Effect of mesofaunal activity on the rehabilitation of sealed soil surfaces

The impact of soil mesofauna on the rehabilitation of soil surfaces sealed by rainfall was investigated in a long-term laboratory experiment. Fifteen undisturbed soil monoliths from the Ap horizon of a Gleyic Podzoluvisol/Haplic Luvisol derived from loess were obtained after conventional tillage and seedbed preparation. The soil of this site is known to be susceptible to surface sealing as a result of rainfall activity. All monoliths were defaunated in a microwave oven and then inoculated with mesofauna, some with 300 individuals of Collembola and others with 200 individuals of Enchytraeidae. Additional monoliths were left uninoculated for comparison. Ten monoliths were then treated with simulated rainfall (intensity: 29 mm h⁻¹; time: 60 min) to form a surface seal. The roughness of all 15 monoliths was measured using a non-contact laser scanner immediately and after 6 and 18 months. Differences in the soil surface roughness were assumed to indicate mesofaunal activities and intrinsic soil processes. Soil surface roughness was significantly different between monoliths with and without rain impact. Monoliths subjected to rainfall showed significant differences in soil surface roughness between those with and without mesofauna as well as between monoliths inoculated with Collembola and Enchytraeidae. The roughness differences detected between unsealed monoliths were not significant. Over the entire experimental time of 18 months the relative changes in sealed uninoculated monoliths were much lower than the alterations as a result of mesofaunal activities. The results show that within a few months the activities of Collembola and Enchytraeidae distinctly contribute to the rehabilitation of sealed soil surfaces and the development of a finely structured soil surface microrelief.     

Quantitative analysis of earthworm burrow systems with respect to biological soil-structure regeneration after soil compaction

 On arable land, tilled with conventional tillage (CT) and conservation tillage (CS) respectively, plots were compacted by wheeling them 6 times with a 5 Mg wheel load in spring 1995. Immediately after compaction, undisturbed soil monoliths were excavated from the compacted and uncompacted plots. The monoliths were defaunated and inoculated with either Lumbricus terrestris or Aporrectodea caliginosa. One monolith from each plot remained uninoculated as a control. After 6 months the monoliths were defaunated again and then scanned with X-ray helical computed tomography. The data were transformed, the void systems inside the monoliths were reconstructed and visualised, and the parameters total void length, total void volume, tortuosity and continuity were quantified. The parameters' values were generally lower in the controls than in the inoculated monoliths. Differences in burrow construction could be explained by the different life strategies of the two earthworm species. Changes in burrow morphology due to tillage system and soil compaction were minor. Only the continuity of the burrow systems clearly changed: decreasing for L. terrestris and increasing for A. caliginosa. This can be explained by a change in the earthworms' burrowing activity to minimise energy expenditure in compacted soil. By extrapolating field data, we concluded that earthworms have great potential for biologically regenerating the soil structure after a single compaction event. Due to higher earthworm abundances in soil managed by CS the regeneration of the soil structure is assumed to be better in these plots than those tilled by CT. Received: 17 December 1997     

Longterm effects of soil compaction and tillage on Collembola and straw decomposition in arable soil

