Deep reclamation loosening of soils: State of the problem,results of research,prospects of application,and degradation changes

The efficiency of deep reclamation loosening used for soils of different types on the main parent rocks in the Nonchernozemic zone (mantle and moraine loams, Permian and varved loamy clays, and clays) is assessed basing on the results of long-term stationary and analytical investigations. The long-term aftereffect of the deep loosening on the density, porosity, water permeability, and the main elements of the soil water regime and factors limiting the use of deep loosening are considered. Over 6–12 years after the deep loosening, in the area, where active and passive loosening by a plough was made, a zone of elevated water permeability is preserved at the depth of 40–75 cm. Based on this phenomenon, a new technology of deep reclamation loosening, which restores the hydraulic connection between the arable and deeper soil layers, is proposed. The data on active deep rippers that provide soil loosening to the depth of 0.9–1.0 m are presented. Some agroecological aspects related to the duration of deep loosening effects on the soils and their productivity are discussed. Recommendations on the application of passive and active loosening and moling of heavy-textured gleyed soils are suggested for the European part of the Nonchernozemic zone in the Russian Federation. Field and laboratory works on estimating the efficiency of deep loosening continued for 15 years (1976–1990) for heavy-textured soils on the loess-like, fine-stratified varved clays, as well as on acid moraine and calcareous Permian clays and loamy clays in Moscow, Vologda, Novgorod, and Kirov oblasts.     

Eigenschaften,Entwicklung und Wert rekultivierter Böden aus Löß im Gebiet des Rheinischen Braunkohlen-Tagebaues

Conditions, genesis and value of recultivated loess soils Physical, chemical, microbiological and micromorphological investigations have been executed on recultivated loess soils deposited between 1963 and 1968 and under agriculture since than. The main results are: 1. Dry deposited materials are often strongly compressed at 50-120 cm depth. Wet and dry deposited materials may be compressed at 30-50 cm by tillage. 2. The new soils show already a notable carbonate metabolism, loss of sodium and magnesium and a certain enrichment of humus and potassium. 3. Well recultivated soils are forming fertile Pararendzina soils, whereas the other ones are developing into difficult Pseudogley soils. 4. Land evaluation gives values of 60 to 80. However, fertility is not as high, and 10-15 should be subtracted from the values. 5. In compressed soils, melioration by deep loosening and drainage is the only method to evoid further degradation. It is, however not free from difficulties.     

Mitigation of subsoil recompaction by light traffic and on-land ploughing: II. Root and yield response

Plough pans have been shown to severely hamper root development, limit rooting depth and reduce crop yields. We evaluated the effect of plough pan re-compaction on root and yield response for winter wheat in a field trial conducted in two neighbouring fields on a sandy loam. Plots were mechanically loosened by a subsoiler to a depth of 35 cm in 1997 and 1998. In 2 years following the loosening operation, perennial grass/clover was grown with limited traffic intensity. Subsequently oats were established and followed by winter wheat. On-land ploughing was compared with traditional mouldboard ploughing. In addition, the plots were either heavy-trafficked (10–18 Mg axle load and ∼200 kPa inflation pressure) or light-trafficked (<6 Mg axle load and <100 kPa inflation pressure). The loosened treatments were referenced by non-loosened soil. Root growth of winter wheat was followed applying the minirhizotron technique. In one of the fields, these measurements were supplemented with core sampling for root length determination approximately at anthesis. Soil water content was followed in one of the fields using time domain reflectometry (TDR). Grain yield and nitrogen content in grain were determined. The adjoining study showed that the combination of heavy traffic and traditional ploughing caused strong recompaction of loosened soil, whereas the combination of light traffic and on-land ploughing produced moderate recompaction. For the loosened plots in one field, the strongly recompacted soil produced 7% lower yield than moderately recompacted soil, whereas no clear difference was found for the other field. No clear difference between the loosened treatments on root growth was observed. Surprisingly, the non-loosened soil performed similar or even better than the loosened and moderately compacted soil. The non-loosened soil facilitated higher root intensity at depth and produced similar yield and N-uptake. Our results suggest that mechanical subsoil loosening of humid sandy loams only is recommendable in case of very severe subsoil compaction. Natural alleviation of subsoil structure induced by changes in soil management may comprise a favourable alternative to mechanical subsoil loosening.     

