Ability of the earthworms Aporrectodea rosea and Aporrectodea trapezoides to increase plant growth and the foliar concentration of elements in wheat (Triticum aestivum cv. spear) in a sandy loam soil

In a greenhouse study, the ability of the earthworms Aporrectodea rosea and A. trapezoides to influence the foliar concentration of elements and the growth of wheat plants was assessed 27 days after sowing in a sandy loam soil. The presence of A. rosea and A. trapezoides (at densities equivalent to 314 and 471 m^-2, respectively) caused a significant increase in the shoot dry weight of wheat. The presence of A. rosea and A. trapezoides (at densities equivalent to 314 and 157 m^-2, respectively) was also associated with a significant increase in the root dry weight of wheat. The presence of A. rosea caused a significant increase in the foliar concentration of Ca, Cu, K, Mn, N, Na, and P, but did not influence the foliar concentration of Al, B, Fe, Mo, Mg, S, and Zn. The presence of A. trapezoides was associated with a significant increase in the foliar concentration of Al, Ca, Fe, K, Mn, N, and Na, but did not influence the foliar concentration of B, Cu, Mo, Mg, P, S, and Zn. These results demonstrate the potential of A. rosea and A. trapezoides to increase the growth of wheat in a sandy loam soil and suggest that the mechanism by which they increased plant growth was, in part, through increasing the availability and uptake of nutrients from this soil.     

Relationships between casts of geophagous earthworms (Lumbricidae,Oligochaeta) and matric potential

A laboratory study was conducted to determine the effects of matric potentials between -25.4 and-2.0 kPa on the mechanical dispersion of fresh and aged casts produced by Aporrectodea caliginosa, A. rosea, and A. trapezoides. We also examined the effects on dispersion of the matric potential at which the air-dried casts were rewetted. Dispersion from subsurface casts up to 6 days old and uningested aggregates was influenced, but dispersion from fresh casts was not influenced, by the matric potential of the soil core from which the samples were collected. Dispersion from subsurface casts and uningested aggregates increased as the matric potential of the soil core increased from -25.4 to -2.0 kPa. Cast dispersion was not influenced by the earthworm species which produced the cast. Little or no clay was mechanically dispersed after the casts had been air-dried and rewetted, and the matric potential at which casts were rewetted had little influence on dispersion.     

Radial pressures generated by the earthworm Aporrectodea rosea

Summary The radial pressures generated by the earthworm Aporrectodea rosea were measured in a study of the conditions under which the worms were able to crack soil discs into which they were encouraged to tunnel. The tensile strength of replicate discs was determined by indirect tension tests and by expansion of rubber membranes in soil discs. Simple engineering theory was used to relate the stress required to fracture a disc with the applied internal stress. Mean values for the radial stress applied by the earthworms in tunnelling through the discs was 230 kPa. With some assumptions about the distribution of muscles across the worm diameter, it was estimated that the mean maximum force generated by all the longitudinal muscles in any segment was 3.2 N.     

Flooding responses of three earthworm species,Allolobophora chlorotica,Aporrectodea caliginosa and Lumbricus rubellus,in a laboratory-controlled environment

To get a better understanding of earthworm’ responses towards flooding, three laboratory experiments were performed with the species Allolobophora chlorotica, Aporrectodea caliginosa and Lumbricus rubellus.Flooding response was determined in a pot experiment, in which the earthworms were incubated for 42 days in flooded or non-flooded soil, with or without heavy metal pollution. To determine moisture preference, earthworms were incubated for 9 days in aquaria with five compartments, containing soil with a moisture gradient (%, w/w), ranging from 35%, 45% (field capacity), 55%, 65% (saturated) to 65%+ (saturated and an extra water layer). Effects on earthworm health were studied by incubating earthworms of each species for 42 days in soil with the same range of moisture contents and determining the dry/wet weight ratio and dry weight gain as an indication of earthworm health.A. chlorotica was tolerant to water, although the worms tended to escape from flooded soil. Their health was significantly lower in the flooded soils (P<0.05). A. caliginosa showed little response to flooding. This species, however, was affected by the heavy metal pollution in the pot experiment. L. rubellus was sensitive towards flooding, with escape and avoidance behaviour being the main mechanism of survival. This species was able to survive when forced to stay in flooded soil for at least 42 days, but this significantly reduced its health (P<0.05).These results suggest that earthworms are able to survive in inundated soils, but there are large differences between species in response to flooding conditions.     

