Abundance Of Microarthropods Research Articles

Humus characteristics and seasonal changes of soil arthropod communities in a natural sessile oak (Quercus petraea L.) stand and adjacent Austrian pine (Pinus nigra Arnold) plantation

In order to assess the effects of conversion of natural stands into plantations, soil invertebrate micro- and macroarthropod communities were evaluated for their abundance and richness in a sessile oak (SO; Quercus petraea L.) stand and adjacent Austrian pine (AP; Pinus nigra Arnold) plantation. Sites were sampled four times a year in 3-month intervals from May 2009 to February 2010. Humus characteristics such as total mass; carbon, lignin, and cellulose contents; and C/N ratio were significantly different between SO and AP. Statistically significant differences were detected on soil pH, carbon and nitrogen contents, and electrical conductivity between the two sites. The number of microarthropods was higher in AP than in the SO site. The annual mean abundance values of microarthropods in a square meter were 67,763 in AP and 50,542 in SO, and the annual mean abundance values of macroarthropods were 921 m(-2) in AP and 427 m(-2) in SO. Among the soil microarthropods, Acari and Collembola were the dominant groups. Shannon's diversity index was more affected by evenness than species number despite the species diversity (H') of soil arthropods being generally higher in the SO stand. The abundance of microarthropods showed clear seasonal trends depending upon the humidity of the soil.

Significance of litter layer in enhancing mesofaunal abundance and microbial biomass nitrogen in sweet corn-white clover living mulch systems

Living mulch is a type of sustainable farming system that consists of cover crops planted either before or with a main crop; a living mulch is maintained as a living ground cover throughout the growing season of the main crop. Microbial biomass and abundance of mesofauna (microarthropods and enchytraeids) are important soil biological parameters in relation to soil function, plant productivity, and nutrient cycling; however, the effects of living mulch on these parameters are not fully understood. In this study we examined the effects of living mulch treatment with nitrogen fertilizer (0, 40, 160, or 200 kg ha−1) on the abundance of soil microarthropods (Oribatida, Mesostigmata, Prostigmata, and Collembola) and the effects of living mulch treatment on the dynamics of the soil biota (mesofauna, microarthropods, enchytraeids, and microbial biomass nitrogen) from spring to autumn. Our results showed that living mulch treatment significantly (p < 0.05) increased the grain weight of the main crop in both experiments. Generally, living mulch treatment had a positive effect on the abundance of mesofauna and microbial biomass nitrogen, despite pesticide usage. Nitrogen levels did not affect the number of microarthropods. The litter layer in living mulch significantly (p < 0.05) enhanced microbial biomass nitrogen and the abundance of Oribatida, Prostigmata, and Collembola. We conclude that living mulch enhances mesofaunal abundance and microbial biomass nitrogen and that the production of a litter layer by living mulch is one of the major mechanisms for this enhancement.

Influence of two exotic earthworm species with different foraging strategies on abundance and composition of boreal microarthropods

In North America, many species of European earthworms have been introduced to northern forests. Facilitative or competitive interactions between these earthworm species may result in non-additive effects on native plant and animal species. We investigated the combined versus individual effects of the litter-dwelling earthworm Dendrobaena octaedra Savigny, 1826 and the deep-burrowing species Lumbricus terrestris L., 1758 on microarthropod assemblages from boreal forest soil by conducting a mesocosm experiment. Soil cores from earthworm-free areas of northern Alberta, Canada, were inoculated with D. octaedra alone, L. terrestris alone, both worm species together, or no earthworms. After 4.5 months, microarthropods were extracted from the soil, counted, and identified to higher taxa. Oribatid mites were further identified to family and genus. Abundance of microarthropods was significantly lower in the treatment containing both species than in the no earthworm treatment and the L. terrestris treatment. Oribatida and Prostigmata/Astigmata differed significantly among treatments and were lowest in the treatment containing both earthworm species, followed by the D. octaedra treatment, although post-hoc pairwise comparisons were not significant. Within the Oribatida, composition differed between the control and L. terrestris treatments as compared to the D. octaedra and both-species treatments, with Suctobelbella and Tectocepheus in particular having higher abundances in the control treatment. Effects of the two earthworm species on microarthropods were neither synergistic nor antagonistic. Our results indicate that earthworms can have strong effects on microarthropod assemblages in boreal forest soils. Future research should examine whether these changes have cascading effects on nutrient cycling, microbial communities, or plant growth.

