Quantification of soil-to-plant transport of recombinant nucleopolyhedrovirus: effects of soil type and moisture, air currents, and precipitation.

Significantly more occlusion bodies (OB) of DuPont viral construct HzSNPV-LqhIT2, expressing a scorpion toxin, were transported by artificial rainfall to cotton plants from sandy soil (70:15:15 sand-silt-clay) than from silt (15:70:15) and significantly more from silt than from clay (15:15:70). The amounts transported by 5 versus 50 mm of precipitation were the same, and transport was zero when there was no precipitation. In treatments that included precipitation, the mean number of viable OB transported to entire, 25- to 35-cm-tall cotton plants ranged from 56 (clay soil, 5 mm of rain) to 226 (sandy soil, 50 mm of rain) OB/plant. In a second experiment, viral transport increased with increasing wind velocity (0, 16, and 31 km/h) and was greater in dry (-1.0 bar of matric potential) than in moist (-0.5 bar) soil. Wind transport was greater for virus in a clay soil than in silt or sand. Only 3.3 x 10(-7) (clay soil, 5 mm rain) to 1.3 x 10(-6) (sandy soil, 50 mm rain) of the OB in surrounding soil in experiment 1 or 1.1 x 10(-7) (-0.5 bar sandy soil, 16-km/h wind) to 1.3 x 10(-6) (-1.0 bar clay soil, 31-km/h wind) in experiment 2 were transported by rainfall or wind to cotton plants. This reduces the risk of environmental release of a recombinant nucleopolyhedrovirus (NPV), because only a very small proportion of recombinant virus in the soil reservoir is transported to vegetation, where it can be ingested by and replicate in new host insects.     

Dispersal of Rhynchosporium secalis conidia from infected barley leaves or straw by simulated rain

Simulated rain (mean drop diameter c. 1 or 3 mm) was allowed to fall for 10 – 15 min on to barley leaves or straw infected by Rhynchosporium secalis (leaf blotch). The leaves were supported on a mesh through which run-off water drained and the straw was supported on a rigid surface on which run-off water collected. The numbers of R. secalis conidia and spore-carrying splash droplets collected by horizontal samplers (microscope slides and pieces of photographic film) decreased rapidly with increasing distance from and increasing height above the sources, with half-distances of 2 – 10 cm. Less than 10% of the spores or droplets reached heights of more than 30 cm. Incident drops 3 mm in diameter produced more spore-carrying droplets and dispersed more conidia than did 1 mm drops. The size category of splash droplets with the greatest proportion of the spore-carrying droplets dispersed by 3 mm drops was 200 – 400 μm, whether the source was infected barley leaves or barley straw. For leaves or straw the greatest proportions of spores were carried in droplets > 1000 μm in diameter. The mean diameter of spore-carrying droplets (478 μm) dispersed from free-draining leaves was less than that of droplets from straw plus run-off water (563 μm). However, the leaf source had more spores cm^-2 and the mean number of spores per droplet was greater (113 as opposed to 6·8) than for the straw source.     

Quantification of Soil-to-Plant Transport of Recombinant Nucleopolyhedrovirus: Effects of Soil Type and Moisture, Air Currents, and Precipitation

Significantly more occlusion bodies (OB) of DuPont viral construct HzSNPV-LqhIT2, expressing a scorpion toxin, were transported by artificial rainfall to cotton plants from sandy soil (70:15:15 sand-silt-clay) than from silt (15:70:15) and significantly more from silt than from clay (15:15:70). The amounts transported by 5 versus 50 mm of precipitation were the same, and transport was zero when there was no precipitation. In treatments that included precipitation, the mean number of viable OB transported to entire, 25- to 35-cm-tall cotton plants ranged from 56 (clay soil, 5 mm of rain) to 226 (sandy soil, 50 mm of rain) OB/plant. In a second experiment, viral transport increased with increasing wind velocity (0, 16, and 31 km/h) and was greater in dry (−1.0 bar of matric potential) than in moist (−0.5 bar) soil. Wind transport was greater for virus in a clay soil than in silt or sand. Only 3.3 × 10⁻⁷ (clay soil, 5 mm rain) to 1.3 × 10⁻⁶ (sandy soil, 50 mm rain) of the OB in surrounding soil in experiment 1 or 1.1 × 10⁻⁷ (−0.5 bar sandy soil, 16-km/h wind) to 1.3 × 10⁻⁶ (−1.0 bar clay soil, 31-km/h wind) in experiment 2 were transported by rainfall or wind to cotton plants. This reduces the risk of environmental release of a recombinant nucleopolyhedrovirus (NPV), because only a very small proportion of recombinant virus in the soil reservoir is transported to vegetation, where it can be ingested by and replicate in new host insects.     

