整秆式甘蔗收割机剥叶过程仿真分析与试验

整秆式甘蔗收割机剥叶机构的作业质量对收获后甘蔗茎秆的蔗叶残留有重要影响，合理的作业参数可有效改善剥叶机构的剥叶质量。该研究通过建立甘蔗剥叶过程仿真模型分析茎秆和剥叶元件的相互作用过程及其应力变化以及茎秆的受力情况，采用单因素仿真试验研究喂入辊筒转速、剥叶辊筒转速及茎秆与剥叶元件搭接长度对茎秆和剥叶元件所受峰值应力的影响规律。在仿真分析的基础上建立甘蔗剥叶作业试验台，采用Box-Behnken试验方案研究关键作业参数对茎秆未剥净率（剥叶后残留蔗叶和叶鞘占剥叶前全部蔗叶和叶鞘的比值）的影响规律并获得最佳作业参数：喂入辊筒转速250 r/min，剥叶辊筒转速540 r/min，茎秆与剥叶元件搭接长度13.9 mm，甘蔗喂入根数1.68根，此时茎秆未剥净率为2.2%。验证试验结果表明，在单根和双根喂入时，甘蔗茎秆未剥净率分别为2.0%和3.1%。通过高速摄像分析叶鞘的剥离过程，并获得最优作业参数下茎秆的输送速度区间为2.3～2.9 m/s。该研究结果为改善甘蔗收割机剥叶效果、提高作业适应性提供参考。     

自动反拉式换位夹持苎麻剥麻机设计与参数优化

针对目前普遍使用且依靠人力喂入及反拉的苎麻剥麻机劳动强度大、安全性差、剥麻质量不稳定等问题,该研究以“川苎11号”苎麻为研究对象,设计了一种自动反拉式换位夹持苎麻剥麻机。首先对苎麻茎秆物理尺寸和力学性能参数进行测量,确定采用双夹持机构与同步带夹持输送、电机驱动夹持机构翻转换位、双滚筒反向剥麻的技术方案。进而对剥麻装置、夹持机构等主要部件进行结构设计和理论分析,确定苎麻剥麻机结构和剥麻滚筒转速、反拉速度、喂入角度等工作参数。然后分析苎麻茎秆剥打过程并建立仿真模型,运用ANSYS/LS-DYNA模块对剥麻过程进行单因素仿真试验,分析了木质部去除量、韧皮部损失量等,仿真结果表明,剥麻滚筒转速、反拉速度、喂入角度分别在350～650 r/min、0.2～0.4 m/s、5°～15°范围内时的剥麻效果较好。根据Box-Behnken试验设计方法,开展三因素三水平正交试验,通过方差分析和响应面分析,得出反拉式换位夹持苎麻剥麻机的最优工作参数为:剥麻滚筒转速451.047 r/min,反拉速度0.319 m/s,喂入角度10.728°;样机试验表明最优工作参数下的平均鲜茎出麻率为5.03%,平均原麻...     

倒伏超级稻割前摘脱台试验

针对目前倒伏超级稻霜前机械化收获存在的问题,设计了一种新型气吸式摘脱台。为优化该摘脱台的设计、确定其关键参数最佳匹配,以倒伏型水稻割前摘脱总损失为评价指标,回收率为参考指标,对摘脱滚筒齿尖线速度、喂入速度、喂入口水平开度与喂入口风速等进行了单因素和正交试验。单因素试验表明：影响摘脱台损失的主要因素是喂入速度、摘脱滚筒齿尖线速度、喂入口风速和喂入口水平开度。正交试验表明：最佳组合为摘脱滚筒齿尖线速度23 m/s,喂入速度0.9 m/s,喂入口水平开度100 mm与喂入口气流速度14 m/s,割前收获顺向倒伏超级稻总损失1.52%。试验结果表明所设计的摘脱台满足倒伏超级稻收获要求,并为超级稻割前摘脱联合收割机摘脱台的设计提供依据。     