Effects of seasonal grazing, drought, fire, and carbon enrichment on soil microarthropods in a desert grassland

This study was designed to test hypotheses about the combined effects of short-term, seasonal grazing with seasonal drought, fire, and carbon enrichment on soil microarthropod communities in a Chihuahuan Desert grassland. The study was conducted in eighteen 0.5 ha plots following three consecutive years of treatment: six plots intensively grazed in summer, six in winter, and six not grazed. There was no difference in perennial grass cover on the summer-grazed and winter-grazed plots. Intensive seasonal grazing had no effect on the abundance and community composition of soil microarthropods. Within each plot there were six subplots: summer rain-out, winter rain-out, burned, glucose amendment, rain-out control and burn-glucose control. Fire and carbon enrichment had no significant effect on soil microarthropod abundance or community composition. The average number of microarthropods ranged from 8915 ± 1422 m−2 in the ungrazed, unburned plots to 7175 ± 1232 m−2 in the winter-grazed, unburned plots. Microarthropod densities in the glucose-amended plots were 8917 ± 4902 m−2 in the winter-grazed plots and 10,731 ± 863 m−2 in the glucose-amended, summer-grazed subplots.The prostigamatid mite, Tydeus sp., was the most abundant microarthropod taxon in all treatment plots.

The impact of the invasive shrubLonicera maackiion the decomposition dynamics of a native plant community

Invasive plants may have variable effects within a given environment depending on their interactions with the dominant native species, yet little research has examined such species-species interactions within a site. Savanna trees with nonoverlapping canopies offer an ideal opportunity to assess associated changes in the ecosystem processes that result from interactions between an invasive species and different native tree species. We examined the influence of the exotic invasive shrub Lonicera maackii on decomposition dynamics under three native tree species: Fraxinus quadrangulata, Quercus muehlenbergii, and Carya ovata. Litter decomposition rates and litter C and N were evaluated over two years using single- and mixed-species litterbags (L. maackii and individual tree species litter); microarthropod abundance was measured at 6 weeks using Tulgren funnels. Litter from the invasive L. maackii decomposed and lost N more rapidly than the litter of the three native tree species. The rate at which L. maackii decomposed depended on its location, with L. maackii litter decomposing and losing N more rapidly under C. ovata than under the other two native tree species. Mixing L. maackii with the native species' litter did not accelerate litter mass loss overall but did result in synergistic N losses at variable times throughout the experiment, further highlighting the variable interaction between native species and L. maackii. Nitrogen loss was significantly higher than expected in mixtures of C. ovata + L. maackii litter at 6 weeks, in F. quadrangulata + L. maackii litter at 12 weeks, and in Q. muehlenbergii + L. maackii litter at 24 weeks. If the effects of invasive species on certain ecosystem processes, such as litter decomposition, are strongly influenced by their association with native species, this could suggest the need for a more nuanced understanding of the vulnerability of ecosystem processes to invasions of L. maackii and potentially other invasive species.

Fifteen years of no till increase soil organic matter, microbial biomass and arthropod diversity in cover crop-based arable cropping systems

The physical, chemical and biological properties of soil may be modified by tillage, fertilization and cover crops. However there is little knowledge on long-term effects on soil properties, notably under Mediterranean climate. Moreover, biological indicators such as micro-arthropods can be used for a cost-effective analysis of soil biodiversity. Here, we studied physical and biological properties of a sandy loam soil in central Italy under a 4-year rotation of maize–durum wheat–cover crop–sunflower–durum wheat–cover crop during 15 years. We analysed the effects of two tillage systems, conventional tillage (CT) and no-tillage (NT); two N fertilization rates, without N and medium N level; and three soil covers: cash crop residue as control, Brassica juncea and Vicia villosa. Results show that no tillage increased soil organic matter content in the upper 10-cm layer (3.31%) compared to the conventional tillage (2.19%). No tillage also improved structure stability and lowered bulk density in the same soil profile. No-tillage systems showed higher soil microbial biomass (+71%) and respiration (+44%), and a higher abundance and diversity of micro-arthropods. We conclude that no tillage is an effective measure to improve the physical and biological quality of soil in Mediterranean conditions. No-tillage positive effect can be enhanced by the right choice of N fertilization and cover crop cultivation. Bio-indicators such as micro-arthropods can be very predictive of soil habitability by organisms.

