Effects of Ledum groenlandicum amendments on soil characteristics and black spruce seedling growth

The effects of leaves and litter of the boreal forest understory shrub, Ledum groenlandicum, on soil characteristics and black spruce (Picea mariana) seedling growth were investigated. Organic and mineral soils, not previously associated with L. groenlandicum, were amended with leaves and litter of this species. The objectives of the present study were: (i) to determine the changes in soil characteristics after amending with L. groenlandicum, (ii) to determine the quantitative variation in the concentration of water-soluble phenolic allelochemicals in mineral and organic soil layers modified by L. groenlandicum and (iii) to study the growth response of black spruce in soils treated with different L. groenlandicum amendments. The amended organic and mineral soils were analyzed for pH, organic matter, PO₄, N, Ba, Cu, Zn, Fe, Mn, Ca, Na, K, Mg, Al and total phenolics equivalence. Results indicate that organic soils amended with L. groenlandicum leaves and litter were significantly different from unamended control soil for most of the chemical characteristics, while amended mineral soil was different from that of unmodified mineral soil for PO₄, organic matter, K and total phenolics equivalence. Water-soluble phenolics from L. groenlandicum and changes in nutrient availability are plausible causes of L. groenlandicum interference with black spruce seedling growth.     

Effect of Ash Pond Soil and Amendments on the Growth and Arbuscular Mycorrhizal Colonization of Allium cepa and Germination of Arachis hypogaea,Lycopersicon esculentum,and Vigna mungo Seeds

The effect of fly ash pond soil on the growth and yield of onion (Allium cepa var. microaggregatum) plants grown in pots was investigated. The fly ash pond soil was amended with combinations of red soil and press mud, a waste product from sugar mills. Water-holding capacity of ash pond soil amended with press mud increased; however, addition of press mud delayed onion bulb development. Onion bulb germination took place rapidly in ash pond soil; however, subsequent bulb development declined. The addition of red soil and press mud increased the growth and yield of onion plants. In all the soils and amendments, onion plant roots were colonized by native arbuscular mycorrhizal species. Both vesicles and arbuscules were present in the roots. Colonization was low in ash pond soil but increased with the addition of red soil. Effect of fly ash pond soil on germination of groundnut (Arachis hypogaea), tomato (Lycopersicon esculentum), and black gram (Vigna mungo) seeds was evaluated and compared with red soil in the laboratory. Ash pond soil increased the germination of tomato seeds but did not affect the germination of groundnut and black gram seeds.     

Evaluation of Argemone mexicana for Control of Root-Infecting Fungi in Tomato

Argemone mexicana L. (Papaveraceae), a tropical annual weed, is known to be phytotoxic to many crop species. This study was designed to examine the possible impact of A. mexicana on root‐infecting fungi, changes in fungal community structure and the growth of tomato. A. mexicana decaying shoots in soil provided a marked decrease in the infectivity of Fusarium solani and Rhizoctonia solani but Macrophomina phaseolina remained unaffected. Plant height and shoot growth of tomato plants increased markedly though high concentration of A. mexicana (5% w/w) was deleterious to tomato plants. General species diversity of soil fungal communities increased in the amended soils over the controls and greater increase in diversity occurred at higher concentrations of decaying A. mexicana. Likewise, equitability and richness components of diversity increased in treatments compared to controls but declined with increasing sampling period. Aspergillus nidulans, Cephaliophora irregularis, Drechslera halodes, Paecilomyces lilacinus and Trichoderma viride were isolated exclusively from the amended soils. Aqueous extract of A. mexicana when applied in soil greatly suppressed all three of the above root‐infecting fungi, and at lower concentration actually enhanced plant growth. The influence of different levels of N‐fertilization with NH₄NO₃ on the modification of the effect of decaying A. mexicana on root‐infecting fungi was also investigated. N‐fertilization to some extent alleviated the phytotoxicity to tomato plants while suppressing the root‐infecting fungi. A. mexicana in conjunction with Pseudomonas aeruginosa, a plant growth‐promoting rhizobacterium, significantly suppressed root‐infecting fungi with concomitant increase in plant growth. Whereas P. aeruginosa was reisolated from the rhizosphere and inner root tissues of tomato, its population slightly declined in the amended soil but not to an extent that could reduce the biocontrol and growth promoting potential of the bacterium.     

