有机肥施用对土壤铜形态的影响研究

选取以猪粪为原料的商品有机肥,通过室内培养试验,采用BCR连续萃取法,研究了不同用量、含不同Cu浓度、不同Zn浓度有机肥的施用对土壤Cu形态变化的影响。选取15,30,45 Mg/hm2 的施肥量进行对比,发现增施有机肥使土壤Cu的氧化物结合态显著减少,有机结合态显著增加,土壤中Cu的活性态含量总体减少。Cu浓度较高的有机肥施入土壤后,使土壤Cu的酸提取态和有机结合态明显增加,增强了土壤Cu的活性。土壤中Cu、Zn的交互作用体现了两种元素对土壤不同组分吸附的竞争优势,相对来说Cu与土壤有机物的亲和力更强,Zn浓度升高能置换出土壤中氧化物结合态Cu。     

不同内源重金属生物炭对Cu和Cd吸附及其对老化作用的响应

为明确老化作用对不同内源污染物生物炭吸附重金属稳定性的影响，该研究以不同污染程度（清洁、中度和重度污染）土壤种植的巨菌草秸秆制备3种不同内源Cu和Cd含量的生物炭RB、SB和JB，分析3种生物炭对Cu和Cd的吸附能力以及干湿和冻融老化对饱和吸附后生物炭中Cu和Cd的生物有效性的影响。结果表明：3种生物炭表面均分布丰富的孔隙结构，RB含有最高的pH值和灰分；生物炭对Cu和Cd的吸附符合Langmuir模型（R2=0.951～0.998），且RB对Cu和Cd的吸附量最大，分别为54.3和37.3 mg/g；与此相同，饱和吸附后RB对Cu和Cd的固持量最大，分别为21.4和4.78 mg/g。与老化前相比，干湿老化较冻融老化更显著地降低了饱和吸附后生物炭中Cu的TCLP浸出含量，促进了Cu从酸溶态和残渣态向还原态和氧化态转化，降低了Cu的环境风险；但是干湿和冻融老化作用增加了饱和吸附后生物炭中Cd的TCLP浸出含量，促进了Cd从残渣态向酸溶态、还原态和氧化态转化，增加了Cd的环境风险。这可能是由于3种生物炭对Cu的吸附主要以表面络合为主，对Cd的吸附以化学沉淀机制为主。总体上，RB生物炭固持最高的Cu和Cd，但是干湿和冻融老化增加了饱和吸附后生物炭Cd环境风险，研究结果对于评估生物炭长期钝化修复稳定性具有一定的指导意义。     

不同有机肥中Cu、 Zn在农田土壤中的有效性与形态归趋

【目的】畜禽粪便有机肥的施用是造成我国农田土壤重金属污染的重要原因之一。本文选用两种典型规模化养殖场畜禽粪便有机肥,研究其在石灰性土壤和酸性土壤上施用1年后Cu、 Zn的有效性和形态归趋,为客观评价畜禽粪便有机肥中重金属进入土壤后的环境行为和生态风险提供理论依据。【方法】采用温室土壤培养试验,在石灰性土壤和酸性土壤上分别设对照(CK)、 施2%鸡粪(CM2%)、 施5%鸡粪(CM5%)、 施与CM2%、 CM5%含等量Cu、 Zn的重金属无机盐溶液(CS2%、 CS5%)、 施2%猪粪(PM2%)、 施5%猪粪(PM5%)、 施与PM2%、 PM5%含等量Cu、 Zn的重金属无机盐溶液(PS2%、 PS5%)9个处理,每个处理设3次重复,在温室条件下培养1年。测定土壤pH值, EDTA提取有效态Cu、 Zn以及采用改进Tessier连续提取法提取的各形态Cu、 Zn的含量,分析鸡粪、 猪粪及等量无机盐溶液中Cu、 Zn进入土壤后的有效性和形态归趋。【结果】施用鸡粪和猪粪1年后,石灰性土壤的pH值降低,酸性土壤的pH值升高,施用5%猪粪时石灰性土壤pH值降低了0.23个单位,酸性土壤pH值升高了0.87个单位。施入鸡粪、 猪粪1年后,石灰性土壤中有效态Zn和酸性土壤中有效态Cu、 Zn含量显著增加,施用5%猪粪时酸性土壤中有效态Cu含量增加了1.95倍,施用5%鸡粪时2种土壤中有效态Cu的含量均显著低于等量无机盐。施用鸡粪和等量无机盐后,2种土壤中交换态和有机结合态Cu的含量显著增加,交换态、 碳酸盐结合态、 有机结合态和铁锰氧化物结合态Zn的含量显著增加; 施用猪粪和等量无机盐后,2种土壤中交换态、 铁锰氧化物结合态和有机结合态Cu的含量显著增加,碳酸盐结合态和铁锰氧化物结合态Zn的含量显著增加。【结论】施用鸡粪、 猪粪提高了石灰性土壤中Zn和酸性土壤中Cu、 Zn的有效性,高用量条件下鸡粪中Cu的有效性低于等量无机盐。1年后, 通过畜禽粪便有机肥带入2种土壤中的Cu 主要以交换态和有机结合态的形式存在,Zn则主要以碳酸盐结合态、 铁锰氧化物结合态和有机结合态的形式存在。2种土壤上有机肥带入的Cu、 Zn转化为铁锰氧化物结合态的比例低于等量无机盐,2种有机肥带入2种土壤中的Cu转化为交换态和有机结合态的比例高于等量无机盐。鸡粪带入的Zn转化为交换态的比例在酸性土壤中低于等量无机盐,但在石灰性土壤中则高于等量无机盐。     