果园秸秆覆盖机弹齿式解捆防堵装置设计与试验

针对果园秸秆覆盖机解捆铺料装置易堵塞问题，该研究基于秸秆解捆过程力学分析，设计了一种弹齿式防堵装置。首先建立防堵装置-秸秆捆离散元模型，通过EDEM仿真比较了加装和未加装防堵装置情况下秸秆扰动情况和出料口秸秆密度变化，阐释了解捆铺料作业过程中秸秆堵塞的形成机制。与未加装防堵装置的仿真结果相比，在刀齿线速度2.3 m/s、秸秆捆前进速度0.05 m/s下，加装防堵装置后出料口内侧秸秆平均密度降低了46%，出料区单位质量流率下的解捆阻力矩降低了28.1%，表明防堵装置可有效降低刀齿扰动区域和出料口秸秆密度，避免秸秆在下料口滞留和高压区形成，进而降低解捆阻力矩。以解捆铺料装置阻力矩标准差为指标开展正交试验，得到最佳工作参数为解捆铺料装置主动辊转速225 r/min、刮板主动辊转速5.0 r/min、弹齿间距100 mm。验证试验表明，与未加装防堵装置相比，185、225和265 r/min三个解捆铺料装置主动辊转速下（刮板主动辊转速和弹齿间距不变），解捆铺料装置阻力矩标准差降低率分别为29.5%、34.0%和30.7%，同时平均阻力矩和峰值阻力矩降低率分别为16.1%和28.5%，所设计的防...     

旋转剪切式青花椒采摘装置设计与试验

针对基于“下桩”采摘方法的青花椒采摘设备存在喂入困难、易堵塞而造成采摘效率低的问题,该研究设计了一种旋转剪切式青花椒采摘装置。首先基于花椒枝物理、力学特性确定旋转剪切式青花椒采摘过程包括花椒枝旋转驱动、花椒枝导向喂入和剪切采摘,剪切采摘功能由往复式切割器实现。并设计双动刀往复式切割器及其传动机构,确定了剪切采摘装置的结构和运动参数。进一步地,运用ANSYS/LS-DYNA构建花椒枝剪切仿真模型,确定最优齿形参数为：刀齿切割角20°,刀齿刃角50°,刀齿厚度2.5 mm,该条件下峰值切割力为3.739 N。最后通过单因素试验确定了花椒枝喂入角度、花椒枝喂入速度、花椒枝旋转速度的取值范围分别为40°～60°、20～40 mm/s、20～40 r/min;并采用BoxBehnken设计法制定三因素二次回归正交组合试验方案,运用Design-Expert 12对试验结果进行方差分析和响应面分析,得到旋转剪切式青花椒采摘装置的最优工作参数为：花椒枝喂入角度55°,花椒枝喂入速度33.21 mm/s,花椒枝旋转速度30 r/min;通过试验验证得出在最优工作参数下,单人单枝喂入时青花椒平均采摘效率...     

玉米果穗剥皮的运动仿真与高速摄像试验

针对玉米剥皮田间试验和室内试验存在玉米品种多样、适收期短等问题,该文提出了采用理论分析、虚拟仿真技术与高速摄像技术相结合的方法,研究果穗在剥皮机构中的运动。首先,对玉米果穗在剥皮机构中的受力及运动进行了理论分析,得到影响果穗剥净率、剥皮效率以及剥皮损失的主要因素;其次,应用ANSYS/LS-DYNA建立了玉米果穗与剥皮机构相互作用有限元仿真模型,获取了剥皮辊不同转速下玉米果穗在剥皮机构中的运动速度、绕自身轴线的角速度和受力情况。仿真结果表明,随着剥皮辊转速的增大,果穗的运动速度由0.2增大到0.4 m/s;果穗绕自身轴线的旋转角速度增加,在0~15 rad/s之间变化;果穗的受力增大,且波动性更强,3种工况下最大受力分别为11.9、14.5和16.3 N。以玉米果穗沿剥皮辊的速度和加速度为验证参数,仿真数据与果穗剥皮高速摄像试验数据进行了对比。结果表明,仿真数据与高速摄像试验结果基本一致,证明了仿真模型可以较好地替代物理试验。该研究结果可为剥皮机构的设计与分析提供了参考。     

旱区全膜双垄沟播履带式玉米联合收获机的设计

针对中国北方旱地全膜双垄沟播玉米种植方式,解决玉米收获过程中的摘穗啃伤、田间作业垄上行走稳定性差及玉米茎秆回收再利用问题,设计了一种履带式玉米穗茎兼收型联合收获机,以及配套的立辊式摘穗割台和茎秆切碎抛送装置。设计的非对称立辊式对行收割结构,可适应玉米全膜双垄沟播收获作业要求,实现了穗茎兼收,提高了秸秆利用率,并总结了立式割台“间隙夹持-倾斜喂入-滑动摘穗”的立式摘穗收获机理。利用立式摘穗试验样机,以机具前进速度、主动链轮转速、摘穗辊直径、切碎刀轴转速为影响因素,果穗损失率、茎秆切碎合格率为评价指标,进行了二次旋转正交组合试验。通过Design-expert 8.0.6数据分析软件,建立各影响因素与指标的数学回归模型,分析了显著因素与评价指标之间的关系,优化试验参数,确定最优参数组合:在机具前进速度3.8m/s、主动链轮转速1150r/min、摘穗辊直径82mm、切碎刀轴转速1650r/min时,果穗损失率为2.61%、茎秆切碎合格率为92.81%。优化模型与田间验证性试验得到的果穗损失率均值2.8%、茎秆切碎合格率均值93.1%相接近,满足旱区全膜双垄沟播玉米收获要求。     