개간 및 답전윤환 인삼재배지에서 유기물처리에 따른 토양생물상 변화

인삼재배에서 논전환밭의 이용이 증가하는 추세이며, 개간밭과 더불어 유기물투입의 효과를 조사할 필요가 있다. 토양생물은 유기물의 분해에 영향을 미치는 중요한 요소이기 때문에 유기물 시용이 토양생태계에 미치는 영향을 조사했다. 유박과 퇴비를 개간밭과 논전환밭에 <TEX>$20Mg\;ha^{-1}$</TEX> 와 <TEX>$40Mg\;ha^{-1}$</TEX>로 투입하였다. 미생물상 변화는 인지 질지방산을 분석하여 검정하였고, 동물상의 변화는 미소동물의 개체밀도를 측정하였다. 미생물에 대한 PLFA 지수나 미소동물의 밀도는 개간밭보다 논전환밭에서 높았다. 개간밭에서는 유기물 투입에 의한 처리간 차이가 적었다. 논전환밭에서는 퇴비 <TEX>$40Mg\;ha^{-1}$</TEX> 처리구에서 날개응애 밀도가 증가하였고, 이들의 밀도는 곰팡이 PLFA와 양의 상관관계가 나타났다. 위의 결과는 개간밭에서 유기물 함량이나 토양생물의 밀도가 낮은 심토로 개간하면 유기물을 투입하여도 토양생물에 대한 효과가 적을 수 있다는 것을 보여준다. 논전환밭에서는 유기물에 대한 토양생물들의 반응이 다르며 토양의 물리화학성도 토양생태계에 영향을 미칠 수 있다. 논전환밭과 개간밭에서는 유기물에 대한 토양생물의 반응이 다르므로, 투입된 유기물의 분해나 이에 따른 양분의 순환이 다를 수 있기 때문에 두 토양에서 시비방법을 다르게 할 필요성이 있다고 생각된다. Cultivation of Korea ginseng in newly reclaimed and paddy-converted fields has been increasing, and evaluation of organic amendment effectiveness is needed in the two soil types. Soil organisms influence organic matter decomposition, and their responses to applications of organic matter were studied. De-oiled cake and compost were applied at <TEX>$20Mg\;ha^{-1}$</TEX> and <TEX>$40Mg\;ha^{-1}$</TEX> in both soil types. Changes in microflora were assessed by analyzing phospholipid fatty acid (PLFA). The abundance of nematodes and microarthropods was measured. Microbial PLFA indicators for microorganisms and microarthropod abundance were greater in reclaimed upland than in paddy-converted soil. There were few differences in the microflora and fauna of reclaimed uplands, regardless of treatment. In paddy-converted soil, the abundance of Oribatida was increased by the application of compost at <TEX>$20Mg\;ha^{-1}$</TEX> and was correlated with PLFA indicators of fungi. The results suggested a minimal influence of organic amendments in reclaimed upland, because the organic matter content and abundance of soil organisms are low in mineral soils. In paddy-converted soil, the effects of organic amendment differ among different soil organisms, and soil properties are important mediators of the effect.

Prescribed Fire and the Abundance of Soil Microarthropods in Northeast Georgia

Abstract We examined the effects of prescribed fire on the abundance of soil microarthropods in a southeastern pine-hardwood forest in northeast Georgia. Using soil cores, the soil microarthropod groups Prostigmata, Oribatida, and Collembola were examined before and after a low-intensity prescribed fire intended for fuels reduction and wildlife habitat improvement. A post-burn evaluation found 100% duff layer coverage and 80% of the understory vegetation consumed. Prostigmata numbers were significantly reduced four months after the burn, with numbers returning to pre-burn levels more than one year later. Although Oribatida and Collembola fluctuated from year to year, we found no significant effects from the burn on those taxa. These results suggest that low-intensity prescribed burning has no lasting negative effects on soil microarthropod populations. The results from this study add to the evidence suggesting the adaptability of southeastern forests to low-intensity prescribed fire.