Weight response to the soil water potential of the earthworm Aporrectodea longa

Summary To assess the ability of endogeic earthworms to tolerate variations in soil water potential, groups of these worms were subjected to different, constant levels of soil water suction () over a period of 17 days. At water suctions varying from 0.3 kPa (pF 0.5) to 1990 kPa (pF 4.3), the earthworms showed no physiological ability to a maintain constant internal water content as assessed by the fresh weight. The relationship between weight loss and the increase in water, suction was modelled and the following critical thresholds were identified: <60 kPa did not affect earthworm weight; >620 kPa led to diapause; between these two values, earthworm weight was closely governed by the variation in . At the intermediate suction of 167 kPa, the exchange of water between the earthworms and the soil was at a maximum, and this value is therefore proposed as the level at which the diapause is induced. These modelled values were the diapause is induced. These modelled values were compared with those obtained under field conditions.     

Survival of Pseudomonas solanacearum biovars 2 and 3 in soil: Effect of moisture and soil type

The survival of Pseudomonas solanacearum biovars 2 and 3 in three soils, a Nambour clay loam, a Beerwah sandy loam and a Redland Bay clay, was compared at pressure potentials of ?0.003, ?0.05 and ?0.15 kPa. The soils were inoculated with mutants of P. solanacearum biovars 2 and 3, resistant to 2000 μg streptomycin sulphate ml^?1 and their survival measured every 6 weeks for 86 weeks in the clay loam and clay and for 52 weeks in the sandy loam. Soil populations declined with the initial drying necessary to bring the soil moisture to the specific pressure potentials; the initial counts for biovar 2 varied between 0.20 and 2.00 × 10⁹ cfu g^?1 soil and for biovar 3 between 0.17 and 1.29 × 10⁹ cfu g^?1 soil.The population decline in soil maintained at a constant pressure potential was expressed as the rate of population decline. Biovar 2 declined more rapidly than biovar 3. The rate of population decline of each biovar at ?0.003 and ?0.05 kPa was greater in clay loam than in sandy loam and at all pressure potentials it was greater in clay loam and sandy loam than in clay. There was also a tendency for the rate of population decline of both biovars to decrease in the drier soil treatments.     

The effects of organic residue quality on growth and reproduction of <Emphasis Type="Italic">Aporrectodea trapezoides</Emphasis> under different moisture conditions in a salt-affected agricultural soil

We studied the effects of organic residues with different C/N ratios and soil moisture contents on the growth and reproduction of the earthworm Aporrectodea trapezoides to investigate potential measures to increase its population in a salt-affected agricultural soil. The experiment consisted of eight treatments in a fully factorial design: low or high C/N ratio organic residue, soil moisture at 75 or 95% field capacity (FC), and salinity (as electrical conductivity (EC)) of 3.07 or 4.77 dS m^?1. It was carried out under controlled laboratory conditions for 4 months. In the low C/N ratio organic residue application, there was a significantly greater mean total dry weight and number of clitellate individuals of A. trapezoides, regardless of the soil moisture and salinity content, which may be due to the greater soil microbial biomass and dissolved organic N (DON) derived from the low C/N ratio organic residue. Generally, more cocoons were found in the application of low C/N ratio clover residue at months 2 and 4. At an EC of 3.07 dS m^?1 and moisture content of 75% field capacity (FC), significantly more hatchlings were found when low C/N ratio clover residue was applied compared to the high C/N ratio wheat residue. High soil moisture content (95% FC) resulted in a significantly greater mean total dry weight of A. trapezoides at months 2 and 4 and significantly more clitellate individuals and cocoons at month 4 compared to the low soil moisture content (75% FC), but only when the low C/N ratio residue was applied. In contrast, high soil moisture content (95% FC) resulted in significantly less hatchling numbers at an EC of 3.07 dS m^?1, only when the low C/N ratio residue was applied. These results suggest that the organic residue type and soil moisture content can regulate the growth and reproduction of the earthworm A. trapezoides, which should help to improve the recovery of their populations in salt-affected agricultural soil.     