模拟酸雨对不同土壤有机碳和作物秸秆分解的影响

为研究酸雨对不同pH值水稻土中有机碳分解的影响,选择酸性（pH 5.48）、碱性（pH 8.18）和中性（pH 6.70）水稻土（分别设置施用秸秆0、15 g·kg^-1土处理）在20 ℃条件下进行40 d的培养试验,各土壤组分别用pH值为6.0、4.5、3.0的模拟雨水将土壤含水量调为400 g·kg^-1(以风干土计).结果表明：秸秆、酸雨和土壤共同对土壤系统CO₂释放产生影响,秸秆的添加可显著提高土壤CO₂释放速率.培养期间,酸雨未显著影响土壤有机碳分解,但对土壤中作物秸秆的分解影响显著. pH 3.0酸雨处理下酸性和碱性土壤中秸秆40 d总分解量比pH 6.0处理高8%;酸雨抑制了中性水稻土中秸秆的分解,pH 3.0酸雨处理下秸秆40 d总分解量比pH 6.0处理低15%.pH 3.0酸雨处理下,酸性水稻土有机碳分解速率分别比中性和碱性水稻土高43%和50%（P<0.05）,秸秆在中性水稻土中分解量分别比其在酸性和碱性水稻土中低17%和16%（P<0.05）.     

Aggregation of Colletotrichum acutatum in Response to Simulated Rain Episodes

The influence of rain splash dispersal on the aggregation and variability of spores of Colletotrichum acutatum, the causal agent of strawberry anthracnose, was studied with simulated rain over a soil surface. In the first experiment, rains with intensities of 15 and 30 mm/h were generated and sampling plates, with a selective medium for Colletotrichum, were positioned under rainshields at both 20 and 60 cm from an inoculum point source (five infected fruit) for 1-min exposure periods. Number of colonies growing in plates were used to measure spore density. For each distance, time, rain intensity, and replication, the mean (m), variance (v), and Lloyd's index of patchiness (LIP) were calculated. Estimated (LIP) exceeded 1, indicating the high variability and clustering of colonies, and hence spores, resulting from splash dispersal. LIP increased with distance from the source and with rain intensity at the greater distance. Aggregation was further quantified by Taylor's power law describing the linear relation between ln (v) and ln (m). The slope (b) of the relation for all data points was 1·67, which was significantly (P < 0·01) greater than 1, a further indication of clustering. Distance form the source had a slight positive effect on b. Colony means (Y) were transformed to Y*=Y^1/5 based on an approximate b of 1·6. Analysis of Y* indicated an expected significant main effect of rain duration and a significant interaction of distance and rain intensity. In another experiment, six infected fruit and the sampling plates were uniformly placed over the surface. LIP again exceeded 1, and Taylor's b equaled 1·63. In a final study, the inoculum source and sampling plates were raised 46 cm above the soil surface. There was a drastic reduction in Y* compared to surface values, supporting the prior hypothesis that surface topography strongly affects splash dispersal. Results indicate that the physical process of splash dispersal produces a degree of aggregation similar to that produced by population dynamic and other ecological processes.     

