银合欢落叶层对苗圃生长的森林一农田作物的他感作用(英文)

利用随机区组试验评估了孟加拉国吉大港大学苗圃内的银合欢落叶对森林作物种白格、黄金檀和农田作物种长豇豆、鹰嘴豆和木豆的他感作用。结果表明,凋落叶诱导抑制作物的萌发和生长,该抑制作用依赖于萃取物浓度、凋落物及受体物种类型。萃取物浓度越高则他感作用越强。受体植物的生长响应随应用的凋落叶而变化。低浓度(10g·m-2)凋落叶对农田作物嫩芽生长有促进作用,而其他浓度的凋落叶则呈现明显的抑制作用,施用的凋落叶浓度越大抑制作用也越大。但是不同处理所表现出的抑制趋势并不均一,根系生长受到的影响大于嫩芽。图3表4参34。     

Allelopathic effects of leaf litters of <Emphasis Type="Italic">Eucalyptus camaldulensis</Emphasis> on some forest and agricultural crops

Allelopathic effects of different doses of Eucalyptus camaldulensis leaf litters were investigated through an experiment in the green house of Institute of Forestry and Environmental Sciences, Chittagong, Bangladesh. Three popular agricultural crops： Falen （Vigna unguiculata）, Chickpea （Cicer arietinum）, Arhor （Cajanus cajan） and two widely used plantation trees： Sada koroi （Albizia procera） and Ipil ipil （Leucaena leucocephala） were selected as bioassay species. Experiment was set on tray at room temperature 27℃. The effects of different doses of leaf litter extracts were compared to the control. Results suggest that leaf litters of E, camaldulesis induced inhibitory effects, It was also found that the effect depend on concentration of extract and litterfall, type of receiver species. Higher concentration of the materials had the higher effect and vice versa. Though all the bioassay species were suppressed some of them showed better performance. Vigna unguiculata, Cicer arietinum are recommended in agroforestry based on this present Experiment output. In mixed plantation, Leucaena leucochephala is a better choice while compared to Albizia procera.     

Micronutrient, magnesium and phosphorus effects on biomass and leaf tissue nutrient concentrations of field grown Leucaena leucocephala

To optimize biomass and crude protein (CP) production for leucaena (Leucaena leucocephala) in southern Texas, field trials were conducted with treatment combinations of three levels of phosphorus (P) , two levels of Mg and two levels of soluble trace element mixture (STEM). The P was banded in the soil while the Mg and micronutrient blend were applied to the foliage. A combination of P (22 kg ha^-1), Mg and STEM fertilizers significantly increased biomass from 2555 kg ha^-1 to 3028 kg ha^-1. This treatment was associated with an increase in leaf CP from 27.9% to 31.0%. P fertilizer had no significant effect on leaf P, but significantly increased leaf nitrogen (N) and leaf copper (Cu). A foliar spray of Mg significantly increased leaf N, P, and Cu. A foliar spray of a complete micronutrient blend increased leaf Cu. Biomass production was correlated positively (decreasing order) with leaf Cu, N, and Mg and negatively with Zn. Leaf N was positively correlated with leaf P and calcium. The critical tissue concentrations (CTC) (where 90% of predicted maximum leaf protein was obtained) were 0.18% and 4.49 mg kg^-1 for leaf P and Cu, respectively. This revised version was published online in June 2006 with corrections to the Cover Date.     

Allelopathic effects of Mikania cordata on forest and agricultural crops in Bangladesh

Mikania cordata, an invasive weed is becoming a problem in the secondary degraded forests and plantations of Bangladesh, not only competing with but also releasing allelochemicals to cultivated crops. Allelopathic effects of the leaves of M. cordata were investigated through an experiment in the green house of the Institute of Forestry and Environmental Sciences, University of Chittagong, Bangladesh. Five economically important agricultural crops(Oryza sativa L., Triticum aestivum L., Vigna sinensis L., Abelmoschus esculentus L. and Amaranthus tricolor L.) and three forest crops(Acacia auriculiformis A.Cunn. ex Benth. Hook, Albizia procera(Roxb.) Benth.,and Paraserianthes falcataria(L.) Nielson) were used as bioassay species. Experiments were conducted on trays at an average room temperature 27 °C. The effects of different concentrations of leaf extracts were compared to controls. Water soluble allelochemicals of M. cordata inhibited the germination and initial growth of the tested agricultural and forest crops. Germination percent of forest crops declined with increasing concentration of extracts.The inhibitory effect on root elongation of forest crops was pronounced, whereas a stimulatory effect was found on P.falcataria up to a concentration of 25 %. Abelmoschus esculentus showed poor germination(%) and low shoot development(0.5 cm) and no development of taproot or lateral roots at treatment of 100 % concentration. Theinhibitory effect was proportional to the concentrations of the extracts with higher concentrations producing stronger inhibitory effects. Lower concentrations showed some stimulatory effect. The inhibitory effect was pronounced in root and lateral root development rather than germination or shoot development of the crops. Mikania cordata should be eradicated for healthy growth and development of the forest and adjacent agricultural crops.     

