稻麦油兼用高速气送式集排器型孔轮设计与试验

针对水稻、小麦、油菜种子播量要求和外形尺寸差异大且稻麦种子流动性不足，导致气送式集排器兼用性不足、高速供种稳定性不佳的问题，该研究设计了一种稻麦油兼用型孔轮。阐述了高速供种工作原理，开展了供种环节充种、携种、投种阶段力学分析，基于最速降线原理设计了型孔壁面曲线，运用EDEM仿真对比分析了不同转速条件下种群运动状态。通过台架试验明确供种速率和供种稳定性较优的转速范围，并构建了稻麦油供种速率回归模型。台架试验结果表明：对于水稻和小麦种子，型孔轮个数16、供种转速30～50 r/min和50～70 r/min时，供种速率稳定性变异系数小于1%，水稻、小麦的供种速率分别为1050.62～1535.87 g/min和4171.82～5073.76 g/min；对于油菜种子，型孔轮个数为1，供种转速为20～30 r/min时，供种速率稳定性变异系数小于0.5%，供种速率为160.42～227.45 g/min；稻麦油供种速率回归模型预测值与试验值相对误差小于2%。水稻旱直播、小麦、油菜田间播种试验表明，作业速度在8～10 km/h时，集排器总排量稳定性变异系数分别为1.32%、1.16%和1.07%，满足稻麦油兼用播种作业标准要求。研究结果可为高速兼用气送式集排器结构改进提供参考。     

畜牧混合废弃物分选装置运行参数试验研究

为验证一种新型畜牧混合废弃物分选装置的功能并制定合理的运行参数,以混合物料含水率MC、进料流量Q、柔性物分离器转速Nr为试验参数,采用二次正交旋转组合试验设计,建立评价指标与试验参数之间的回归模型,并运用目标优化的方法对模型进行优化。研究结果表明,试验样机能够实现混合物组分的按类分选,试验因素组合为含水率87.8%,物料流量41.6 L/min,柔性物分离器转速64.5 r/min时可获得最高的柔性杂质分离率;在以上因素情况下,以沉降性杂质分离率及物料损失率作为评价指标,试验得出沉降性杂质分离器的最佳转速为6 r/min。研究为提高畜牧混合废弃物分选装置的分离性能及结构优化提供了依据。     

小型甘蔗收获机切割器试验研究

小型甘蔗收割机切割器必须具有切割功耗(切割扭矩)和切割损失小的特点。通过正交试验，对影响这两个评价指标的切割参数进行单、多因素试验，得出切割参数的主次顺序，即刀盘转速、刀盘倾角、刀刃滑切角。进而采用正交多项式回归分析方法对试验数据进行处理，获得影响这两个评价指标的数学模型。利用该模型对切割参数进行优化，获得切割损失和切割功耗均较小的最佳切割参数组合：刀盘转速为685 r/min，刀盘倾角为9°，刀刃滑切角为26°，从而为小型甘蔗收割机切割器设计提供依据。     

分段螺旋式甘草茎秆揉切装置设计与试验

针对全混合日粮饲草料揉切需求，该研究设计了一种分段螺旋式甘草茎秆揉切装置，对分段螺旋叶片的主体结构和搅龙结构参数进行设计，建立了刃口曲线方程，分析了装置揉切机理，并试制了分段螺旋式甘草茎秆揉切装置试验台。以搅龙转速、加工时间、填充系数、刀片与底壳间隙为因素，以粒度、破节率、单位质量能耗为指标，开展四因素三水平Box-Behnken试验，对试验结果进行方差分析和二次回归拟合，得出各因素对粒度影响显著性由大到小为加工时间、搅龙转速、填充系数、刀片与底壳间隙；对破节率的影响显著性由大到小为加工时间、填充系数、搅龙转速、刀片与底壳间隙；对单位质量能耗的影响显著性由大到小为填充系数、加工时间、搅龙转速、刀片与底壳间隙。对交互影响因素进行响应曲面分析并进行参数优化验证试验，结果表明：当搅龙转速为25 r/min、加工时间为12 min、填充系数为0.46、刀片与底壳间隙为15 mm时，甘草茎秆的揉切粉碎粒度为11.76 mm，破节率为83.27%，此时单位质量能耗为9 959.82 J/kg，试验值与模型理论值误差不超过7%，参数优化模型合理，满足作业要求。研究结果可为全混合日粮搅拌机的研发提供理论依据。     

气力集排式变量排肥系统分层施肥量调节装置研制

为提高分层施肥作业中肥料分配的精确性和稳定性,实现化肥按比例分层施用,该文设计了一种气力集排式变量排肥系统分层施肥量调节装置,通过理论分析与参数计算确定了分层施肥量调节装置关键部件的结构和基本工作参数。运用离散元法与计算流体动力学耦合仿真方法,选取拨齿旋转锥的转速、入口风速和施肥速率为试验因素,以各出肥口出肥量的变异系数为试验指标,进行二次旋转正交组合仿真试验,建立了试验指标与影响因素的回归模型。在旋转锥转速735r/min、入口风速36 m/s、施肥速率0.42kg/s、分肥比例1:2条件下,对分层施肥量调节装置进行了台架试验,试验结果表明,各出肥口出肥量变异系数均小于5.18%,分肥比例误差小于2.68%,与仿真试验优化所得结果相吻合,满足施肥作业要求。研究结果可为气力集排式排肥装置的设计与优化提供技术参考与理论支撑。     

