生物有机肥和复合微生物菌剂对黄瓜产量和品质的影响

采用正交试验研究了生物有机肥和复合微生物菌剂对黄瓜产量、品质、农药残留以及毒害元素吸收的影响。结果表明,生物有机肥能使黄瓜数量平均每株增产12.5%,维生素C含量提高99.21%,氨基酸含量提高41.10%,有效降解黄瓜中多菌灵的残留,抑制黄瓜对Pb和As的吸收;微生物菌剂能使黄瓜数量比对照增加29.29%,产量增加22.76%,维生素C含量提高7.68%,氨基酸含量增加73.56%,对百菌清有很好的降解作用。     

Biological characteristics of Streptomyces albospinus CT205 and its biocontrol potential against cucumber Fusarium wilt

In a dual-culture assay, Streptomyces albospinus CT205 inhibited the growth of Fusarium oxysporum in vitro, the casual agent of widespread Fusarium wilt, probably due to the production of chitinase, β-glucanase, and a heat-resistant antagonistic substance. Pot and field experiments were performed to investigate the effects of S. albospinus CT205 alone or combined with organic fertiliser (BOF-CT205) on control of Fusarium wilt. Pot experiments showed that BOF-CT205 treatments obtained the lowest disease index (23.2), compared with organic fertiliser (OF, 55.3), strain CT205 (66.2), and control (72.5) treatments. In the field experiment, BOF-CT205 treatment yielded significantly lower disease incidences than the control, with reductions of ca. 55%. Cucumber yields in the same treatments were significantly higher than in the control, with increases of approximately 30% in the OF treatment. The cucumber yield was maximised in the BOF-CT205 in field experiments, reaching 8.3 × 104 kg ha^?1. The application of BOF-CT205 reduced the presence of the pathogen in the cucumber rhizosphere. In conclusion, S. albospinus CT205 was demonstrated to be a promising biocontrol agent for cucumber wilt, and the most effective treatment was the application of BOF-CT205.     

Interactions between green spruce aphid (Elatobium abietinum (Walker)) and Norway and Sitka spruce under high and low nutrient conditions

1 Green spruce aphid (Elatobium abietinum) is a serious pest of spruce (Picea spp.) in north‐west Europe, causing defoliation of one‐year‐old and older needles. 2 Relationships between population development of E. abietinum, needle loss and tree growth were compared for five pure genotypes of Sitka spruce and mixed‐genotype material of Sitka and Norway spruce, grown under high and low nutrient conditions. 3 Despite wide differences in flushing date between spruce genotypes, E. abietinum populations peaked on the same date on each genotype and on the mixed‐genotype material, irrespective of nutrient supply. 4 Larger aphid populations developed on trees grown under high nutrient conditions than under low nutrients. However, more needles were lost per aphid in the low nutrient treatment and overall defoliation rates in the two nutrient treatments were similar. 5 Total aphid numbers differed significantly between Sitka spruce genotypes within nutrient treatments, but not in relation to bud‐burst or needle terpene content. Reductions in height growth caused by infestation were greater (15–44%), and related to mean aphid densities and defoliation, in the low nutrient treatment, but were smaller (11–27%) and not related to aphid density and defoliation in the high nutrient treatment. 6 Development of E. abietinum populations was similar on Norway and Sitka spruce, but Norway spruce lost fewer needles. However, the effects of infestation on tree growth were more closely related to aphid density and were similar for Norway and Sitka spruce. 7 Infestation caused a decrease in total root dry weight of Norway and Sitka spruce in proportion to the reductions observed in above‐ground growth.     

Plants and fertilisers as drivers of change in microbial community structure and function in soils

Here we report on a range of studies designed to understand the link between diversity and function in soils and in particular how plants and fertilisers might interact with microbial community dynamics in soils. The data presented indicate that although plants and fertilisers do impact on microbial community structure, the relationship between diversity, community structure and function remains complex and difficult to interpret using currently available chemical and molecular fingerprinting techniques. The paper assesses plants and management practices as drivers of change in soil and argues that whilst understanding diversity per se is unlikely to contribute to our understanding of function, an appreciation of what causes communities to change and also the relative importance of such drivers, could lead to new insights into the sustainable management and conservation of soils and natural resources.     

Growth of Slender Banksia from seedling planting,with and without fertiliser

Slender Banksia (Banksia attenuata) is a primary component of declining Banksia woodlands around Perth, south‐western Australia. It is important that its re‐establishment be promoted, but there are little data on its growth rates and response to applied nutrients. To quantify longer‐term growth rate, I periodically measured heights of Slender Banksia planted mid‐2005 over 7½ years. Without fertiliser, these seedlings grew slowly to about 1½ m. In mid‐2009, I planted Slender Banksia on the same site, with and without fertiliser tablets, and evaluated survival, growth and root development over 1½ years. First‐summer Slender Banksia seedling survival of around 30% was not unusual for this species. Low‐phosphorus native plant fertiliser tablets increased growth significantly.     