黄瓜种子及其萌发期的化感作用研究

以大白菜、萝卜、番茄和黄瓜种子为受体,采用实验室培养皿种子发芽生物测试法研究了黄瓜种子浸提液、种子萌发、胚根和芽苗分泌物、芽苗腐解物和芽苗浸提液的化感效应。结果表明:(1)黄瓜种子浸提液对大白菜、萝卜、番茄和黄瓜种子萌发均有化感抑制作用,即黄瓜种子内含有某些化感抑制物质。(2)在水浸提过的黄瓜种子萌发过程中,它不仅对其近邻套种的大白菜、萝卜和番茄种子萌发产生化感抑制作用,而且其胚根和芽苗分泌物对后茬播种的4种蔬菜种子发芽也表现出不同程度的化感抑制作用;黄瓜芽苗腐解物和芽苗水浸提液也对各受体蔬菜种子发芽与生长产生不同程度的化感抑制作用,且随着腐解芽苗量的增加或浸提液浓度的升高,各受体蔬菜种子的发芽指标值、化感效应指数值和综合效应值随之降低。(3)黄瓜种子浸提液及芽苗各器官的化感物质对黄瓜种子的萌发与生长产生了自毒作用,且黄瓜芽苗腐解物、芽苗浸提液、胚根及芽苗分泌物对受体黄瓜的自毒作用均为最大。研究发现,黄瓜种子浸提液、种子萌发时期以及芽苗各器官的化感物质主要是通过抑制受体胚根的生长而起化感抑制作用,即受体蔬菜种子胚根对化感效应最为敏感;因黄瓜种子及萌发期释放化感物质的途径有所不同,导致受体大白菜、萝卜、黄瓜和番茄的化感响应也不相同;在黄瓜种子萌发和芽苗生长的早期,化感物质即开始在芽苗体内进行合成与积累,一部分可通过胚根和芽苗分泌途径释放到环境中,另一部分可通过芽苗腐解途径释放化感物质,并对受体蔬菜种子萌发与生长表现出较强的化感抑制作用。     

离体蒜苗挥发物的化感作用及其成分分析

采用半密闭容器法研究了离体蒜苗挥发物对黄瓜、番茄、萝卜的化感作用,并对其成分进行了GC-MS分析。结果表明:蒜苗挥发物对黄瓜的种子萌发及幼苗生长表现为低促高抑的双重浓度效应,对番茄和萝卜则表现出抑制作用,并且随供体蒜苗质量的增大,抑制作用增强;供体蒜苗质量低于400g时,受体植株SOD、POD、CAT、PPO、PAL等活性增强,供体质量为400g时,受体作物上述酶活性均降低;离体蒜苗挥发物的主要化学成分为二烯丙基二硫化物(23.33%)、1,3-二噻烷(18.34%)和邻苯二甲酸二丁酯(6.30%)。     

Allelopathic effect of Pluchea lanceolata (Asteraceae) on characteristics of four soils and tomato and mustard growth

The effect of the leachate of the noxious weed Pluchea lanceolata was explored using mustard and tomato seedling growth bioassays of four soil types (sandy loam, clay loam, silty loam, and sand). The objectives of the present study were: 1) to determine how soil chemistry changes after addition of leachate and leaves of the weed; 2) to determine what level of input to the soil does not cause significant differences from those of weed-associated soils under field conditions; and 3) to determine whether soil texture affects bioassay results. Leaf leachates of the weed were added to four soil types in different dilutions, and soils were analyzed for pH, electrical conductivity, organic matter, Cl, PO₄, exchangeable Cu^{+ +}, Zn^{+ +}, Na⁺, K⁺, Mg^{+ +}, and Ca^{+ +}, and total phenolics. These results indicated that the leachates of the weed altered chemical characteristics of each soil type. Concentration of phenolics in treatment of each soil type was dilution-dependent. Leachates were more inhibitory on sandy loam and clay loam than on silty loam and sand. Present study indicated that in allelopathic bioassays, amended soils that are nonsignificantly different from weed-associated soils should be taken. Further, present investigations confirmed the significance of good control soil with nonsignificantly altered chemical characteristics from those of natural soils, as well as soil texture to establish allelopathy of ecological relevance.     

