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1.
 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  相似文献   

2.
Soil compaction is an often-recorded characteristic of degraded soils, and—along with soil sealing and contamination—frequently found in urban habitats. Knowledge about the impact of soil degradation on the ecosystem functioning in urban environments is limited, although urbanization is the major ongoing land use change worldwide. Since urban soils are a potential habitat for soil animals, and burrowing soil fauna exerts a profound impact on the structure and functioning of soils, we studied the impact of increased bulk densities on the ability of Enchytraeus albidus (Enchytraeidae: Oligochaeta) to penetrate compacted soils. Moreover, it was our aim to characterize the influence of the worms on the mobilization of nutrients in urban soils. E. albidus was able to enter compacted sandy loamy soil columns with a bulk density of up to approx. 1.4 g cm−3, but only up to approx. 1.0 g cm−3 in pure sandy soil columns. Soil compaction increased the amounts of water-extractable sodium (7.5%) and magnesium (13.4%) compared to the non-compacted soil. Presence of E. albidus in the non-compacted soil resulted in higher water-extractable concentrations of sodium (17.4%), potassium (16.8%), calcium (11.3%), magnesium (13.2%), dissolved organic carbon (DOC, 14.5%) and nitrate (20.4%) in soil extracts. In the compacted soil, however, the enhanced nutrient availability due to the activity of the enchytraeids was less pronounced than in the non-compacted soil. Although the concentrations of DOC (13.5%), nitrate (15.6%), calcium (5.8%) and magnesium (4.0%) were significantly higher in the presence of E. albidus than in the columns without animals, the performance of the animals was partly impaired. This was most likely due to the higher penetration resistance of the compacted soils. The degree of compaction investigated in this study was relatively low-chosen to allow for the colonization of the soils by E. albidus. We conclude that the observed negative effects of increased bulk densities on the activity of soil enchytraeids can occur in any more frequented city park, thereby decreasing turnover rates and the supply of soil nutrients in urban ecosystems.  相似文献   

3.
Soil compaction prevents turfgrass roots from growing deep into the soil and may limit access to water and nutrients. The objective of this study was to characterize the ability of turfgrass roots to penetrate a compacted subsurface layer. Seven turfgrasses were grown in soil columns. Each column was divided into three sections with the top and bottom packed to a bulk density of 1.6 g cm?3, and the middle (treatment) layer packed to 1.6, 1.7, 1.8, 1.9, or 2.0 g cm?3. Subsurface compaction reduced root mass for two of the species, and inhibited deep root growth in all seven species, with the greatest reduction occurring between 1.7 and 1.8 g cm?3. There appears to be little difference between species in ability to penetrate compacted soils, suggesting that soil preparation and routine management practices, rather than grass selection, is the more viable way to handle soil compaction problems in turf.  相似文献   

4.
Soil compaction is widespread but tends to be most prevalent where heavy machinery is used in landfill sites, agriculture and forestry. Three forest sites strongly disturbed by heavy logging machinery were chosen to test the physical effects of different levels of compaction on soil bacterial community structure and soil functions. Community analysis comprised microbial biomass C and T-RFLP genetic profiling. Machine passes, irrespective of the compaction level, considerably modified soil structural characteristics at two soil depths (5–10 cm; 15–20 cm). Total porosity decreased up to 17% in the severe compaction. Reflected in this overall decline were large decreases in macroporosity (>50 μm). Reduction in macroporosity was associated with higher water retention and restricted gas exchange in compacted soils. The strongest effect was observed in the severely compacted wheel tracks where air and water conductivities were reduced permanently to 10% or even lower of the original conductivities of undisturbed soils. Very slow drainage in combination with a dramatically reduced gas permeability led to unfavorable soil conditions in severely disturbed traffic lanes reflecting the changes in the total bacterial community structures at both soil depths. Additionally, microbial biomass C tended to be lower in compacted soil. Our results indicate that the type of severe treatments imposed at these forest sites may have strong adverse effects on long-term soil sustainability.  相似文献   