Soil microarthropod response to the application of entomopathogenic nematode-killed insects in maize and flower strip habitats

Abstract Insects killed by entomopathogenic nematodes (EPN) represent a resource with which soil arthropods can interact. These interactions can be positive for EPN (e.g., arthropods serve as parasitic or phoretic hosts) or negative (e.g., EPN serve as prey). Plant diversity and soil disturbance may influence these interactions. We investigated the effects of maize and flower strip habitats on microarthropod abundance and community composition in soil surrounding greater wax moth larvae, Galleria mellonella, infected with the EPN Steinernema carpocapsae (Sc). In the first year of the experiment (2005), we compared microarthropod communities responding to burial of Sc-killed insects with a control (no soil disturbance). In 2006, we added two control treatments: burial of freezer-killed insects and sham burial. Soil samples (including G. mellonella) were collected 2 and 20 days (2005) or 2 and 12 days (2006) after application. In 2005, arthropod abundance and community composition were similar between maize and flower strip habitats. In 2006, we detected more arthropods in the maize than the flower strips. In both years, community composition differed between treatments providing resources (Sc-killed and freezer-killed insects) and those without (sham burial and no disturbance), with the greatest difference on the final sampling date. Soil surrounding Sc-killed and freezer-killed insects contained more dipterans, acarid mites, staphylinid beetles, onychiurid and entomobryid collembolans, and immature and male mesostigmatid mites than soil at sham burial and no disturbance sites. Most of these taxa are capable of nematophagy; however, EPN relative abundance was not associated with arthropod community composition.

Few apparent short-term effects of elevated soil temperature and increased frequency of summer precipitation on the abundance and taxonomic diversity of desert soil micro- and meso-fauna

Frequent hydration and drying of soils in arid systems can accelerate desert carbon and nitrogen mobilization due to respiration, microbial death, and release of intracellular solutes. Because desert microinvertebrates can mediate nutrient cycling, and the autotrophic components of crusts are known to be sensitive to rapid desiccation due to elevated temperatures after wetting events, we studied whether altered soil temperature and frequency of summer precipitation can also affect the composition of food web consumer functional groups. We conducted a two-year field study with experimentally-elevated temperature and frequency of summer precipitation in the Colorado Plateau desert, measuring the change in abundance of nematodes, protozoans, and microarthropods. We hypothesized that microfauna would be more adversely affected by the combination of elevated temperature and frequency of summer precipitation than either effect alone, as found previously for phototrophic crust biota. Microfauna experienced normal seasonal fluctuations in abundance, but the effect of elevated temperature and frequency of summer precipitation was statistically non-significant for most microfaunal groups, except amoebae. The seasonal increase in abundance of amoebae was reduced with combined elevated temperature and increased frequency of summer precipitation compared to either treatment alone, but comparable with control (untreated) plots. Based on our findings, we suggest that desert soil microfauna are relatively more tolerant to increases in ambient temperature and frequency of summer precipitation than the autotrophic components of biological soil crust at the surface.

Biological functioning of PAH-polluted and thermal desorption-treated soils assessed by fauna and microbial bioindicators

A large number of soil bioindicators were used to assess biological diversity and activity in soil polluted with polycyclic aromatic hydrocarbons (PAHs) and the same soil after thermal desorption (TD) treatment. Abundance and biodiversity of bacteria, fungi, protozoa, nematodes and microarthropods, as well as functional parameters such as enzymatic activities and soil respiration, were assessed during a two year period of in situ monitoring. We investigated the influence of vegetation (spontaneous vegetation and Medicago sativa) and TD treatment on biological functioning. Multivariate analysis was performed to analyze the whole data set. A principal response curve (PRC) technique was used to evaluate the different treatments (various vegetation and contaminated vs. TD soil) contrasted with control (bare) soil over time. Our results indicated the value of using a number of complementary bioindicators, describing both diversity and functions, to assess the influence of vegetation on soil and discriminate polluted from thermal desorption (TD)-treated soil. Plants had an influence on the abundance and activity of all organisms examined in our study, favoring the whole trophic chain development. However, although TD-treated soil had a high abundance and diversity of microorganisms and fauna, enzymatic activities were weak because of the strong physical and chemical modifications of this soil.

