Water and bromide transport in a heterogeneous glacial sand

We investigated water flow and bromide transport under agricultural field conditions, using TDR and tensiometer measurements as well as a bromide tracer experiment. The soil, an Albic Luvisol consisting of sand covering glacial loam, is highly heterogeneous with polygon nets formed by sand‐filled frost wedges. Water flow and bromide transport are influenced by the thickness of the glacial sand horizon and the soil structure. Both cause a variation of the actual evapotranspiration up to ± 25 mm/yr. Water and bromide are preferentially transported on the inclined soil layer boundaries into the sand wedges. From there infiltrating water may be redistributed into the surrounding glacial till. Approximately, the depths of the bromide centers of mass can be deduced using the piston flow concept. Small‐scale mass balances of the tracer show that vertical sections with bromide deficits and bromide surpluses are well balanced within a horizontal range of 1.8 m to 2.8 m. This distance is interpreted as the lateral influence of the sand wedges.     

Addition of lignin to lime materials for expedited pH increase and improved vertical mobility of lime in no‐till soils

Soil acidification caused by long‐term nitrogen (N) fertilizer applications has been a growing concern for dryland crop production in both tilled and no‐till soils in the Pacific Northwest (PNW). Many no‐till soils have stratified soil pH in the 5–10 cm depth due to repeated N fertilizer applications at this depth. In the PNW, the practice of liming to correct low soil pH is complicated due to lack of affordable lime sources and because the inherent difficulty in ameliorating stratified soil acidity in no‐till systems. An intact soil‐column incubation study was conducted to investigate whether mixing lime materials with lignin‐containing black liquor—a by‐product from the pulp industry—could elevate soil pH change in both conventional and no‐till systems and expedite vertical downward movement of lime in no‐till system. Results indicate that mixing lime with black liquor has the potential to not only elevate the increase in soil pH in both conventional till and no‐till systems, but also accelerate downward movement of lime to correct soil pH below the soil surface. Mixing agricultural lime or super fine micro lime with black liquor increased soil pH to a depth of 25–30 cm within 147 days after surface application to a no‐till soil.     

黑龙江垦区农田土壤养分平衡分析与评价

养分资源高效利用是农业绿色发展的重要环节。黑龙江垦区是中国粮食主产区之一,对其进行农田土壤养分平衡评价至关重要。该研究以黑龙江垦区为研究对象,采用农田土壤养分平衡方法,分析与评价其2000-2018年农田土壤氮、磷、钾养分输入与输出情况。结果表明:1)2000-2018年黑龙江垦区农田土壤氮、磷、钾输入与输出整体呈现"平稳-增长-下降后平稳"的趋势,养分输入以化肥为主,养分输出以籽粒和秸秆为主。2)黑龙江垦区农田土壤单位面积养分输入量较为稳定,并且所带来的经济效益在增加。3)2017年以来黑龙江垦区农田土壤氮和钾处于养分平衡状态,而磷处于养分盈余状态。2018年黑龙江垦区氮、磷、钾利用效率分别为51.03%、27.98%、10.04%。建议黑龙江垦区大力推广有机无机肥配施,开展农田土壤养分平衡长期调查与监测,促进区域农业绿色发展。     

Effect of artificial soil compaction in landfill capping systems on anisotropy of air‐permeability

Soil air permeability is an important parameter which governs the aeration in soils that significantly promotes the root growth of field and grassland species and leads, in turn, to higher levels of evapotranspiration. The German Landfill Directive (2009) requires a rigid or a minimal shrinking capping system that ensures a high evapotranspiration rate to decrease the infiltration rate through the underlying waste body and therefore the leachate generation. This research is focussed on the questions if compacted glacial till can ensure the required rigidity and if and how air permeability is affected by soil compaction. The objective was to compare air‐filled porosity and the direction‐dependency of air permeability of a capping soil when assuming rigid and non‐rigid conditions considering a shrinkage factor. Intact soil cores were sampled in vertical and horizontal direction in 0.05, 0.2, 0.5, and 0.8 m depths at two profiles of a mineral landfill capping system at the Rastorf landfill in Northern Germany. Desiccation experiments were carried out on differently‐compacted soils and soil shrinkage was measured with a 3D laser triangulation device, while the air permeability was estimated with an air flow meter. The results indicate that the “engineered” soil structure which was predominately platy due to a layered installation, led to a more anisotropic behaviour and therefore to higher air permeability in horizontal than in vertical direction. The compacted installation of the capping system seems to be effective and observes the statutory required more‐or‐less rigid system, otherwise, soil shrinkage would lead to vertical cracks and a more pronounced isotropic behaviour.     