5.
In the deserts of Kuwait in general and in Al‐Salmi area in particular, soil compaction and sealing are the most significant mechanisms of land degradation. In the present study, soil compaction and sealing in the Al‐Salmi area are assessed. The study is based on analysis of satellite images and aerial photographs, besides field measurements and laboratory investigations. Based on this study, a recent map is prepared for the concerned area. It shows three different soil classes. These are highly compacted (8\8 per cent), slightly compacted (1\7 per cent), and almost non‐compacted or natural (89\5 per cent). Soil compaction in Al‐Salmi area causes adverse changes in soil physical properties, e.g. infiltration rate, bulk density and soil strength. The infiltration capacity of the compacted soils has decreased by 18\46 to 91\96 per cent in comparison with non‐compacted soils. The bulk density for the compacted soil varies between 1\6 and 1\7 g cm−3, whereas it varies between 1\2 and 1\35 g cm−3 in the non‐compacted soils, that is an increased of 29\97 per cent. In some sites, the physical properties show small or no difference between compacted and natural soils due to the effect of soil sealing (crustation). Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

6.
Growth and symbiotic activity of legumes are reduced by high soil compaction and mediated by Nod factors (LCO, lipo-chitooligosaccharides) application. Our objective was to assess the combined effects of soil compaction and Nod factors application on growth and symbiotic activity of pea. The experiment was two factorial and included soil compaction (1.30 g cm−3 – not compacted (control) and 1.55 g cm−3 – compacted soil), and Nod factors concentration (control without addition of Nod factors and use of 260 nM Nod solution) for each soil compaction. The soil (Haplic Luvisol) was packed into pots, pea (Pisum sativum L.) seeds were soaked with Nod factors solution or water and then plants were grown for 46 days. This study has shown that soil compaction and treatments of pea seeds with Nod factors influenced pea growth and symbiotic activity. Soil compaction significantly reduced pea growth parameters, namely plant height, dry mass, leaf area, root mass and root length and symbiotic parameters, namely mass of nodules, dry mass of an individual nodule, nitrogenase activity and total nitrogen content in plant in comparison to the non-compacted treatment. Treatment of seeds with Nod factors generally improved nearly all of the above parameters. Nitrogenase activity per pot and total plant nitrogen content were significantly reduced by soil compaction and increased by application of Nod factors in plants grown in not compacted soil. Our results demonstrate that increased symbiotic activity resulting from Nod factors addition may mitigate adverse effect of soil compaction on plant growth.  相似文献   

7.
One of the key issues to increase soil productivity in the Sahel is to ensure water infiltration and storage in the soil. We hypothesised that reducing tillage from annual to biennial ploughing and the use of organic matter, like compost, would better sustain soil hydraulic properties. The study had the objective to propose sustainable soil fertility management techniques in the cotton–maize cropping systems. The effects of reduced tillage (RT) and annual ploughing (AP) combined with compost application (Co) on soil infiltration parameters were assessed on two soil types. Topsoil mean saturated hydraulic conductivities (Ks) were between 9 and 48 mm h−1 in the Luvisol, while in the Lixisol they were between 18 and 275 mm h−1. In the two soil types compost additions with reduced tillage or with annual ploughing had the largest effect on Ks. Soil hydraulic behaviour was in reasonable agreement with soil pore size distribution (mean values varied from 19.5 to 237 μm) modified by tillage frequency and organo-mineral fertilization. Already the first 3 years of this study showed that use of organic matter, improved soil infiltration characteristics when annual ploughing was used. Also biennial ploughing showed promising results and may be a useful strategy for smallholders to manage these soils.  相似文献   

