CeO2纳米颗粒催化柴油燃烧氧化特性分析

为了深入了解柴油中添加Ce O2纳米催化剂后生成颗粒的氧化特性,该文配制了Ce O2质量分数分别为0、50、100 mg/kg的纳米催化燃油,利用微粒分级采样装置采集柴油机燃用3种燃料生成的颗粒样品,采用扫描电镜研究了Ce O2质量分数对颗粒形貌特征的影响,通过热重分析方法研究了升温速率、Ce O2质量分数对颗粒氧化特性的影响并采用Coast-Redfern方法计算了颗粒的活化能。结果表明:颗粒群为团簇状结构,粒径范围在20~70 nm之间;随着Ce O2质量分数增加,颗粒平均粒径减小,粒径向小粒径方向移动,计盒维数增大。随着升温速率的增加,颗粒氧化过程出现滞后现象,氧化反应区域变宽,初始氧化温度、峰值失重温度和氧化终止温度增高,失重率峰值变小。升温速率对颗粒反应活化能影响较小。升温速率相同时,随着Ce O2质量分数的增加,颗粒的反应活化能、初始氧化温度、峰值失重温度和氧化终止温度均降低,Ce O2质量分数越高,降幅越大。Ce O2纳米催化剂添加到柴油后,使颗粒粒径变小,并能促进颗粒的氧化,降低颗粒起燃温度,可有效降低柴油机微粒捕集器(diesel particulate filter,DPF)再生温度和延长再生周期,对柴油机排气净化具有重要的意义。     

纳米燃油添加剂CeO2提高柴油燃烧效率减少排放

研制新型高效燃油添加剂已成为控制发动机燃烧与排放的重要课题,纳米CeO2颗粒因其独特物理化学性质使其在催化燃烧和尾气净化领域具有独特的作用.通过向柴油中添加微量纳米CeO2颗粒,配制成质量分数为50 mg/L和100 mg/L的CeO2-柴油混合燃料,标记为D50C和D100C,以柴油(Diesel)为参照,并在186FA柴油机上对比研究了这3种燃料的燃烧与排放性能.结果表明:通过加入表面活性剂CTAB和超声处理物理化学方法可使纳米CeO2颗粒稳定悬浮于柴油中.标定转速全负荷下发动机燃用D50C和D100C后缸内压力峰值、压升率峰值和放热率峰值都有略微增加的趋势,而其对应的曲轴转角相应提前,滞燃期分别相应缩短1 o和2o曲轴转角.发动机燃油D50C和D100C后燃油消耗率略有降低,有效热效率有所增加.纳米CeO2颗粒添加至柴油中4种常规污染物都有不同程度的降低,且随其添加量增加越发明显.相比于纯柴油,标定转速全负荷下,D50C和D100C的比油耗分别降低约1.6%和2.3%,有效热效率分别增加约1.7%和2.3%.D50C和D100C的CO、HC、NOx和烟度排放平均分别降低3.4%和6.5%、15.1%和18.4%、2.4%和5.4%、4.0%和7.8%.D50C和D100C混合燃料的成本分别比柴油上升约0.8%和1.6%.综合来看,微量添加纳米CeO2颗粒可在略微增加燃油价格的前提下,即可实现发动机的高效燃烧与节能减排,因而是一种性能优良的燃油添加剂.     

柴油机双卷流燃烧室内外室燃油匹配分析

为了分析双卷流燃烧室内室燃油质量分数对发动机性能的影响,研究了双卷流燃烧室最佳的内室燃油质量分数范围。首先利用AVL Fire软件仿真计算不同油束夹角下双卷流燃烧室内室燃油质量分数变化,分析内室燃油质量分数变化对发动机的动力性和排放性能的影响,发现内室燃油质量分数约为10%~20%时,发动机指示功率较高,碳烟排放较低。然后总结归纳了内室燃油质量分数随喷油提前角和转速变化的规律。转速增大,内室燃油质量分数减小;喷油提前角增大,内室燃油质量分数增大。研究表明转速提高时,适当增加喷油提前角可以保证内室燃油质量分数处于较优值,使柴油机取得较佳性能。该研究可为双卷流燃烧系统的燃油匹配提供参考。     