Earthworms (Aporrectodea spp.; Lumbricidae) cause soil structure problems in young Dutch polders

The presence of earthworms in relation to clay soil structure problems in arable fields in the Flevopolders (the Netherlands) was studied. Recently, farmers in this area have had difficulty in harvesting potatoes in predominantly wet years. After a dry period, soil particles in the top layer of the potato ridges form a platy structure and are difficult to sieve. Locally, this resulted in many clods, and sometimes harvesting proved impossible. In the field, significantly more earthworms (mainly Aporrectodea caliginosa and A. rosea) were observed in the problem parts than in the non-problem parts. A macrocosm study showed significantly more settlement and soil stickiness and an increasing number of large clods caused by greater numbers of A. caliginosa. The results of this study reveal earthworms to be the main factor affecting the state of the soil and causing the harvesting problems.     

Axial pressures generated by the earthworm Aporrectodea rosea

Summary The axial forces generated by the earthworm Aporrectodea rosea were measured by directing the earthworm to tunnel into soil discs mounted on an electronic balance connected to a datalogger. The area over which the force acted was estimated from the size of the hole created by the tunnelling. The maximum force recorded by an individual worm was 0.760 N and the mean maximum value was 0.465 N. The maximum pressures recorded was 116.5 kPa, while the mean maximum pressure was 72.8 kPa. These axial pressures are approximately one-tenth of the maximum axial pressure recorded for plant roots. The statistical distribution of activity as the worms tunnelled through the soil discs was analysed. Pressures recorded were well in excess of physiologically measured pressures and the generation of forces within muscles to achieve these pressures was calculated by some assumptions. It was estimated that there is a maximum tension in the circular muscles of 0.15 N per segment of the worm.     

Population dynamics of the earthworm Aporrectodea trapezoides (Annelida: Lumbricidae) in a Western Australian pasture soil

Summary The changes in size and age-composition of an earthworm population were studied in a Western Australian pasture developed since 1912. The population size in the surface 10 cm was estimated by handsorting during the cool wet season (19 weeks from May to September). Two species, both exotic, were found, Aporrectodea tranpezoides (Lumbricidae) and Microscolex dubius (Acanthodrilidae). Of the 615 individual speciemens collected, 99.7% were A. trapezoides. The abundance of A. trapezoides increased from 58 m^-2 at the time of the opening rains to 170 m^-2 (88.6 g live weight m^-2) after 10.5 weeks. Near the end of the wet season (in October) the density was 37 m^-2. At the time of the opening rains the population consisted of juvenile and semimature individuals. Clitellate earthworms were found 1 month later and predominated from August (10.5 weeks) to the end of the season. Egg capsules were found from August through October. Egg capsules incubated in the laboratory at 16°C hatched on average after 42 days and produced two juveniles. Juvenile and immature earthworms collected from a quiescent state at the end of summer matured within 1 month when reared in moist soil in the laboratory.     

The use of resource patches by earthworms

A field experiment was established to assess the effects of additional organic matter on earthworm populations. Bags of soil (15 cm deep) were placed in a pasture at Balhannah, South Australia, at the beginning of autumn 1991. The bags were initially seeded with five individuals ofAporrectodea trapezoides, and 250 g dried sheep manure was added to most bags. Manure was added either in pellet or milled form, and applied either on the surface, in the 5–10 cm layer, or evenly dispersed over 15 cm. In harvests during weeks 7,9, and 11 after the start of the experiment,A. trapezoides and three other species,A. caliginosa, A. rosea, andMicroscolex dubius, were recovered from the bags. Bags with added manure had significantly higher numbers of each species than bags with no manure. During the 4-week sampling period (weeks 7–11) the numbers ofM. dubius recovered per bag decreased, whileA. rosea increased. Total earthworm numbers were not influenced by either the form or the location of application of the manure. Earthworms were sampled from three depths, 0–5, 5–10, and 10–15 cm. Both numbers and biomass of earthworms were positively correlated with the location of the manure. Cocoons ofAporrectodea spp. were more abundant when the manure was milled and evenly dispersed, and were consistently located in the lower soil layers, regardless of the form or location of manure.     