Soil core samples were taken from May 1996 to October 1996 at four week intervals to assess the longterm effects of compaction due to soil tillage on Collembola in arable land. Two different tillage systems were studied: conservation tillage (CS) with rotary harrowing to 120 mm depth and conventional tillage (CT) with a mould board plough to 300 mm depth. Soil compaction was achieved by wheeling with graded loads: 0t, 2 × 2.5t and 6 × 5.0t (wheeling frequency × wheel load) in early spring 1995. Litter decomposition rate was investigated by the minicontainer-method, using two different mesh-sizes: 20 μm (excluding mesofauna) and 500 μ (including mesofauna). The substrate used was winter wheat straw, corresponding to the crop cultivated on the field.We recorded 25 species of Collembola. The abundance of Collembola during the growing season was at a minimum in June in both tillage systems. Thereafter, numbers of individuals increased, probably due to better nutrition. Mesaphorura krausbaueri s.l. was eudominant in CS. In CT Folsomia fimetaria and M. krausbaueri s.l. reached high abundances at the end of August. Harvesting and tilling supported population growth in CS, while numbers in CT decreased. The collembolan species showed different preferences in regard to the tillage system and the grade of compaction. During the first 4 weeks of exposure the decomposition rate of straw was highest. The decomposition rate in the minicontainers with 20 μm mesh-size was higher due to better moisture conditions for the microorganisms. After harvest and tilling the decomposition rate increased, especially in the CS-plots, because of aeration and incorporation of residues. Population fluctuation in the minicontainers was caused by migration of Collembola in response to changing moisture conditions. The main species in the minicontainers were large and mobile. Compared to the surrounding soil, species diversity was reduced.     

Burrowing ability of the earthworm Aporrectodea longa limited by soil compaction and water potential

Summary Adult earthworms (Aporrectodea longa) were maintained for 199 days in soil columns (h=30 cm; ø=10 cm) where the water potential ranged from -7 to-65 kPa and compaction from 50 to 350 kPa. The weight of casts on the soil surface was measured at the end of two periods of activity (spring and autumn). Cast production increased with bulk density, but the activity of earthworms was limited both by the mechanical strength of the soil and by decreasing water potential. The results obtained in the laboratory conditions of this study were consistent with field observations on casting and burrowing activities. The effects of water potential and soil compaction on these activities were estimated.     

Regeneration of compacted soil aggregates by earthworm activity

Soil compaction is a problem of modern agriculture, caused by heavy machinery when used in unsuitable, especially moist, conditions. Some regeneration processes in compacted loess soil were studied in a field experiment near Relliehausen, at the edge of the Solling mountains in Lower Saxony, Germany. Conventional tillage (CT) and conservation tillage (CS) systems were compared. The compaction was induced by the use of different wheel loads. The influence of earthworms was determined by comparing soil aggregates and casts with respect to dry and moist porosity, swelling, and water stable aggregation. For visualisation of the microstructure, a scanning electron microscope was used. The casts were obtained from two earthworm species living for 6 months in the laboratory in monoliths, taken on the plots after the wheeling procedure. The casts showed 10-20% higher values for porosity and about 50% higher swelling values than comparable soil aggregates, while the relative water stability was ca. 10% lower. We conclude that casts are looser and less stable than aggregates from the soil the earthworms ingested. To show the ecological relevance of the changes in the casts, the cast production per hectare per year was calculated. It was especially high in the most loaded soil under CS with endogeic species.     

Vulnerability of Bavarian silty loam soil to compaction under heavy wheel traffic: impacts of tillage method and soil water content