Comparative field performance of some agricultural crops under a canopy of Populus deltoides and Ulmus wallichiana

The performance of maize, beans and sunflower was evalu-ated under a canopy of Populus deltoides and Ulmus wallichiana at Fac-ulty of Agriculture, Wadura. The germination, growth and yield of the three...     

Yield-density effects on growth and biomass partitioning in Leucaena leucocephala seedlings

Experiments were conducted to study the effects of density on growth and biomass partitioning of Leucaena leucocephala seedlings.Four plantations with densities of 10,000,20,000,40,000,and 80,000 seedlings ha^-1 were evaluated only from 15 to 25 months after planting.At 15 months,crown height and width decreased with increasing density.Seedling height/dbh ratios increased with increasing density.Biomass increased with greater density according to the yield–density effect equation,which was evident for all densities.With increasing age,biomass division to branches and leaves increased,whereas partitioning to roots decreased in the 10,000 and 20,000 seedlings ha-1 plantings.Partitioning to branches and leaves remained relatively steady,while partitioning to roots increased in the 40,000 and 80,000 seedlings ha^-1 plantings.Biomass division into stem and bark components remained relatively steady in all densities.Yield–density and organ yield–density curves shifted upward with increasing seedling age on a log–log graph throughout the experimental period.     

Effect of alley cropping with Leucaena leucocephala and fertilizer application on yield of vegetable crops

Field experiments were conducted to investigate the effect of alley cropping vegetable crops with Leucaena leucocephala (Lam.) de Wit for two seasons on a sandy loam Oxic paleustalf in southwestern Nigeria. Four vegetable crops (Amaranthus cruentus L.; Celosia argentea L.; Okra, Hibiscus esculentus L.; and tomato, Lycopersicon esculentum Mill.) were grown in control plots and in 4-m wide alleys between established Leucaena hedgerows without and with fertilizer (30 N-13 P-24 K kg ha^–1). Leucaena prunings yielded large dry biomass and nutrients during both seasons. Yield of four vegetable crops responded more to fertilizer in control than in alley cropped treatments. Better yield of vegetables in alley cropped plots was in part due to following effect of the Leucaena hedgerows. Fertilizer application increased mean yields of Amaranthus, Celosia, okra and tomato by 325, 164, 47 and 94% in control plots and by 36, 26, 4 and 20% in alley cropped plots, respectively. For both seasons, yields were not significantly different between alley cropped with and without fertilizer and the control with fertilizer treatments. Yield was least in control without fertilizer. Alley cropping with Leucaena can reduce fertilizer requirement for vegetable production. Cost and return analysis using 1988 prices indicated that alley cropping with vegetable crops can be profitable.c/o Miss Maureen Larkin, L. W. Lambourn & Company, 26 Dingwall Road, Croydon CR9 3EE, England     

Substitution of nitrogen requirement of maize through leaf biomass of Leucaena leucocephala: agronomic and economic considerations

In a 3-year field study, the effects of substitution of nitrogen requirement of maize through Leucaena leaves were studied on runoff, soil loss, maize and wheat yield and economic returns. The treatments were (1) 80 kg N ha^-;1 all through Leucaena leaves (80 L), (2) 40 kg N through Leucaena leaves + 40 kg N ha^-;1 through fertilizer (40 L + 40 F), (3) 20 kg N through Leucaena leaves + 60 kg N ha^-;1 through fertilizer (20 L + 60 F), (4) 80 kg N ha^-;1 all through fertilizer (80 F), and (5) control (No fertilizer). Green Leucaena leaf biomass (containing 3.3% N on dry basis) was incorporated every year in 15 cm top soil two weeks before sowing of summer maize.Other treatments being almost equal, runoff was reduced marginally in treatment 20 L + 60 F which was attributed to better crop growth in this treatment. Mean minimum soil loss (6.202 t ha^-;1) also occurred in treatment 20 L + 60 F. Soil loss in 80 L was 13% less than in 80 F. Maize yield was at par in 80 L and 80 F. However, mean maximum yield of maize was obtained with 20 L + 60 F.Residual effect of incorporation of Leucaena leaves to maize crop was observed on wheat yield. The mean yield differences were statistically at par in all the treatments except control. The total mean net returns were statistically at par in 80 L and 80 F. However, significantly higher mean net returns (Rs 6811 ha^-;1; one US$ = Rs30) were obtained with 20 L + 60 F. Substitution of N through Leucaena leaves even in small quantity may be helpful to small holders, particularly where chemical fertilizers are in short supply or too expensive.     