Microcosm investigations into the influence of sheep manure on the behaviour of the geophagous earthworms Aporrectodea trapezoides and Microscolex dubuis

A series of experiments was conducted over 96 h in 240-mm-deep soil microcosms, to assess the effect of the presence and distribution of sheep manure over the soil surface on the vertical and horizontal distribution of burrows and numbers of the earthworms Aporrectodea trapezoides and Microscolex dubius. Within some microcosms the dung was placed on half of the soil surface and this caused aggregation, with over two-thirds of the earthworms being found in the soil directly under the manure. The presence of surface-applied sheep manure caused both species to aggregate in the surface soil. In contrast, without manure, A. trapezoides was evenly distributed throughout the soil profile while M. dubius aggregated in the deeper soil. The pattern of burrow construction was also influenced by the presence of surface manure. In the absence of manure, burrows of both species were evenly distributed through the soil, but in the presence of surface manure M. dubius constructed proportionally more burrows close to the surface. Both species constructed approximately twice the burrow area in the absence than in the presence of surface manure. For both species the daily rate of burrow construction decreased over the experimental period. From these data we inferred that there was more widespread and active foraging behaviour in both species when organic food material was scarce. M. dubius differed from A. trapezoides in that it more strongly concentrated foraging activity in the vicinity of the manure food source.     

Earthworm burrowing in laboratory microcosms as influenced by soil temperature and moisture

Earthworm burrows contribute to soil macroporosity and support diverse microbial communities. It is not well known how fluctuations in soil temperature and moisture affect the burrowing activities of earthworms. The objective of this experiment was to evaluate the maximum depth and length of burrows created by the endogeic earthworm Aporrectodea caliginosa (Savigny) and the anecic earthworm Lumbricus terrestris L. for a range of temperatures (5–20 °C) and soil water potentials (−5 and −11 kPa). The laboratory microcosm was a plexiglass chamber (45 cm high, 45 cm wide) containing 0.14 m² of pre-moistened soil and litter, designed to house a single earthworm for 7 days. Earthworm mass, surface casting and burrowing activities were affected significantly by soil temperature, moisture and the temperature×moisture interaction. Burrow length and maximum burrow depth increased with increasing temperature, but there was less burrowing in wetter soil (−5 kPa) than drier soil (−11 kPa). Weight gain and surface casting, however, were greater in soil at −5 kPa than −11 kPa. Our results suggest more intensive feeding and limited burrowing in wetter soil than drier soil. Earthworms inhabiting the non-compacted, drier soil may have pushed aside particles without ingesting them to create burrows. The result was that earthworms explored a larger volume of soil, deeper in the chamber, when the soil was drier. How these burrowing activities may affect the community structure and activity of soil microorganisms and microfauna in the drilosphere remains to be determined.     

DMPP硝化抑制效果受其浓度、施用方式及土壤基质势的影响

The efficacy of nitrification inhibitors depends on soil properties and environmental conditions. The nitrification inhibitor 3.4-dimethylpyrazole phosphate （DMPP） was investigated in a sandy loam and a loamy soil to study its effectiveness as influenced by inhibitor concentration, application form, and soil matric potential. DMPP was applied with concentrations up to 34.6 mg DMPP kg^-1 soil as solution or as ammonium-sulfate/ammonium-nitrate granules formulated with DMPP. DMPP inhibited the oxidation of ammonium in both soils, but this effect was more pronounced in the sandy loam than in the loamy soil. When applied as solution, increasing DMPP concentrations up to 7 mg DMPP kg^-1 soil had no influence on the inhibition. The effectiveness of DMPP formulated as fertilizer granules was superior to the liquid application of DMPP and NH4^＋, particularly in the loamy soil. Without DMPP, a decline in soil matric potential down to -600 kPa decreased nitrification in both soils, but this effect was more pronounced in the sandy loam than in the loamy soil. DMPP was most effective in the sandy loam particularly under conditions of higher soil moisture, i.e., under conditions favorable for nitrate leaching.     