Effect of inorganic N on the population,in vitro colonization and morphology of Acetobacter diazotrophicus (syn. Gluconacetobacter diazotrophicus)

We investigated whether Acetobacter diazotrophicus (syn.Gluconacetobacter diazotrophicus) could be recovered only from sugarcane plants either with low or no application of fertiliser N. We report here the enrichment and enumeration of A. diazotrophicus from high N-fertilised samples where high heterotrophic populations reduce the numbers of A. diazotrophicus ultimately diminshing its isolation frequency as reported earlier. The growth medium of micropropagated sugarcane seedlings of the varieties Co 8021, Co 86249, Co 86010, Co 86032, and Co 87025 was amended with potassium nitrate, ammonium nitrate, ammonium chloride and urea. The colonisation and AR activity of A. diazotrophicus were affected in the presence of high levels (25 mM) of ammonium chloride and ammonium nitrate but remained unaffected in low levels of N (i.e 1/10th of MS liquid medium) and with high levels of potassium nitrate (25 mM) and urea (500 ppm). A. diazotrophicus was detected in the inoculated plants both at low and high levels of N based on the amplification of a specific 16S rRNA gene fragment using PCR based method targeting a stretch of 445 bp with primers AC and DI. High levels of N in the growth medium induced morphological changes on A. diazotrophicus cells resulting in long pleomorphic cells. The percentage of pleomorphic cells was in the decending order from NH₄NO₃, NH₄Cl, KNO₃, and urea. These changes were more prominent in ammonium chloride and ammonium nitrate than potassium nitrate, urea and N free medium. The morphological changes and the increased heterotrophic populations may play a role on the survival ofA. diazotrophicus in high N-fertilised samples/environments.     

Inoculation of sugar mill by-products compost with N2-fixing bacteria

Inoculation of sugar mill by-products compost with N₂-fixing bacteria may improve its quality by increasing total N and available P. Compost was inoculated with Azotobacter vinelandii(ATCC 478), Beijerinckia derxii (ATCC 49361), and Azospirillumsp. TS8, each alone and all three together. Numbers of all N₂-fixing bacteria in compost declined from an initial population of 5×10⁵cellsg^–1 during incubation. The population of Azotobacter declined to approximately 2×10²cellsg^–1 and the population of Beijerinckia and Azospirillum declined to approximately 9×10³ and 3.5×10⁴cellsg^–1 respectively, at day 50. Inoculation with N₂-fixing bacteria increased acetylene reduction, total N by 6–16 and available P by 25–30% in comparison to the uninoculated control. Increasing the N content and P availability of compost increases its value and there may be additional benefit from providing N₂ fixing bacteria.     

Effects of rates of a nematicide and of fertiliser on the growth and yield of cultivars of potato which differ in their tolerance of damage by potato cyst nematodes (Globodera rostochiensis andG. pallida)

Potato plants growing in soil heavily infested with potato cyst nematode (PCN) contained less N, P and K in their leaf dry matter than plants growing in the same soil treated with a nematicide. These differences were less in tolerant than intolerant cultivars. Applying additonal fertiliser increased the growth of untreated plants more than that of nematicide-treated plants and nematicides increased growth most in plots receiving the lowest rate of fertiliser. Overall, the results are consistent with the hypothesis that damage by invading juveniles of PCN decreases the effectiveness of the potato root system leading to a chronic deficiency of one or more nutrients and a consequential reduction in the rate of top growth.     

Primates create seedling growth hotspots through pattern of dung deposition

Primates play important roles in tropical forests through seed dispersal and herbivory. They comprise a large part of the biomass of forest communities and tend to have clumped patterns of defecations (i.e. at favoured food trees or sleeping sites). Therefore, they may also play important roles in accelerating ecosystem nutrient cycling. Here we conduct a controlled growth experiment to quantify the effect of the addition of primate dung on the growth of both light‐demanding and shade‐tolerant seedlings over 1 year in Kibale National Park, Uganda. A mixed model analysis revealed that light‐demanding species were affected by the natural dung treatment and plants with small initial size had accelerated growth, whereas there was no effect on plant growth for shade‐tolerant species. The long‐term implications of increased dung deposition on the local tree community are unclear as shade‐tolerant species may only show an effect over the long‐term and light‐demanding species may only be able to take advantage of the increased growth if subsequently exposed to high light conditions, such as a treefall gap.