Areal Extent of Preferential Flow with Profile Depth in Sand and Clay Monoliths

During recent years much attention has been focused on the role of large pores in soil as a preferred route for solute movement. However, most studies have failed to relate the macropore areal extent to profile depth, which was done in this study. The areal extent of pores participating in displacement of water and contaminants with soil depth and its hydrological significance was investigated in two texturally different soils, both under ponded and transient flow conditions. Soil monoliths (1?m long, 0.3?m diameter) of a clay soil and a sandy soil were used for this purpose. Water (100?mm) stained with acid red (azophloxine) at a concentration of 3.8?g/L was applied to each monolith under the two hydro-logically different regimes. Subsequently, they were cut in 0.1-m increments and each transect was examined visually and recorded graphically for the areal extent of stained soil. A considerably larger area was stained at each depth in the sand compared with the clay soil, for example, around 83 and 22% at 70-cm depth in the sand and clay, respectively, under ponded flow conditions. In the clay soil, a much smaller area was stained throughout the soil profile when the soil was exposed to transient compared with ponded flow conditions. Below the topsoil (30-cm depth), the mean stained area was less than 10% under transient flow conditions, whereas up to about 50% was stained under ponded flow conditions. This difference did not occur in the sand. Even though the infiltration rate was much higher in the sand (i.e., the time periods required to infiltrate 100?mm of stained solution were, on average, 33?min for the sand monoliths and 4?h 21?min for the clay monoliths), the arrival time of stained solution in leachate was considerably faster in the clay (on average, 1?h 8?min in the clay under ponded flow conditions, whereas only clear water eluted in the sand monoliths throughout the experiment). These results clearly show that preferential flow in clay soils is a major route for the displacement of contaminants through the soil profile.     

秸秆预处理对土壤微生物量及呼吸活性的影响

冬小麦秸秆经8．0g·L^-1H2O2(pH11．0)溶液、12．5g·L^-1 NaOH溶液或H2SO4溶液浸泡8h并80℃烘干后,与无机N一起加入土壤,进行室内25℃恒温培养试验,在不同时间测定土壤微生物量C、N和CO2释放速率。结果表明,培养前期,秸秆预处理使土壤微生物量C数量增加了1．0～1．4倍,但降低了土壤微生物的呼吸活性;培养后期,NaOH和H2SO4处理使土壤微生物量C分别下降了28％和42％,但增加了土壤微生物的呼吸活性;H2O2处理则使土壤微生物量N增加90％;土壤微生物区系中的真菌比例在不同时刻有所增加,表明将秸秆预处理后施入土壤,将对土壤中微生物数量和呼吸活性产生一定影响。     

Influence of soil factors,fertilizers and manures on pathogenicity ofRhizoctonia solani onVigna species

Rhizoctonia solani caused maximum mortality of mung bean seedlings at 20°C, and the disease incidence decreased with increase of temperature; 30° was optimum for mycelial growth of the fungusin vitro. The fungus grew best in nutrient broth of pH 5.5 but infected mung bean and pea seedlings more severely in neutral and alkaline river sand than in the sand adjusted to acidic reaction. The disease incidence was higher in adequately moist sandy loam and less in soil under moisture stress. Incidence of cowpea seedling rot was higher in heavy-textured loam and silt loam soils than in light-textured sandy- and loamy sand. Addition of montmorillonite and kaolinite in the sandy soil increased the disease incidence, but these clays reduced fungus growth in culture. More seedling rot occurred in the sandy soil fertilized with urea, potassium nitrate, monocalcium phosphate, or potassium dihydrogen phosphate while soil application of ammonium nitrate, potassium chloride, or potassium sulphate decreased the disease. In tests with combined soil application of N (as urea), P (as monocalcium phosphate) and K (as potassium chloride), disease incidence was more in all combinations having P. Among the six micronutrients tested, only boron reduced the disease incidence significantly both in presence and absence of NPK fertilizers. Farm-yard manure and biogas sludge aggravated seedling rot but their water extracts decreased it. Humic acid, extracted from farm-yard manure, increased the disease incidence but was inhibitory to fungus growth in culture. Green manure also resulted in more disease.     

Vermicompost substitution influences growth, physiological disorders, fruit yield and quality of strawberry (Fragaria x ananassa Duch.)