Effects of Tillage on Soil Microarthropods in Winter Wheat

A long-term tillage study plot was sampled to evaluate the effects of tillage on soil-dwelling microarthropods. Soil (300 cm3) was sampled on four dates during two growing seasons from conventional and no-till plots of winter wheat. Microarthropods were extracted using Tullgren funnels and enumerated into seven taxonomic categories: 1) Total abundance, 2) Oribatida, 3) Mesostigmata, 4) Prostigmata, 5) Astigmata, 6) Collembola, and 7) other invertebrates. Abundance within six of the seven groups was greater in no-till than conventionally tilled soil on seven of the eight sampling dates: 1) Total abundance in conventional till 6.44 ± 1.68 and 21.39 ± 5.35 in no-till, 2) Oribatida in conventional till 1.06 ± 0.36 and 7.33 ± 2.23 in no till, and 3) Other invertebrates in conventional till 4.50 ± 0.82 and 10.67 ± 2.85 in no till. The Mesostigmata and Collembola showed significant differences between conventionally tilled and no-till plots on multiple dates. In contrast, mites in the group Prostigmata were more abundant in conventionally tilled soil (3.89 ± 1.13 versus 2.00 ± 0.88 in no till). Abundance of soil microarthropods in no-till plots generally increased (21.39 ± 5.35 in Season 1 to 42.42 ± 4.59 in Season 2), which might indicate gradual recovery of the habitat. Assessments of soil quality in no-till agricultural systems should include evaluations of beneficial soil fauna such as microarthropods.

Are grasslands important habitats for soil microarthropod conservation?

Biodiversity has been a focal aim of environmental protection since the Rio conference, but only with the beginning of the new millennium did soil biodiversity become an important aspect of international policy. Edaphic fauna play a key role in many soil functions, such as organic matter decomposition, humus formation and nutrient element cycling; moreover, affect the porosity, aeration, infiltration and distribution of organic matter in soil horizons, modifying soil structure and improving its fertility. The ecosystem services provided by soil animals are becoming progressively lost due to agricultural practice intensification, which causes a reduction in both abundance and taxonomic diversity of soil communities. In the present study, a permanent grassland habitat was studied in order to evaluate its potential as a soil biodiversity reservoir in agroecosystems. Grassland samples were compared with samples from a semi-natural woodland area and an arable land site. Microarthropod abundances, Acari/Collembola ratio (A/C), Shannon diversity index (H′) and evenness index (E) were calculated. QBS-ar index was used in order to evaluate soil biological quality. Microarthropod communities of the three land use typologies differed in both the observed groups and their abundance. Steady soil taxa characterized both woodland and grassland soils, whereas their abundances were significantly higher in woodland soil. Taxon diversity and soil biological quality in the grasslands did not differ from the woodland samples. The microarthropod community in the arable land showed a reduction both in taxa numbers and soil biological quality compared with the other sites. Soil biological quality and edaphic community composition highlighted the importance of grassland habitats in the protection of soil biodiversity.

Dynamics of zoomicrobial complexes upon decomposition of plant litter in spruce forests of the southern taiga

Comparative studies of the composition and abundance of soil-dwelling invertebrates (microarthropods, nematodes, and testate amoebas) and micromycetes in the course of leaf and needle litter decomposition were conducted in two types of spruce forests on white-podzolic and brown forest soils in a field experiment. The analysis of the destruction dynamics has revealed a correlation between the rate of the litter mass loss and the abundance of microarthropods and testate amoebas in the decomposing plant residues. The highest amplitude of the seasonal fluctuations in the number of invertebrates was found for the micromycetes and nematodes as compared to that for the testate amoebas and microarthropods. In the complexes of micromycetes and invertebrates, changes in the dominants were revealed at the different stages of the decomposition. The litter’s composition was found to be the main factor affecting the composition and abundance of the zoomicrobial complex of the destroyers. The type of biogeocenosis less influenced the abundance of pedobionts, but it determined their taxonomic composition to a greater extent. A significant inverse correlation was revealed between the number of micromycetes and that of small soil invertebrates.