8.
Soil porosity and organic matter content influence the hydrology, thermal status and productivity of agricultural soils. Shape, size and continuity of soil pores are determined by tillage practices. Thus appropriate tillage and mulch management can conserve residual soil moisture during the post rainy season. This can play a key role in enhancing productivity under the rainfed ecosystem of subhumid region in eastern India. A field study was carried out on a fine loamy soil from 1993–1994 to 1995–1996. Two tillage treatments were conventional ploughing (150 mm depth) and shallow ploughing (90 mm) depth. Each tillage practice was tested with three mulch management viz., no mulch, soil dust mulch and rice (Oryza sativa L.) straw mulch. Soil organic carbon, bulk density, moisture retentivity, soil temperature with productivity and water use pattern of barley (Hordium vulgare L.) were measured.Reduction in ploughing depth resulted in nominal increase in profile (0.0–1.2 m) moisture status, yield, and soil thermal status at 14:00 and water use efficiency (WUE). However, it decreased the magnitude of soil temperature in the morning (07:00). Straw mulch conserved 19–21 mm of moisture in the profile (1.2 m) over the unmulched condition. Both soil dust and rice straw mulching elevated soil thermal status at 07:00 as compared to unmulched condition, but this trend was reversed at 14:00. Straw mulching significantly increased grain yield and WUE over soil dust mulch and unmulched condition. Impact of straw mulch was more pronounced under shallow ploughing depth. Shallow tillage with rice straw mulching is recommended to the farmers to obtain higher level of yield and water use efficiency.  相似文献   

9.
Soil compaction and soil moisture are important factors influencing denitrification and N2O emission from fertilized soils. We analyzed the combined effects of these factors on the emission of N2O, N2 and CO2 from undisturbed soil cores fertilized with (150 kg N ha−1) in a laboratory experiment. The soil cores were collected from differently compacted areas in a potato field, i.e. the ridges (ρD=1.03 g cm−3), the interrow area (ρD=1.24 g cm−3), and the tractor compacted interrow area (ρD=1.64 g cm−3), and adjusted to constant soil moisture levels between 40 and 98% water-filled pore space (WFPS).High N2O emissions were a result of denitrification and occurred at a WFPS≥70% in all compaction treatments. N2 production occurred only at the highest soil moisture level (≥90% WFPS) but it was considerably smaller than the N2O-N emission in most cases. There was no soil moisture effect on CO2 emission from the differently compacted soils with the exception of the highest soil moisture level (98% WFPS) of the tractor-compacted soil in which soil respiration was significantly reduced. The maximum N2O emission rates from all treatments occurred after rewetting of dry soil. This rewetting effect increased with the amount of water added. The results show the importance of increased carbon availability and associated respiratory O2 consumption induced by soil drying and rewetting for the emissions of N2O.  相似文献   

10.
It is crucial to advance the understanding of the soil carbon dioxide (CO2) flux and environmental factors for a better comprehension of carbon dynamics in subtropical ecosystems. Red soil, one of the typical agricultural soils in subtropical China, plays important roles in the global carbon budget due to their large potential to sequester C and replenish atmospheric C through soil CO2 flux. We examined the relationship between soil CO2 flux and environmental determinants in four different land use types of subtropical red soil-paddy (P), orchard (O), woodland (W) and upland (U) using static closed chamber method. Objectives were to evaluate the relationship of soil temperature, water-filled pore space (WFPS), and dissolved organic carbon (DOC) with the soil CO2 flux. Soil CO2 fluxes were measured on each site about every 14 days between 09:00 and 11:00 a.m. during 14-July 2004 to 25-April 2007 at the experimental station of Heshengqiao at Xianning, Hubei, China. Soil CO2 fluxes revealed seasonal fluctuations, with the tendency that maximum values occurred in summer, minimum in winter and intermediate values in spring and autumn except for paddy soil when it was submerged. Further, significant differences in soil CO2 fluxes were observed among the four soils, following the order of P > O > U  W. Average soil CO2 fluxes were estimated as 901 ± 114, 727 ± 55, 554 ± 22 and 533 ± 27 (±S.D.) g CO2 m−2 year−1 in paddy, orchard, upland and woodland soils, respectively. Variations in soil CO2 flux were related to soil temperature, WFPS, and dissolved organic carbon with a combined R2 of 0.49–0.75. Soil temperature was an important variable controlling 26–59% of soil CO2 flux variability. The interaction of soil temperature and WFPS could explain 31–60% of soil CO2 flux variations for all the land use types. We conclude that soil CO2 flux from red soil is under environmental controls, soil temperature being the main variable, which interact with WFPS and DOC to control the supply of readily mineralizable substrates.  相似文献   