Studies were conducted to determine the effect of vermicompost on growth, physiological disorders, fruit yield and quality of 'Chandler' strawberry. For this, 4 levels of vermicompost (2.5, 5.0, 7.5 and 10.0tha(-1)) were supplemented with inorganic fertilizers to balance fertilizer requirement of strawberry under semi-arid region of northern India. The vermicompost was incorporated into top 10cm layer of soil, which was supplemented on the basis of chemical analysis, with amount of inorganic N, P, K fertilizer calculated to equalize the recommended dose of nutrients. Vermicompost application increased plant spread (10.7%), leaf area (23.1%) and dry matter (20.7%), and increased total fruit yield (32.7%). Substitution of vermicompost drastically reduced the incidence of physiological disorders like albinism (16.1-4.5%); fruit malformation (11.5-4.0%) and occurrence of grey mould (10.4-2.1%) in strawberry indicating that vermicompost had significant role in reducing nutrient-related disorders and disease like Botrytis rot, and thereby increasing the marketable fruit yield up to 58.6% with better quality parameters. Fruit harvested from plant receiving vermicompost were firmer, have higher TSS, ascorbic acid content and lower acidity, and have attractive colour. All these parameters appeared to be dose dependent and best results were achieved @ 7.5tha(-1), however, beyond this dose of vermicompost, there was not significant influence on these parameters.     

长期免耕秸秆覆盖对寒地草甸土土壤物理性质的影响

黑龙江地处中温带地区,农田秸秆量大,不同秸秆还田技术与耕作制度结合对土壤物理性质的影响尚不明确.通过2010-2017年连续8年的田间定位试验,研究免耕条件下秸秆覆盖对草甸土土壤物理性质的影响.试验设秸秆无覆盖区(0%)、30%覆盖量(30%)、60%覆盖量(60%)、100%覆盖量(100%)4个处理.结果表明: 免耕条件下,秸秆覆盖可使土壤容重增加0.10～0.20 g·cm^-3,差异达到显著水平,并随覆盖量增加呈递增趋势;秸秆覆盖使土壤固相率比无覆盖增加2.5%～7.8%;土壤温度随秸秆覆盖量增加降幅增大,表层尤为明显,0～5 cm土层温度降幅1.87～2.90 ℃;土壤含水量随秸秆覆盖量增加呈增加趋势,与无覆盖相比差异显著,0～5 cm土层增加幅度为6.4%～10.2%;秸秆覆盖使土壤总孔隙和直径>0.05 mm通气孔隙减少,0.05～0.002 mm有效孔隙增加,覆盖量越大增加越明显,对土壤无效孔隙的影响不规律.长期秸秆覆盖增加了土壤紧实度和土壤水分,降低了土壤温度和土壤总孔隙,增加了0～5 cm土层土壤有效孔隙.     

Overwintering form of the causal agent of shot hole disease in Khorasan Razavi, Iran

Shot hole disease of stone fruit trees caused by some plant pathogenic fungi is a major constraint to stone fruit production worldwide where the trees are grown. Identification of the causal agents of the disease and their overwintering forms in stone fruit trees of Khorasan Razavi was necessary for disease management programs. Buds, twigs, fallen leaves and fruits were collected from the infected peach, apricot, nectarine and almond trees in winter 2007. The samples were superficially disinfested in 1% sodium hypochlorite for 2-3 min and then in 70% ethanol for 45 sec. Two to three fragments of 4x4 mm from each tissue were separately cultured on 2% water agar and potato dextrose agar (PDA), and purified on PDA. Just a pathogenic fungal species, Wilsonomyces corpophilus was isolated from the infected buds and twigs. No microorganism was isolated from the fallen leaves and fruits collected from underneath of the infested stone fruit trees. Pathogenicity of the fungus was examined on detached shoots of current year of four varieties of stone fruit trees. Fungal discs were placed under the bark of the bud base. Control shoots were similarly treated with sterile PDA discs. Inoculated shoots were placed in a humid growth chamber at 25 degrees C. Fungal hyphae appeared at 30 days post inoculation. Control shoots were asymptomatic. Pathogenicity intensities or lesion lengths were significantly different among the four varieties tested. A completely randomised design with five replicates was employed to measure the number of spores in infested buds and twigs of each variety of stone fruit tree. The samples were sliced and placed into a glass tube of centrifuge containing 3 ml of sterile distilled water. They were mixed on a vortex mixer for 30-40 min and centrifuged at 3000 rpm for 5 min. Pelleted material from each sample was suspended in 500 microl of sterile distilled water and the spores were counted using a hemocytometre. Results revealed that the fungus overwinters as hyphae and conidia in the infected buds, and as hyphae and globular chlamydospores in twig lesions.     