Soybean seedling root growth as influenced by soil texture,matric suction and bulk density

Abstract

Laboratory experiments were conducted under controlled conditions to determine the effect of five matric suctions (0.05, 0.10, 0.30, 1.00 and 3.00 bars) and three bulk densities (1.10, 1.30 and 1.50 g.cm^?3) on the moisture content, penetrometer resistance and soybean (Glycine max L.) root growth in six different soil textural groups (sand, silt, clay and their combinations).

The different textural groups were compacted in PVC pipes 4.4 cm ID and 10 cm long and placed in pressure cells to obtain the desired matric suction. After equilibrium five pregerminated soybean seedlings were fixed on the soil surface. At the end of 48 hours root elongation was measured.

There was an increase in root growth in all the textural groups at all the bulk densities when the matric suction was increased from 0.05 to 0.30 bar. There was however a gradual decrease in root growth as the matric suction increased from 0.30 to 3.0 bars. The reduction in root growth at low and high matric suctions was related to moisture content, change in soil resistance and redox status of the soil system.

The measured penetrometer resistance values were directly related to the level of compaction, soil matric suction and also were dependent upon the texture. Close relationships were recorded between redox potentials and soil matric suction.     

非饱和土双应力变量广义土水特征曲线模型验证

利用基于轴平移技术的Geo-Expert高级型应力相关土-水特征曲线压力板仪研究不同覆土压力(0、40、100、200 k Pa)对南阳膨胀土土水特征曲线(soil-water characteristic curve,SWCC)的影响;并对提出的考虑土体变形及多孔隙分布形态的双应力变量广义SWCC表征方程进行如下试验验证:1)不同覆土压力下微多孔隙分布形态的南阳膨胀土侧限固结试验及脱湿试验SWCC验证;2)零净法向应力状态双孔隙尺度硅藻土双峰SWCC试验验证;3)不同净围压状态下单孔隙尺度韩国残积土SWCC试验验证;4)多应力路径下法国Bapaume黄土,不同初始干密度下日本Edosaki砂土在脱湿-吸湿过程SWCC试验验证;并比较分析新方程与van Genuchten方程及Fredlund等方程的差异性。结果表明:1)覆土压力会显著改变膨胀土结构及孔隙通道,进而改变SWCC边界效应区、过渡区形态;也改变了双重孔隙尺度土壤的进气值;第1个波峰SWCC进气值均在1 k Pa左右;相比于零覆土压力试样,40、100、200 k Pa覆土压力试样第2个波峰SWCC进气值分别高4.74、17.58、67.23 k Pa;2)未考虑净法向应力影响的单应力状态多峰SWCC、考虑侧限双应力状态多峰SWCC、各向同性净法向应力单峰SWCC、不同脱湿-吸湿路径SWCC及不同初始干密度的SWCC试验拟合曲线均表明,双应力广义SWCC具有包容复杂影响因素的能力;3)新方程能够利用至少3个土-水数据即可拟合出具有较高的精度的整条SWCC。研究为定量描述土壤的持水、渗透及强度特性提供参考。     

Leaching of genetically modified Pseudomonas fluorescens through intact soil microcosms: Influence of soil type

Summary The leaching of a genetically modified Pseudomonas fluorescens through soil was investigated using intact (undisturbed) soil microcosms over a 2-month period. The microcosms comprised large cylindrical cores of three contrasting soil types (a loamy sand, a sandy loam, and a clay loam) supporting a grass/clover sward. Late log-phase cells of Pseudomonas fluorescens containing lux genes encoding for bioluminescence were applied to the surface of the soil cores. Eighteen hours after application of the inocula, the microcosms were subjected to simulated rain events (9 mm per event) at 3-day intervals and leachates were analysed for the concentration of genetically modified bacteria. The lux-modified pseudomonads were detected immediately in leachate from the clay looam with a steady decline in the concentration of cells with time. Leaching of pseudomonads from the sandy loam and loamy sand only occurred over a few rain events and total recoveries from the leachate were lower than from the clay loam. Leaching patterns are discussed in relation to differences in structure of topsoil and subsoil, which determine the pathways of water flow, and to the matric potential at inoculation, which determines the pore-size classes into which cells were first introduced.     

