南方席草生产机械化现状及发展趋势

席草生产在南方部分县(市、区)是农业支柱产业之一。本文在论述席草生产机械化现状，分析其存在问题和近期发展趋势的基础上，提出了加快席草业机械化发展需要采取的对策。     

Nitrapyrin effectiveness in reducing nitrous oxide emissions decreases at low doses of urea in an Andosol

In the tropics,frequent nitrogen(N)fertilization of grazing areas can potentially increase nitrous oxide(N₂O)emissions.The application of nitrification inhibitors has been reported as an effective management practice for potentially reducing N loss from the soil-plant system and improving N use efficiency(NUE).The aim of this study was to determine the effect of the co-application of nitrapyrin(a nitrification inhibitor,NI)and urea in a tropical Andosol on the behavior of N and the emissions of N₂O from autotrophic and heterotrophic nitrification.A greenhouse experiment was performed using a soil(pH 5.9,organic matter content 78 g kg^-1,and N 5.6 g kg^-1)sown with Cynodon nlemfuensis at 60%water-filled pore space to quantify total N₂O emissions,N₂O derived from fertilizer,soil ammonium(NH₄⁺)and nitrate(NO₃^-),and NUE.The study included treatments that received deionized water only(control,NI).No significant differences were observed in soil NH₄⁺content between the UR and UR+NI treatments,probably because of soil mineralization and NO₃^-produced by heterotrophic nitrification,which is not effectively inhibited by nitrapyrin.After 56 d,N₂O emissions in UR(0.51±0.12 mg N₂O-N concluded that the soil organic N mineralization and heterotrophic nitrification are the main processes of NH₄⁺and NO₃^-production.Additionally,it was found that N₂O emissions were partially a consequence of the direct oxidation of the soil's organic N via heterotrophic nitrification coupled to denitrification.Finally,the results suggest that nitrapyrin would likely exert significant mitigation on N₂O emissions only if a substantial N surplus exists in soils with high organic matter content.     

不同草带空间分布对坡面细沟侵蚀调控机制

为了研究植被对坡面细沟侵蚀调控机制,采用模拟降雨试验,结合激光扫描方法,分析了不同草带分布沟坡面细沟侵蚀发生、发展过程。结果表明:草带位于梁峁坡下部60%,植被调控侵蚀效果最优,相比裸坡减少径流量7.4%,减少产沙量62.9%,相比蓄水减沙功效而言更具直接拦沙的功能。植被通过调控细沟侵蚀的发生、发展、发育过程实现了对土壤侵蚀的调控作用,尤其是对沟坡侵蚀产沙的调控作用;而且这种对侵蚀的调控作用不仅改变了细沟侵蚀发生的位置,而且改变了径流和侵蚀过程以及侵蚀方式;细沟侵蚀已经向面蚀(片蚀)转化,大幅度降低侵蚀程度。研究结果揭示了植被可以通过影响侵蚀方式来调控侵蚀输沙过程,有助于加深坡面植被对细沟侵蚀发育形态作用机理的理解。     

不同草被格局下的坡面流水力学特性

通过室内放水冲刷试验,研究不同草被格局(随机格局、草方格、带状、斑块状及光滑玻璃对照)下的坡面流水力学特性变化。试验在8种流量(0.15,0.30,0.45,0.60,0.75,0.90,1.05,1.20 L/s)和3种坡度(3°,6°,9°)下进行。结果表明:(1)与光滑玻璃面相比,草被覆盖坡面可以雍高水位1.02～1.38倍,减缓流速6.52%～36.73%;随着流量和坡度的增大,流速呈幂函数递增(R~20.95)。(2)雷诺数与流量间存在显著的线性正相关关系(R~20.99),与坡度和草被格局无明显相关关系;草被覆盖可以有效降低坡面弗劳德数。(3)随流量和坡度的增大,草被覆盖下的坡面流型态从层流—缓流或急流过渡到紊流—急流。(4)随着流量的增大,坡面流阻力系数呈幂函数递减(R~20.86),坡度对坡面流阻力系数无显著影响(p0.05)。(5)不同草被格局雍高水位的作用为随机格局斑块状草方格带状,对流速的减缓作用为随机格局带状斑块状草方格,坡面弗劳德数为斑块状带状草方格随机格局,抗蚀能力为随机格局草方格带状斑块状。     

基于HYDRUS-1D的城市草地土壤水分模拟——以扬州市人工草地为例

[目的] 研究城市化背景下草地土壤水分运动规律,为提升海绵城市建设水平提供科学依据和技术支撑。[方法] 以江苏省扬州大学扬子津校区农水与水文生态试验场的人工草地为研究区,利用实测降雨和同期土壤含水量数据对不同降雨事件下的雨水入渗深度进行分析。通过HYDRUS-1D模型对研究区土壤含水量变化过程进行模拟。[结果] 在小雨（<10 mm）和中雨（10~25 mm）事件中,研究区草地的雨水入渗深度分别小于15 cm和30 cm;在大雨（25~50 mm）到暴雨（>50 mm）事件中,雨水入渗深度通常超过30 cm,或可达60 cm以上;土壤含水量模拟值与实测值的均方根误差范围为0.012～0.034 cm³/cm³。[结论] 不同等级降雨事件下的草地雨水入渗深度存在明显差异,入渗深度总体上随着降雨量的增加而增加;HYDRUS-1D模型能够准确模拟不同等级降雨事件下的城市人工草地区雨水入渗深度。     