陇东旱地果园覆沙对苹果树蒸腾耗水及果实品质的影响

针对甘肃陇东旱地苹果园季节性干旱问题,以15年生长富2号苹果树为试材,测定果园覆沙后土壤水分、温度,以及果树主干液流速率、叶片气孔导度、果实品质等指标.结果表明：果园覆盖5 cm厚河沙,2-4月地温升高幅度低于1 ℃,6、7月晴天地温升高2.44 ℃,阴天地温升高2.61 ℃;在果树生长季节土壤含水量始终保持在田间持水量的60%以上.土壤含水量较高的时期（H期）晴天,树干液流曲线呈“几”字形宽峰曲线,覆沙处理液流启动时间较对照提前0.6 h,峰值较对照高25.5%,阴天峰值较对照高165.6%,且液流活动时间延长;土壤含水量较低的时期（L期）晴天,覆沙处理液流呈单峰曲线,启动时间较对照提前0.5～1 h,峰值在794 g·h^-1左右,而阴天液流启动时间较对照提前近1 h,峰值较对照高311.0%.3-7月对照的棵间蒸发量（E_s）较覆沙处理高156.0%,过多的地面蒸发是造成果树缺水的主要原因.覆沙后果实单果质量显著提高,果实硬度略有降低,果实可溶性固形物、维生素C、总糖、有机酸含量均有所提高.     

Increased growth response of strawberry roots to a commercial extract from <Emphasis Type="Italic">Durvillaea potatorum</Emphasis> and <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis>

The withdrawal of soil fumigants like methyl bromide is forcing strawberry growers to consider supplementary and alternative ways of producing crops. In addition to controlling soil-borne pests, soil fumigation causes an increased growth response in strawberry roots, and the use of biostimulants may offer an alternative to replace this response. We tested the hypothesis that treatment with a commercial extract (Seasol®) from the seaweeds Duvillaea potatorum and Ascophyllum nodosum can increase root growth, and transplant (runner) and fruit yields of strawberry. From 2014 to 2016, we conducted three field trials on strawberry farms in the nursery sector at Toolangi and in the fruiting sector at Coldstream in Victoria, Australia. We applied the seaweed extract as a monthly drench (10 L ha^?1) to two cultivars of strawberry (‘Albion’ and ‘Fortuna’), compared with an untreated control. In the nursery sector, use of the extract significantly increased the density of secondary roots (feeder roots) on harvested runners by up to 22%. Treatment with the extract also significantly increased yields of marketable runners by 8–19%. In the fruit sector, use of the extract significantly increased the root length density (root length per volume of soil) of strawberry plants by 38% and marketable fruit yields by 8%. Root length density at final harvest and marketable fruit yield of strawberry were highly correlated (r?=?0.94). This relationship provides an insight into the mode of action of seaweed extracts and is discussed. Overall, the results show the potential benefits of the integrated use of seaweed extracts in strawberry production across the nursery and fruit sectors, and their promise for supplementing or replacing the increased growth response provided by soil fumigants.     

降雨和汇流对黑土区坡面土壤侵蚀的影响试验研究

东北黑土区上坡汇流对坡面土壤侵蚀有重要影响,因此辨析降雨和汇流对黑土区坡面土壤侵蚀的影响对农田土壤侵蚀防治有重要意义。通过设计不同降雨强度和汇流速率以及二者组合的模拟降雨及上方汇流试验,分析了降雨和汇流对黑土坡面侵蚀的影响及其贡献。试验处理包括两个降雨强度(50 mm/h和100 mm/h)、两个汇流速率(50 mm/h和100 mm/h,即:10 L/min和20 L/min)、以及4种不同降雨强度和汇流速率的组合((50+50)mm/h、(50+100)mm/h、(100+50)mm/h和(100+100)mm/h)。结果表明,在50 mm/h和100 mm/h上方汇流引起的坡面侵蚀量仅分别是50 mm/h和100 mm/h降雨引起坡面侵蚀量的1.9%和0.6%;当降雨强度和坡上方汇流速率分别由50 mm/h增加至100 mm/h时,降雨试验处理下的坡面侵蚀量增加6.1倍,汇流试验处理下的坡面侵蚀量增加3.2倍,说明降雨对坡面土壤侵蚀的影响显著大于汇流的作用。在降雨和汇流组合试验中,总供水强度(降雨强度+汇流速率)为150 mm/h时,降雨强度为100 mm/h和汇流速率为50 mm/h组合试验的坡面侵蚀量是降雨强度为50 mm/h和汇流速率为100 mm/h组合试验坡面侵蚀量的7.9倍。在相同汇流条件下,降雨强度由50 mm/h增加到100 mm/h时,降雨强度的增加对坡面侵蚀量的贡献率为89.6%-99.5%;而在相同降雨条件下,坡面汇流速率由50 mm/h增加100 mm/h时,汇流速率的增加对坡面侵蚀量的贡献率为17.2%-78.7%,说明在东北黑土区防治坡面汇流对坡面土壤侵蚀影响也尤为重要。     

