A new <Emphasis Type="Italic">Rhizoctonia</Emphasis> sp. closely related to <Emphasis Type="Italic">Waitea circinata</Emphasis> causes a new disease of creeping bentgrass

Isolates of an unidentified Rhizoctonia sp. (UR isolates) were obtained from creeping bentgrass and Kentucky bluegrass with reddish brown sheath and foliar rots. Because the UR isolates anastomosed with isolates of three varieties of Waitea circinata (var. oryzae, var. zeae, and var. circinata), colony morphology, hyphal growth rate at different temperatures, pathogenicity, sequence analysis of the internal transcribed spacers (ITS) region of ribosomal RNA genes (rDNA) were compared. The colony color of mature UR isolates was distinct from isolates of the other three varieties of W. circinata. In pathogenicity tests on creeping bentgrass, the severity of the disease caused by UR isolates was significantly higher than that caused by the three varieties of W. circinata. Sequence similarities of the rDNA-ITS region between UR isolates and between isolates within each variety were high (97–100%), but they were lower among isolates from UR and the varieties of W. circinata (88–94%). In a phylogenetic tree based on the rDNA-ITS sequences, UR isolates formed a cluster separate from each of the clusters formed by the three varieties of W. circinata. These results indicate that the UR isolates clearly differ from the three varieties of W. circinata. We therefore propose that the UR isolates be classified as new Rhizoctonia sp. that are closely related to W. circinata and that the disease on creeping bentgrass should be called Waitea reddish-brown patch disease (Sekikasshoku-hagusare-byo in Japanese).     

Resistance to Rhizoctonia solani AG‐2‐2 (IIIB) in creeping bentgrass plants transformed with pepper esterase gene PepEST

A pepper esterase (PepEST) gene was introduced into creeping bentgrass (Agrostis stolonifera) by Agrobacterium‐mediated transformation. Purified recombinant PepEST proteins were sufficient to inhibit the growth of the fungal pathogens Rhizoctonia solani AG2‐2 (IIIB) (causing brown patch) and Sclerotinia homoeocarpa (dollar spot), but not the oomycete responsible for pythium blight, Pythium aphanidermatum. PepEST proteins were most effective against R. solani. After genetic transformation of creeping bentgrass with PepEST, the genomic integration of transgenes bar and PepEST was confirmed by Southern blot analysis, and their expression was also validated by northern blot and western blot analyses. Disease severity on R. solani‐inoculated leaves of transgenic plants was <10% compared to ca. 50% in non‐transgenic plants. Microscopic observation of infected leaves indicated that PepEST inhibited the growth of hyphae upon fungal infection.     

Spatial and temporal dynamics of Meloidogyne minor on creeping bentgrass in golf greens

Meloidogyne minor, first reported on potatoes in the Netherlands in 2004, is an emerging nematode pest in Europe. It damages turfgrass, particularly creeping bentgrass (Agrostis stolonifera) grown on sandy soils such as those of golf greens. However, little is known of the nematode's life history and pathology. In this study, the spatial and temporal distribution of M. minor on a creeping bentgrass green in Ireland was determined over a 15 month period. Cores were taken on transects across yellowing patches of grass caused by nematode damage. Second‐stage juveniles (J2) were absent from the soil from November to February, when soil temperatures were below 10°C. Both galls and egg masses were present throughout the year but were more abundant in late summer and early autumn. More J2, galls and egg masses were present in the top 10 cm of soil than at a depth of 11–20 cm. The nematode population tended to decrease as distance from the centre of the yellow patches increased. The diameter of visual symptoms (yellow patches) was also recorded over the 15 months. The mean diameter of five sampled patches increased from 23·7 cm in June 2003 to 45·2 cm in August 2004. There were 158–193 galls per 100 cm³ soil at the margin of the visible infested area, indicating that this could be the threshold level for visible symptoms.     