The interrelationship between the cultivation of crops and soil‐strength dynamics

It is well accepted that the penetration resistance of soils is, among others factors, highly sensitive to the moisture status of the soil. This study tested the hypothesis of whether the dewatering of a soil by crops of varying dewatering capacities significantly affects the soil's penetration resistance and whether this contributes to an exceedance of the commonly accepted root‐growth threshold already in the range of plant‐available water. During a 22‐month period between March 2002 and December 2003, the soil water content of a former lignite strip mine in E Germany was studied. The soil had been restored with Saalian glacial till. Plots contained two different crops, a 3 y–old stand of lucerne (Medicago sativa L.) and a 7 y–old stand of wild rye (Secale multicaule L.). Soil water contents under the two crops were converted on the basis of the water‐retention characteristics into water tensions, allowing an investigation of the changes in the measured water content in the wider context of the water availability to the crops. During both growing seasons, the water tension under lucerne exceeded the permanent‐wilting point (10^4.2 hPa) for up to 20 weeks between 0 and 90 cm, which is equal to a predicted penetration resistance of >15 MPa. Water tensions under the wild rye rose only up to a maximum of 10³ hPa for the same period, so that the predicted penetration‐resistance values remained constantly <5 MPa. Our findings demonstrate that the dewatering by plants during the growing seasons affects the actual strength of the soil, which can lead to the exceeding of the commonly accepted root‐growth threshold.     

Functional dependencies of soil CO2 emissions on soil biological properties in northern German agricultural soils derived from a glacial till

Agricultural soil CO₂ emissions and their controlling factors have recently received increased attention because of the high potential of carbon sequestration and their importance in soil fertility. Several parameters of soil structure, chemistry, and microbiology were monitored along with soil CO₂ emissions in research conducted in soils derived from a glacial till. The investigation was carried out during the 2012 growing season in Northern Germany. Higher potentials of soil CO₂ emissions were found in grassland (20.40 µg g^?1 dry weight h^?1) compared to arable land (5.59 µg g^?1 dry weight h^?1) within the incubating temperature from 5°C to 40°C and incubating moisture from 30% to 70% water holding capacity (WHC) of soils taken during the growing season. For agricultural soils regardless of pasture and arable management, we suggested nine key factors that influence changes in soil CO₂ emissions including soil temperature, metabolic quotient, bulk density, WHC, percentage of silt, bacterial biomass, pH, soil organic carbon, and hot water soluble carbon (glucose equivalent) based on principal component analysis and hierarchical cluster analysis. Slightly different key factors were proposed concerning individual land use types, however, the most important factors for soil CO₂ emissions of agricultural soils in Northern Germany were proved to be metabolic quotient and soil temperature. Our results are valuable in providing key influencing factors for soil CO₂ emission changes in grassland and arable land with respect to soil respiration, physical status, nutrition supply, and microbe-related parameters.     

基于行走式近红外反射光谱和偏最小二乘法的冰碛土中土壤碳和粘粒含量制图研究

Characterizing spatial variability of soil attributes, using traditional soil sampling and laboratory analysis, is cost prohibitive. The potential benefit of managing soils on a site-specific basis is well established. High variations in glacial till soil render detailed soil mapping difficult with limited number of soil samples. To overcome this problem, this paper demonstrates the feasibility of soil carbon and clay mapping using the newly developed on-the-go near-infrared reflectance spectroscopy (NIRS). Compared with the geostatistics method, the partial least squares regression (PLSR), with NIRS measurements, could yield a more detailed map for both soil carbon and clay. Further, by using independent validation dataset, the accuracy of predicting could be improved significantly for soil clay content and only slightly for soil carbon content. Owing to the complexity of field conditions, more work on data processing and calibration modeling might be necessary for using on-the-go NIRS measurements.     