紫色土区不同秸秆还田量对土壤线虫群落的影响

为了研究不同秸秆还田量对紫色土区土壤线虫群落的影响, 作者于2011年5月和9月对川中丘陵区的100% (RMW1)、50%(RMW2)、30%(RMW3)和空白对照(CK)4种秸秆还田量的农田土壤线虫进行了调查。结果发现, 随着秸秆还田量的下降, 土壤线虫的群落结构有一定变化。总体上, 群落密度、食真菌类群和捕食-杂食类群的密度呈波动增加; 食细菌类群的密度持续增加; 植物寄生类群密度、Shannon-Wiener多样性指数(H')、植物寄生成熟指数(PPI)和瓦斯乐斯卡指数(WI)呈先增加后下降的变化趋势, 且多样性指数在秸秆还田量为30-50%之间最高; 类群数、自由生活成熟指数(MI)、线虫通路比值(CR)则先下降后增加; 所有变化均不显著(P > 0.05)。土壤速效钾含量随秸秆还田量的增加显著提高(P < 0.05), 且与线虫群落多样性指数呈显著负相关(P < 0.05)。研究结果表明, 在紫色土区秸秆还田主要是通过改变土壤钾含量对土壤线虫群落产生影响, 且秸秆还田量在30-50%之间时有利于维持线虫群落多样性。     

Influence of Insect Larvae and Plant Roots on the Host-finding Behaviour of Heterorhabditis megidis

We studied the host-finding and dispersion behaviour of Heterorhabditis megidis (strain NLHE 87.3) in the presence of Galleria mellonella or Otiorhynchus sulcatus larvae and strawberry roots. In large Petri dishes (19 cm diameter) filled with moist sand (8% w/w), and incubated at 15°C over 24 h, infective juveniles (IJs) responded positively to the presence of G. mellonella , to roots of a single strawberry plant and to O. sulcatus larvae in direct contact with roots of a single strawberry plant. A neutral or negative response was observed when IJs were presented with only O. sulcatus larvae or a combination of several strawberry plants with O. sulcatus larvae, either in contact or not in contact with the roots. IJs responded strongly to the combination of plant roots and feeding larvae indicating that the tritrophic interaction formed by IJs - O. sulcatus larvae - strawberry plants may be an infochemical-mediated interaction.     

不同浓度石灰氮对黄瓜连作土壤微生物生物量及酶活性的影响

为分析比较不同浓度石灰氮对连作黄瓜田土壤环境的作用效果,通过2年温室定位试验,在黄瓜秸秆还田的基础上以不施石灰氮为对照(CK),研究施用\[高浓度石灰氮1350 kg·hm^-2(CaCN₂ 90)、中浓度石灰氮900 kg·hm^-2(CaCN₂ 60)、低浓度石灰氮450 kg·hm^-2(CaCN₂ 30)\]对连作黄瓜土壤微生物生物量碳(SMBC)、微生物生物量氮(SMBN)及酶活性的影响.结果表明：与其他处理相比,CaCN₂ 90显著降低苗期0～10 cm 土层SMBC,但增加了初瓜期后0～20 cm土层SMBC.施用石灰氮处理均显著提高了末瓜期0～20 cm土层SMBC及盛瓜期至末瓜期0～10 cm土层SMBN,但第1年（2012年）不同石灰氮用量间无明显规律,第2年(2013年)盛瓜期后SMBN随着石灰氮施用浓度的增加而升高.施用石灰氮有利于秸秆的腐熟,提高土壤有机质含量,且石灰氮浓度越高越有利于秸秆的腐熟.相比对照,施用石灰氮能有效提升土壤脲酶、过氧化氢酶和多酚氧化酶活性,其中脲酶活性随石灰氮浓度的增加升高,而多酚氧化酶活性随石灰氮浓度的增加而降低,CaCN₂ 60可有效提高过氧化氢酶活性.相关分析表明：土壤有机质、脲酶及过氧化氢酶活性与SMBC、SMBN呈极显著正相关,多酚氧化酶活性与SMBC、SMBN呈显著负相关.表明黄瓜秸秆还田后施用石灰氮900 kg·hm^-2能够改善温室黄瓜连作田土壤环境,有效减缓温室黄瓜连作障碍.     