Soil compaction caused by traffic of heavy vehicles and machinery has become a problem of world-wide concern. The aims of this study were to evaluate and compare the changes in bulk density, soil strength, porosity, saturated hydraulic conductivity and air permeability during sugar beet (Beta vulgaris L.) harvesting on a typical Bavarian soil (Regosol) as well as to assess the most appropriate variable factors that fit with the effective controlling of subsequent compaction. The field experiments, measurements and laboratory testing were carried out in Freising, Germany. Two tillage systems (conventional plough tillage and reduced chisel tillage) were used in the experiments. The soil water contents were adjusted to 0.17 g g⁻¹ (w₁), 0.27 g g⁻¹ (w₂) and 0.35 g g⁻¹ (w₃).Taking the increase in bulk density, the decrease in air permeability and reduction of wide coarse pore size porosity (−6 kPa) into account, it seems that CT (ploughing to a depth of 0.25 m followed by two passes of rotary harrow to a depth 0.05 m) of plots were compacted to a depth of at least 0.25 m and at most 0.40 m in high soil water (w₃) conditions. The trends were similar for “CT w₁” (low soil water content) plots. However, it seems that “CT w₁” plots were less affected than “CT w₃” plots with regard to bulk density increases under partial load. In contrast, diminishments of wide coarse pores (−6 kPa) and narrow (tight) coarse pores (−30 kPa) were significantly higher in “CT w₁” plots down to 0.4 m. Among CT plots, the best physical properties were obtained at medium soil water (w₂) content. No significant increase in bulk density and no significant decrease in coarse pore size porosity and total porosity below 0.2 m were observed at medium soil water content. The soil water content seemed to be the most decisive factor.It is likely that, CS (chiselling to a depth of 0.13 m followed by two passes of rotary harrow to a depth 0.05 m) plots were less affected by traffic treatments than CT plots. Considering the proportion of coarse pore size porosity (structural porosity) and total porosity, no compaction effects below 0.3 m were found. Medium soil water content (w₂) provides better soil conditions after traffic with regard to wide coarse pore size porosity (−6 kPa), air permeability (at 6 and 30 kPa water suction), total porosity and bulk density. Proportion of wide coarse pores, air permeability and bulk density seems to be suitable parameters to detect soil compaction under the conditions tested.     

Assessing the impact of Diplocardia ornata on physical and chemical properties of compacted forest soil in microcosms

 The influence of compaction on Diplocardia ornata (Smith) burrowing and casting activities, soil aggregation, and nutrient changes in a forest soil were investigated using pot microcosms. Treatments included two levels each of compaction, organic matter, and earthworms. Both burrowing and casting activities were more abundant in uncompacted soil than in compacted soil. Bulk density decreased in microcosms of compacted soil containing D. ornata from 1.76 g cm^–3 to 1.49 g cm^–3 over the study period. The overall percent of aggregates in the same size classes in compacted soil was less than the percent of aggregates in uncompacted soil. The mean percent of aggregates in earthworm casts for size classes 0.25–1.00 mm was higher for compacted soil than for uncompacted soil. The reverse was true for aggregates in class sizes 2.00–4.00 mm. Soil compaction also affected soil microbial biomass carbon and soil inorganic N concentrations. These results indicate that the burrowing and casting activities of earthworms in compacted forest soils, as in soils of agricultural and pastured lands, can help ameliorate disturbed soils by improving aggregation, reducing bulk density, and increasing nutrient availability. Received: 1 September 1999     

Assessment of earthworm burrowing efficiency in compacted soil with a combination of morphological and soil physical measurements

Summary Column experiments were carried out to quantify the effect of earthworms on compacted soil. The earthworms (Lumbricus terrestris) were able to burrow into soil which was artificially compacted to a pore volume as low as 40%; they may also penetrate an artificial plough pan deep in the soil. The effect of the burrowing activity of Lumbricus terrestris was quantified by measuring hydraulic conductivities and infiltration rates through the whole soil column (19 cm wide, 40 cm long). Morphological parameters, mainly the vertically projected burrow depth, were correlated with the saturated hydraulic conductivity. The amount of casts deposited by Lumbricus terrestris on the soil surface increased with the degree of soil compaction. The bulk density of casts was always less than that of the original soil.     