粗纤维饲料粒度评价装置的试验研究

该文对应用震动筛分法进行粗纤维饲料的粒度评价进行了研究，对可能应用的4种筛组进行了具体的试验。提出了评价颗粒分布均匀性的分布绝对误差的指标，并筛选出最优的颗粒分离筛组——方框冲孔筛组，此筛组按试验研究得出最佳的参数组合为：充满系数0.4～0.6(对全混合日粮充满系数可达0.9～0.95)，筛分时间2～5 min。     

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。     

小粒牧草种子丸粒化包衣数值模拟与试验

针对小粒牧草种子丸粒化包衣时包衣质量不高、丸化合格率较低等问题,该研究采用理论方法,分析种粉颗粒在包衣锅内的运动过程、受力情况,构建种粉颗粒与包衣锅相互作用力学模型,获取影响种子包衣质量的主要因素。利用EDEM软件模拟包衣设备中不同结构参数下物料混合情况,探究结构参数对种粉混合效果的影响,以粉料的变异系数为评价指标,以包衣机甩盘直径、包衣机边缘倾角和包衣机转速为影响因素开展优化试验,得到最优参数组合为包衣机甩盘直径309.9 mm、包衣机边缘倾角61.9°和包衣机转速10.1 r/s。利用搭建的物理试验平台进行种子丸粒化包衣验证试验,结构参数优化后的包衣锅物理试验平均丸化合格率得到提升。进一步优化种子丸粒化包衣质量,探究粘结过程中粉料、药液对丸粒化包衣的影响。对丸粒化包衣机进行工艺参数正交试验,得到最佳工艺参数组合为单次供粉量为10 g、单次供液量为15 mL和包衣时长为7 min。在最优工作结构参数与工艺参数组合下,种子丸粒化包衣试验质量较高,研究结果可为其他不规则种子包衣提供参考。     

全混合日粮混合质量评价指标试验方法的研究

该文利用双轴卧式全混合日粮混合机，对全混合日粮混合质量评价指标的试验方法进行了研究。根据已有的资料，全混合日粮混合质量评价的指标确定为混合均匀度和粒度。在全混合日粮混合均匀度评价指标的测定方法试验中得出，高粱作为示踪物的示踪剂法更简单、合理、可行，而盐分含量分析法稳定性及准确性更好。经对全混合日粮粒度测定方法的试验研究得出，采用振动筛分法进行全混合日粮粒度的测量评价可行，最适宜的评价方法为选用孔径为Ф19 mm、Ф8 mm、Ф5 mm和底盘组成的冲孔筛组，用SSZ-750型振动筛分机筛分100 g样品5 min，然后分析各层筛面上物料比例即可进行粒度评价。     

再生稻促芽追肥机研制

再生稻再生季促芽肥的用量较小,因此对排肥器排量准确性和排肥均匀性具有较高要求。现有再生稻追肥机械较难满足再生稻促芽肥追施准确性和均匀性要求的问题。该研究综合槽轮排肥器和齿式排肥器的优点,结合具有较好分气性能的导流板式分气装置,设计了一种可与再生稻收割机配合使用的气力式再生稻促芽追肥机。追肥机采用两级排肥器进行排肥,主要由上方槽轮与下方多组齿式排肥轮组成。首先根据常用促芽肥外形尺寸确定了两级排肥器中槽轮、齿式排肥轮的主要结构参数,然后通过理论计算结合离散元仿真试验,确定了槽轮与齿式排肥轮转速的最佳传动比为1∶1.8,此时排肥器排肥最均匀,断条现象发生较少,肥料无堆积。对分气装置进行仿真模拟试验发现,随着导流板开口角度的增大,各排气口流速一致性变异系数先降低后增大,当开口角度为48°时,变异系数最小,为5.65%,此时分气装置各排气口流速差异最小、分气效果最优,各排气口平均风速为19.37 m/s,满足设计要求。对两级排肥器进行离散元仿真试验发现,在10～20 r/min转速范围内,各排肥口排肥量一致性变异系数随转速的增大先减小后增大,最大值为2.57%,满足施肥标准中各行排肥量一致性变异系数小于7%的要求。最后,以小粒径尿素为试验材料,以排肥槽轮转速为试验因素,以排肥速率、各行排肥量变异系数、排肥均匀性变异系数为评价指标,进行样机排肥性能试验。结果表明：在10～20 r/min转速范围内,排肥速率随排肥槽轮转速的增加而增大,排肥速率变化范围为672.9～1447.6 g/min,可与收割机作业速度相匹配;各行排肥量一致性变异系数为2.14%～3.09%,各排肥口排量均匀性变异系数为20.99%～27.01%,均满足NY/T1003-2006追肥机械作业标准要求。研究结果可为再生稻追肥机设计提供重要参考。     

“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     

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.     

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.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.