Effect of Sowing Time on the Incidence of Bud Blight in Soybean (Glycine max L. Merr.)

The incidence of soybean bud blight in soybeans in Brazil is sporadic in most of the production areas but is endemic in a few others. Tobacco streak virus (TSV), the causal agent, is transmitted by thrips. The vector population starts declining everytime the amount of accumulated rain is over 300 mm. A four year trial (1986—1990) indicated that by delaying the sowing time it was possible to drastically reduce the incidence of the disease, allowing farmers to grow a cash crop. Significant correlations were observed between percentage of infection, number of days with rain, total of accumulated rain and total of thrips surveyed. A multiple linear regression (y = 23.93 + 0.7 × 1—0.06 × 2) that accounted for 80 % of the variation was obtained, considering percentage of infected plants (y), total of thrips (×1) and total of accumulated rain (×2). Results indicated that farmers should sow during the month of December, in areas where the disease is endemic.     

不同施肥条件下秸秆碳在表层和深层土壤团聚体中的分配与固存

长期施肥引起表层和深层土壤水、热、养分和微生物活性的分异,进而影响秸秆碳在土壤中的分解和周转过程。本研究基于沈阳农业大学长期定位实验站,分别将不同施肥处理表层(0～20 cm)和深层(40～60 cm)土壤与¹³C标记秸秆混合进行田间试验,通过分析团聚体中有机碳含量和δ¹³C值,对比秸秆碳在表层和深层土壤团聚体中分配的差异,探讨施肥对秸秆碳在土壤团聚体中固定的影响。结果表明: 与施肥(包括单施氮肥和有机肥配施氮肥)处理相比,不施肥处理分别使表层土壤<0.053 mm和深层土壤>0.25 mm团聚体中秸秆碳含量增加了106.7%和34.2%;秸秆碳对深层土壤>0.053 mm团聚体有机碳的贡献率约为表层土壤的2.0倍;秸秆碳分配到表层土壤>0.25 mm和<0.25 mm团聚体的比例平均分别为22.6%和11.4%,分配到深层土壤的相应比例分别为29.4%和8.8%。总之,秸秆添加促进了深层土壤大团聚体碳源的更新和固存,提高了深层土壤的固碳潜力。     

粉红聚端孢侵染新红星苹果的侵入途径与侵染时期

粉红聚端孢Trichothecium roseum引致的苹果霉心病发生严重。对于新红星品种,T. roseum的侵染过程尚未明确。本研究利用T. roseum荧光标记菌株TR45分析其在新红星品种上的侵染时期和侵入通道。发现T. roseum可以侵染花器组织,引起枯萎坏死;落花后10-15 d,受侵染的花器残体被萼片包裹于萼筒内,随后T. roseum从离生花柱合并处的孔口部位入侵进入合生花柱,沿花柱内的多细胞毛状体间扩展;花后30 d左右,花柱缝逐渐开裂,随果实膨大心室腔壁也开裂,逐渐形成一条贯通萼筒与心室开放通道——萼窦;花后60 d左右,T. roseum的菌丝沿着萼窦扩展进入心室腔,从心室上的裂缝进入果肉组织,最终引起果实霉心。本研究结果有助于解析新红星苹果品种发病重以及难防治的原因,对苹果霉心病防控新策略构建具有重要理论意义。