保护性耕作下大豆农田土壤呼吸及影响因素分析

为了探讨保护性耕作对旱作农田土壤呼吸的影响,采用LI6400-09仪器(LI6400便携式光合作用系统连接6400-09呼吸室)在重庆北碚西南大学试验农场对平作(T)、垄作(R)、平作+覆盖(TS)、垄作+覆盖(RS)、平作+覆盖+秸秆速腐剂(TSD)、垄作+覆盖+秸秆速腐剂(RSD)6种处理下的西南紫色土丘陵区小麦/玉米/大豆套作体系中大豆生长季节的土壤呼吸及其水、热、生物因子进行测定和分析,探讨西南丘陵区保护性耕作下大豆农田土壤呼吸及其影响因素。结果表明,大豆整个生育期内土壤呼吸先缓慢增强,到开花期开始增长迅速,成熟期明显下降。不同处理土壤呼吸速率存在差异,表现为TTSD>TS、R>RSD>RS,土壤呼吸的土温敏感指标Q10值排序为TS>TSD>RS=R>T>RSD。秸秆覆盖处理的土壤呼吸对于土壤温度敏感性较高,垄作则降低了土壤温度敏感性。5 cm土层的土壤含水量高低排序为TSD>RSD>TS>RS>T>R。本研究中土壤呼吸与土壤水分呈抛物线函数关系,垄作处理下土壤呼吸与土壤水分正相关,达到显著水平;其他处理均表现负相关,其中TS达到极显著水平。在大豆农田生态系统中优势类群有弹尾目、螨目和双翅目,干漏斗法、陷阱法捕获的土壤动物与土壤呼吸均没有显著的相关关系,两种方法所得土壤动物数量加总与土壤呼吸进行相关分析,发现处理T相关系数达到显著水平,r=0.901,P=0.037。     

Collembolans feeding on soil affect carbon and nitrogen mineralization by their influence on microbial and nematode activities

We manipulated Collembola Folsomia candida Willem density and observed the density effect on carbon and nitrogen mineralization and on nematodes in microcosms filled with mineral soil. Collembolan densities were 0 (control), 25 (low), 100 (medium), and 400 (high) individuals per microcosm. The Collembola enhanced soil respiration and nitrogen mineralization rate in a density-dependent manner (P < 0.05). The correlation between collembolan density and the metabolic quotient of microbes, qCO₂, was weakly positive (r = 0.44, P < 0.05). Collembola did not affect microbial biomass. These results suggested that enhanced carbon and nitrogen mineralization was an indirect effect of Collembola mediated by increased microbial activity. Collembola changed the C_nema/C_mic ratio, but only when present at the low density. Thus, Collembola had both positive and negative effects on the nematode population. The positive impact probably depends on the enhancement of microbial activity due to Collembola grazing behavior, while the negative effect appears to result from predation of nematodes.     

Organic textile dye improves the visual assessment of the bait-lamina test

Rapid ecosystem assessments are needed for large-scale ecotoxicological studies and coordinated distributed experiments. Bait-lamina stripes are commonly used as a standardized method to assess decomposer activity, but it is often difficult to distinguish bait substrate from soil. In the present study our aim was to identify a dyeing method that improves the precision of visual assessment of decomposition rates, while having negligible side effects. We compared five different dyes (food dye, Easter Grass, organic textile dye, ink, and wall paint) with control substrate in microcosms containing either acidic or alkaline soil with two introduced Collembola species (Folsomia candida and Sinella coeca). Organic textile dye showed the highest precision of visual assessment, and had no detectable side effects on decomposition rates, soil microbial activity (biomass and respiration), or Collembola densities. We recommend using organic textile dye to improve the bait-lamina test due to the high precision and the ease of preparation.     

Comparison of soil arthropods and earthworms from conventional and no-tillage agroecosystems

Soil-arthropod and earthworm densities (number m⁻²) were higher (P < 0.05) under no-tillage than conventional tillage practices. Enchytraeid worms were higher in conventional tillage. Two predaceous groups, ground beetles (Carabidae: Coleoptera) and spiders (Araneae), comprised more than one-half of all soil macroarthropods collected. All major microarthropod suborders (Oribatids, Prostigmatids, Mesostigmatids, and the order Collembola) were higher (P < 0.01) under no-tillage than conventional tillage. High soil-arthropod and earthworm densities under no-tillage systems suggest an expanded and beneficial involvement for these soil fauna in crop-residue-decomposition processes.     