Effect of freezing and thawing processes on some physical properties of saline–sodic soils mixed with sewage sludge or fly ash

Dispersion of saline–sodic soils was rather difficult to leach. Therefore, negative effects of freeze–thaw on soil physical properties should be reduced by inexpensive and practical methods. This study investigates the effect of freeze–thaw cycles (3, 6, and 9) on wet aggregate stability, bulk density, and permeability coefficient in three soils with different electrical conductivity and exchangeable sodium percentage levels (soil I: 5.30 dS m⁻¹, 47.51%; soil II: 42.80 dS m⁻¹, 55.45%; soil III: 36.30 dS m⁻¹, 59.34%) which consist of different proportions of sewage sludge and fly ash by volume (10%, 20%, and 30%). The experiment was conducted under laboratory conditions using disturbed and non-cropped soil samples mixed with sewage sludge and fly ash. Soils mixed with sewage sludge produced higher aggregate stability and permeability coefficients and lower bulk density values as compared to the soils mixed with fly ash. Sewage sludge added with a rate of 30% eliminated the negative effects of freeze–thaw processes on wet aggregate stability. Freeze–thaw processes did not affect the bulk density of the soils II and III, which were mixed with sewage sludge. However, fly ash addition decreased the bulk density of these soils very significantly after nine freeze–thaw cycles. Addition of sewage sludge or fly ash with rates of 20% and 30% significantly increased the permeability coefficients in soil I after nine freeze–thaw cycles. Results indicated that addition of sewage sludge and/or fly ash to saline–sodic soils could be alternative way for reducing negative effects of freezing–thawing on soil wet aggregate stability, bulk density, and permeability coefficient.     

Langjährige Verdichtungswirkung durch unterschiedliche Achslasten auf einem Löß-Ackerstandort

Long-term compaction effects on loess derived soils by distinct axle loads Field traffic may cause subsoil compaction of arable land and can deteriorate growing conditions of plants. In a case study the state of compaction of two adjacent fields on loess derived soil (field A and field B) was examined, which belong to two neighbouring farms. Within the past 20 years the maximum axle loads on both fields differed greatly (4 Mg and 8.9 Mg). Both fields were compared with a bordering ridge under permanent grass, which had not been loaded mechanically in recent years. The aim of this study was to evaluate the state of compaction as affected by the impact of vehicular field traffic. It was found that in the depth range of a traffic-pan in field A (about 40 cm) the penetration resistance was higher than in the corresponding depth under grass, but substantially lower than in field B. Bulk density and air capacity are similarly different between locations. The vertical compressive stress as a function of soil depth was calculated for the maximum axle loads that occur on both fields under wet conditions. For the 40 cm depth on field A stress values were near 60 kPa, but on field B the values were about 130 kPa. The loading stresses, acting on the soil during one season, were assessed from the weight of the vehicles and the travel distance per area. The accumulated stress was by 17% higher on field B than on field A. On field A the compactive stress of loading ended at about 40 cm depth. On farm B, however, with much higher axle loads during sugarbeet harvest, the compactive stress extended to about 70 cm soil depth. This case study demonstrates that the state of compactness of agricultural fields will be strongly dependent on the intensity of vehicular traffic, which comprises axle load as well as time and frequency of passages.     

Effektive Durchwurzelungstiefe,Sickerwasserbildung und Nitratverlagerung in tiefgründigen Lößböden eines Trockengebietes

Effective rooting depth, percolation water, and nitrate leaching in deeply developed loess soils of a water‐shortage area In 14 deeply developed loess soils, high amounts of mineral nitrogen (N) were measured within the first meter, whereas several nitrate depth profiles up to more than three meters resulted in low and medium nitrate values. The maximum depth of water uptake was measured in two years on four representative sites with regard to soil and crop properties. The maximum depth of water uptake was always considerably deeper than 200 cm, with a maximum of 290 cm (alfalfa). It is assumed that roots take up nitrogen even in this depth. The calculation of the effective rooting depth resulted in noticeably higher values (for wheat between 160 cm and 185 cm) than those given by the ”︁German Instructions for Soil Mapping” (AG Boden, 1994), the ”︁Regulations of the German Organisation for Water Management and Land Improvement” (DVWK, 1995) or the ”︁German Institute for Standardization” (DIN, 1998). As a result of low annual precipitation (normally less than 600 mm), only a minor part of the high amounts of nitrate within the root zone was leached into deeper soil layers. We conclude that it is not possible to predict the potential groundwater pollution with nitrate on the basis of the mineral N content in the first meter of the soil profile.     