Mechanical properties of metastable glacial till before and after water‐induced compaction

The mechanical properties of metastable soils have been approached from different backgrounds by civil engineers and soil scientists, with the main focus being on water‐induced self‐compaction rates. This study was conducted to determine the rebound‐recompression properties of metastable soil before and after wetting and to study the effect of water‐induced compaction on the mechanical stability depending on the overburden pressure. Rebound and recompression properties were measured with oedometer tests using sieved sandy loam, taken from a nonweathered Saalian glacial till layer, as the metastable test soil. The mechanical stability (preconsolidation load) of the dry and wetted soil was derived mathematically from recompression data after the test soil was unloaded. Void‐ratio changes during unloading and reloading were on a low level (Δe = 0.03). Rebound and recompression rates of the dry samples increased with load, whereas the void‐ratio change was twofold higher during recompression. Rebound rates of the wetted samples tended to decrease with load, while the recompression rates remained constant. Preconsolidation load calculated for the dry samples overestimated the simulated overburden pressure, whereas the wetted samples showed a high congruence. In both cases, the point of greatest curvature estimated in the earlier step of deviation gave values that were more realistic to the loads from which the unloading started. Our results indicate that both dry compaction and water‐induced compaction induce primarily plastic deformation. Furthermore, we found that in both the dry and wetted state the mechanical stability of the soil reflecting the overburden pressure remained constant.     

Long‐term effects of lime and gypsum additions on no‐till corn and soybean yield and soil chemical properties in southern Brazil

A long‐term experiment on a clayey, kaolinitic, thermic Rhodic Hapludox where dolomitic lime was applied to the surface (either at 4.5 t/ha or at 1.5 t/ha per yr for 3 yr), or incorporated into the topsoil (4.5 t/ha), and gypsum applied to the surface (3, 6, and 9 t/ha), was carried out to evaluate their effects on soil profile chemical properties and yields of corn (Zea mays L.) and soybean (Glycine max L. Merrill). Lime applied to the soil surface at either full or split rates, or incorporated and surface‐applied gypsum had long‐lasting effects on soil acidity or calcium and sulphur availability respectively, as measured 8 yr after application. Grain yields of corn and soybean were not influenced by liming. Gypsum at 9 t/ha significantly increased corn grain yields by 7 and 8% respectively 7–10 yr after application, but did not affect soybean grain yields. The differences in response of the corn and soybean crops to gypsum might be related to the Ca²⁺ uptake by plants because of cation exchange properties of roots, being smaller for corn than for soybean. The use of gypsum in no‐till systems becomes more viable when corn is grown with a greater frequency in crop rotation.     

Natural 13C abundance and soil carbon dynamics under long‐term residue retention in a no‐till maize system

Residue retention and reduced tillage are both conservation agricultural practices that may enhance soil organic carbon (SOC) stabilization in soil. We evaluated the long‐term effects of no‐till (NT) and stover retention from maize on SOC dynamics in a Rayne silt loam Typic Hapludults in Ohio. The six treatments consisted of retaining 0, 25, 50, 75, 100 and 200% of maize residues on each 3 × 3 m plot from the crop of previous year. Soil samples were obtained after 9 yrs of establishing the experiment. The whole soil (0–10 and 10–20 cm of soil depths) samples under different treatments were analysed for total C, total N, recalcitrant C (NaOCl treated sample) and ¹³C isotopic abundance (0–10 cm soil depth). Complete removal of stover for a period of 9 yrs significantly (P < 0.01) decreased soil C content (15.5 g/kg), whereas 200% of stover retention had the maximum soil C concentration (23.1 g/kg). Relative distribution of C for all the treatments in different fractions comprised of 55–58% as labile and 42–45% as recalcitrant. Retention of residue did not significantly affect total C and N concentration in 10–20 cm depth. ¹³C isotopic signature data indicated that C₄‐C (maize‐derived C) was the dominant fraction of C in the top 0–10 cm of soil layer under NT with maize‐derived C accounting for as high as 80% of the total SOC concentration. Contribution of C₄‐C or maize‐derived C was 71–84% in recalcitrant fraction in different residue retained plots. Residue management is imperative to increase SOC concentrations and long‐term agro‐ecosystem necessitates residue retention for stabilizing C in light‐textured soils.     

