冷链专用蓄冷托盘设计与控温运输性能测试

目前蓄冷冷藏运输车普遍采用车体和蓄冷装置一体化设计,存在重心偏高、控温范围窄、蓄冷剂充注量与运输时间难以合理匹配等问题。基于此,该文设计并建造一款集标准托盘、蓄冷槽、蓄冷盒等装置于一体的冷链专用蓄冷托盘。蓄冷托盘适用于包括仓储、运输装备在内的全程冷链环境,该设备采用分体式设计,运用时利用夜间低谷电充冷,相变材料（Phase Change Material,PCM）种类和质量可根据运输货物实际情况灵活搭配。从而达到按需蓄冷、灵活控温、降低重心、节能降耗等多重目标。试验结果表明,使用水凝胶为PCM,质量为100、200、300 kg时,车厢控温时间可达1～3 d,基本满足中短途冷藏运输需要。同时,循环通风可将车内平均温度由9.3、6.9、6.7 ℃降至5.7、4.6、3.3 ℃。在车厢温度均匀性方面,无循环通风时,车厢温度场水平分层严重,截面间最高温差分别为2.8、2.8、3.2 ℃,截面内最大温差4.2、4.1、6.6 ℃;循环通风后,截面间和截面内最大温差分别降至0.4、0.4、0.5 ℃和0.8、0.9、0.7 ℃,降幅分别为85.7%、85.7%、84.4%和81.0%、78.0%、89.4%。与传统蓄冷冷藏车（300 kg PCM）相比,温度绝对不均匀度系数由2.5下降至1.2,下降52.0%;车厢重心高度由1.46 m下降至0.77 m,车厢重心下降47.3%。研究可为冷链节能低碳发展提供借鉴,为蓄冷冷藏运输装备拓展应用及优化设计提供参考。     

蓄冷保温箱真空隔热蓄冷控温传热模型与验证

为掌握不同参数对蓄冷控温特性的影响,建立了真空隔热蓄冷控温试验平台,以脐橙为试验对象,根据热平衡理论,建立蓄冷控温传热数学模型,并进行试验验证,进一步分析了不同参数对蓄冷控温特性的影响。数学模型计算结果表明,随着真空隔热板厚度的增加,在0~8℃温度的控温时间越长;当外界恒温30℃、真空隔热板厚度为25 mm时,0~8℃温区控温时长为106.14 h。试验结果表明,模型计算结果与试验结果吻合,控温时长平均误差为2.60%;当外界平均温度为33.5℃、真空隔热板厚度为20 mm、有太阳辐射时,在30 min内试验平台内温度由29.5℃降至7.2℃,降温速度较快。应用数学模型分析不同参数影响,结果表明:不同车速对传热速率的影响不显著;传热速率随着真空绝热板厚度的增加而下降,下降趋势呈指数变化;相同控温时长时,所需蓄冷剂质量与真空绝热板厚度呈指数变化;真空绝热板越厚,温度下降速率越快;太阳辐射会使控温时长缩短13.79%。该研究结果为蓄冷控温型运输装备的结构优化设计及蓄冷剂的选型、用量提供一定的参考价值。     

纳米复合相变蓄冷材料的制备及蓄冷特性分析

针对生鲜冷链物流领域冷藏运输温度要求,通过差示扫描量热仪（DifferentialScanning Calorimeter,DSC）对甘氨酸、山梨醇、甘露醇、氯化钾进行筛选,经优化后配置出主储能为0.6mol/L甘氨酸+0.1mol/L山梨醇（命名为TA2）,以此体系为基液添加纳米二氧化钛和纳米氧化铝,并添加高吸水性树脂（Super Absorbent Polymer,SAP）对防泄漏现象进行优化,探究添加纳米粒子后复合相变蓄冷材料的相变潜热和热循环稳定性。将该复合材料应用于自制保温箱,以水晶梨为试验对象进行了蓄冷箱保冷特性试验,对比蓄冷保温箱载货与空载情况下箱内各点的温度变化,综合考虑蓄冷保温箱内蓄冷剂侧面布置和顶层布置加侧面布置这两种摆放方式对保冷性能的影响。结果显示,添加质量分数为0.5%的纳米二氧化钛粒子可使基液的导热系数达到最大值,经优化的最终材料为TA2+0.5%TiO2 + 0.25%SAP,相变潜热为294.57 J/g,Onset温度为-5.8 ℃,经过200次循环试验,复合材料热性能稳定。蓄冷剂以侧布加顶布的摆放方式下的大部分箱内空间平均温度为1.9 ℃,可在0～5 ℃保持480 min,温度场更均匀,利于保持生鲜产品新鲜度。研究结果为相变材料在生鲜冷链物流中的研制及应用提供参考。     