Mineralselektive K-Freisetzung aus Böden mit Oktodecylammonium-Ionen (nc = 18)

Mineral-selective K release from soils by octodecylammonium- ions (n_c = 18) n_c18-releasable potassium was determined on soils of five different areas. n_c18-releasable K is the potassium which is displaced by octodecylammonium ions (ODA). Because the main sources of this potassium are trioctahedral micas, it is called briefly biotite-K. The investigated soils are from different areas in Bavaria (loess and clay stone derived soils, alluvial soils); partly the locations are K fertilizer trials. Soils of known age are locations from the Niederrhein terraces (Holocene soils). In the 0.2–2 μm (coarse clay) and 2–6 μm (fine silt) fractions the biotite-K content lies between 12 and 40% of total K. At given fractionation the highest amounts of K were released from the coarse clay of the soils. In the loess soils rich in silt the biotite-K pool in the medium and coarse silt fractions was also considerable. Clay soils showing poor K supplying power (K fertilizer trials) in the field are characterized by very low biotite-K quantities in all silt fractions. In the Holocene soils the age of which varies between 4 000 and 8 000 years the ODA releaseable values are greater than in the loess soils. In all fractions of the young Holocene soils the released K is greater than in the same fractions of the old Holocene soils. Calculated to a soil depth of 60 cm the K release in kg/ha reaches from 25 000 (young soil form) to 17 000 (old soil form).     

Soil loosening on permanent raised-beds in arid northwest China

Poor lateral water infiltration into permanently raised beds (PRB) can reduce crop yield and water use efficiency (WUE) in dryland agriculture. Especially for densely planted crops the reduced soil moisture affects seedling emergence and causes slow crop growth. Soil loosening with three different types of cutters was tested to overcome this problem of wide PRB in this study. A field experiment with five treatments (traditional tillage, bed without soil loosening, bed with soil loosening by two-edge cutter, bed with soil loosening by flat cutter and bed with soil loosening by V-shaped cutter) was conducted in the Hexi Corridor, northwest China, on spring wheat in 2005 and 2006. The effects of soil loosening and the performances of the three cutters were assessed based on 2 years of soil moisture, bulk density, temperature, spring wheat growth, yield, WUE, power and fuel consumption data. Soil loosening significantly increased lateral water infiltration and thus improved soil water content by 3–8% to 100 cm depth and soil temperature by 0.2–0.4 °C to 30 cm depth compared to beds without soil loosening on sandy-loam soil in 100 cm wide bed systems. Furthermore, bulk density at 10–20 cm depth was about 7.4% lower for bed with soil loosening treatments than for bed without soil loosening. The best results were achieved by the V-shaped cutter, which at a slight additional fuel consumption of 0.46–0.84 l ha⁻¹ offered the greatest benefits to spring wheat yield and WUE. Spring wheat yields increased by 5% and WUE improved by 38% compared to traditional tillage due to higher soil moisture and temperature, lower bulk density and faster growth. The improvements in WUE have tremendous implications in the arid areas of northwest China where agriculture relies heavily on irrigation, but water resources are scarce. We conclude therefore that soil loosening by V-shaped cutter is an efficient way to remove poor water infiltration, and significantly improve yield and WUE for wide beds under PRB farming system in arid areas of northwest China.     