Effects of pulp mill solids and three composts on early growth of tomatoes

Compost has been proposed as a means of simultaneously diverting organic materials from landfills while producing a valuable product that improves tilth, organic matter content and nutrient supply of agricultural soils. Composts manufactured from different source materials may have markedly different properties however, even if they meet all regulatory requirements. We compared the capacity of composts made from three different combinations of organic wastes (horse manure and bedding, mink farm wastes, municipal solid waste (MSW) and sewage sludge) along with clarifier solids from a chemo-thermomechanical pulp mill, to enhance the growth of tomato (Lycopersicon esculentum L.) seedlings grown in nutrient-poor organic potting soil. Germination and seedling emergence of tomatoes, cress (Lapidium sativum L.) or radish (Raphanus sativus L.) were tested to assess phytotoxicity of the four amendments. Mink farm compost and horse manure compost stimulated root and shoot growth of tomato seedlings but MSW compost and pulp mill solids were strongly inhibitory. MSW compost and unamended potting soil also inhibited seedling emergence and pulp mill solids produced stunting and deformities in radish and cress seedlings. Both toxic constituents and nutrient imbalances may be responsible for the growth-inhibiting effects of these amendments. Application of pulp mill solids to agricultural soil without composting may lead to deleterious effects on vegetable crops.     

Growth of bedding plants in commercial potting substrate amended with vermicompost

Vermicompost has been promoted as a viable alternative container media component for the horticulture industry. The purpose of this research was to investigate the use of vermicompost at different points in the production cycle of tomato, marigold, pepper, and cornflower. The incorporation of vermicompost of pig manure origin into germination media up to 20% v/v enhanced shoot and root weight, leaf area, and shoot:root ratios of both tomato and French marigold seedlings; however amendment with vermicompost had little influence on pepper and cornflower seedling growth. Moreover there was no effect on the germination of seed of any species. When seedlings of tomato, French marigold, and cornflower were transplanted into 6-cell packs there was greater plant growth in media amended with vermicompost compared to the control media, and the greatest growth when vermicompost was amended into both the germination and transplant media. This effect was increased when seedlings in the transplant media were irrigated with water containing fertilizer.     

Growth response of selected vegetable crops to spent mushroom compost application in a controlled environment

Summary Snap bean, cucumber, radish, spinach, and tomato seedlings and plants were grown in soils amended with 0, 10, 20, 30 and 50% spent mushroom compost (SMC) under greenhouse conditions. While total seedling emergence was not affected by the addition of SMC, the rate of seedling emergence was delayed. Increased growth was observed in the range of 30 to 50% SMC. The elemental content in seedling tissue indicated an antagonism among K, Ca, and Mg for ion uptake. Increased plant growth and yield were obtained with addition of 20 to 30% SMC; those grown at 50% SMC exhibited some stunting. The limiting factor in the use of SMC appeared to be its high soluble salts content.     