鸡白细胞介素2（IL-2）DNA-壳聚糖纳米粒的制备及体外转染

构建了携带鸡白细胞介素2(IL-2)编码基因的重组真核表达质粒,通过复凝聚法制备了含有该重组真核表达质粒的壳聚糖纳米粒子.对制备的IL-2DNA-壳聚糖纳米粒子(IL-2 DNA-chitosan nanoparticles)进行了表征.纳米粒子呈球形,粒径分布范围为50～500nm,表面带正电,电势为+17.8mV,DNA质量占纳米粒子总质量的40.2%.DNA酶保护性、稳定性和体外释放试验证明,制备的纳米粒子在微酸性(pH 6.0)和微碱性(pH 7.4)环境中稳定性较高,可保护携带的DNA分子不被0.6～0.8U/mL DNA酶的降解.用制备的纳米粒子转染Df-1细胞系,间接免疫荧光检测结果证明,该纳米粒子可携带质粒DNA进入细胞,使携带的外源基因获得表达.流式细胞术检测证明,纳米粒子的转染效率为0.2%,与裸DNA转染对照组相比较,包封入壳聚糖纳米粒子中可提高DNA的转染效率.     

催化剂存储还原柴油机NO_x排放的试验

为了验证NSR催化剂对柴油机NOx排放的存储还原性能,该文采用浸渍法制备了一系列NSR催化剂:x Ce(25-x)Ba/γ-Al2O3(x为质量分数,且x=8~12)和Pt10Ce15Ba/γ-Al2O3催化剂,并利用X射线衍射、扫描电子显微镜、能谱仪和透射电子显微镜对其性能进行表征;通过台架试验,研究了10Ce15Ba/γ-Al2O3和Pt10Ce15Ba/γ-Al2O3催化剂对NOx排放的存储还原性能。结果表明,Ba O和Ce O2的粒径变化范围为5~20 nm。随着x值增加,Ce O2晶粒尺寸变大且分散性变差;当x=10时,Ba O晶粒尺寸细小且分散性最好。当柴油机负荷低于50%时,10Ce15Ba/γ-Al2O3催化剂对NOx主要以吸附为主,NOx脱除率最高达80%;当柴油机负荷高于50%时,NOx开始脱附并被还原成N2,NOx脱除率最高为60%。与10Ce15Ba/γ-Al2O3催化剂作用相比,Pt10Ce15Ba/γ-Al2O3催化剂对NOx的吸附和脱除性能较好,其中柴油机负荷低于50%时,NOx脱除率接近100%,柴油机负荷高于50%时,NOx脱除率最高为75%。研究结果对NSR催化剂的开发以及在排放后处理领域的应用具有指导意义。     

葵花籽壳纳米纤维素制备工艺优化及其表征

为了充分利用葵花籽的工业生产副产物,该文以葵花籽壳为原料,采用硫酸水解法制备葵花籽壳纳米纤维素。通过单因素试验研究了酸解温度、酸解时间、硫酸质量分数和液料比4个因素对纳米纤维素得率的影响,应用响应面法对工艺参数进行优化,并对制备得到的纳米纤维素进行了透射电镜(transmission electron microscopy,TEM)、红外光谱(Fourier transform infrared spectroscopy,FT-IR)和X-射线衍射(X-ray diffraction,XRD)等分析。结果表明:当酸解温度为42℃、酸解时间为83.71 min、硫酸质量分数为59.97%、液料比为12.33:1时,预测得出纳米纤维素得率为31.67%,验证试验纳米纤维素得率为31.31%。制备的葵花籽壳纳米纤维素呈棒状,直径为10~30 nm,长度为150~300 nm,仍然具有纤维素的基本化学结构,结晶度较高,属于典型的纤维素Ⅰ型结晶结构。该文研究结果可以为葵花籽的综合利用提供参考。     

纳米二氧化硅/纳米纤维素复合材料制备及性能分析

使用造纸方法快速成功的制备了纳米纤维素,纳米二氧化硅复合材料,对并材料的力学性能,热性能和吸湿性能进行了分析。研究结果表明:随着纳米二氧化硅的添加量逐步提高,纳米复合材料的理论密度逐渐下降,材料的拉伸性能和模量值都有大幅度的下降。材料热解的初始降解温度和热解活化能随着纳米二氧化硅质量分数的增多提升,当纳米二氧化硅质量分数为20%时,材料初始热解温度为280℃。纳米复合材料的含水率随着吸湿时间的延长而增加,且随着纳米二氧化硅添加量的增多,材料的最终含水率不断提高,当纳米二氧化硅质量分数为20%时,纳米复合材料的最终含水率约26%,纳米复合材料的表面接触角值仅为40.4°。该研究结果可为制备了纳米纤维素/纳米二氧化硅复合材料提供参考。     