EXCLOSURE EFFECTS ON RECOVERY OF SELECTED SOIL PROPERTIES IN A MIXED BROADLEAF FOREST RECREATION SITE

Human‐caused trampling that results from excessive recreational use has caused damage to soil and vegetation in forest ecosystems in the Belgrad Forest of Istanbul. The objectives of this study were to examine effects of exclosure on selected soil properties and to determine the recovery time required for soil characteristics in a broadleaf forest recreation site. Litter biomass and topsoil (0–15 cm) were sampled in the forest, exclosure and recreational sites, and soil samples were analysed for saturation capacity, permeability, bulk density, total porosity, organic matter, root biomass, electrical conductivity and soil pH. Results showed that saturation capacity, permeability, total porosity and organic matter increased whereas bulk density decreased significantly in the topsoil under the exclosure, and all these soil properties in the topsoil of the exclosure were greater than those of recreational site. When effects of main factors were compared, averaging over sampling year and soil sampling depth, soils from the exclosure had significantly greater saturation capacity, permeability, total porosity, organic matter and litter biomass and lower bulk density values than the soils from recreational site. Six years of exclosure was effective in improving most of the soil properties in the topsoil. When topsoil and subsoil are considered together, it is obvious that a longer time period is needed for soil recovery in the forest recreational sites. Copyright © 2011 John Wiley & Sons, Ltd.     

Mitigation of subsoil recompaction by light traffic and on-land ploughing: I. Soil response

Mechanically loosened subsoil has been shown to be prone to recompaction. We addressed a sandy loam that had been mechanically loosened by a subsoiler to a depth of 35 cm in 1997 and again in 1998. Perennial grass/clover was grown with limited traffic intensity in 1999 and 2000. A recompaction experiment was conducted in 2001 and 2002 when the soil was grown with oat and winter wheat, respectively. Using the formerly loosened plots, on-land ploughing was compared with traditional mouldboard ploughing with the tractor wheels in the furrow. In addition, the loosened plots were either light-trafficked (<6 Mg axle load and <100 kPa inflation pressure) or heavy-trafficked (10–18 Mg axle load and 200 kPa inflation pressure), respectively. Finally, the soil loosened by non-inversion deep tillage was referenced with a conventional ploughing–harrowing tillage system that never received the subsoil treatment. The conventional treatment was also grown with the grass/clover in 1999 and 2000. On-land ploughing and light traffic was applied in 2001 and 2002 instead of traditional ploughing and traffic for the conventional treatment. Penetration resistance and bulk density was recorded in the field. Undisturbed soil cores were taken in 1998, 1999 and 2002 from the 7–14, 18–27 and 25–30 cm layer and used for measuring total porosity, pores >30 μm and air permeability at −100 hPa matric potential. The results showed that on-land ploughing mitigated recompaction of the upper part of the formerly loosened subsoil. In contrast, only small differences in recompaction between heavy and light traffic were observed. The mitigation of subsoil recompaction was needed for the loosened soil to provide an upper subsoil with similar—not better—pore characteristics than the non-loosened soil in the conventional treatment. The structural conditions in the plough pan improved for the conventional treatment from 1998 to 2002 as indicated by an almost doubling in air permeability. This was interpreted as being related to the growing of grass/clover ley in 1999 and 2000 combined with a shift from traditional tillage and traffic to on-land ploughing and light traffic when growing cereals in 2001 and 2002. Results on root growth and crop yield are reported in an adjoining paper.     

Die Bedeutung der K-Ca-Austauschisotherme für eine Beurteilung der K-Versorgung der Pflanzen bei Lößböden

K-Ca-exchange isothermes of soils from loess and the potassium supply of plants From 80 Ap-horizons of Luvisols and Phaeozems on loess from south of Hannover K-Ca-exchange isotherms and cation concentrations in saturation extracts were investigated. Though not K deficient these soils show a very wide range of available K. From the very high K-concentrations in the saturation extracts (up to 3 meq/1) of part of the soils it was concluded, that mass flow should be sufficient for plant needs of K. The only soil property varying the exchange isotherms seems to be the clay content (Fig. 4). In order to calculate available K from the exchange isotherms in the same way as available water from pF characteristics the isotherms were extended down to activity ratios, according to literature, marginal for plant uptake of K (Fig. 6). The estimated soil K content, sufficient for plant in loess soils, amounts to about half that considered marginal by the regional extension service. With the assumption that so called non exchangeable, but plant available K is essentially very slowly exchangeable, an experiment was performed at 80°C to accelerate the exchange and to establish a true equilibrium. The comparison between the new exchange curve and the 25°C curve (Fig. 8) seems to reveal additional 180–450 kg/ha · 30 cm bound with equal free energy of exchange as easily exchangeable K.     

