揉碎玉米秸秆螺旋输送性能试验分析

针对螺旋输送装置输送农业纤维物料功耗大、生产率低、效率低等问题,该文分析了螺旋输送装置的输送性能指标和螺旋叶片受力,找出了影响叶片受力的主要因素。利用自行研制的压力测试系统和功耗测试系统对螺旋叶片受到的压力和输送装置的功耗进行了测试。针对螺旋叶片所受压力、输送功耗、生产率和输送效率等输送性能指标,研究了螺距、螺旋轴转速和喂入量对输送性能的影响。结果表明,在喂入量70 kg/min、螺旋轴转速58 r/min、螺距160～300 mm的范围内,当螺距250 mm时平均输送功耗最低,为294.63 W;螺距为300 mm时输送效率和生产率最高,分别为90%和58 kg/min。在螺距250 mm、喂入量70 kg/min、转速58～148 r/min的范围内,当转速117 r/min时生产率最高,为65 kg/min。在螺距250 mm、螺旋轴转速117 r/min、喂入量10～70 kg/min的范围内,当喂入量70 kg/min时生产率最高,为42 kg/min。该研究为研制适合输送农业纤维物料的螺旋输送装置提供了参考。     

揉碎玉米秸秆螺旋输送理论模型分析与试验

针对农业纤维物料螺旋输送机理不明确、输送功耗大、生产率低等问题,该文对揉碎玉米秸秆的螺旋输送过程进行理论分析,建立了同时考虑物料的压缩特性、螺距的变化及螺旋轴离心力作用的物料所受压力、螺旋输送装置的生产率和功耗的数学模型,并通过轴向推力、生产率和功耗试验数据修正了上述模型。结果表明,当喂入量30 kg/min、转速58 r/min、螺距在160~300 mm的范围内变化时,压力、生产率和功耗的理论值与实测值的相对误差分别在11.7%、8.6%和5.9%以内;当螺距250 mm、喂入量30 kg/min、螺旋轴转速在58~148 r/min的范围内变化时,压力、生产率和功耗的理论值与实测值的相对误差分别在5.1%、6.9%和5.4%以内;当螺距250 mm、转速58 r/min、喂入量在10~70 kg/min的范围内变化时,压力及生产率和功耗的理论值与实测值的相对误差分别在5.9%、5.8%和5.2%以内。该研究为适合输送农业纤维物料的螺旋输送装置的设计及生产提供较为精确的理论依据。     

叶片式秸秆抛送装置功耗分析与参数优化

为了降低叶片式抛送装置功耗、提高抛送效率,该文采用理论分析与试验研究相结合的方法建立了考虑气流影响的、适合各种叶片倾角的叶片式抛送装置功耗数学模型,并利用虚拟样机进行优化,以抛送功耗最小为目标函数,对抛送装置结构参数、运动参数进行参数化分析.结果表明,叶轮外径700 mm、转速650~2000 r/min时,采用径向叶片、转速为650 r/min时比功耗最小.通过参数化分析得到不同工况时叶片式抛送装置结构参数与运动参数的最佳配置,为实际叶片式抛送装置的设计生产提供较精确的理论依据,并对节能降耗有着重要的现实意义.     

螺旋不连续加料装置结构优化与性能仿真

为了解决目前螺旋加料装置不连续加料量不稳定、能耗高等问题,开展螺旋不连续加料装置的结构优化与性能仿真研究。首先分析螺旋加料性能指标以及螺旋加料装置不同结构参数对其不连续加料性能影响;其次,以外径100mm螺旋不连续加料作为研究对象,以单位加料量消耗的能量最小为优化目标,选取螺旋体的内径、螺距以及工作转速为优化设计变量,确定对应约束条件,采用随机方向优化算法,得到优化结果是:转速65r/min,内径40mm,螺距85mm。最后,利用离散单元法仿真分析不同内径和螺距对颗粒填充率、加料量变化和加料能耗等加料性能的影响,结果表明:内径50mm和螺距100mm时加料稳定性与能耗综合表现较好,而在内径40mm、螺距85mm时综合性能最好。该研究结果可为加料稳定、低能耗的螺旋加料装置的设计提供参考。     

Structure optimization and performance simulation of screw discontinuous feeding device

为了解决目前螺旋加料装置不连续加料量不稳定、能耗高等问题,开展螺旋不连续加料装置的结构优化与性能仿真研究。首先分析螺旋加料性能指标以及螺旋加料装置不同结构参数对其不连续加料性能影响;其次,以外径100 mm螺旋不连续加料作为研究对象,以单位加料量消耗的能量最小为优化目标,选取螺旋体的内径、螺距以及工作转速为优化设计变量,确定对应约束条件,采用随机方向优化算法,得到优化结果是：转速65 r/min,内径40 mm,螺距85 mm。最后,利用离散单元法仿真分析不同内径和螺距对颗粒填充率、加料量变化和加料能耗等加料性能的影响,结果表明：内径50 mm和螺距100 mm时加料稳定性与能耗综合表现较好,而在内径40 mm、螺距85 mm时综合性能最好。该研究结果可为加料稳定、低能耗的螺旋加料装置的设计提供参考。     