Comparison of the effect of market crop wastes and chemical soil fertility amendments on insect pests, natural enemies and yield of Brassica oleracea

Field studies were conducted over three growing seasons during 2 years to assess the relative effect of market crop waste (MCW)‐derived soil fertility amendments and conventional fertiliser (NPK) on tritrophic relations as well as yield performance of white cabbage. A randomised complete block design with four treatments and a control replicated four times was used. Treatments were (a) MCW compost incorporated in the soil, (b) uncomposted MCW incorporated in the soil, (c) uncomposted MCW applied as surface mulch, (d) a conventional chemical fertiliser (NPK) incorporated in the soil and (e) the untreated control. Results indicated that relative to NPK‐amended plants, MCW‐amended cabbage performed better in plant growth parameters as well as yield, despite having sustained aphid and Plutella xylostella infestations that could be as much as double as those in the NPK treatment. Natural enemy occurrence followed the trend of host insect infestations. The average yield performance and net financial benefits from MCW‐compost‐amended plants were three‐fold as that of NPK‐amended plants. Soil analysis results indicated an advantage in soil quality accruing from the MCW amendments. This study, therefore, provides documentation for the utilisation of MCW, previously handled as garbage to be disposed of, as a key component in integrated management of insect pests and depleted soils in crop production in sub‐Saharan Africa and beyond.     

Organic matter inputs create variable resource patches on Puerto Rican landslides

Landslides are a frequent disturbance in montane tropical rainforests that result in heterogeneous environments for plant and soil development. Natural inputs of organic matter and associated nutrients contribute to soil fertility patchiness within landslides. To test the importance of organic matter and nutrient addition to landslide soil fertility and plant growth, we mixed three types of organic matter substrates that are common to landslides (Cecropia leaves, Cyathea fronds, and forest soil) and commercial fertilizer into recently eroded soil on five landslides in Puerto Rico. In addition, we sowed seeds of two common landslide colonists (Paspalum and Phytolacca) into the soil treatment plots in order to test treatment effects on seed germination and seedling growth. Soils, seed germination, and seedling growth were monitored for one year and the field experiment was replicated in a one-year screen-house experiment. Despite highly variable initial landslide conditions, responses to soil treatments were similar across all five landslides. The forest soil addition increased total soil nitrogen and soil organic matter on landslides within 60 days, whereas Cecropia leaves provided increased soil organic matter only after 210 days. Commercial fertilizer increased plant-available soil nitrogen and phosphorus within 60 days, and also increased seed germination of Paspalum seeds when compared to soils treated with Cecropia leaves. Despite these positive effects of treatments on soils and germination, there were no treatment effects on seedling growth in the field, perhaps due to leaching or other losses of soil nutrients evident in the lack of significant treatment differences in soil resources at 370 days. In the screen-house, forest soil and commercial fertilizer treatments significantly increased soil fertility and seedling growth of both Paspalum and Phytolacca compared to control treatments. These different responses to three common types of organic matter inputs create patchy soil conditions with important implications for plant colonization and landslide succession.     

石蒜对萝卜、黄瓜、番茄和油菜幼苗的化感效应

在室内用离体生测方法研究了石蒜水浸提物对萝卜、黄瓜、番茄和油菜的化感效应.结果表明, 石蒜水浸提物对4种植物种子的萌发和幼苗生长均具有较强的抑制作用.4种受体作物中,以番茄最为敏感,最低浓度0.0125 g·ml^-1处理下,番茄种子完全受到抑制不能萌发,油菜、萝卜与黄瓜种子的萌发抑制率分别为17.73％、14.97％和2.65％.相同浓度处理时,石蒜水浸提物对萝卜、黄瓜及油菜芽的生长抑制作用高于对根的抑制作用.采用去胚乳小麦生长法和高梁河沙法测定了石蒜甲醇浸提物对光合作用和非光合作用抑制活性.结果表明,石蒜甲醇浸提物对去胚乳小麦和高梁的生长有较强的抑制作用,对高梁芽和根生长的抑制作用高于对去胚乳小麦根和芽生长的抑制,说明石蒜对植物的化感效应主要体现在抑制非光合作用活性上,但也一定程度地抑制植物的光合作用.     