Rainfall effects on erosion of earthworm casts and phosphorus transfers by water runoff

 We investigated whether, under a temperate climate and in a maize crop, earthworm casts could contribute to soil erosion and further favour the exportation of phosphorus by runoff waters. Recording of casts was made in compacted (wheel-tracks) and non-compacted inter-rows, for a 2-month period in spring. To assess the rainfall impact on cast evolution, half of the observation sites were protected against rain splash by a nylon mesh placed above the soil surface. The water runoff was collected and analysed for sediment contents and phosphorus concentration. The mean annual production of surface casts was calculated to be 34 kg (dry weight) year^–1 kg^–1 earthworm (fresh weight). Synchronization between cast erosion and rainfall events was shown under natural conditions (unprotected sites). The erosion rate was 4 times greater over rainy periods than dry ones, reaching 80% of cast numbers. It appeared that not the runoff effect but the splash effect, due to the kinetics of the drops, disrupted casts. Newly formed casts disappeared first, with the erosion rate decreasing twofold for casts more than 10 days old. Cast erosion and runoff, as well as worm casting activity, were greater under compacted sites than under non-compacted sites, indicating an influence of earthworms on soil erosion from compacted soils. The total phosphorus content was similar in casts and uningested soil (0.80 mg phosphorus g^–1). Potential phosphorus losses from cast erosion was calculated to reach 25–49 mg phosphorus m^–2 per rainfall event depending on soil compaction. The amounts of particulate phosphorus recovered in water runoff after each rainfall event varied from 1 mg to 11 mg phosphorus. These results are compared and discussed. Received: 20 October 1998     

Sensitivity to cadmium of the standard test species Folsomia candida compared to two other species, Onychiurus yodai and Sinella umesaoi (Collembola)

Knowing whether test species used for single-species toxicity tests are representative of other species provides valuable information because contaminant effects are often extrapolated to the community level based on these tests. To evaluate how representative the sensitivity of the standard test collembolan species Folsomia candida is for Collembola, we devised toxicity tests using the collembolan species Onychiurus yodai and Sinella umesaoi, which exhibit life-forms different from F. candida. Sensitivity to cadmium (Cd) was compared between F. candida and the novel test species. The 50% effective concentrations for reproduction were 154.7, 72.2 and 40.9 mg Cd/kg dry soil for O. yodai, F. candida and S. umesaoi, respectively. Thus, the reproductive sensitivity of F. candida to Cd was between that of the other two species. Increasing reproductive sensitivity to Cd corresponded to increasing activity levels and a more surface-dwelling life-form. Our data may facilitate the generalisation of effect data for F. candida to other species.     

Land-use impacts on surface runoff and soil detachment within agricultural sloping lands in Northern Vietnam

Two consecutive years of investigation on soil surface features, surface runoff and soil detachment within 1-m² microplots on 40% slope highlighted the effects of land-use change, vegetation cover and biological activity on the water pathways in Northern Vietnam. Three replicate plots were set up on each of five land-uses: cassava (CAS), grass fodder of Bracharia ruziziensis (BRA), a 3-year old fallow (FAL), tree stands of Acacia mangium and Venicia montana (FOR), and a fallow with regrowth of Eucalyptus regularly cut (EUC). The second year, two of the microplots under FAL and EUC were treated with herbicide (FALh, EUCh), one of them was burnt (FALh+b, EUCh+b). The highest yearly surface runoff coefficient of 16%, and soil detachment rate of 700 g m^− 2 yr^− 1 in average with a maximum of 1305 g m^− 2 yr^− 1 have been recorded under CAS. On FALh and FALh+b, runoff ratios were 8.7 and 13.5%, respectively and detachment rates were 86 and 389 g m^− 2. On FAL and BRA the yearly runoff ratio varied from 5.9 to 9.8% but the detachment rate was limited at 24 to 35 g m^− 2. FOR and EUC annual runoff was ≤ 3.1% and annual soil detachment ≤ 71 g m^− 2. These values were very low compared to the values reported on steep slopes in Laos within similar climate and vegetation cover.The runoff and detachment rates underlined the importance of rainfall intensities, soil physical properties, soil surface features, soil vegetation cover and biological activity. The annual surface runoff was highly correlated to the soil surface crusting. CAS and BRA plots were prone to crusting especially after weeding at the onset of the rainy season, when the soil surface was still uncovered. Soil bioturbation (earthworm casting activity) was the second factor that explains local variation of surface runoff and soil detachment. The continuous production of earthworms casts on soil surface, especially on FOR and EUC microplots, induced a marked surface roughness and reduced the surface runoff. The production of casts was very limited in FAL and completely absent in CAS microplots. So it is evident that our results confirm the deleterious effects of cassava on soil and water conservation.     