主动旋转集行式清秸装置设计与试验

针对东北地区在秸秆全量粉碎还田条件下玉米免耕播种作业时,被动分茬式清秸装置清秸率低,主动条旋式清秸装置草土混埋造成出苗率低的问题,该研究设计了一种主动旋转集行式清秸装置,首先通过理论分析与参数计算确定了清秸弹齿关键部件结构和工作参数。进一步运用土槽试验的方法,选取机组前进速度、清秸弹齿转速和清秸弹齿渗透量为试验因素,以种带清秸率为试验指标,进行二次旋转正交组合试验,建立了试验指标与影响因素回归模型,确定清秸装置最优作业参数组合为机具前进速度1.4 m/s,清秸弹齿转速400 r/min,弹齿渗透量19 mm。并通过田间试验对该装置作业性能进行验证。试验结果表明,最优参数组合下,20 cm宽度种带清秸率为98.3%,平均作业功率为605 W,满足东北地区玉米免耕播种作业农艺和技术要求。该研究可为免耕作业机具清秸装置设计提供参考。     

梳齿起膜气力脱膜式耕层残膜回收机研制

为了解决耕层残膜污染问题，该研究设计了一种梳齿起膜气力脱膜式耕层残膜回收机。该机主要由机架、梳齿、梳齿辊、重力沉降室、离心风机组成。梳齿辊是该回收机的核心机构，其辊筒上布置有多排梳齿，通过梳齿辊的旋转实现松土和残膜-土壤分离；利用EDEM离散元软件建立梳齿辊模型，仿真研究了梳齿排列方式和梳齿结构对梳齿辊入土过程中前进阻力和阻力矩的影响，确定了齿刀螺旋排列方式。吸膜机构的作用是实现残膜的连续回收及膜土分离。建立了残膜在吸膜区的运动学方程，通过对方程分析求解，探明了梳齿辊转速和吸膜口风速对残膜运动轨迹的影响，确定梳齿辊转速应小于120 r/min，吸膜口风速应大于15 m/s。为了获得回收机的最佳作业参数组合，进行了土槽响应曲面优化试验，得出最佳参数组合：吸膜口与竖直面之间的角度为-7°、机具前进速度为2 km/h、梳齿辊转速为100 r/min、吸膜口风速为22 m/s。田间试验结果表明：最佳参数组合作业时，残膜拾净率为55.04%，比预测值小1.63%，优化方法可靠。     

苎麻茎秆台架切割试验与分析

为了给苎麻收割机的研制提供切割理论基础,该文进行了苎麻茎秆切割参数的试验研究。该文利用自行设计的试验台架进行苎麻茎秆的切割试验,研究往复式单动刀及双动刀切割器不同刀片几何参数(刀片长度、刀刃类型)、不同切割线速度和不同茎秆喂入速度对切割性能(切割功耗、切割质量和综合评分值)的影响。根据各个因素特点,论文采用多因素正交试验的方法确立两水平因素(刀刃类型、刀片长度和动刀组数)的最优水平组合,然后固定两水平因素的最优水平组合,以切割线速度和茎秆喂入速度为试验因素进行二次回归正交旋转设计试验来获得因素的最佳参数。根据多因素正交试验结果,采用往复式双动刀切割器,选用锯齿刃长刀片(120 mm)为最优水平组合。根据二次回归正交旋转设计试验结果,当切割线速度为0.878 9 m/s、茎秆喂入速度为0.862 4 m/s时,单位长度割幅切割功率最小,为281.408 4 W;当切割线速度为1.161 4 m/s、茎秆喂入速度为0.711 7 m/s时,单位面积切割失败株数最少,为5.691 1株;当切割线速度为1.092 0 m/s、茎秆喂入速度为0.722 9 m/s时,评分值最高,为86.7180分。综合试验结果,苎麻切割试验理论最佳水平组合为:切割线速度1.092 0 m/s、茎秆喂入速度0.722 9 m/s,采用往复式双动刀切割器,选用锯齿刃长刀片(120 mm),此时单位长度割幅切割功率为318.814 5 W,单位面积切割失败株数为6.006 4株。研究结果为后续苎麻收割机切割部件的研制以及切割行走速比的选择提供了基础理论数据。     

“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.