Herbicidal efficacy and selectivity of pyribenzoxim in turfgrasses

Three field trials were conducted from 2003–2004 at Utsunomiya University, Japan, to evaluate the safety and herbicidal activity of pyribenzoxim (benzophenone O -[2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxybenzoyl]oxime) in turfgrass. Pyribenzoxim showed a high level of safety in bentgrass ( Agrostis palustris Huds.) and zoysiagrass ( Zoysia matrella ) ≤ 300 g ai ha⁻¹ and it controlled various major grass weeds, including annual bluegrass ( Poa annua L.), large crabgrass ( Digitaria sanguinalis L.), and green foxtail ( Setaria viridis L.), and broadleaf weeds, including common dandelion ( Taraxacum officinale Weber), horseweed ( Erigeron canadensis L.), shepherd's-purse ( Capsella bursa-pastoris (L.) Medic.), common chickweed ( Stellaria media L.), common lambsquarters ( Chenopodium album L.), creeping woodsorrel ( Oxalis corniculata L.), and common dayflower ( Commelina communis L.) by fall or spring application. In comparison with bispyribac-sodium (sodium 2,6-[bis(4,6-dimethoxy-2-pyrimidin-2-yl)oxy]benzoate), pyribenzoxim showed a higher safety level in bentgrass and a stronger herbicidal activity on grass weeds; in particular, annual bluegrass and large crabgrass.     

Managing earthworm casts (Oligochaeta: Lumbricidae) in turfgrass using a natural byproduct of tea oil (Camellia sp.) manufacture

BACKGROUND: Earthworm casts are a worldwide problem on golf courses and sports fields when they disrupt the playability, aesthetics and maintenance of closely mowed playing surfaces. Currently, no pesticides are labeled for earthworms in the United States. Tea seed pellets (TSPs), a saponin‐rich byproduct of Camellia oleifera Abel oil manufacture, were tested for expelling earthworms and reducing casts on creeping bentgrass turf. The fate of expelled worms, methods for removing them and impacts on pest and beneficial arthropods were also evaluated. RESULTS: Application of TSPs at 2.93 kg 100 m^?2, followed by irrigation, quickly expelled earthworms from the soil. A single application reduced casts by 80–95% for at least 5 weeks. Mowing or sweeping removed expelled earthworms from putting green surfaces. Most expelled earthworms burrowed down when transferred to untreated turf, but few survived. Bioassay‐guided fractionation confirmed the vermicidal activity results from a mix of saponins. TSPs did not reduce the abundance of beneficial soil arthropods, nor did they control black cutworms or white grubs in treated turf. CONCLUSION: TSPs are an effective botanical vermicide that could be useful for selectively managing earthworm casts on closely mowed turfgrass. They might also be used to suppress earthworms in grassy strips alongside runways to reduce bird strike hazard at airports. Copyright © 2009 Society of Chemical Industry     

Seed germination, seedling establishment and growth patterns of wrinklegrass (Ischaemum rugosum Salisb.)

Several laboratory and glasshouse experiments were conducted to assess seed germination, seedling establishment and growth patterns of wrinklegrass (Ischaemum rugosum Salisb.) influenced by temperature and light regimes, and chemical media. Wrinklegrass was a positively photoblastic species, and seed germination was temperature‐dependent and light‐mediated. Seeds soaked in distilled water for 24 h, or oven‐dried at the respective temperature regimes of 15, 20, 25, 30, 35, or 40°C prior to treatment in distilled water and incubated in darkness, failed to germinate. Likewise, no germination prevailed when the seeds were exposed to similar temperature regimes and treated with 0.2 m KNO₃, 5% H₂O₂ or 0.01 m HNO₃, and incubated under continuous darkness. Seeds treated with 5% H₂O₂ at 30°C, or oven‐dried and treated with 0.01% M HNO₃ at 35°C registered 10 and 20% germination. Approximately 75 and 90% of the light‐exposed seeds for all treatments germinated in the first three and six days at 25°C. No germination occurred at 15°C in the first three days after treatment. Seeds subjected to 40°C for six days after treatment recorded 36% germination. The optimum temperatures for seed germination were 25–30°C. Seed drying and soaking treatments widened the windows of the optimal temperatures for wrinklegrass germination. The acidic media of KNO₃, H₂O₂ or HNO₃ favored seed germination. Less than 5% of seed germination occurred with burial or water inundation at depths exceeding 2 cm. Seed burial or inundation at ≥2 cm depths inhibited seed germination. Seeds sown onto moist paddy soils registered ca. 50% germination. Free‐floating seeds on the water surface registered ca. 98% germination within the first six days after seeding. The mean number of seedlings that survived was inversely proportional to water depths, with close to 100% mortality at the 14 cm depths of inundation. Both plant height and seedling survival were linearly proportional to the amount of root mass of seedlings which penetrated the soil. The weed was a prolific seed producer (ca. 6000 seeds/genet or 18 000 seeds/genet per year). The vegetative and reproductive efforts of each wrinklegrass plant registered values of 0.68 and 0.32, respectively.     