新农药甲硫嘧磺隆的醇解动力学及机理研究

甲硫嘧磺隆,试验代号为HNPC-C9908,化学名称为2-（4-甲氧基-6-甲硫基嘧啶-2-基）氨基甲酰基氨基磺酰基苯甲酸甲酯,是我国具有自主知识产权的新型磺酰脲类除草剂,主要用于麦田杂草的防除。采用HPLC和LC/MS研究了甲硫嘧磺隆的醇解动力学及其机理。结果表明,甲硫嘧磺隆在甲醇和乙醇中可发生快速的醇解反应,并可用一级动力学方程很好描述,其醇解半衰期分别为10.6和11.6 d,说明醇解反应可能是磺酰脲类化合物的普遍特征之一。甲硫嘧磺隆的醇解反应因温度、pH值、甲醇含量以及有效成分浓度而异。甲硫嘧磺隆的醇解速率随温度升高而加快,其在15、25、35和45 ℃等4个温度下的醇解半衰期分别为41.0 d、10.6 d、3.8 d和13.0 h,温度效应系数为28.06;甲硫嘧磺隆醇解反应的活化能和活化焓与温度之间无明显相关性,其平均活化能和活化焓分别为186.28和183.71 kJ·mol^-1,而活化熵绝对值则随温度升高而增加,表现出良好的相关性,其平均活化熵为－11.28 kJ·mol^-1·K^-1,说明甲硫嘧磺隆的醇解主要为双分子亲核取代反应;甲硫嘧磺隆在酸性醇液中的降解速率明显快于中性和碱性醇溶液中的降解速率,其在pH5、7和9的甲醇液中的醇解半衰期分别为6.8、172.2和109.5 d;当甲醇含量为40%、50%、60%、70％、80％、90％和100％时,甲硫嘧磺隆的降解半衰期为27．8、30．7、30．1、43．3、42．5、43．9和10．6d,而在纯水中的半衰期为29．4d;在浓度较低（5mg·L^-1）时,甲硫嘧磺隆的醇解速率较慢,其醇解半衰期为32．2d,而当增加到10和20mg·L^-1时,对甲硫嘧磺隆的醇解速率影响不大。甲硫嘧磺隆醇解的主要途径是分子中脲桥裂解生成2-苯甲酸甲酯基磺酰基氨基甲酸酯和2-氨基-4-甲氧基-6-甲硫基嘧啶。     

纳米氧化锌改性LDPE食品包装薄膜中锌粒子的迁移规律

为探究纳米氧化锌改性(low-density polyethylene,LDPE)薄膜中纳米锌粒子的迁移规律,依照欧盟法规(EU)No.10/2011,分别采用蒸馏水、30 g/L乙酸溶液、体积分数10%的乙醇溶液、体积分数95%的乙醇溶液作为中性、酸性、脂肪性和酒精性食品模拟物,研究在不同温度条件下(40、70℃)纳米锌粒子的迁移情况,同时探究微波和紫外处理对迁移结果的影响。研究发现,纳米锌粒子在4种食品模拟物中的迁移量从高到低依次为:酸性食品模拟物、中性食品模拟物、酒精性食品模拟物和脂肪性食品模拟物,并且随温度的升高,纳米锌粒子的迁移量增大。此外,微波处理能促进纳米锌粒子的迁移,而紫外处理则没有促进效果。纳米锌粒子的迁移量范围为0.52~14.17 mg/kg。根据欧盟规定所允许的最大迁移量5 mg/kg,迁移试验表明纳米氧化锌改性LDPE薄膜还需要进一步开展减少纳米粒子迁移的研究工作,以确保其在食品包装中的安全使用。     

沼液负压蒸发浓缩装置的设计与试验

为了解决沼液浓缩过程中有效成分流失的问题,采用低温负压蒸发浓缩的方法,结合沼液的理化性质,对沼液负压蒸发浓缩装置的主体部分(蒸发罐)和辅助设备(冷凝器、循环液槽、真空泵)分别进行了参数设计计算和设备选型,并在自制20 L负压蒸发浓缩装置上进行了系列试验。试验结果表明:当温度低于80℃时,沼液的有机质含量基本不变,蒸发温度高于80℃之后,有机质含量明显下降,80~100℃的变化率为9.4%;随着温度的升高,氮磷钾含量不断下降,氮含量流失最大,最大变化率为13%。蒸发浓缩后的沼液中有机质和氮磷钾含量随真空度的增大而升高;随着真空度的升高,沼液的蒸发温度逐渐降低,蒸发量不断增大,绝对真空度为0.025 MPa时,最低蒸发温度为67℃,蒸发量最高能达到8 324 m L/(m2·h),蒸发率为28.75%;绝对真空度维持在0.04 MPa到0.05 MPa之间,温度在75~80℃时,蒸发量能达到7 700 m L/(m2·h),蒸发率为26%左右。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.