Der Einfluß künstlicher vertikaler Grobporen in einer verdichteten Bodenmatrix auf das Wachstum von Winterweizen I. Wachstum von Winterweizen auf einer Parabraunerde aus Löß

The influence of artificial vertical macropores in a compacted soil on the growth of winterwheat. I. Growth of winterwheat on an alfisol derived from loess In field experiments on a compacted alfisol it was investigated, how artificially made vertical macropores in the compacted structure influence water extraction and growth of winterwheat compared to the compacted structure without vertical macropores and to the loosened structure. The experiments were carried out in two subsequent years with different precipitation (308, 0 and 440, 1 mm in the period of November until August of both growth periods). The influence of the different soil structure was most pronounced during periods of increasing water tension. Compared to the compacted structure, water extraction as well as yield was improved by the vertical artificial macropores to a similar extend as by the loosened structure. Both structures increased water extraction from deeper parts of the soil (25-50 cm). The beneficial effects of the vertical macropores were more pronounced in the dry compared to the wet year. Despite of the unequal distribution of roots in the compacted structure with vertical macropores, water extraction from the soil between the macropores was not negatively affected.     

Variations of Soil Organic Carbon Following Land Use Change on Deep‐Loess Hillsopes in China

Land use change is a key factor driving changes in soil organic carbon (SOC) around the world. However, the changes in SOC following land use changes have not been fully elucidated, especially for deep soils (>100 cm). Thus, we investigated the variations of SOC under different land uses (cropland, jujube orchard, 7‐year‐old grassland and 30‐year‐old grassland) on hillslopes in the Yuanzegou watershed of the Loess Plateau in China based on soil datasets related to soils within the 0–100 cm. Furthermore, we quantified the contribution of deep‐layer SOC (200–1,800 cm) to that of whole soil profiles based on soil datasets within the 0–1,800 cm. The results showed that in shallow profiles (0–100 cm), land uses significantly (p  < 0·05) influenced the distribution of SOC contents and stocks in surface layer (0–20 cm) but not subsurface layers (20–100 cm). Pearson correlation analysis indicated that soil texture fractions and total N were significantly (p  < 0·05 or 0·01) correlated with SOC content, which may have masked effects of land use change on SOC. In deep profiles (0–1,800 cm), SOC stock generally decreased with soil depth. But deep soils showed high SOC sequestration capacity. The SOC accumulated in the 100–1,800 m equalled 90·6%, 91·6%, 87·5% and 88·6% of amounts in the top 100 cm under cropland, 7‐year‐old grassland, 30‐year‐old grassland and jujube orchard, respectively. The results provide insights into SOC dynamics following land use changes and stressed the importance of deep‐layer SOC in estimating SOC inventory in deep loess soils. Copyright © 2017 John Wiley & Sons, Ltd.     

Soil pore-water environment and CO2 emission in a Luvisol as influenced by contrasting tillage

Little is known how contrasting tillage (deep ploughing, top- and sub-soil loosening with straight or bent leg cultivator [BLC], direct drilling [DD]) affect important soil physical properties (total porosity [TP], pore size distribution [PSD], water release characteristics [WRC]) and CO₂ emissions from a Luvisol. The study was aimed to alleviate compaction on land that had been under reduced tillage for 4 successive years. Undisturbed core samples were collected from 5–10, 15–20 and 25–30 cm depths for soil WRCs, TP and pore-size distribution determination. A closed chamber method was used to quantify the CO₂ emissions from the soil. Soil loosening with straight or BLC produced the highest total soil porosity (on average 0.48 m³ m^?3) within 5–30 cm soil layer, while conventional tillage (CT) gave 6%, DD up to 25% reduction. Sub-surface loosening with a BLC was the most effective tool to increase the amount of macro- and mesopores in the top- and sub-soil layers. It produced 21% more macro- and mesopores within 25–30 cm soil layer as compared to the soil loosened with a straight leg cultivator. Plant available water content under CT and DD was lower as compared to that under deep loosening with straight or BLC (23% and 18%, respectively). DD produced 12% lower soil surface net carbon dioxide exchange rate than CT and by 25–28% lower than deep soil loosening with straight or BLC. The increase in micropores within 25–30 cm soil layer caused net carbon dioxide exchange rate reduction. The amount of mesopores within the whole 5–30 cm soil layer acted as a direct dominant factor influencing net CO₂ exchange rate (NCER) (Pxy = ?3.063; r = 0.86).     

