铁高效型.随后,以小金海棠(Malus xiaojinensis Cheng et Jiang)实生苗为基础,建立小金海棠开放授粉杂交后代群体.1990年,从自然实生群体中初选出育种优系.经复选比较试验,选育出苹果无性系砧木中砧1号.中砧1号染色体数为四倍体(2n=4x=68),具有无融合生殖能力,去雄套袋坐果率85％以上.与苹果栽培品种嫁接亲和性好,苗干直立性好,固地性强,半矮化,矮化程度、提早结果作用及丰产能力均与苹果半矮化砧木M7相近.果实风味甜,适口性好,品质极佳.抗苹果早期落叶病和枝干轮纹病,高抗苹果褪绿叶斑病毒(CLSV)、茎痘病毒(SPV)及茎沟槽病毒(SGV)等潜隐病毒.在石灰母质土壤地区用作苹果自根砧木,可有效避免缺铁黄化现象的发生.