污泥对苗圃生长的银合欢幼苗发芽和初期长势的影响

研究了不同类型的污泥(城市的、工业的和住宅污泥)对苗圃生长的银合欢幼苗田间萌发、生长和分枝的影响.播种前先将不同类型污泥的混合物与养分匮乏的自然林土壤混合.播种的3和6月后,记录幼苗大田发芽、分枝状况和其他物理生长参数(枝条或根长、活力指数、茎直径、叶片数、分枝或根鲜重和干重、总的生物量干重增长)等.与对照幼苗相比,混合污泥的土壤中生长的幼苗田间发芽、分枝状况及其他生长参数均发生了显著变化.与其它条件生长的幼苗相比,住宅污泥与土壤混合(1:1)条件生长的3月龄和6月龄幼苗分枝数和分枝鲜或干重均最高.就生长参数而言,住宅污泥与自然林土壤混合(1:1)生长的幼苗长势最好.研究表明:退化的土壤补偿以住宅污泥可促进银合欢的田间发芽、生长以及分枝的形成.图1表3参29.     

施肥对叶用银杏生长及叶产量的影响

通过对沿海盐碱地生长的5年生叶用银杏实生苗施用N、P、K、NP、NK、PK和NPK等7组肥料试验结果表明,施肥对苗高高峰期的生长有明显的促进作用,其中用N、P等部分处理全年苗高生长量较大;所有施肥处理叶产量的增加值均大于对照,但以N肥效果最好。因此,在沿海盐碱地上应施用N肥或P肥来培育银杏叶用园。     

Shading effects of alley cropped Leucaena leucocephala on weed biomass and maize yield at Mtwapa,Coast Province,Kenya

Reductions of up to 90% in weed biomass was observed under Leucaena leucocephala alley cropping with varying tree between (2,4 and 8 m) and within-row spacing combinations when compared to crop-only control. An increase of 24 to 76 % in maize yields of alley cropped plots compared to the crop-only control was also recorded. The 2m alley widths closed canopy faster than the 4 and 8m, and hence realized highest weed biomass reduction during the short-fallow period between two cropping seasons. At the end of the short fallow period, substantial fuelwood (up to 8 t ha ^–1) was realized.     

Biomass,decomposition and nutrient release of Vaccinium myrtillus leaf litter in four forest stands

Biomass and nutrient transfer (N, P, K, Ca, Mg) of bilberry (Vaccinium myrtillus L.) leaf litter fall, as well as decomposition and nutrient release, were studied in four mature forest stands situated in Central and South Sweden. Bilberry leaf litter fall amounted to between 33 and 55 kg ha^‐1 yr^‐1 in the four stands. Only minor differences between sites were noted for litter concentrations of N, P and Ca, whereas K and Mg showed somewhat larger variability. Relative amounts of the five nutrient elements in the litter fall were generally in the order N > Ca > K > Mg > P. The amounts of nutrients returned to the forest floor by the annual leaf litter fall in the stands ranged from 0.4 to 0.8 kg ha^‐1 for N, 0.4 to 0.6 kg ha^‐1 for Ca, 0.2 to 0.7 kg ha^‐1 for K, 0.1 to 0.2 kg ha^‐1 for Mg and 0.04 to 0.08 kg ha^‐1 for P.

The decomposition of the local bilberry leaf litter was followed by means of litterbags during three years. At all sites there was an extremely rapid mass loss from the litter (between 45% and 54%) during the first four to five months of decomposition. After this initial phase, the decomposition rates decreased markedly and after three years the accumulated mass losses of the litters varied between 64% and 78% at the studied sites. After two and three years of decomposition, three of the sites exhibited almost similar litter mass losses whereas at the fourth site the litter was decomposed to a significantly lower degree. The pattern of nutrient release from the decomposing bilberry leaf litter differed somewhat from site to site. Minor differences were, however, noted for P, Ca and Mg while N and K were more strongly retained in the litter at one of the sites.     