渭北旱塬不同程度土壤侵蚀及生产力恢复试验

土壤侵蚀会降低生产力,影响作物产量,因此,恢复土壤生产力是人们普遍关注的问题。采用人工模拟土壤侵蚀方法,对侵蚀状况下的土壤进行生产力研究,并配以施肥探索土壤生产力的恢复情况。结果显示：I）施肥可以改善土壤的物理性状,侵蚀土壤的含水量降低,密度增加,孔隙度减小;2）在无肥下,土壤中有机质及其他养分质量分数均随侵蚀程度的加深而减少,施肥可以增加土壤中有机质及各养分的质量分数,但施肥后各养分的质量分数整体上仍呈现出随侵蚀深而降低的趋势;3）土壤侵蚀会减少玉米的生物量,平均每侵蚀1am土层,玉米生物量下降0．38％,施肥可以在一定程度上弥补侵蚀所造成的损失;4）同生物量的变化情况,玉米产量也呈现出随侵蚀程度加深而逐渐下降的趋势,每流失1cm土层,玉米产量平均下降2．49％,施肥能够提高一定的玉米产量,在剥离地表20cm、剥离地表10cm、原状未扰动土和覆盖10cm表土4种不同的地表处理下,常规施肥下的玉米产量比无肥分别提高2．44％、2．13％、1．50％和1．23％,过量施肥比无肥分别提高2．99％、2．56％、1．98％、1．14％。     

Influence of afforestation on soil genesis,morphology and properties in glacial till deposits

A study of soil morphological, physical and chemical properties was performed in woodland of different ages, in which spruce (Picea abies), aspen (Populus tremula) and birch (Betula pendula) growing stocks have colonized former agricultural land. The aim of the study was to clarify changes in soil genesis, morphology and properties due to the afforestation of abandoned agricultural land in glacial till deposits. The research showed that soil in these deposits (loamy sand, loam, clay) retains the morphological properties of agricultural land for up to 100 years. Secondary podzolization features in the soil profiles were observed within 100 years of the start of afforestation, whereas the diagnostic properties of Albic and Spodic horizons had not developed in the soil profile after 200 years. This study demonstrated that the morphological and physico-chemical properties of forest litter horizons, including the accumulation of organic substances, are dependent on forest age; however, changes in the properties of mineral soil horizons are mainly related to woodland age. Following the afforestation of agricultural lands, changes in soil pH_KCl, organic matter content and extractable Al and Fe concentrations occur more rapidly than changes in soil diagnostic properties and profile formation.     

施用碱稳定固体减轻酸性土壤的酸度和铝毒

A pot experiment was catried out to study alleviation of soil acidity and Al toxicity by applying analkaline-stabilised sewage sludge product (biosolids) to an acid clay sandy loam (pH 5.7) and a strongly acidsandy loam (pH 4.5). Barley (Hondeum vulgare L. cv. Forrester) was used as a test crop and was grownin the sewage sludge-amended (33.5 t sludge DM ha^-1) and unamended soils. The results showed that thealka1ine biosloids increased soil pH from 5.7 to 6.9 for the clay sandy loam and from 4.5 to 6.0 for the sandyloam. The sludge product decreased KCl-extractable Al from 0.1 to 0.0 cmol kg^-1 for the former soil and from 4.0 to 0.1 cmol kg^-1 for the latter soil. As a result, barley plants grew much better and grain yield increased greatly in the amended treatments compared with the unamended controls. These observations indicate that alkaline-stabilised biosolids can be used as a liming material for remedying Al phytotoxicity instrongly acid soils by increasing soil pH and lowering Al bioavailability.     