玉米果穗螺旋摩擦输送装置的输送性能试验

为解决小型玉米联合收获机上难于配置果穗输送装置的问题,该文利用自制玉米果穗输送试验台,试验研究了玉米果穗螺旋摩擦输送搅龙的叶片高度、导向侧板倾角、导向侧板位置角、搅龙升运角和搅龙转速等对玉米果穗输送性能的影响,验证了玉米果穗输送装置对不同状态果穗的适应性。果穗处于下降侧输送、螺旋叶片高度20 mm、转速300 r/min、侧板位置角70°、侧板倾角75°的情况下,可以较好的完成玉米果穗的输送,有效避免了传统螺旋输送装置输送过程中引起的果穗损伤。     

油菜高速直播机开畦沟装置刀组优化与试验

针对长江中下游现有油菜机驱动型开畦沟装置高速（≥10 km/h）作业存在功耗较大、沟形不稳定的现实问题,该研究设计了一种刀体低阻触土面近似为螺旋桨叶面的类螺桨式开畦沟装置。基于运动学、动力学设计了由4组刀盘组成的类螺桨式刀组,确定了影响其作业功耗、作业质量的关键参数范围。基于EDEM软件开展了刀片刃型、螺距角及弯折角的单因素试验,结果表明：后磨刃耕阻最小,螺距角增大使刀片耕阻先减小后增大、抛土性能下降,弯折角增大使整体耕阻减小、抛土性能下降;1～4号刀盘的刃角结构为后磨刃,螺距角分别为7°、5°、4°、3°,折弯角分别为120°、120°、90°、90°时阻力较小,抛土性能较好。以螺距角、作业速度和刀盘转速为因子的Box-Behnken仿真试验,采用遗传算法对功耗和抛土性能进行多目标优化,结果表明：作业速度、刀盘转速、螺距角增大均使功耗上升,其中作业速度影响最大;作业速度降低、刀盘转速增高均使抛土效率提高;优化后1～4号刀盘对应的的螺距角分别为6.7°、4.7°、3.5°、2.5°;作业速度6、9、12 km/h时刀盘较优转速分别为540、620、810 r/min,优化刀组作业功耗低...     

脱出物喂入量对多风道清选装置内部气流场的影响

为研究联合收获机脱粒装置脱出物喂入量对清选装置内部气流场的影响,研制了多风道清选试验台,在清选室内振动筛上、下方分别布置25个气流速度测点,并在风机转速1 350 r/min、鱼鳞筛开度22 mm、分风板Ⅰ倾角24°、分风板Ⅱ倾角20°的额定工作参数下,采用VS110型热线式风速仪对清选装置内部无脱出物和1~4 kg/s脱出物喂入量工况分别进行气流场测量试验。试验结果表明:各测点的气流速度随脱出物喂入量的增大而有着不同程度的减小;无脱出物时各测点的气流速度最大,喂入量每增大1 kg/s,振动筛上方测点的气流速度下降1.2%~16.4%,振动筛下方测点的气流速度下降1.4%~9.3%;特别是在最大4 kg/s喂入量时,振动筛上方气流速度衰减较多,比无脱出物时气流速度下降12.6%~30.7%;相同喂入量条件下,振动筛横向1/3、2/3处的气流速度比1/2处大,振动筛纵向筛面上方前部气流速度较小、中后部气流速度较大、筛尾处气流有所回升。研究结果为多风道清选装置的设计和田间试验时参数调整提供依据。     

轮式拖拉机水田轮辙覆土装置设计与试验

以轮式拖拉机为动力的水稻精量穴播机作业时会在田面压出宽而深的轮辙,严重影响播种质量。为此,该文提出了一种变螺距等径螺旋覆土方式。该文分析了覆土原理,进行了运泥过程动力学和运动学分析,建立了螺旋覆土器的运泥量数学模型,经过理论计算和优化设计,确定了螺旋外径为250 mm、内径80 mm 和最大螺距200 mm 等关键参数。田间试验结果表明：在拖拉机轮辙自动填覆系数大于0.6,拖拉机前进速度不超过1 m/s 条件下,轮辙覆土装置能较好的填覆辙深不超过250 mm,辙宽小于400 mm 的轮辙,并保持泥面平整,满足实际生产要求。研究结果可为拖拉机轮辙覆土装置的研究和设计提供依据。     

立式有机肥螺旋撒肥装置设计与试验

针对有机肥黏度大、流动性差、粘结成块后抛撒困难的问题，该研究设计了一种带撒肥叶片的立式有机肥螺旋撒肥装置。通过建立有机肥在抛撒过程中的运动学模型，对撒肥距离、撒肥幅宽进行分析，确定影响撒肥效果的主要因素。以撒肥均匀度和撒肥幅宽为试验指标，以螺旋轴转速、撒肥圆盘倾斜角度、螺旋叶片螺距为试验因素进行旋转正交试验。运用Design-Expert软件对试验结果进行参数优化，通过验证试验对优化后的参数进行验证，结果表明：当螺旋轴转速为385.0 r/min，撒肥圆盘倾斜角度为16.0°，螺旋叶片螺距为360.0 mm时，撒肥均匀度横向变异系数为14%，撒肥幅宽为8.1 m，满足有机肥撒肥机作业标准及田间作业要求。该研究可为有机肥撒肥机的设计和优化提供参考。     

“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.