Density-dependent grazing on the extraradical hyphal network of the arbuscular mycorrhizal fungus, Glomus intraradices, by the collembolan, Folsomia candida

The effect of microarthropod density on the relative palatibility of selected microfungi and on the integrity of extraradical arbuscular-mycorrhizal (AM) hyphal networks was examined. A series of microcosm experiments were conducted using two conidial fungi (Alternaria alternata and Trichoderma harzianum), one AM fungus (Glomus intraradices) and the microarthropod Folsomia candida (Collembola). We did not detect a significant effect of athropod density on food preference. Food preferences for conidial over mycorrhizal hyphae were consistent across a wide range of collembolan densities. Collembolan density did, however, have a significant effect on the numbers of extraradical AM hyphae which were severed from the plant root in vitro. Even in the presence of a preferred food source, numbers of severed AM hyphal networks increased with increasing collembolan density. Also, the fecundity of Folsomia candida increased in the presence of preferred food sources. We conclude that microarthropod population densities are influenced by the fungal species available and that the potential of microarthropods to impair the efficacy of AM symbioses is density-dependent. Received: 16 May 1997     

Decomposition of straw in relation to tillage,moisture, and arthropod abundance in a semi-arid tropical Alfisol

The decomposition of rice straw was studied in relation to straw moisture and the abundance of soil arthropods, such as Acarina, Collembola, and miscellaneous groups dominated by termites [Odontotermes obesus (Rambur) and Microtermes obesi Holmgren], across tillage treatments (no tillage, shallow tillage, and deep tillage) in Alfisols of the semi-arid tropics in India from August 1989 to July 1990. In the straw, across the treatments, Acarina were dominant (>70% of the total arthropods), and Collembola were a minor component. O. obesus and M. obesi foraged straw together under the cover of an earthern sheet. A larger number of arthropods was recorded during the rainy season, but they were either negligible or absent during the dry season. The abundance of arthropods and mass loss of straw was greater in coarse-mesh bags than in the fine-mesh bags. Their abundance was significantly affected by tillage treatments and season (P<0.01). In the beginning, it was significantly greater in the no-tillage and shallow-tillage than in the deep-tillage treatment. The mass loss was 46% of the initial mass during the first 60 days, and more than 90% after 330 days of decomposition. Tillage had a significant effect on mass loss, particularly after 330 days, and the no tillage treatment led to a greater mass loss. Multiple linear regression analysis revealed that the moisture content of the straw and the abundance of arthropods had significantly affected the mass loss in both fine-and coarse-mesh bags across the tillage managements.Visiting Scientist (under the Rockefeller Foundation Environmental Research Fellowship in International Agriculture) in Resource Management Program at ICRISAT, India     

Effects of fallow system and cropping frequency upon quantity and composition of earthworm casts