11.
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.  相似文献   

12.
On 26 December 2004, a tsunami caused extensive loss of life, damaged property and degraded agricultural land in the province of Aceh, Indonesia. While some of the associated soil chemical changes have been documented, information on soil physical properties is sparse. The objective of this study was to quantify physical properties of some tsunami-affected upland agricultural soils in Aceh, Indonesia. Soil was sampled approximately 21/2 years after the tsunami, from the 0–0.1 m, 0.1–0.3 m and 0.3–0.5 m depths in four sites in the villages of Kling Cot Aroun in Aceh Besar sub-district, Kuta Kruen in Aceh Utara sub-district, Udjong Blang Mesjid in Bireuen sub-district and Meue in Pidie Jaya sub-district on the east coast of Aceh. These sites were located within 1 km from the sea at elevations ranging from 0 to 5 m ASL. The soils were Ultisols except for Meue, which was an Entisol. Soil properties measured were bulk density, structural stability and particle size distribution. Soil water retention, pore-size distribution and saturated hydraulic conductivity were estimated by inserting the values of bulk density, clay, sand and silt contents into pedotransfer functions from the literature. The analyses conducted during this study did not permit us to ascertain what proportion of the soil particles were of tsunami-origin. Nonetheless, deposition of finer-textured material may have occurred in two of the sites. In comparison with the greyish-white, coarse textured soil in the rest of the profile, a finer-textured yellow horizon was present in the lower slopes of the Udjong Blang Mesjid site. At Meue, clay and silt contents were higher in the surface 0.3 m than in the 0.3–0.5 m depth, although a distinct horizon was absent. Particle size distribution in all sites was dominated by the sand fraction, although clay and silt contents were relatively high (20–30 g 100 g− 1) at Kuta Kruen. Among the sand fractions, fine sand (0.02–0.25 mm) was highest at Kling Cot Aroun, Kuta Kruen and in the “yellow horizon” at Udjong Blang Mesjid, making them more prone to hardsetting and compaction after intensive tillage. Soil compaction was present in all sites with that in the “yellow horizon” at Udjong Blang Mesjid being highest. The relatively low porosity in this layer may be beneficial, as it is likely to reduce the high rates of water drainage and nutrient leaching in this sandy soil. The more compacted soils were characterised by higher numbers of micropores (r, pore radius < 4.3 μm), lower water retention at saturation, smaller numbers of macropores (r > 14.3 μm), lower hydraulic conductivity and intensive gleying, indicating frequent waterlogging. The soils in all depths from Kling Cot Aroun and the “yellow horizon” at Udjong Blang Mesjid were very dispersive, that at Meue moderately dispersive in the 0.3–0.5 m depth but stable in the 0–0.1 m depth, and at Kuta Kruen very stable in all depths. Soil physical degradation was a feature of the soils examined, and its amelioration will be the key to improving and sustaining crop yields in these soils. Possible management interventions include organic amendments such as compost or manure, and minimum tillage options such permanent beds or zero tillage with retention of crop residues as in situ mulch together with suitable cover crops.  相似文献   

13.
The initially high level of soil compaction in some direct sowing systems might suggest that the impact of subsequent traffic would be minimal, but data have not been consistent. In the other hand on freshly tilled soils, traffic causes significant increments in soil compaction. The aim of this paper was to quantify the interaction of the soil cone index and rut depth induced by traffic of two different weight tractors in two tillage regimes: (a) soil with 10 years under direct sowing system and (b) soil historically worked in conventional tillage system. Treatments included five different traffic frequencies (0, 1, 3, 5 and 10 passes repeatedly on the same track). The work was performed in the South of the Rolling Pampa region, Buenos Aires State, Argentina at 34°55′S, 57°57′W. Variables measured were (1) cone index in the 0–600 mm depth profile and (2) rut depth. Tyre sizes and rut depth/tyre width ratio are particularly important respect to compaction produced in the soil for different number of passes. Until five passes of tractor (2WD), ground pressure is responsible of the topsoil compaction. Until five passes the tyre with low rut depth/tyre width ratio reduced topsoil compaction. Finally, the farmer should pay attention to the axle load, the tyre size and the soil water content at the traffic moment.  相似文献   