水汽压差与钾素互作对高温下番茄营养吸收与光合特性的影响

空气水汽压差（VPD）是植物水分运输的主要驱动力,影响作物对营养的吸收。探究不同VPD与钾素对高温下作物营养元素的吸收与光合特性的影响对夏季番茄合理施肥与环境管理具有重要意义。试验以‘金棚14-6’番茄为试材,采用盆栽方式,设置2个VPD水平（高VPD、低VPD）与3个钾素水平 (2、4、8 mmol·L^-1)共6个处理,分析了VPD与钾素互作对高温下番茄幼苗氮磷钾吸收、气体交换参数、光合和CO₂响应等的影响。结果表明：与高VPD相比,降低VPD会对番茄植株各器官的氮、磷、钾含量产生稀释效应, 但随着钾素水平的提高,氮、磷、钾的积累量均会显著增加,各元素积累量分别增加了99.6%、98.1%和44.7%（氮）,57.4%、50.4%和51.6%（磷）,145.9%、71.5%和30.6%（钾）。在低VPD下,中钾水平更有利于干物质和氮、磷、钾元素的积累,其叶片的氮素积累量和叶片水势显著高于其他5个处理;且低VPD下的植株具有较大的光照、CO₂浓度适应区间和高光合及相关参数,包括光合速率P_n、气孔导度G_s、光饱和点LSP、表观量子效率AQY、暗呼吸速率R_d和初始羧化效率CE等,且均在中钾水平时取得最大值;同时蒸腾速率T_r、光补偿点LCP与光呼吸速率R_p等均显著降低。综上可知,高VPD下高钾水平和低VPD下中钾水平提高了番茄的光合性能、氮磷钾元素吸收量和干物质积累量,可作为夏季高温施肥与环境管理指标。     

Identification of a tractable model system and oxalic acid-dependent symptom development of the dollar spot pathogen Clarireedia jacksonii

Clarireedia jacksonii causes dollar spot disease of cool-season turfgrasses in the United States and produces the phytotoxin oxalic acid. The role of oxalic acid in host–pathogen interactions of C. jacksonii is unknown and there are multiple challenges to studying these interactions in natural turfgrass hosts. Consequently, identification of model plants to study C. jacksonii–host interactions and the role of oxalic acid in pathogenesis is necessary. Controlled environment inoculation assays were used to evaluate pathogenesis of C. jacksonii in various model plants and investigate the role of oxalic acid in symptom development. Observations at microscopic and macroscopic levels demonstrated that infection progressed similarly in all monocots tested (creeping bentgrass, wheat, barley, rice, Brachypodium distachyon) but not in the dicot Arabidopsis thaliana. Plant oxalic acid content increased from near zero to around 0.2–0.4 mM following inoculation with C. jacksonii in creeping bentgrass, barley, and wheat. Conversely, oxalic acid content remained near zero in A. thaliana and was not well correlated with inoculation in rice and B. distachyon, both of which had higher endogenous oxalic acid levels than other monocots. Time-course oxalic acid quantification experiments with creeping bentgrass and B. distachyon further supported a link between symptom development and in planta oxalic acid content and identified 48 hr postinoculation as a critical time-point for investigating the role of oxalic acid in C. jacksonii pathogenesis. These studies demonstrate that various monocots can serve as tractable model systems for studying C. jacksonii–host interactions and that increases in oxalic acid content are associated with C. jacksonii symptom development.     