The effects of agricultural use on the structure and physical properties of three soil types

This investigation was carried out to determine the influence of the use of soils on their morphological structure and properties. Three soil types (i.e. Haplic Phaeozem derived from loess, Orthic Luvisol derived from loess and Orthic Luvisol derived from sandy loam) were involved. In each soil unit, profiles lying at a small distance from one another were taken for detailed examination. The main difference between the soils within each unit was the use to which they were put. The following soils were selected for evaluation: (A) soil from natural forest habitat; (B) soil cultivated in farms with a very low level of mechanisation; (C) soil cultivated in farms which had been completely mechanised for many years; (D) soil used for many years in a vegetable garden, similar to hortisol.

In the selected profiles the morphological features, soil structure in all genetic horizons, granulometric composition, humus content, pH, density, air and water capacity and air permeability were analysed.

It was found that the transition from forest soil management to agricultural use leads not only to the formation of an arable-humus horizon and to changes in structure but also to changes of the physico-chemical properties of soils. Soils under agricultural use manifest a lower level of acidification than forest soils, as well as a different distribution of organic matter. In all agricultural soils, increased compaction of humus horizons was observed, compared with the corresponding horizons of forest soils, as well as changes in other physical features. The use of heavy machines over many years in field operations results in increased density of the soil and deterioration of soil structure. This effect is greater in soils with low colloids and organic matter contents.     

Wirkung mechanischer Belastung auf Gefüge und Ertragsleistung einer Löss‐Parabraunerde mit zwei Bearbeitungssystemen

Effect of mechanical stress on structure and productivity of a loess‐derived Luvisol with conventional and conservation tillage In Germany farmers are committed to caring for the land by a soil protection law. Yet vehicles with ever increasing axle load endanger productivity and environmental quality of arable soils. In spring of 1995 a field experiment was startet on a wet silty Luvisol to test the effect of single mechanical loading on soil and crop characteristics, when managed by mouldboard ploughing (PL) or conservation tillage (CT). CT soils are considered to be more resistant against compactive stresses and to recover from degeneration more rapidly than PL soils. Beside an unwheeled control the loading treatments were light (2 × 2.5 t; number of wheel passes times wheel load); medium (2 × 5 t) and high (6 × 5 t). In 1995 even light loading of the PL soil caused a significant yield decline by 50% in spring barley, but this happened on CT soil only with high loading. In subsequent years with winter wheat and winter barley yield decline was less distinct. Loading of PL soil reduced total root length (from 4 to 1 km m⁻²) and rooting depth (from 70—90 to 40—70 cm), but on CT soil only root length was diminished by high loading. A tillage‐traffic pan (30—35 cm) hindered subsoil rooting in PL, which was favored in CT by earthworm channels. High loading caused compaction to at least 50 cm depth. Within the pan of the PL soil, penetration resistance attained 5 MPa and bulk density 1.65 g cm⁻³. In the CT soil the zone of maximum compaction was closer to the surface (15—25 cm). In PL soil the saturated hydraulic conductivity and the O₂‐diffusion coefficient gradually decreased with loading, but in CT soil only with heavy loading. The compacted top soil was broken in subsequent years by ploughing (PL: 25 cm) or rotary implements (CT: 5—8 cm). With PL, structure in the pan layer and subsoil did not recover, and rooting depth was still limited. Some restoration, however, was indicated with CT. Here transmitting properties increased in time, which was attributed to the reconstruction of root and earthworm channels, as demonstrated by computer tomography. We conclude that in silty soils compacted layers below ploughing depth will hardly be regenerated by internal processes. CT soils are less susceptible to loading, but high stresses are harmful too. Therefore recommending CT as a measure for protecting soil from compaction would not be enough, considering the present development towards heavy field machinery.     