基于多参数耦合的蓄冷温控箱冷板对流换热参数优化

蓄冷温控箱利用低温相变材料储存冷量,通过缓慢释放调节并保持箱内温度,目前仍存在冷量释放速率无法控制、剩余冷量预测难等问题,而蓄冷板表面对流换热系数直接影响冷量的释放速率。针对以上问题,搭建了蓄冷板表面对流换热系数测量试验平台,研究不同环境及蓄冷板参数对表面对流换热系数的影响。采用二次回归正交试验设计方案,探究了蓄冷区进口空气流速、进口空气温度、蓄冷板传热面积以及蓄冷板间距对表面对流换热系数的影响,并对结果进行分析,建立了表面对流换热系数二阶预测模型,获得影响表面对流换热系数大小较显著的因素及较优的参数组合。试验结果表明：各因素间存在明显交互作用,进口空气温度和蓄冷板传热面积的交互效应最大;通过响应曲面法建立的表面对流换热系数预测模型,得到最优参数组合为：进口空气流速4 m/s,进口空气温度25 ℃,蓄冷板传热面积0.455 m2,蓄冷板间距0.04 m,R2值为0.927 4,变异系数CV为5.78%。回归模型计算结果与试验结果吻合,最大误差为3.58%,平均相对误差为2.69%,表明该模型可以快速、准确地预测不同条件下的蓄冷板表面对流换热系数。试验结果为蓄冷温控箱冷量释放速率精准调控及剩余冷量预测提供参考。     

冷藏车温度场不均匀度对蔬菜保鲜效果的影响

为了提高在冷藏运输过程中果蔬的品质,研究了冷藏车厢内部的温度场。冷藏车内合理的温度场,可以保证冷量的均匀分配,节约能耗,降低干耗及冻害损失,提高果蔬保鲜质量。该文以质量损失率、细胞膜渗透率、维生素C含量和叶绿素含量的变化作为评价指标,对不均匀度分别为3.71、5.68和8.36的温度场中贮藏的3种蔬菜(娃娃菜、尖椒和金针菇)品质的变化情况进行比较。结果表明,冷藏车内温度场的均匀程度与果蔬保鲜的效果成正比关系,不均匀度较低的温度场中贮藏的果蔬保持了较好的新鲜度。该文研究为冷藏车的优化设计提供了参考依据。     

基于热管的自然冷源制冰技术方案的初步试验(简报)

中国北方地区每年有4个月的时间日平均温度在-10℃以下,为了充分利用冬季的自然低温制冰作为贮藏的冷源,设计了一种热管式制冰装置,利用冰箱模拟低温天气环境,研究了风速和温度对结冰效果的影响。试验结果表明:所设计的热管式制冰装置不需消耗额外能源即可成功制冰;当风速在0～2.5m/s范围变化时,结冰厚度增大,在温度为-11℃条件下,冰层直径最大可达75mm;温度越低,结冰厚度越大。     

不同贮藏温度下养殖大黄鱼货架期预测模型的构建

为探讨不同温度范围内导致产品腐败的原因和开发货架期预测模型,通过对低温(0～10℃)、室温(25℃)和变温贮藏下养殖大黄鱼感官、理化和微生物质量指标和细菌种群的研究,确定上述温度条件下的货架期和特定腐败菌,开发出3种货架期预测模型,并用恒温和波动温度下的货架期进行验证。结果表明,养殖大黄鱼低温下的货架期为5.4～17.8d,特定腐败菌为腐败希瓦氏菌和假单胞菌,室温下货架期仅1.1d,特定腐败菌为弧菌和肠杆菌。依据相对腐败速率与温度的相关性,开发出Exponential、School-field和Square-root货架期预测模型,模型参数表观活化能Ea、最小温度Tmin和温度特性系数a分别为74kJ/mol、-10℃和0.11,并用3、7、10℃恒温和变温下的货架期对模型进行验证,相对误差分别为0%～13.8%、-0.9%～9.8%和-0.2%～-22.1%,表明School-field和Exponential货架期模型性能优于Square-root货架期模型,能快速有效预测0～25℃范围的大黄鱼品质。该文将为进一步研发集包装、贮藏和流通等为一体的水产品品质智能化预警系统提供依据。     