Effects of long‐term fertilization on the weed growth and community composition in a double‐rice ecosystem during the fallow period

The vegetation cover during the non‐cropping season could have important implications for the maintenance and recovery of soil fertility, as well as for biodiversity conservation in croplands. In this study, five fertilization regimes (control: non‐fertilization; N: inorganic N fertilization; P: inorganic P fertilization; NPK: balanced fertilization with inorganic N, P and K; NPKM: balanced NPK plus farmyard manure) were conducted from 1981 in a double‐rice (Oryza sativa L.)‐cropping system in subtropical China. The effects of long‐term fertilization were investigated on the weed growth, diversity and community structure during the fallow period. The results showed that, relative to the control, both inorganic fertilization alone (N, P and NPK) and NPKM in the rice‐growing season significantly increased the weed density and biomass during the fallow period in the paddy field. There was no significant difference in the weed species richness (the number of species) among the treatments. Compared with the control, fertilization tended to reduce the weed diversity (Shannon's H′) and evenness (Shannon's E), especially in the N treatment. Long‐term fertilization resulted in a significant shift in weed community's composition during the fallow period. The weed community's structure was affected by soil nutrients in the order P > N > K.     

Fertilization affects severity of disease caused by fungal plant pathogens

Commercial fertilizers are commonly applied in farming to maximize crop yield. Lifting nutrient limitation to plant growth when water and light conditions are sufficient may permit plants to grow to the maximum of their ability; however, plant ability to resist pathogen infections is also modified. A meta‐analysis was conducted on 57 articles to identify the way plant disease severity of fungal pathogen‐induced infection is modified following fertilization, and the key regulators of such an effect. The analysis largely focused on N fertilization events in order to minimize the effect of heterogeneity that could result from differences in the way different nutrient fertilizers are able to modify plant disease severity. Fungal pathogen identity and fungal pathogen lifestyle were the main significant regulators affecting the extent of the modification of plant disease resistance following N fertilization, whereas contradictory results were obtained with the susceptibility of plant species. No differences were detected between pot or field experiments and following artificial or natural infection. Although in the vast majority of instances N fertilization increased disease severity, characteristic plant species and fungal pathogens could be identified for which disease severity following N fertilization declined. It is concluded that the potential of some plant species such as Solanum spp. to show reduced disease severity following N fertilization requires further investigation, as in such cases N fertilization could potentially be used as an additional means of suppressing fungal pathogens.     

Use of multispectral radiometry for assessment of rhizoctonia blight in creeping bentgrass

ABSTRACT The ability to identify diseases early and quantify severity accurately is crucial in plant disease assessment and management. This study was conducted to assess changes in the spectral reflectance of sunlight from plots of creeping bentgrass during infection by Rhizoctonia solani, the cause of Rhizoctonia blight, and to evaluate multispectral radiometry as a tool to quantify Rhizoctonia blight severity. After inoculation of 6-year-old creeping bentgrass turf with R. solani anastomosis group 2-2, reflectance of sunlight from the foliar canopy was measured at light wavelengths of 460 nm (blue) to 810 nm (near infrared [NIR]), at 50-nm intervals. Visual estimates of disease severity and percentage of canopy reflectance were made daily throughout each of three epidemics of Rhizoctonia blight from the onset of visible symptoms until maximum disease severity was reached. In each experiment, linear regression analysis revealed a significant reduction in the percentage of NIR (760 and 810 nm) reflectance as disease severity increased. However, in the majority of analyses, regression models explained <50% of the variability between components. Multispectrum radiometry appears to function best when used to assess differences in disease severity at discrete points in time rather than over an entire epidemic.     