Soils of the loess region in China

The loess region of northwestern China is located in the middle reaches of the Huanghe River and is mostly composed of the loess plateau. The region has a loess cover largely ranging in thickness from 30 to 80 m. Main broad groups of soils formed in loess are the heilu soils, huangmian soils, lou soils, sierozem, castanozem, and drab soils. Distribution of the soils tends to parallel that of climate but is also affected by topography and past farming practices. All soils are calcareous to the surface, a reflection of the semiarid and arid climates. Calcic horizons are well expressed in sierozems, evident in castanozems and drab soils and not clearly defined in heilu soils. Average thickness of the surface, humus layer ranges from 30 cm in sierozems to 100 cm in heilu soils. The lou soils are distinctive in having one humus layer at the surface due to additions of earthy manure during long periods of cultivation plus a deeper humus layer from the original drab soil profile. Clay distribution curves show a distinct maximum in drab soil profiles and slight or no maxima in the others.Water is limiting for plant growth over most of the region, although drought hazards become progressively greater from southeast to northwest. In the middle of the region and for some distance to the northwest, cultivation must include fallowing during summers or for entire years to store water for crops. Further to the northwest, layers of sand about 10 cm thick are spread over fields to increase infiltration and reduce moisture losses. In the extreme northwestern part, crops are not grown and the soils are in meadow for grazing livestock.Amounts of nutrient elements in the soils have a rather wide range. Nitrogen is deficient generally and must be added for successful production. Biological fixation of the element by legumes is the most effective method of adding the element. Total phosphorus is not low but available forms are; phosphorus fertilization increases crop yields. Potassium supplies are currently adequate in the soils. Amounts of zinc, manganese, boron, copper and molybdenum in available forms seem to be low in many soils but their applications are limited.     

Initiale Bodenentwicklung in aufgespültem Löß und Hafenschlick

Initial soil development in loess and harbourbasin mud reclaimed by slurry poldering In the Rhenish Brown Coal Strip Mining Area initial soil development was investigated for 6–15 and 15–25 years old loamy-silty loess soils reclaimed by slurry poldering. In the Emden environs the same analyses were applied to 6, 17, and 28 years old silty-clayey harbour-mud soils, also reclaimed by slurry application. The most prominent results when comparing these two types of soil are as follows: The mud soils show higher contents of clay and organic matter. Therefore they reveal more favourable characteristics concerning cation-exchange capacity, soil physical and soil biological properties in comparison to those of the loess soils. In both types of soils cation-exchange-capacity and soil biological activity increase in the Ap-horizon over time. The soil physical characteristics of the mud soils markedly improve in the run of the development, whereas those of the loess soils hardly improve. It remains a subject of discussion, since what stage of development mud soils should be classified as sea-marshes/“Kleimarschen” and loess soils as rendzinas.     

Compaction of forest soils with heavy logging machinery affects soil bacterial community structure

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.     

Soil compaction and soil management – a review

Soil compaction is an important component of the land degradation syndrome which is an issue for soil management throughout the world. It is a long standing phenomenon not only associated with agriculture but also with forest harvesting, amenity land use, pipeline installation, land restoration and wildlife trampling. This review concentrates on the impact of soil compaction on practical soil management issues, an area not previously reviewed. It discusses in the context of the current situation, the causes, identification, effects and alleviation of compaction. The principal causes are when compressive forces derived from wheels, tillage machinery and from the trampling of animals, act on compressible soil. Compact soils can also be found under natural conditions without human or animal involvement. Compaction alters many soil properties and adverse effects are mostly linked to a reduction in permeability to air, water and roots. Many methods can be used to measure the changes. In practical situations, the use of visual and tactile methods directly in the field is recommended. The worst problems tend to occur when root crops and vegetables are harvested from soils at or wetter than field capacity. As discussed by a farmer, the effects on crop uniformity and quality (as well as a reduction in yield) can be marked. By contrast, rendzinas and other calcareous soils growing mainly cereals are comparatively free of compaction problems. The effect of a given level of compaction is related to both weather and climate; where soil moisture deficits are large, a restriction in root depth may have severe effects but the same level of compaction may have a negligible effect where moisture deficits are small. Topsoil compaction in sloping landscapes enhances runoff and may induce erosion particularly along wheeltracks, with consequent off‐farm environmental impacts. Indirect effects of compaction include denitrification which is likely to lead to nitrogen deficiency in crops. The effects of heavy tractors and harvesters can to some extent be compensated for by a reduction in tyre pressures although there is concern that deep‐seated compaction may occur. Techniques for loosening compaction up to depths of 45 cm are well established but to correct deeper problems presents difficulties. Several authors recommend that monitoring of soil physical conditions, including compaction, should be part of routine soil management.