江西省农业科研单位发展的思考*

在我国，农业科研单位大多属于事业单位，主要从事农业相关领域的知识创新、技术创新、技术产品研发及成果转化和示范推广工作。农业科研单位为农业科技进步做出了突出贡献，但由于受体制和机制等因素影响，其发展也面临一系列问题和困难。文章以江西省为例，通过了解江西省农业科研单位发展的现状，剖析存在的问题，并查找存在问题的原因，进而对加快江西省农业科研单位发展提出了思路与建议，以期为相关决策部门提供参考依据。     

Effects and side effects of penicillin injection in huanglongbing affected grapefruit trees

Trunk injection with penicillin has been tested to control citrus huanglongbing (HLB), but side effects and environmental safety must be assured before approval of penicillin injection can be considered. We investigated effects of penicillin injection on densities of Candidatus Liberibacter asiaticus (Las) in leaves, as well as culturable bacterial populations in rhizospheres and petioles of grapefruit trees in field and greenhouse experiments. Trees were injected with penicillin G, and leaf and root concentrations were assessed in bioassays with Bacillus subtilis. Las densities were determined by qPCR, and bacteria were isolated on a low carbon medium from roots plus rhizosphere and surface-sterilized petioles at various times after penicillin injection. Selected bacterial isolates were tested for penicillin resistance (20 μg/mL) and glyphosate resistance (7000 μg/mL), because glyphosate is widely used and cross-resistance against antibiotics had been documented. One month after penicillin injection half of the greenhouse trees were inoculated with Phytophthora nicotianae. Cycle threshold (Ct) values of Las in old and young leaves significantly increased 90 days after trunk injection with penicillin. Bacterial populations in petioles and root-rhizospheres initially increased after penicillin injections, probably due to nutrient release, then returned to control levels after one week. Penicillin resistance was common in isolates from penicillin-injected and control trees (30–94%). Significantly more glyphosate resistant than sensitive isolates were penicillin resistant (81% versus 52%). Phytophthora root rot was not increased after penicillin injection. Thus, side effects of penicillin injection tested here were minimal, while Las titers were reduced after three months.     

刀齿排布旋向对免耕覆秸精播机清秸单体性能的影响

为探寻定轴钢齿种床整备装置作业执行部件清秸单体因刀齿排布旋向不同而对其作业性能及负载的影响,该文在介绍左、右螺旋清秸单体的机构组成及工作原理的基础上,理论分析确定其等距切土节距条件,依此确定了玉米大垄双行清秸单体参数,并进行运动学仿真,仿真验证了等距切土节距条件的正确,并对比分析总结两者打击规律:刀轴纵向前进,侧向旋转,刀齿按序号1~9次序依次与地面进行打击,左旋清秸单体刀齿沿作业方向打击位置排序为186429753,右旋清秸单为594837261,单头螺线刀齿打击方向,左旋清秸单体与作业方向相同,打击间距等于4个节距,整体采用反向插补式打击;右旋清秸单体与作业方向相反,打击间距等于2个节距,整体采用推进式打击,且两者具有相同的螺旋进距及切土节距。利用仿真模拟及田间试验的方法对两者的载荷状况及作业性能进行对比分析,左、右螺旋清秸单体仿真切土平均阻力及离散度分别0.0658 k N、66.2及0.062 k N、60.1;田间扭矩消耗均值、标准差及根茬清除率分别为64.6 N·m、7.2、93.8%及62.7 N·m、5.1、95.3%,右旋清秸单体所有评价指标除根茬清除率外皆小于左旋清秸单体,表明右旋清秸单体具有较小的载荷消耗、载荷波动及较佳的作业性能。该研究可为具有排布特性的土壤耕作机具研究提供参考。     

Soil water effects on the use of heat units to predict crop residue carbon and nitrogen mineralization

Soil heat units (degree days) have previously been shown to predict net N mineralization from crop residues and papermil sludge. The present study was designed to identity the effects of soil water potential on predictions of mineralization with heat units and to compare field and laboratory results of white lupin (Lupinus albus L. cv. Ultra) N mineralization. Lupin-amended soil and unamended controls were incubated at factorial combinations of temperature (15, 20, and 25°C) and soil moisture (-0.30,-0.03, and-0.01 MPa) for 198 days. Incorporation of the lupin residue resulted in net N immobilization. No net N mineralization had been observed for any temperature at a soil moisture level of-0.30 MPa by the close of the incubation study. The number of heat units that accumulated until commencement of net N mineralization did not differ for five of the six remaining temperature x water treatment combinations.The number of heat units that accumulated until net N mineralization began (2058–2814 degree-days) in the present study were similar to those reported in a complementary field study (1990–2360 degree-days). Temperature and moisture interactively affected lupin-residue C mineralization. The cumulative substrate C that had evolved by the time of net N mineralization did not differ for a given temperature between soil moisture levels of-0.03 and-0.01 MPa. Heat units were not useful for describing crop-residue C mineralization in this study. Heat units appear to adequately predict net N mineralization from organic residues at soil water potentials within the-0.03 to-0.01 MPa range, but may not be valid for prolonged drier conditions.     