包气带土壤pH对灌溉施肥响应的变异过程

为了分析灌溉施肥活动引起的包气带土壤pH值变异特征及其对地球化学条件的响应,通过历时3 a的野外原位灌溉施肥试验,应用不同季节灌前、灌后6 m土层中不同深度的测定资料,系统分析了土壤pH对灌溉、施肥的响应过程,结果表明：各深度pH值呈弱变异性（CV=1.01%~2.28%）,与灌溉前相比,灌后土壤pH值的均值和变异系数均呈现明显的变化;灌前包气带各层pH具有强烈的空间自相关性,灌后受水分、基质等相互作用影响,pH的空间自相关性有所减弱,C₀/(C₀+C)和变程a分别由7.23 m和3.54 m(灌前0 d)减少到3.26 m和2.76 m(灌后第10天)。土壤基质是决定土壤酸碱性的主要因素,在灌溉施肥活动对pH的响应过程中,地球化学条件（土壤含水量、土壤温度、土壤有机质(SOM)、氧化还原电位（RP）等)、土壤基质组成和氮底物浓度（NH⁺₄-N）等的交互作用影响pH的动态。土壤含水量和温度单独对pH影响不显著,两者交互作用对pH有显著影响。引起土壤pH变化的主要变异源为Cl^-、土壤有机质(SOM)、NO^-₃-N、NH⁺₄-N等营养物质和不同空间深度土壤基质的差异,表明灌溉施肥改变了包气带pH地球化学动力场、营养物质和土壤基质的交互作用,引起各深度的生物地球化学反应,控制pH值的空间变异特性。当包气带介质土壤水分变化时,首先营养物氨态氮以分子态或水合态形式被介质吸附,H⁺得到释放,使得灌后第4天pH值下降。随着氨氧化过程中H⁺的释放,pH在灌前和灌后第10天和第30天有显著差异。氨的氧化引起硝酸盐含量不断增加,使得硝酸盐对pH值的影响在灌后不断增强,相关系数由0.24(0 d,P<0.05)增加到0.41(30 d,P<0.01),而氨态氮对pH值的影响逐步降低,相关系数由0.43(0 d,P<0.01)降低为0.19(30 d,P>0.05)。     

局部根区滴灌与穴施尿素对土壤氮素空间分布的影响

为研究节水灌溉条件下穴施尿素、滴灌施肥对土壤铵态氮、硝态氮和碱解氮运移的影响,2019年在甘肃农业大学遮雨棚内开展施肥与灌溉试验,采用穴施尿素和滴灌施肥两种施肥方式,施纯氮量240 kg·hm^-2和180 kg·hm^-2,充分灌溉量和局部根区滴灌量分别是14 L和7 L。测定在距离滴头水平30 cm、垂直40 cm范围内土壤铵态氮、硝态氮和碱解氮含量,分析施肥与灌溉后土壤氮素转化及迁移特征。结果表明,土壤硝态氮更容易随灌水发生水平迁移,而土壤铵态氮更容易向土壤纵深迁移。土壤氮素含量的空间变异大小依次为：硝态氮>铵态氮>碱解氮;土壤硝态氮、铵态氮和碱解氮含量的平均变幅分别为32%~40%、26%~37%和6%~12%。局部根区滴灌土壤硝态氮含量的空间变幅比充分灌溉减小16%~20%。穴施尿素土壤铵态氮含量的空间变幅比滴灌施肥减小12%~28%。穴施尿素和局部根区滴灌调控土壤氮素转化速率,赋予肥料养分缓释性能,从而提高土壤氮素供应能力。因此,穴施尿素结合局部根区滴灌是较优的施肥与灌溉方式。     