Functional relationships of nodulation response and biomass production at nursery stages of two fast-growing, leguminousmultipurpose tree species in Bangladesh: Albizia saman and Leucaena leucocephala

This study was carried out to assess the relationship of the status of nodulation （i.e., the number of nodules, their shape and size） in root and biomass production of plant growth parameters （i.e., number of leaves, root and shoot lengths, root biomass and shoot biomass） in Albizia saman and Leucaena leucocephala. The assessment started 60 days after seeding. The study revealed that nodulation response and biomass production in both species showed significant dif- ferences over time （p 〈 0.05） in all variables except in the root-shoot ratio （oven-dry） of L. leucocephala. The study also showed significant differences （p 〈 0.05） in nodule formation and biomass production at the end of the study period be- tween the two species except in the number of nodules and leaves and the green root-shoot ratio. There were strong pos- itive correlations between nodule formation and biomass production, i.e., the number of nodules and the age of plants, the number of nodules and leaves, as well as the number of nodules and biomass （root biomass and shoot biomass） in both species. The results obtained using principal component analysis （PCA） and correlation coefficients of the different characteristics of nodulation and biomass production were similar in both species. The PCA showed that shoot biomass （shoot green weight and shoot oven-dry weight） is positively correlated with PC1 （with an eigenvalue of 7.50） and root length is positively correlated with PC2 （with an eigenvalue of 0.19） in the case of A. saman. In the case of L. leucocephala, the PCA revealed that root biomass （root green weight and root oven-dry weight）, shoot biomass and shoot length are also positively correlated with PC1, while nodule formation and the number of leaves are positively correlated with PC2 （with an eigenvalue PC1 of 6.92 and PC2 of 0.49）.     

冀北山地不同树种组成桦木林枯落物及土壤水文效应

为弄清不同树种组成的林分对林地枯落物及土壤持水能力的影响,采用浸泡法和双环法对冀北山地5种不同树种组成的桦木林进行研究,结果表明:1林地枯落物半分解层储量均大于未分解层,总储量变化范围为12.85~20.87t/hm~2,白桦纯林储量最大,阔叶混交林最小;2枯落物最大持水量变化范围为73.27~106.99t/hm~2,有效拦蓄量变化范围为59.22~81.86t/hm~2,均为杨桦混交林最大、落桦混交林最小;3枯落物持水量与浸泡时间呈对数关系,随时间推移逐渐增大,而吸水速率与浸泡时间呈指数关系,随浸泡时间推移而逐渐下降;4土壤容重是油松白桦林最大、杨桦混交林最小,总孔隙度是杨桦混交林最大(60.66%)、阔叶混交林次之(59.31%)、油松白桦林最小(45.43%),土壤最大持水量和有效持水量均是杨桦混交林最大、阔叶混交林次之、油松白桦林最小;5土壤入渗速率和入渗时间呈明显幂函数关系。综合来看,杨桦混交林和阔叶混交林枯落物和土壤持水能力较强。     

Allelopathic effects of invasive Eucalyptus camaldulensis on germination and early growth of four native species in the Western Cape,South Africa

Eucalyptus camaldulensis Dehnh. (red river gum; Myrtaceae) is an invasive tree in riparian habitats of the Western Cape, South Africa, where it replaces indigenous vegetation and affects ecosystem functioning. These invasions lead to changes in river geomorphology and reduction in stream flow. The mechanisms that drive these effects are poorly understood. The potential for allelopathic effects of aqueous extracts of E. camaldulensis tissues and of soil and litter collected beneath E. camaldulensis trees on the germination and seedling growth of four selected native plant species was investigated in a greenhouse experiment. Soils collected beneath E. camaldulensis trees were used in three treatments: untreated soils, sterilised soils and sterilised soils overlaid with a eucalypt litter layer. In addition, soils collected from underneath native species were used in two treatments: untreated soils and soils overlaid with a eucalypt litter layer. All soil treatments were watered with three E. camaldulensis leaf, bark and root aqueous treatments. Compounds present in the aqueous extracts and fresh samples were identified using gas chromatography. Soil and aqueous treatments showed varying effects on germination and seedling growth of the four native species. Germination and seedling growth of Olea europaea subsp. africana and Dimorphotheca pluvialis were significantly reduced by E. camaldulensis root and bark aqueous extracts as well as by the soils treatments. The addition of eucalypt litter to native and sterilised soils reduced shoot and root growth of all four native species. Compounds such as -phellandrene, eucalyptol, p-menth-1-en-8-ol and -pinene, which have the potential to inhibit germination and plant growth, were identified in E. camaldulensis aqueous extracts and fresh samples. Although the methods applied in this study had limitations (e.g. lack of control treatment to litter addition), the results provide an additional motivation to prioritise removal of invasive E. camaldulensis stands from riparian ecosystems. Restoration initiatives should target native species that are not negatively affected by allelopathy.     