14.
We measured the terpene concentration in pentane and water extracts from soil horizons (litter, organic, top and low mineral) and from roots growing in top and low mineral horizons on a distance gradient from Pinus halepensis L. trees growing alone on a grassland. Terpene concentrations in pentane were higher than in water extracts, although β-caryophyllene showed relatively high solubility in water. The litter and roots were important sources of terpenes in soil. Alpha-pinene dominated in roots growing in both “top” (A1) and “low” (B) mineral horizons (123 ± 36 μg g−1 or 14 ± 5 mg m−2) and roots in low mineral horizon (270 ± 91 μg g−1 or 7 ± 2 mg m−2). Beta-caryophyllene dominated in litter (1469 ± 331 μg g−1 or 2004 ± 481 mg m−2). Terpene concentration in soil decreased with increasing distance to the trunk. This is likely to be related to changes in litter and roots type on the distance gradient from pine to grass and herbs. The relative contributions of all compounds, except α-pinene, were similar in the mineral soils and litter. This suggests that litter of P. halepensis is probably the main source of major terpene compounds. However, long-term emissions of α-pinene from P. halepensis roots might also contribute to α-pinene concentrations in rhizosphere soils.  相似文献   

15.
Deep tillage that is used before vine plantation to remove old vine roots and loosen subsoil may induce physical soil degradation that could affect soil structure and vine water supply. The objective of the study was to experimentally evaluate the effect of deep tillage on soil structure. The impacts on soil structure of two deep tillage techniques, i.e. deep ploughing and ripper, and two contrasted soil water conditions were compared in a experimental field by combining morphological observations, bulk density and saturated hydraulic conductivity measurements. These three methods were found very complementary to analyse and discriminate the impact of the different treatments. The proportion of compacted zones and mean bulk density increased from the initial plot (0.15 m2 m−2, 1.45 Mg m−3) to a maximum in the case of the deep ploughing under wet conditions plot (0.60 m2 m−2, 1.60 Mg m−3). The main results showed that (i) a significant soil compaction was observed after wet conditions only, (ii) deep ploughing produced more soil compaction than ripper because of a greater volume of soil affected by wheeling in the former operation and (iii) a specific response of soils is significatively observed in the case of deep ploughing only with an increase of compacted zones fragmentation in relation to a decrease of clay content.  相似文献   