三峡库区消落带典型草被对氮磷污染物迁移的影响

为明确三峡库区消落带草被对农业面源污染防治的作用,采用野外放水冲刷试验,分析草带对地表径流中氮磷的拦截率和冲刷前后氮磷含量在土壤内的空间变化,研究消落带典型草被对氮磷污染物迁移的影响。结果表明:(1)草带拦截污染物的效率总体较好,对NO_3~--N的拦截率最高,达93.5%～99.3%。拦截率与草带宽度成正比,与冲刷强度成反比。(2)冲刷前后TN、TP、NO_3~--N和NH_4~+-N污染物含量的变化率最大值分别为2.30,1.96,5.01,4.75,均出现在小区下坡。随着草带宽度增加以及冲刷强度的减弱,污染物含量的变化率增大。(3)各氮磷污染物在0—10 cm土层的变化率较大,变化范围为0.91～5.01。TN、TP和NH_4~+-N在10—30 cm土层的变化率普遍接近1,而NO_3~--N在该土层依然存在较大的变化率。(4)RDA结果显示,影响冲刷前后污染物变化最大的因子是土层深度,其次是坡位、草带宽度、冲刷强度。综上,消落带草被能够有效拦截污染物并促进其向土壤内部迁移,在消落带草本植物恢复及面源污染防治过程中应注意增加消落带草被覆盖宽度,减小高强度降雨径流的影响,促进污染物在上坡位被拦截并进一步向土壤内部迁移,降低污染物向上覆水释放的风险,为三峡库区消落带草本植被恢复及农业面源污染防治提供理论依据。     

草鱼出血病细胞疫苗微囊制备与体外释放研究

以海藻酸钠、壳聚糖以及草鱼出血病细胞灭活疫苗为原材料,采用复凝聚法制备草鱼出血病口服微囊疫苗。通过单因素试验和正交试验,研究了海藻酸钠浓度、壳聚糖浓度、氯化钙浓度以及加入疫苗体积对微囊疫苗包封率的影响,确定了其最佳制备工艺。结果显示,各因素对草鱼出血病微囊疫苗包封率的影响程度由大到小依次为：海藻酸钠浓度＞疫苗加入量＞壳聚糖浓度＞氯化钙浓度;制备草鱼出血病微囊疫苗的最佳工艺为：海藻酸钠浓度为1.5%,壳聚糖浓度为1%,氯化钙浓度为4%,加入疫苗体积为2 mL。该微囊疫苗平均粒径为（7.02±3.95）μm,平均包封率为60.53%,平均载蛋白量为8.12 mg/g,在pH 7.4的PBS溶液、生理盐水溶液中具有良好的释放性能。     

新时期对基层农机推广人员素质的要求及提高措施

我国农机事业的迅速发展,要求有一支高素质的农机推广人员队伍。探讨新时期加强基层农机推广人员素质的必要性,总结对基层农机推广人员的素质要求,提出提高农机推广人员素质的可行性建议。     

Effect of drought on biomass allocation in two invasive and two native grass species dominating the mixed‐grass prairie

Control of exotic plant species invading the native prairie relies on our understanding of the eco‐physiological mechanisms responsible for the spread of these species as they compete with native plants for soil resources. We used a greenhouse pot experiment to study vegetative biomass allocation in response to drought stress in two exotic grass species, Kentucky bluegrass (Poa pratensis L.) and smooth brome (Bromus inermis Leyss), and two native species, western wheatgrass (Pascopyrum smithii (Rydb.) A. Löve) and green needlegrass (Stipa viridula Trin.). The experiment was conducted over 3 months in 2010 and again in 2011 in a factorial design of four species and two drought treatments. The proportional data of biomass allocation to shoots, roots, rhizomes and crowns (shoot base) of grass seedlings were analysed by both the nonparametric Mann–Whitney U‐test on the original data and one‐way anova on the arcsine‐transformed data. Our data suggest a clear distinction between the two invasive and two native species in potential competitiveness in soil resource use, with the two exotic species having higher biomass allocation to roots than the two native species and the native species having a higher biomass allocation to crowns than the two exotic species. It is interesting to note that the strongly rhizomatous smooth brome did not produce rhizomes in the first season's growth, regardless of the water stress level. The effect of drought stress on biomass allocation manifested itself more on rhizomes or crowns than on roots or shoots of the four studied grass species, with the effects species‐specific in nature.     

新疆橡胶草锈病病原菌的分离与鉴定

【目的】研究引起新疆伊犁橡胶草锈病的病原菌种类,为该病的有效防控提供科学依据。【方法】按照柯赫氏法则,分离田间橡胶草锈病病原并接种健康橡胶草以验证其致病性,采用显微镜观察橡胶草锈菌夏孢子形态,应用真菌通用引物NL1/NL4和锈菌通用引物ITS5-u/ITS4rust分别对锈菌的28S rDNA和ITS基因序列进行PCR扩增和测序,通过ITS序列构建系统发育树分析该菌种属地位。【结果】田间病样分离获得的锈菌可侵染健康株并且发病症状与田间症状一致。橡胶草锈菌夏孢子近球形、椭圆形或卵圆形,大小为(24~32 × 21~26) μm,淡黄色至栗褐色,有刺,单胞,壁厚为1~2.5 μm。新疆伊犁橡胶草锈菌与山柳菊柄锈菌最为接近,其序列同源性达到了99.06%。【结论】引起新疆伊犁橡胶草锈病的病原菌为山柳菊柄锈菌。