Nematicides and field population of enchytraeids and earthworms

Enchytraeid and earthworm populations of a Typic Haplaquoll soil after application of the nematicides oxamyl and phenamiphos were examined for 1 yr. The nematicides had no effect on enchytraeid numbers, which were positively correlated with soil moisture and the previous month's rainfall. Earthworm populations were dominated by Allolobophora caliginosa (Savigny) with A. trapezoides (Duges) and Eiseniella tetraedra (Savigny) also present. Both nematicides initially depressed earthworm numbers and the effects of phenamiphos appeared to persist until the soil became wet in Autumn. Earthworm numbers were positively correlated with soil moisture and previous month's rainfall. Enchytraeid numbers at 2.5–5 cm depth were negatively correlated with soil temperature. Numbers of enchytraeids at 0–2.5 cm depth and earthworms were not significantly related to soil temperature.     

土壤质地对柱花草生长发育、生物量及土壤肥力变化的影响

采用大田试验的方法,在云南省元谋县小雷宰流域内壤土、砂壤土和重壤土3种质地土壤上,以热研5号柱花草为材料,研究土壤质地对柱花草生长发育、生物量及土壤有机质、有机碳、全氮和全磷的影响。试验结果表明:3种土壤质地上种植柱花草,柱花草地上部和地下部生长量和生物量表现幼苗期增加缓慢,而分枝期后增加快的趋势。壤土耕性好,兼有砂土和重壤土的优点,有利柱花草地上部分的生长发育,柱花草地上部生长量、生物量及改善土壤肥力方面显著高于重壤土。砂壤土有利于柱花草根系向深层土壤生长,柱花草地下部生长量、生物量及根瘤显著高于种植在重壤土。在3种土壤质地种植柱花草后,土壤有机质、有机碳、全氮和全磷均有上升趋势。综合而言,通气性和保肥保水能力居中的壤土更适合柱花草的生长发育及干物质的积累。     

Effect of management practices and cropping systems on earthworm abundance and microbial activity in Sanborn Field: a 115-year-old agricultural field

Sanborn Field, an agricultural demonstration field at the University of Missouri-Columbia, has over 100 years of cropping histories and management practices implemented at this site. We examined the effect of these cropping systems and management practices on earthworm populations and microbial activity. A field experiment was conducted to characterize and quantify earthworms and to determine the microbial activity in the same selected plots. We sampled 14 plots at the site, six of which were the original plots established in 1888 with the same cropping histories and management, and eight of which had been modified over the years to accommodate changing farmer needs and scientific questions. Earthworms and soil samples were collected in the spring and fall of 1999. Aporrectodea trapezoides, Aporrectodea caliginosa, and Lumbricus terrestris were the dominant species found in this field. Lumbricus terrestris was commonly associated with the no-tillage plot at Sanborn Field. Due partly to soil moisture conditions, most of the species were found and identified during the spring. Microbial activity, as expected, was greatest during the spring. Manure, no-tillage and crop rotations that include legumes had the greatest earthworm abundance and microbial activity. In general, where no fertility treatments were added to soil or where food sources were lacking, earthworm abundance decreased significantly. The abundance of earthworms found in this field reflected the cropping history and management practices used recently and within the last 100 years. In most cases, microbial activity showed similar trends as earthworm density. However, some dynamic microbial transformations, like nitrification, do not always follow the same trend as potential soil quality biotic indicators. Earthworms, along with microbial activity, may serve as useful soil quality indicators in sustained and short-term field trials.