Observations on autotoxic effects on seed germination and seedling growth in Cirsium palustre from a spring area in Jutland, Denmark

Ethanol extracts from fresh leaves of Cirsium palustre (L.) Scop. were tested for inhibitory effects on the germination of own seeds, and dried leaves were ground and incorporated in soil to determine if growth of own seedlings was affected. Leaf extracts strongly inhibited seed germination, and leaf residues seedling growth. Inhibition was apparently not mediated by effects on pH or by nutrient deficiency.     

栗与美国板栗化感作用的比较

以种子发芽率和发芽势为种子萌发参数, 以胚根、胚芽长度和鲜重变化为幼苗生长参数, 研究了栗(Castanea mollissima)叶水提取物对双子叶植物莴苣(Lactuca sativa)、萝卜(Raphanus sativus)、黄瓜(Cucumis sativus), 和单子叶植物洋葱(Allium cepa)、水稻(Oryza sativa)、小麦(Triticum aestivum)的化感作用; 比较了美国板栗(Castanea dentata)与栗叶水提取物及经X-5大孔树脂分离获得的11个洗脱组分间的化感作用强弱; 利用液相色谱-质谱联用技术结合标准物质的反证实验, 解析了美国板栗与栗化感作用最强分离组分的物质结构。研究结果表明, 栗叶化感效应强于美国板栗; 美国板栗与栗化感作用最强分离组分中(5:5洗脱组分)存在绿原酸、对羟基苯甲酸、原儿茶酸和没食子酸等物质。在利用栗基因恢复美国板栗种群时, 有必要考虑美国板栗与栗植物化学生态特性的差异。     

Do high-nickel leaves shed by the nickel hyperaccumulator Alyssum murale inhibit seed germination of competing plants?

Elemental allelopathy suggests that nickel (Ni)-rich leaves shed by hyperaccumulators inhibit the germination and growth of nearby plant species. Here, the germination of eight herbaceous species following addition of Alyssum murale biomass or Ni(NO3)2, with the same Ni level added to soil, was assessed. The distribution of Ni in soil was tested by determining Ni phytoavailability and speciation over time. Phytoavailable Ni in soil amended with biomass declined rapidly over time due to Ni binding to iron (Fe)/manganese (Mn) oxides in the soil. No significant effects on seed germination were observed. Unlike the Ni complex in Alyssum biomass, more Ni remained soluble and phytoavailable in soil amended with Ni(NO3)2, thus significantly inhibiting seed germination. High-Ni leaves shed by hyperaccumulators did not appear to create a 'toxic zone' around the plants and inhibit germination or growth of competing plants. The lack of an allelopathic effect was probably related to low Ni availability.     

Influence of Ultraviolet Radiation on Germination and Early Seedling Growth

The influence of UV-B radiation (280–320 nm) from filtered and unfiltered FS-40 fluorescent sunlamps on germination and early seedling growth was examined for a range of vegetables (tomato, radish, cucumber, lettuce, and bean) and field crops (wheat, cotton, soybean, and millet). Continuous exposure of seeds for 3 days to 26.9 × 10⁻² W × m⁻² UV-B radiation (280–320 nm) at 25°C, had a slight effect on fresh weight of seedlings but no appreciable influence on germination percentage, or dry weight of seedlings. Extending the time of exposure to 6 days, however, resulted in abnormal seedling growth in all species but wheat. Typical responses were short, stubby roots, bronzing of the cotyledons, increased pigmentation, and abnormal curvature of the shoots.     