Bodengesellschaften von geomorphen Einheiten unter Berücksichtigung des Gefügestils im Stormarner Jungmoränengebiet (Brandenburger Stadium) in Nordwestdeutschland

Soil associations of different geomorpholocical units of a younger‐moraine area in Schleswig‐Holstein (NW Germany) considering matter fluxes As result of a detailed mapping work, the soil association of different geomorpholocical units of a younger‐moraine area (“Stormarner Jungmoränengebiet”) in Schleswig‐Holstein (NW Germany) is analyzed taking into account soil development in vertical and horizontal direction. The consequences for classification of soil types and soil associations are discussed. We distinguished between different patterns of matter fluxes (unilateral coupling, mutual coupling, no coupling of soils). By morphometric analysis of the relief, five geomorpholocical units were distinguished: till‐plains with dead‐ice kettles (I), tongue‐like basin with moraine slopes (II), terminal‐push moraine (III), moraine slopes with gutter valley (IV), und terminal‐push moraine valley with steep slopes (V). In the examination area with its intense agricultural land use, the regular sequence of erosion and accumulation of soils is a typical consequence of unilateral water‐flow direction. Thus, the truncated Stagnic Luvisols/Anthrosols association is dominating. We suggest to classify the truncated Luvisol with a Bt horizon exposed directly to the surface at the level of soil subtypes in the German soil‐classification system. Additionally soils in depressions such as Calcic Gleysols, Histosols and “subhydric soils”, which are influenced by solute and solid‐matter input, are frequently encountered. Within the till‐plains, a compensation of the relief by (historical) soil erosion took place, recognizable by the high percentage of Anthrosols (20 %). Therefore, no recent lateral transport of solid material can be found. The steep moraine slopes partly already show Regosols, thus indicating a high erosion potential (erosion rate for geomorphical unit IV: 13 t ha^–1 y^–1). In the depressions intersected with small streams, the afflux caused by mills led to an additional peat development.     

Cover crop effects on nitrogen mineralization and availability in conservation tillage cotton

Understanding cover crop influences on N availability is important for developing N management strategies in conservation tillage systems. Two cover crops, cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.), were evaluated for effects on N availability to cotton (Gossypium hirsutum L.) in a Typic Kanhapludult soil at Watkinsville, Ga. Seed cotton yields following clover and rye were 882 kg ha^–1 and 1,205 kg ha^–1, respectively, in 1997 and were 1,561 kg ha^–1 and 2,352 kg ha^–1, respectively, in 1998. In 1997, cotton biomass, leaf area index, and N were greater on some dates following crimson clover than following rye but not in 1998. During 1997, net soil N mineralized increased with time in both systems, but a similar response was not observed in 1998. Net soil N mineralization rates following crimson clover and rye averaged, respectively, 0.58 kg and 0.34 kg N ha^–1 day^–1 in 1997 and 0.58 kg and 0.23 kg N ha^–1 day^–1 in 1998. Total soil N mineralized during the cotton growing season ranged from 60 kg ha^–1 to 80 kg ha^–1 following crimson clover and from 30 kg ha^–1 to 50 kg ha^–1 following rye. Soil N mineralization correlated positively with heat units and cumulative heat units. Net soil N mineralization rates were 0.023 kg ha^–1 heat unit^–1 once net mineralization began. Soil heat units appeared to be a useful tool for evaluating N mineralization potential. Nearly 40% of the rye and 60% of the clover biomass decomposed during the 6 weeks prior to cotton planting, with nearly 35 kg N ha^–1 mineralized from clover.     

白水江自然保护区次级自然单元植物优先保护评价

以构建的次级自然单元植物优先保护评价指标体系及层次分析法(AHP)运算结果为依据,对白水江自然保护区次级自然单元(沟系)进行了划分和优先保护评价.结果表明:中东部的让水河流域汇聚了保护区亚热带和温带的多种植物种类,同时也是国家重点保护、珍稀濒危、特有、单(寡)型类型集中分布的区域,是保护区植物保护的最优先区;由于海拔和...     

鸭池河水电站地下埋管外压稳定计

针对鸭池河水电站地下埋管外压稳定性问题，采用半解析柱壳有限条元法、Mises法和《水电站压力钢管设计规范》（SL281-2003）所推荐的方法对地下埋管的的局部稳定性、整体稳定性、加劲环的稳定性进行了计算，并通过比较分析，得出一系列对压力钢管设计有参考价值的结论，供水电站地下埋管抗外压稳定性设计参考。     

水电机组效率在线监测系统

水电机组效率在线监测系统在水电厂运行中具有十分重要的意义，是水电站实现经济运行及机组状态检修的基础。介绍了利用AdLink NuDAM系列模块进行数据采集的方法，以及效率在线监测系统中参数监测、数据录入、处理、打印、报表、曲线绘制、参数设置等各项功能。介绍了NuDAM与微机通讯方式、数据保存以及利用最小二乘法绘制机组动力特性曲线的方法。运行实例表明该系统运行稳定可靠。     

水轮发电机组多路智能化温度巡检装置

为了提高水轮发电机组的温度巡检装置的性能，在分析温度巡检装置发展现状的基础上，找出其不足，研制出了以Intel80C196KC嵌入式微处理器为核心的水轮发电机组多智能化温度巡检装置。该装置具有抗干扰能力强、测量精度高、与系统组网方便、掉电数据保护、操作方便、显示直观等优点。