基于TCLP法研究纳米羟基磷灰石对污染土壤重金属的固定

通过室内培养试验,研究了纳米羟基磷灰石对土壤重金属的固定和修复,并通过毒性溶出试验TCLP（Toxicity Characteristic Leaching Procedure）对同定效果进行了评价。结果表明,纳米羟基磷灰石的施入显著降低了土壤中Cu和Zn的生物有效性,而且土壤中Cu和Zn有效态的含量与纳米羟基磷灰石的施用量呈显著负相关。其主要原因为纳米羟基磷灰石的水解释放大量OH^-离子,导致土壤pH增加;此外纳米羟基磷灰石吸附固定重金属进而降低了土壤中重金属的有效性。包施不如同等材料用量混施的钝化效果好,且所用时间较长,但包施具有将所施材料和被吸附重金属移出土壤体系的优点。     

喀斯特林地土壤重金属形态特征及其评价

通过野外调查与室内分析,对喀斯特林地土壤重金属全量及形态构成进行了调查,对土壤重金属污染及其生物有效性进行了评价,并探讨分析了土壤重金属与土壤pH值的相关性。结果表明:中性土壤As,Cd,Cu,Ni,Pb,Zn及Cr全量均大于酸性土壤的全量;As以酸溶态为主,Cd,Cu,Ni,Pb,Zn及Cr以残渣态为主,残渣态土壤重金属比例为中性高于酸性土壤;酸性和中性土壤重金属Pb全量、中性土壤的As和Cu全量均高于贵州土壤背景值;中性和酸性土壤重金属As,Cd和Ni全量及酸性土壤重金属Cu全量超过土壤环境质量二级标准值;酸性土壤为轻度污染,中性土壤为中度污染;重金属生物有效性表现为AsCdCrNiPbZnCu,酸性土壤As生物有效性指数最高,与中性土壤相比,酸性土壤重金属生物有效性高;Cu全量、可氧化态Pb、残渣态Cu与pH值呈极显著正相关,酸溶态Zn与pH值呈极显著负相关,酸溶态Cr与pH值呈显著负相关,残渣态As与pH值呈显著正相关。喀斯特林地土壤主要受到As,Cd,Cu,Ni这4种重金属的影响,除As外,其余3种元素属于"高背境,低活性"状态。     

培养条件下生物炭对土壤锌的吸附作用

将稻壳分别在350℃和550℃热解温度下制备成生物质炭,按土壤质量的1%、3%和5%的添加量施入土壤中,保持一定的土壤含水率,探究施入生物炭的土壤对重金属锌吸附的影响。结果表明,土壤中施入生物炭之后,会提高土壤对重金属的吸附固定能力,生物炭的添加量越高,土壤对锌的最大吸附量越大。在试验开始阶段,随着生物炭的老化,土壤对锌的吸附性能会增强,同时土壤对锌的解吸率降低,随着时间的延长,生物炭与土壤发生的共腐殖化过程,导致土壤对锌的吸附性能逐渐降低,同时土壤对锌的解吸率提高。     

秸秆生物质炭吸附溶液中Cu2+ 的影响因素研究

生物质炭在吸附土壤中重金属和有机污染物方面发挥着重要作用,然而关于生物质炭吸附重金属的影响因素研究较少。以小麦和玉米秸秆为原料制备生物质炭,分析了生物质炭和溶液性质对水溶液中Cu2+吸附的影响。结果表明生物质炭可有效吸附Cu2+,且不易解吸。Cu2+吸附量随pH和Cu2+初始浓度的升高而增加;高温炭对Cu2+的吸附随离子强度增强而增大;柠檬酸抑制低温炭对Cu2+的吸附,而腐植酸促进Cu2+吸附;生物质炭灰分对Cu2+吸附无显著影响。     