DISTURBANCE,LIFE HISTORY STRATEGIES,AND SEED FATES IN ALPINE HERBFIELD COMMUNITIES

Species responses to disturbance are governed primarily by their life history and physiological traits and by the characteristics of the disturbance. Species reproductive traits are especially important in determining the potential of species to establish and to persist following disturbance. Herein, I review available literature on relationships among disturbance, species life histories, and seed fates in tundra environments. Research conducted on these relationships in alpine herbfield vegetation on the Beartooth Plateau, Montana, over the past 9 yr by my colleagues and myself is synthesized. In tundra environments, species reproductive capacities are often similar to those in more temperate environments, but short, cool growing seasons constrain seed production and reduce seedling growth and survival. Highly variable growing season conditions result in large differences in seed production and seedling establishment among years. On disturbed sites, disturbance characteristics determine the seed and seedling environment and influence rates of establishment. In these windy environments, relationships among soil surface characteristics and seed morphological attributes determine both the horizontal and vertical movement of seeds on exposed soils. Once seeds are incorporated into the soil, soil physical and chemical properties determine temperature and nutrient regimes and have the greatest effects on seed germination and seedling growth and survival. Examining the seed fates of herbfield species with varying life histories illustrates that the identities of species that establish following disturbance are largely predictable from their reproductive traits. Disturbance characteristics determine the success of different reproductive strategies and significantly influence community structure.     

Utilisation of blue-green algae as biofertilisers

Biologically active compounds may be liberated from blue-green algae growing on the surface of moist soils. Such compounds may also be released as exudates from algae grown in liquid culture.This report describes inoculation of soils in pots, containing radish or tomato plants, with algal suspensions or exudates, which resulted in increased growth rates of both plants and increased their overall yield. Autoclaved exudates were generally as effective as fresh exudates. Interaction of effects between the various active substances depends on the algal species and method by which the soils are amended.     

Application of composted sewage sludge (CSS) as a soil amendment for turfgrass growth

We studied the growth of perennial ryegrass in soils amended with 5–100% composted sewage sludge (CSS), and the impacts of CSS amendment on soil physical and chemical properties. Soils amended with ≤20% CSS did not significantly affect the seedling emergence, while the contents of chlorophyll, nitrogen, phosphorous, and potassium of perennial ryegrass grown in such soils were greatly improved. Bulk density, water retention, and nutrient contents of the soil were also improved with the amendment of CSS, but high CSS contents introduced excessive amounts of heavy metals and soluble salts. Results show that Cu, Zn, and Pb accumulated slightly (up to ∼2.3 times) in clippings of perennial ryegrass grown in CSS-amended soils compared to those grown in the base and reference soils, while no significant Cd absorption in shoots of perennial ryegrass occurred. The detrimental effects on seedling emergence and turfgrass growth observed on substrates with high (≥40%) CSS contents were mainly attributed to the presence of high soluble salt concentrations. The findings suggest that addition of CSS at 10–20% levels can greatly improve the soil nutrient supply for turfgrass growth without significantly affecting heavy metal and soluble salt contents of the soil.     

The allelopathic potential of alfalfa root medicagenic acid glycosides and their fate in soil environments

Summary The allelopathic effect of alfalfa (Medicago media Pers.) and red clover (Trifolium pratense L.) root saponins on winter wheat seedling growth and the fate of these chemicals in soil environments were studied. Seed germination, seedling and test fungus growth were suppressed by water and by alcohol extracts of alfalfa roots, and by crude saponins of alfalfa roots, indicating that medicagenic acid glycosides are the inhibitor. Powdered alfalfa roots inhibited wheat seedling growth when added to sand. At concentrations as low as 0.25% (w/w) the root system was completely destroyed whereas seedling shoots suffered little damage. Red clover roots caused some wheat growth inhibition when incorporated to sand, but their effect was much lower than in the alfalfa root treatment. Soil textures had a significant influence on the inhibitory effect of alfalfa roots. The inhibition of seedling growth was more pronounced on light than on heavy soils. This was attribted to the higher sorption of inhibitors by heavy soils. Incubation of alfalfa roots mixed into loose sand, coarse sand, loamy sand and clay loam for a period of 0–8 days resulted in decreased toxicity to bothT. viride and wheat seedlings. This decrease occurred more quickly in heavier soils than in loose sand, due to the hydrolysis of glycosides by soil microorganisms. Soil microbes were capable of detoxifying medicagenic acid glycosides by partial hydrolysis of sugar chain to aglycone. These findings illustrate the importance of medicagenic acid glycosides as an inhibitor of wheat seedling growth, and of their fate in different soil environments.