Climate change effects on soil microarthropod abundance and community structure

Long-term ecosystem responses to climate change strongly depend on how the soil subsystem and its inhabitants respond to these perturbations. Using open-top chambers, we studied the response of soil microarthropods to single and combined effects of ambient and elevated atmospheric [CO2], ambient and elevated temperatures and changes in precipitation in constructed old-fields in Tennessee, USA. Microarthropods were assessed five years after treatments were initiated and samples were collected in both November and June. Across treatments, mites and collembola were the most dominant microarthropod groups collected.We did not detect any treatment effects on microarthropod abundance. In November, but not in June, microarthropod richness, however, was affected by the climate change treatments. In November, total microarthropod richness was lower in dry than in wet treatments, and in ambient temperature treatments, richness was higher under elevated [CO2] than under ambient [CO2]. Differential responses of individual taxa to the climate change treatments resulted in shifts in community composition. In general, the precipitation and warming treatments explained most of the variation in community composition. Across treatments, we found that collembola abundance and richness were positively related to soil moisture content, and that negative relationships between collembola abundance and richness and soil temperature could be explained by temperature-related shifts in soil moisture content.Our data demonstrate how simultaneously acting climate change factors can affect the structure of soil microarthropod communities in old-field ecosystems. Overall, changes in soil moisture content, either as direct effect of changes in precipitation or as indirect effect of warming or elevated [CO2], had a larger impact on microarthropod communities than did the direct effects of the warming and elevated [CO2] treatments. Moisture-induced shifts in soil microarthropod abundance and community composition may have important impacts on ecosystem functions, such as decomposition, under future climatic change.

Carbon resources, soil organisms, and nitrogen availability: Landscape patterns in a northern hardwood forest

The interactions among different components of detrital food webs are likely to influence carbon processing and linkages between C and nutrient cycling. Our objective was to identify potentially important interactions in detrital food webs at the Hubbard Brook Experimental Forest, NH, USA, by exploring relationships among C resources, microbial biomass, microarthropod abundance and nitrogen availability as they vary across the landscape. We found significant spatial variation in microarthropod abundance in the forest floor across elevation zones in two watersheds, with consistently higher abundance in low-elevation hardwoods and upper conifer zones and lower abundance in mid- and high-elevation hardwoods. The same pattern was observed in the Oe horizon for microbial biomass C and respiration but not for N transformations; however, no patterns were observed in the Oa horizon. Microarthropod abundance and microbial biomass C were significantly positively correlated, but neither were related to forest floor mass or to annual aboveground fine litterfall flux. Instead, a positive correlation with fine root biomass suggests that C supply from roots plays a key role in the fungal channel of the detrital food web of these forests. The lack of relationship between patterns of microarthropod abundance and net N mineralization leads us to hypothesize that spatial patterns of nitrogen availability are not closely linked to variation in carbon flow through the detrital food web, within this forested landscape. In contrast, microarthropod abundance and net N mineralization did exhibit similar interannual variation and may respond to the same temporal controls.

3514 Smoking attributable cancer morbidity, mortality and years of potential life lost in Uzbekistan

A rice field and a non-cultivated area in Agartala (Tripura, India) were sampled for soil microarthropods: Oribatida, other mites, Collembola, other insects, and other microarthropods. The temporal fluctuations in the microarthropod abundances of the two sites were compared. Microarthropod abundances were similar in the two ecosystems. The group and temporal diversities were higher in the rice field than in the waste land.

Influence of 10 years of conservation tillage on some biological properties of a fine sandy loam in the potato phase of two crop rotations in Atlantic Canada

Conservation practices in potato (Solanum tuberosum L.) cropping systems can reduce excess tillage, provide crop residue cover, and maintain crop productivity; however, little is known about their long-term influence on soil biota and biological properties. Conservation tillage was evaluated in two potato rotations: a 2-yr barley-potato rotation and 3-yr clover-based (barley-red clover-potato) rotation initiated in 1994 on a fine sandy loam (Orthic Podzol) in Prince Edward Island, eastern Canada. Soil samples were obtained in 2003 from the 0- to 10-cm soil depth of the potato phase of both rotations to evaluate the influence of conservation, compared with conventional tillage, on changes in soil fertility, soil structural properties, soil C and N fractions, soil-borne pathogens, nematode communities, and micro-arthropod (Collembola and Acari) communities. The 3-yr conservation tillage practice improved soil structural stability, increased soil extractable P and K, increased soil organic C and total N and their particulate fractions, compared with the other treatments. Comparisons with earlier studies indicated that soil organic C had reached an equilibrium level at the 0- to 10-cm soil depth. Reduction of potato disease caused by Rhizoctonia solani was evident in the 3-yr rotation, compared with the 2-yr rotation, but was not influenced by tillage practice. Plant parasitic nematodes were not greatly influenced by rotation and tillage treatments; however, densities of the beneficial bacterial-feeding nematodes were increased under the 3-yr conservation tillage treatment. The abundance of micro-arthropods was increased by conservation tillage, while their diversity was mainly influenced by the rotation cycle rather than tillage practice. Overall, the 3-yr conservation tillage treatment provided a more beneficial soil biological condition than the other treatments, especially when compared with the 2-yr conventional tillage practice. Key words: Conservation systems, potato rotation, fine sandy loam, soil fertility, soil organic C and N fractions, soil structure, soil-borne pathogens, nematode, Collembola; Acari