The quantities of earthworm surface casts were monitored in traditional bush fallow regrowth (BFR), Pueraria phaseoloides live mulch (PLM), Leucaena leucocephala alley cropping (LAC) and undisturbed forest. The fallow systems were planted to maize/cassava intercrop either permanently or for one year after three years of fallow i.e. at 100 and 25% cropping frequencies. Earthworm casting activity was lower in fields cropped after clearing three year old fallow than in the respective permanently cropped fallow management system. The reduction in casting was related both to the degree of biomass removed through burning and to re-establishment of cover crops. Higher exchangeable cation concentration in the soil did not cause increased casting activity. Concentrations of organic C, total N and exchangeable Ca and Mg in casts were significantly higher than in the 0–15 cm topsoil. Exchangeable Ca and Mg in casts did not significantly differ between treatments, with the exception of significantly higher Mg in casts after three years of P. phaseoloides fallow. Topsoil (0–15 cm) exchangeable Ca and Mg were not correlated with cast exchangeable Ca and Mg, but concentrations of organic C and total N in casts were significantly correlated with organic C and total N in the topsoil. Coefficients of variability of organic C, total N and exchangeable Ca and Mg were about twice as high in the soil than in casts. Significant negative correlations between the cast to soil ratio (cast enrichment factor) of organic C, total N and exchangeable Ca and Mg and the respective concentrations in the soil show that earthworms are increasingly selective in organic carbon and nutrient uptake as these parameters of soil fertility are declining.     

Quantifying surface and subsurface cast production by earthworms under controlled laboratory conditions

Earthworm casts, formed when organic substrates and soil minerals pass through the digestive tract, may protect soil organic matter from biological degradation if they persist in the soil. Yet, the stability of casts is affected by their location in the soil profile because surface casts are exposed to more disruptive forces (wetting-drying, freezing-thawing) than subsurface casts. It is not known whether environmental conditions affect the proportions of surface and subsurface casts produced by earthworms. This study investigated how surface and subsurface cast production by juveniles of Aporrectodea spp. and Lumbricus spp. was affected by temperature. Two juveniles of Aporrectodea spp. or Lumbricus spp. were added to plexiglass chambers filled with soil, and five replicate chambers were incubated in the dark at 5°C, 10°C, 15°C or 20°C for 1 week. Most of the casts produced by Aporrectodea spp. and Lumbricus spp. were surface casts, with <10% of casts deposited below the soil surface. The earthworms studied produced more casts, and a greater proportion of surface casts, as the soil temperature increased. These results can be used to estimate the quantity of surface and subsurface casts produced by earthworm populations under field conditions and determine the susceptibility of cast-associated organic matter to decomposition in the medium- to long-term.     

生物耕作对土壤理化特性、酶活性及青花菜生长和品质的影响

通过田间试验,研究生物耕作(接种蚯蚓)对土壤理化性质、酶活性及青花菜生长和产量品质的影响。试验设置了传统机械旋耕(CK)、免耕(T1)以及生物耕作(T2)3个处理。研究结果表明:(1)生物耕作能有效提高耕层不同部位的土壤养分含量和含水量,其中尤以5～20 cm土层较为明显,生物耕作处理土壤有机质、全氮、有效磷含量以及含水量依次比传统机械旋耕(CK)增长58.33%、68.93%、67.06%和16.19%;与传统机械旋耕(CK)相比,生物耕作处理大大提升了土壤过氧化氢酶、脲酶以及蔗糖酶的活性,其中脲酶、蔗糖酶与CK之间差异显著(P<0.05)。(2)生物耕作处理下青花菜的株高、开展度、叶长、叶宽等指标与CK和T1之间差异显著(P<0.05);各处理间青花菜的叶绿素相对含量差异不大,生物耕作处理增强了青花菜在各生长期的净光合速率。(3)生物耕作处理大幅提高了青花菜品质,生物耕作处理下的青花菜Vc含量是CK的1.2倍,硫代葡萄糖苷含量分别比T1处理和CK高1.05 mol·g-1和3.29 mol·g-1,差异均达到显著水平;各处理间可溶性糖含量差异不显著。因此,在传统的农业生态系统中,培育土壤有益动物的生物数量(生物耕作)可提高土壤养分和酶活性,对改善农田土壤肥力有着重要意义。