日光温室平板微热管阵列蓄热墙体热性能试验

为提高日光温室复合结构墙体热稳定层的温度并提升温室墙体材料的蓄热性能,该研究提出一种新型日光温室平板微热管阵列蓄热墙体(Micro Heat Pipe Array,MHPA),搭建了小型MHPA墙体温室试验台,采用对比试验的方法,结合温室墙体温度、墙体蓄放热量以及温室环境温度等评价参数,对比分析了典型日MHPA墙体的蓄放热特性及其改善温室热环境效果。结果表明,与普通温室相比,冬季典型晴天,放热时段(17:00至次日9:00)MHPA墙体内表面平均温度提高1.6～2.3℃,由室内向室外沿墙体厚度方向0～370 mm区域内MHPA墙体内部的平均温度提高2.7～4.0℃;MHPA温室的平均温室环境温度提升1.2～1.5℃,地表面平均温度提升0.6～1.0℃;MHPA墙体的日总蓄热量提高了8.93%～14.35%,日总放热量提高了2.24%～8.07%,且在夜间23:00至次日7:00 MHPA墙体的放热速率高于普通墙体的,平均提升11.53%。因此,MHPA墙体引入于日光温室墙体中可提升温室墙体材料的蓄放热性能,改善温室热环境。该结果可为日光温室平板微热管阵列蓄热墙体的应用提供参考。     

基于空载温度场模拟与试验的冷藏车冷板布置方式优选

该文通过计算流体力学(computational fluid dynamics,CFD)对常见的3种不同冷板布置方式(冷板顶置、冷板侧置、冷板部分顶置部分侧置)下的空载冷藏车厢内温度场进行了10 h的非稳态数值模拟研究。结果表明:在10 h的非稳态模拟研究中,在车厢高度方向上由上往下,空气温度都呈现逐渐上升的趋势;在车厢长度方向上,靠近车厢中心的区域空气温度更低。壁面附近空气温度较高,温度梯度较大。其中,在冷板侧置的方式下,厢内整体温度较低,各测点温度在-9.5~-7℃范围内,且温度均匀性较好;在冷板部分顶置部分侧置的方式中,各测点温度在起始阶段温差较大,在末段温差有所缩小,最终各测点温度为-9~-7.2℃,测点整体温度与温差稍好于冷板顶置的方式。同时,冷板侧置的方式下,车厢的可用空间较小;冷板顶置的方式的可用容积较大,但是冷板布置于车厢顶部,充注共晶液后会导致车辆重心的上升,降低了冷藏车在运行时的稳定性;冷板部分顶置部分侧置的方式可用空间及重心介于冷板侧置的方式与冷板顶置的方式之间。综上所述,考虑到冷板侧置的冷板布置方式对货物的影响,优先选用冷板部分顶置部分侧置、冷板顶置的方式。综合考虑冷板布置方式对货物的影响,冷藏车厢内可用容积、冷藏车厢的重心高度等因素,研制了2种不同冷板布置方式的冷板冷藏车厢,对车内的温度场进行空载试验,结果表明冷板部分侧置、部分顶置的方式较为合理。同时经过10 h的试验,实测温度与模拟仿真温度的平均偏差为0.9℃,绝对误差在2.5℃以内,说明计算模型可以用于冷藏车厢内温度场的模拟。研究结果可为优化冷板冷藏车的冷板布置方式提供依据。     

不同冷链物流过程对金枪鱼品质及组织形态的影响

为研究物流过程中温度变化对金枪鱼品质及组织形态的影响,试验模拟5种不同物流过程,测定金枪鱼肉感官、色差、持水力、质构以及肌纤维间隙。结果表明,超低温冻藏大目金枪鱼肉的品质受物流过程中温度变化影响显著,储运、销售过程始终保持在-55℃的完整冷链下能够使金枪鱼肉保持良好品质;随着储运过程中温度变化次数增多、幅度增大,鱼肉劣化显著,其中,经2次-18℃运输的金枪鱼肉在冻藏末期组织松散、肌纤维间隙达17.20μm,在4℃家用冰箱中贮藏12 h后感官评分、红度值、持水力、硬度和咀嚼性分别为-0.81、5.2、53.08%、1.128 N和58.03,其质量甚至低于物流过程始终保持在-18℃而不产生温度变化的鱼肉。若运输过程不具备超低温冷藏车,仅靠超低温贮藏并不能减缓鱼肉品质劣变,此时应适当调节贮藏温度,尽量避免储运期间的温度变化;相较于2℃冷藏销售,-18℃冷冻柜销售能够使金枪鱼肉保持较好品质。研究结果可为金枪鱼储运和销售提供参考。     

“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.     

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.     

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.     

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.