SPATIAL GROWTH OF CYNODON DACTYLON (L.) PERS.*

Summary. Small sprigs of Cynodon dactylon (L.) Pers., were planted and grown without competition from weeds and crops for 2 1/2 years. The plant spread by means of above-ground creeping stolons and subterranean rhizomes which could also emerge as aerial shoots, producing in their turn new stolons and rhizomes. Initially there was linear extension of stolons and rhizomes, following which gaps in the sod were filled by stolon branching and new shoots. There was no preferential direction of stolon elongation and established sods developed an approximately circular shape and expanded concentrically. The rate of increase in sod area was similar in both years of observation but radial extension was smaller in the second year than in young plants. The mean sod area was 25 m² after 2½ years of growth, and mean monthly area increment was 0·9 m². Growth almost stopped in the cold season and exceeded 2 m² per month in the summer. The plants had extended up to 3·9 m from the plant centre after 2 1/2 years. The number of flowering culms per sod, produced only in the warm season, was directly proportional to sod area; seeds were infertile in the Newe Ya'ar area. After 2½ years of growth about 70% of the rhizome dry weight was present in the upper 20 cm of soil. Few rhizomes penetrated deeper than 40 cm. More than 60% of the rhizomes were present within 1 m radius of the plant centre and 90% were present within 2 m radius. Croissance spatiale de Cynodon dactylon (L.) Pers.     

有机-无机肥配施对黄土高原半干旱区农田土壤N2O排放的影响

为探明不同施肥方式对旱作麦田土壤N₂O排放的影响,以不施肥(CK)为对照,设置单施有机肥(M)、单施无机肥(N)、有机-无机肥配施(MN)3种施肥方式,采用静态箱-气相色谱法对春小麦地土壤N₂O排放通量进行测定,并对其影响因子(NO^-₃-N、NH⁺₄-N、土壤温度、土壤含水量)和春小麦产量进行同期测定。结果表明：春小麦地在整个生育期内表现为N₂O排放源,各处理均在施肥后出现N₂O排放峰。不同处理土壤N₂O累积排放量表现为N>MN>M>CK,N₂O净损失量(以氮计算)为1.175 8～1.428 kg·hm^-2,占当季施氮量的1.12%～1.36%,有机-无机肥配施降低了氮肥中氮素以气态形式的损失量。MN、N、M处理春小麦产量分别较CK处理增加了45.1%、31.0%、18.8%,各处理土壤NO^-_3<...     

Calcium reducesBotrytis c1nerea damages to plants ofRuscus hypoglossum

Plants ofRuscus hypoglossum L. were grown in containers with perlite, an inert medium, or with soil, under similar-to-commercial conditions, for three winter seasons. Constant fertilization with soluble calcium [Ca(NO₃)₂] through the root zone resulted in a reduction of up to 78% in postharvest rot caused by artificial inoculation withBotrytis cinerea Pers. ex Fr. Control plants were treated by fertilization with N,P,K and all other elements, identical to the fertilizer containing calcium. Foliar application of Ca(NO₃)₂ to ruscus bushes or application of this compound or of CaCl₂ or CaSO₄ to mature cut branches standing in water, resulted also in a significant reduction in postharvest phylloclade rot. Application of CaSO₄ and Ca(H2PO₄)₂ + CaSO₄ to ruscus plants, from fertilizers containing 22% Ca and releasing the cation gradually, effectively reduced the susceptibility of cut branches to infection by_{B. cinerea.}     

Effects of phosphorus and light intensity on the growth and competition of the two weed species,Veronica persica and Chorispora tenella

Veronica persica Poir. (Persian speedwell) is an invasive alien weed species in the upland soils throughout China. Its dominance in weed flora could be alleviated by Chorispora tenella (Pall.) (tender chorispora) in P‐poor soils and in an intense light environment. Here, three experiments in growth chambers were carried out in order to explore the effect of P and light intensity on the growth and competition of V. persica and C. tenella, the pH value in their rhizospheres, and the kinetic parameters (K_m and V_max) of the H₂PO₄^‐ uptake by the two weed species. The ANOVA results showed that the light intensity and P level in the soil obviously influenced the growth of the two weed species. However, the effect of the P level in the soil was greater for V. persica and the effect of the light intensity was greater for C. tenella. The restriction of the growth of V. persica by a low P level in the soil was much more than that of C. tenella, but it was reversed in the two species in relation to a low light intensity. In addition, the pH was lower in the rhizosphere of C. tenella after the P‐deficient treatment and there was a lower K_m in the uptake of H₂PO₄^‐ than for V. persica, suggesting that C. tenella could adapt to a low‐P environment more easily. In conclusion, C. tenella growing together with V. persica had a competitive advantage under high‐light‐intensity and low‐P‐level conditions, but it lost its advantage with an increase in P fertilization and a decrease in light intensity.     