The effect of young Leucaena leucocephala (Lam) De Wit hedges on the growth and yield of maize,sweet potato and cowpea in an agroforestry system in Sierra Leone

An investigation was undertaken at Senehun — Kamajei, a high rainfall region in Sierra Leone, to assess the effects of Leucaena leucocephala, on the growth and productivity of maize, cowpea and sweet potato. The experiment was laid out in a completely randomised design with four replicates of each treatment. The treatments and controls were: (i) pure crops of maize, cowpea, sweet potato, Leucaena clean weeded and unweeded and (ii) intercrops of Leucaena with the food crops, both (iii) with and without applied fertilizers after the first year.The growth of Leucaena was slow but nevertheless tended to reduce grain yields of maize, and tuber and vine yields of sweet potato in the rows in the immediate vicinity of the trees, especially in the nitrogen-treated plots. The maize, in particular, caused an improvement in the early height growth of the trees.     

含羞草叶子提取物对常见农作物种子萌发生长的抑制作用

观察了含羞草叶子提取物对孟加拉常见农作物种子萌发生长的抑制作用.实验在27-30℃的室温和24小时的光照条件下进行.结果表明：不同浓度的含羞草叶子提取物明显影响所选的植物种子根,茎和侧根的延长和生长.生物学测定表明：高浓度（50%-100%）的提取物有较强的抑制作用.而低浓度 （10%-25%） 的提取物的抑制作用较弱.研究还显示,提取物对植物根和侧根的抑制作用比对种子萌发和茎的生长抑制作用更显著.     

马尾松-木荷混交造林效果的调查研究

我国南方立地条件差的低丘岗地,营造马尾松纯林易遭病虫危害,水土流失严重,林地肥力降低,难于成材,为此,对江西高安县9年生马尾松-木荷混交林及其纯林进行了综合调查研究,设立标准地,进行林分生长量、生物量、叶面积、根系、土壤、植被、病虫害、枯落物、水土流失、小气候等观测研究。结果表明,混交林的树高、胸径、每公顷立木蓄积量分别比纯松林大30 9%、31 7%、10 7%,生物量是纯松林的2 24倍,枯落物是纯松、荷林的3 37、1 96倍,病虫害的株发生率、水土流失、小气候等的改善均优于纯松林。松 荷混交林是我国亚热带地区,尤其是低丘岗地上值得推广的优良针阔混交类型。在生产上,建议进行株间、行间或小块状混交,或星散状混交,马尾松、木荷混交比例为5～3∶1,初植株行距为1 2m×1 2m、1 5m×1 5m或2m×2m,密度为4440～6944株·hm-2。     

Leucaena + maize alley cropping in Malawi. Part 2: Residual P and leaf management effects on maize nutrition and soil properties

Agroforestry systems involving leaf removal for animal fodder may result in rapid depletion of soil fertility. The purpose of this research was to determine if the effects of leaf removal on soil fertility parameters and maize yield in a Leucaena leucocephala alley cropping system could be reversed. Three leaf management strategies in a Leucaena alley cropping trial that had been in effect from 1987 to 1991 were investigated: 1) leaves returned, 2) leaves removed, and 3) leaves removed, with 100 kg inorganic N ha⁻¹ added. In the 1990/91 season, a 3⁴ confounded factorial design was utilized to investigate the effects of leaf management strategy, N rate (0, 30 and 60 kg N ha⁻¹); maize plant population (14,800, 29,600, and 44,400 plants ha⁻¹); and P rate (0, 18, and 35 kg P ha⁻¹). In the 1991/92 and 1992/93 seasons, leaves were applied equally to all plots, and no P was applied. The N rate and plant population treatments were continued, and the same confounded factorial design was implemented to investigate residual leaf management strategy, residual P rate, n rate, and plant population. The yield gap between the plots where leaves had been returned vs. removed narrowed each season due to uniform leaf application. Application of N improved yields during both seasons. Residual effects of the initial P application decreased to only 10% of the total yield in 1992/93. Plant population affected yields only during the season of very good rainfall. Leaf additions resulted in a relative increase in soil pH, total N,and exchangeable Ca, Mg, and K and a decrease C/N ratio in plots that had not previously received leaves. Leaves supplied more K and Zn to the upper 15 cm of soil than were being extracted by the maize crop, but uniform leaf additions eliminated differences in K and Zn uptake. Plant Zn uptake decreased with increasing P rate and plant population, and increased with increasing N rate and a history of leaf return. The results show that applying leaves equilibrated yields within two seasons, and resulted in a relative improvement of several soil properties. The residual effect from P applications was not adequate to maximize yields.