16.
In the Horqin Sand Land, more than half of the original pasture area has been converted to farmland over the last century. A field experiment was conducted from 2000 to 2001 on five croplands in the Horqin Sand Land of Inner Mongolia to examine differences in soil properties, crop productivity and irrigation effects across different soils in the region to assess their relative suitability for cultivation, in the face of continued pressure for conversion of these generally fragile, sandy soils to agriculture.Two irrigated croplands studied were originally sandy meadow (ISM) and sandy grassland (ISG), and three dry croplands were from sandy meadow (DSM), sandy grassland (DSG) and fixed sand dunes (DFD). Results showed that most measured properties of soils, and crop productivity, differed among the five croplands. The silt + clay fraction, bulk density, organic matter content, total N and P, available N and P, average soil moisture and temperature, plant height and aboveground biomass were as follows in the DSM|DSG|DFD soils: 51.1%|47.5%|24.3%; 1.44 g/cm3|1.49 g/cm3|1.58 g/cm3; 6.3 g/kg|4.6 g/kg|3.4 g/kg; 0.55 g/kg|0.33 g/kg|0.21 g/kg; 0.21 g/kg|0.17 g/kg|0.13 g/kg; 27.0 mg/kg|13.7 mg/kg|7.7 mg/kg; 2.9 mg/kg|2.9 mg/kg|3.0 mg/kg; 9.4%|7.0%|6.2%; 21.4 °C|21.7 °C|22.0 °C; 225 cm|220 cm|181 cm; and 2116 g/m2|1864 g/m2|1338 g/m2. Corresponding values for ISM|ISG soils were: 54.3%|47.9%; 1.42 g/cm3|1.49 g/cm3; 8.5 g/kg|6.4 g/kg; 0.58 g/kg|0.42 g/kg; 0.20 g/kg|0.19 g/kg; 29.0 mg/kg|23.3 mg/kg; 4.7 mg/kg|7.9 mg/kg; 13.0%|10.1%; 21.0 °C|21.1 °C; 266 cm|245 cm; and 2958 g/m2|2702 g/m2.In general, the ecological origin of a cropland was a stronger determinant of its current characteristics than was irrigation history, although irrigation was correlated with significantly increased organic matter content, some soil nutrient levels, and aboveground biomass productivity. Results indicate that fixed sand dunes should not be converted to cropland because of their very sandy and poorer soil, lower biomass productivity and greater wind-erosion risk. Although both the sandy meadow and sandy grassland may be reclaimed for farming, the cropland derived from the sandy meadow had higher resistance to wind erosion and higher crop productivity, so is somewhat more suitable than sandy grassland.  相似文献   

17.
To test the assumption that changes to earthworm communities subsequently affect macroporosity and then soil water infiltration, we carried out a 3 year study of the earthworm communities in a experimental site having six experimental treatments: 2 tillage management systems and 3 cropping systems. The tillage management was either conventional (CT; annual mouldboard ploughing up to −30 cm depth) or reduced (RT; rotary harrow up to −7 cm depth). The 3 cropping systems were established to obtain a wide range of soil compaction intensities depending on the crop rotations and the rules of decision making. In the spring of 2005, the impact of these different treatments on earthworm induced macroporosity and water infiltration was studied. During the 3 years of observation, tillage management had a significant effect on bulk density (1.27 in CT and 1.49 mg m−3 in RT) whereas cropping system had a significant effect on bulk density in RT plots only. Tillage management did not significantly affect earthworm abundance but significantly influenced the ecological type of earthworms found in each plot (anecic were more abundant in RT). On the contrary cropping system did have a significant negative effect on earthworm abundance (104 and 129 ind. m−2 in the less and most compacted plots, respectively). Significantly higher numbers of Aporrectodea giardi and lower numbers of Aporrectodea caliginosa were found in the most compacted plots. CT affected all classes of porosity leading to a significant decrease in the number of pores and their continuity. Only larger pores, with a diameter superior to 6 mm, however, were adversely affected by soil compaction. Tillage management did not change water infiltration, probably because the increase in macroporosity in RT plots was offset by a significant increase in soil bulk density. However, cropping system had a significant effect on water infiltration (119 vs 79 mm h−1 in the less and most compacted plots, respectively). In RT plots, a significant correlation was observed between larger macropores (diameter > 6 mm) and water infiltration illustrating the potential positive effect of earthworms in these plots.  相似文献   

18.
Abstract

Crops can be effectively grown on hardpan soils and water effectively used from deep in the profile if hard layers in soils can be penetrated or if they are broken up by tillage. Addition of gypsum to the soil or exploitation of genetic differences in root penetrability may help improve root penetration through hard layers with less need to depend on the energy requirements of deep tillage. To test this theory, a single‐grained Ap horizon of Norfolk loamy sand soil was compacted into soil columns to compare root penetrability of soybean [Glycine max (L.) Merr.] genotypes Essex and PI 416937 in the presence and absence of gypsum and at two soil compaction levels (columns with uniform compaction at 1.4 g cm‐1 and columns with increasing compaction with depth from 1.4 to 1.75 g cm‐1). Compaction treatments were imposed by constructing soil columns composed of 2.5‐cm‐deep, 7.5‐cm‐diameter cylindrical cores compacted to predetermined bulk densities (1.40,1.55,1.65,and 1.75 g cm.3). Soil penetration resistances were measured on duplicate cores using a 3‐mm‐diameter cone‐tipped penetrometer. Columns were not watered during the study; soybean genotypes were grown in the columns until they died. Both genotypes lived one day longer in columns with lower bulk density and penetration resistance. Although root growth was more abundant for Essex than for PI 416937, root growth of PI 416937 was not decreased by compaction as much as it was for Essex. These results suggest that PI 416937 may possess the genetic capability to produce more root growth in soils with high penetration resistance. This study suggests that genetic improvement for root growth in soils with hard or acidic layers may potentially reduce our dependence on tillage. Gypsum did not affect root growth in this study.  相似文献   