Effects of N, P and K on Striga asiatica (L.) Kuntze seed germination and infestation of sorghum

Sorghum (Sorghum bicolor (L.) Moench) plants were grown in pots with 12.5 and 50 mg applied N kg^?1 soil. With an increase of soil N, the Striga asiatica (L.) Kuntze infestation, as well as the sorghum shoot dry matter losses due to infestation, decreased. The relative differences in stimulant capacity to induce Striga seed germination among the four sorghum genotypes were not consistent over the 0 to 150 mg N 1^?1 range. The sorghum root exudate was considerably more active at 0 mg N 1^?1, than at 30 mg N 1^?1, and the stimulant produced at 150 mg N 1^?1 failed to induce Striga seed germination. Presence of N in the growth medium considerably reduced the effectiveness of the stimulating substance produced by sorghum roots, whereas K promoted stimulant activity only in the absence of N. The presence or absence of P in the growth medium did not affect Striga seed germinability, probably due to the inability of this element to interfere with the production or activity of the stimulating substance from the host plants. It can be concluded, therefore, that sorghum plants seem to produce active root exudate only in conditions of N deficiency.     

施氮和覆膜对旱作春玉米农田土壤微生物量和土壤酶活性的影响

为研究长期不同施氮水平和覆膜对黄土高原旱作春玉米高产体系土壤微生物活性的影响,设置田间试验包含施氮水平和覆膜2个因子,施氮量分别为0（N0）、100 kg·hm^-2（N100）、250 kg·hm^-2（N250）和400 kg·hm^-2（N400）,每个施氮水平下分别有覆膜（F）与不覆膜（B）处理,供试玉米品种为先玉335。2014年采集0~10 cm和10~20 cm土层土壤样品,测定土壤微生物量和酶活性,分析微生物量计量学特征并进行综合评价。结果表明,无论覆膜与否,土壤微生物量碳、氮和磷均随施氮量的增加而增加（除不覆膜时N400处理）,施氮量高于250 kg·hm^-2时土壤微生物量增加不显著。覆膜对土壤微生物量碳、氮无显著影响,而显著增加土壤微生物量磷;覆膜在一定程度上降低N0、N100和N400处理土壤微生物量碳氮比,施氮则显著增加微生物量碳氮比和微生物量氮磷比。0~10 cm土层脲酶活性随施氮量的增加而增加,但覆膜对脲酶活性无显著影响。覆膜和施氮均显著增加碱性磷酸酶活性,0~10 cm和10~20 cm土层覆膜N400处理碱性磷酸酶活性在相应土层最大,分别为1.49 mg·g^-1·d^-1和1.61 mg·g^-1·d^-1。主成分分析结果表明施氮量为250 kg·hm^-2时土壤微生物活性最强。研究表明无论覆膜与否,250 kg·hm^-2的施氮量是该地区适宜的施氮量。     

Note: Corn stalk borer (<Emphasis Type="Italic">Sesamia nonagrioides</Emphasis>) infestation on sorghum in central Greece

Sweet sorghum (Sorghum bicolor (L.) Moench) was introduced recently into Greece and is being cultivated experimentally for the production of liquid biofuel. A pilot survey was conducted in October 2005 to provide information on the species composition and density of its lepidopterous stem borers, which appear to cause severe losses in production. The dominant pest in that season wasSesamia nonagrioides Lefebvre, with a mean density of 1.41 larvae per plant. Larvae were sampled from various plant internodes and found to have a preference for the lower ones. Analysis of variance showed no significant effects on larval density of the irrigation levels or of the organic — conventional soil fertilization method. A significant negative correlation was found between the body length ofS. nonagrioides larvae and the internode from which they were retrieved. This is the first published report of sorghum borer pests in Greece. http://www.phytoparasitica.org posting Feb. 7, 2007.