Physico-chemical indicators and microarthropod communities as influenced by no-till, conventional tillage and nitrogen fertilisation after four years of continuous maize

A multidisciplinary study was carried out over four years in Northern Italy on a silt loam under continuous maize. The experimental design was a split-plot with four replicates; the main factor was the soil management system, conventional tillage (CT) or no-tillage (NT), while the secondary factor was N fertilisation. At the end of the trial, soil samples were taken from all plots at four depths (from 0 to 20 cm). In these samples the following were determined: pH, soil organic carbon (SOC), total N, available P, exchangeable K, cation exchange capacity (CEC), electrical conductivity (EC) and water aggregate stability (WAS). Soil compaction was measured during the last three years, after maize harvesting. To study the microarthropod community, soil samples (0–10 cm depth) were taken six times over the four years. Our results show that NT significantly increased SOC (+15.8%), total N (+9.6%), C/N (+5.3%), exchangeable K (+37.1%) and WAS (+64.8%). The stratification ratio for exchangeable K reached 2.15 for NT plots. N fertilisation, on the other hand, had no significant effect on most of the physico-chemical indicators, except for pH, CEC and EC. Soil compaction was significantly higher for NT compared with CT up to a depth of 25–30 cm. During the last year, interesting reductions in soil penetration resistance for NT were measured, up to 300–430 kPa in the 2.5–12.5 cm layer. As for the microarthropods, Acari were more sensitive to tillage compared with Collembola, and the Wardle V index proved to be a good indicator of the response to tillage. N fertilisation with 300 kg N ha −1 had a negative effect on the total microarthropod abundance. The Shannon diversity index gave fluctuating and significantly different results: over the years results were split alternately between the two tillage systems. The QBS-ar index, calculated for all the four years of the study, ranged between 48 and 72, values typical of intensively cultivated soils. The results obtained suggested that it was not influenced by the tillage system. Therefore, this index seems to be unsuitable for detecting the influence of tillage management and N fertilisation on the microarthropod community.

Influence of conservation tillage and crop rotation on the resilience of an intensive long-term potato cropping system: Restoration of soil biological properties after the potato phase

Conservation tillage in potato ( Solanum tuberosum L.) systems, in cool-humid climatic regions, can benefit soil physical and biological properties. However, insight is needed on how the combination of conservation tillage and crop rotation enhances the resilience of intensive short-term potato cropping systems, specifically the restoration of the soil condition after the perturbations that occur in the potato phase. A long-term 3-year rotation (potato-barley-red clover) and conservation tillage study was initiated in 1994 on a fine sandy loam in Prince Edward Island, eastern Canada. Over a 3-year period (2004–2006), soil physical (bulk density) and biological (C and N fractions, structural stability; densities of plant parasitic and bacterial-feeding nematodes, and micro-arthropod abundance and diversity) properties were monitored over each phase of the crop rotation cycle to assess the restoration or rejuvenation of the surface (0–10 cm) soil condition. Conservation compared to conventional tillage, increased soil organic C, large water-stable macro-aggregates, and soil particulate C and N in the potato year only. After the potato phase, rotation crops were associated with the further restoration of all soil C and N fractions and soil structural stability indices; and also increases in soil microbial biomass C and microbial activity indices, and soil Collembola abundance. Soil nematode densities showed some incidences of treatment differences but no clear trends. The study indicated that conservation tillage has a positive influence on soil biological properties and that the 3-year rotation successfully restored many of the soil parameters that had declined in the potato year.