煤矸石酸性水释放对土壤重金属化学行为的影响

利用微波消解法和Tessier的5步连续提取法分析测定了韩城燎原矿区高硫煤矸石堆放场不同深度土壤的9种重金属含量和不同赋存形态,并结合重金属分配系数分析了它们的释放迁移能力。结果表明,堆放场土壤重金属As、Cd、Cr、Cu、Ni、Pb、Sn、V、Zn的均值皆超过远离堆放场土壤背景值和中国土壤背景值,其中以As、Cd、Zn为最显著。在不断接受煤矸石堆放场雨水淋溶释放的酸性水入渗条件下,污染土壤中重金属的生物有效性和迁移性为:CdZnNiSnPbCuAsCrV。由于受到土壤含水率和有机质的影响,在土壤40—60cm范围内,重金属Cd、Cr、Cu、Ni、Pb、Zn释放迁移能力为最弱。酸性水入渗对As、Cd释放迁移能力影响较小,而对Cd释放迁移能力影响较大。     

大豆秸秆生物炭对铅锌尾矿污染土壤的修复作用

采用盆栽空心菜的方法,研究了大豆桔杆生物炭对铅锌尾矿污染土壤的修复作用。污染土壤中Cu、Zn、Pb和Cd含量分别为50,400,1 119,3.4mg/kg。结果表明:土壤无论是否受到铅锌尾矿污染,添加3%生物炭(w/w)均能显著提高土壤pH;3%生物炭能够抑制铅锌尾矿污染导致的土壤pH降低。大豆桔杆生物炭对尾矿污染土壤和未污染土壤中重金属有效态的影响不同,与未污染土壤相比,3%生物炭的钝化作用不能抵消铅锌尾矿污染导致的重金属有效态含量的增加。铅锌尾矿污染抑制空心菜生长;施加3%生物炭可以消除铅锌尾矿污染对空心菜生长的抑制作用。生物炭显著降低污染土壤空心菜根部重金属含量,而对地上部分的影响,不同元素表现出不同的特点;3%生物炭能够阻控铅锌尾矿污染土壤中Cu、Zn、Pb和Cd向空心菜地上部迁移富集。大豆桔杆生物炭对空心菜吸收重金属的影响,在铅锌尾矿污染土壤和未污染土壤上表现不同,存在元素之间的拮抗作用以及由于生物炭提高空心菜生物量所产生的稀释作用。在研究设置条件下,与未污染土壤相比,从空心菜生物量和可食部分吸收重金属含量来评价,施加3%大豆桔杆生物炭可以修复铅锌尾矿导致的土壤污染。     

三种改性小麦秸秆生物炭表征及其对Cu2+的吸附性能

为研究改性生物炭在水溶液中对Cu2+的吸附性能,利用硅酸钠溶液、氯化镁溶液、过氧化氢溶液制备了3种不同改性小麦秸秆生物炭,通过使用扫描电镜-X射线能量色散光谱（scanning electron microscopy combined with energy dispersive X-ray spectroscopy,SEM-EDS）和傅里叶红外光谱（Fourier infrared spectroscopy,FTIR）等技术对改性前后的生物炭进行表征分析,探究其表面形貌、官能团等性质变化。硅酸钠改性生物炭（sodium silicate modified biochar,SBC）的比表面积与孔容最大,分别为43.69 m2/g、5.30 cm3/g,比未改性生物炭（biochar,BC）（6.02 m2/g、1.40 cm3/g）分别增加了6.25、2.79倍。由SEM-EDS结果表明,改性生物炭均出现C元素质量分数下降、O元素质量分数增加的现象,其中,SBC的C元素和O元素质量分数变化最大,且SBC和氯化镁改性生物炭（magnesium chloride modified biochar,MBC）上负载了大量含Si和Mg的颗粒。FTIR结果表明,改性处理均能增强官能团的峰值,硅酸钠改性增强程度最大。另外,过氧化氢改性生物炭（hydrogen peroxide modified biochar,HBC）、BC、MBC 和SBC对Cu2+的吸附动力学过程更符合准一级动力学模型,BC、MBC、SBC对Cu2+的等温吸附过程更符合Langmuir模型,HBC对Cu2+的等温吸附过程更符合Freundlich模型。分析吸附模型参数可知,改性生物炭MBC、SBC和HBC中,SBC对Cu2+的吸附能力更强,其理论吸附量可以达到230.20 mg/g,该结果可为改性生物炭对Cu2+污染水体的治理提供理论依据。     

“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.