19.
Integrated evaluation of soil physical properties using the least limiting water range (LLWR) approach may allow a better knowledge of soil water availability. We determined the LLWR for four tillage practices consisted of conventional tillage (CT), reduced tillage (RT), no-tillage (NT) and fallow no-tillage (NTf). In addition, LLWR was determined for abandoned soils (i.e. control), compacted soils, ploughed compacted soils and abandoned soils with super absorbent polymers (SAPs) application. Soil water retention, penetration resistance (PR), air-filled porosity and bulk density were determined for the 0–5 and 0–25-cm depths. Mean LLWR (0.07–0.08 cm3 cm?3) was lower in compacted soils than the soils under CT, NT, NTf, RT, tilled, abandoned and SAP practices but it was not different among tillage practices. The values of LLWR were 0.12 cm3 cm?3 for NT and CT. LLWR for tilled plots (0.12 cm3 cm?3) became greater than compacted soils by 1.3 times. Analysis of the lower and upper limits of the LLWR further indicated that PR was the only limiting factor for soil water content, but aeration was not a limiting factor. The LLWR was more dependent on soil water content at permanent wilting point and at PR.  相似文献   

20.

Purpose

Soil compaction resulting from mechanisation of forest operations reduces air permeability and hydraulic conductivity of soil and can result in the development of hydromorphic and/or anoxic conditions. These hydromorphic conditions can affect physico-chemical properties of the soils. However, early detection of these effects on mineralogical portion of soils is methodologically difficult.

Materials and methods

To analyse the effects of soil compaction on iron minerals in loamy Luvisol, three compacted and three non-compacted soil profiles up to the depth of 50 cm were collected from an artificially deforested and compacted soils after 2 years of treatment. Soil was compacted with the help of 25 Mg wheeler’s load to increase the dry bulk density of soil from 1.21?±?0.05 to 1.45?±?0.1 g cm?3. Soil samples were analysed by X-ray diffraction (XRD) and were treated by citrate bicarbonate (CB) and dithionite citrate bicarbonate (DCB) under controlled conditions. Major and minor elements (Fe, Al, Mg, Si and Mn) were analysed by ICP-AES in the CB and DCB extracts.

Results and discussion

It was found that X-ray diffraction is not an enough sensitive method to detect the quick mineralogical changes due to soil compaction. Results obtained from CB-DCB extractions showed that soil compaction resulted in larger CB and smaller DCB extractable elements as compared to non-compacted soil. Labile Fe was found 30 % of total Fe oxides in compacted soil against 10–14 % in non-compacted soils. Compaction thus resulted in Fe transfer from non-labile to labile oxides (s.l.). Results showed that soil compaction leads to the reduction of Fe3+ to Fe2+. The effects of hydromorphic conditions due to soil compaction were observed up to the depth of 35 cm in forest soil profile. Furthermore, a close association of Al with Fe oxides was observed in the soil samples, while Mn and Si were mainly released from other sources, Mg showing an intermediate behaviour.

Conclusions

Hydromorphic conditions owing to soil compaction affect the mobility and crystallisation process of iron mineral. CB-DCB selective extraction technique, in contrast to XRD technique, can be effectively used to examine the possible effects of soil compaction on iron minerals.
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