Assessing the effect of crop residue removal on soil organic carbon storage and microbial activity in a no‐till cropping system

Changes in agricultural management strategies have received much attention in recent years with a view to increasing or maintaining the amount of carbon (C) sequestered as soil organic C (SOC). In many parts of the world, minimum or no‐till management has been promoted as a means of improving soil quality, reducing losses of erosion and potentially increasing SOC stocks. However, no‐till systems can become problematic and potentially disease‐prone, especially due to high crop residue loadings. Consequently, residue removal either by harvesting or burning off may be employed to reduce these pressures. Here, we examined the effect of crop residue removal on C storage in soil that had been under no‐till management for 20 yr. We predicted improved physical properties (i.e. lower bulk density) and greater microbial activity under the residue retention soils due to greater readily available C and nutrients derived from crop residues. In contrast, we predicted relative reductions in SOC in the no residue soils due to a lack of available residue‐derived C for microbial use. Residue removal caused a relative C loss from the soil, which was related to C input, amount of nutrient availability and microbial activity. We demonstrate the importance of maintaining crop residue cover in no‐till cropping systems for soil function and highlight the potentially deleterious effects of changing management strategy to increased residue harvesting or removal by burning.     

新疆兵团垦区水土流失及治理对策

新疆兵团垦区是新疆的重要组成部分,它广泛遍布于全疆各地,自然环境隶属新疆大 环境,但由于其在新疆的分布特点,它又有其自身水土流失特点.本文通过对全疆自然环境 调查,分析了兵团垦区水土流失现象,并根据兵团垦区所处环境特点围绕绿洲从3个方面制定水土流失治理方法,结合各业制定适合兵团垦区水土流失治理的措施.     

Changes in soil acidity and related variables over 25 years in the North Pennine Uplands, UK

Abstract. Soil profiles, first sampled between 1963 and 1973, were resampled in 1991 in an upland area with modertely high deposition of pollutants. One hundred horizons from 32 profiles, representing 10 different soil subgroups were analysed for pH and seven variables related to pH, using the same laboratory methods on both sampling occasions. To allow comparisons to be made with results obtained with these old methods, analysis of the 1991 samples was repeated for some determinands using the methods currently used in the analytical laboratory. Organic and A horizons show a consistent increase in acidity between samplings. Although brown soils and lithomorphic soils have increased in acidity throughout their depth, gleys and podzols have decreased in acidity at depth, probably because of poor water transmission downwards into these horizons. Correlations with other determinands suggest that the dominant process in the soils is leaching of basic cations and their replacement on exchange sites by protons and probably aluminium ions. A cause of the increase in soil acidity is likely to be the deposition of atmospherically transported pollutants.     

Cyanobacteria in alkaline soil and the effect of cyanobacteria inoculation with pyrite amendments on their reclamation

The succession of cyanobacteria was studied in a usar (alfisol, solonetz, alkaline) soil, located in a tropical region of upper Gangetic plain, following the first rainfall for a period of 10 months (i.e., July–April). A dozen cyanobacteria were identified to grow on the soil surface and their appearance was in the following order: Microcoleus sp., Calothrix brevissima, Scytonema sp., Cylindrosprmum licheniformae, Cylindrosprmum fertilissima, Nostoc calcicola, Nostoc punctiformae, Aphanothece parietina, Nostoc commune, Aulosira fertilissima, Phormidium sp., and Oscillatoria sp. Among these cyanobacteria, N. calcicola was the dominant species. N. calcicola was inoculated on the alkaline soil and incubated under ambient conditions in the light for 2 years in the laboratory. Changes in soil properties were more rapid after the incorporation of pyrite (FeS₂). Recovery was monitored by using a filamentous heterocystous cyanobacterium N. calcicola and its bicarbonate-resistant (HCO₃^–R) mutant. The mutant strain showed better response to modification of soil pH following growth in soil.     

Reclamation of a coastal reclaimed tidal land soil by gypsum and rice straw

This study was to evaluate the application effect of gypsum and rice straw on the saline–sodic soils of coastal reclaimed tidal lands during newly reclamation process by leaching method. Soil used in the lysimeter experiment is classified as Greyic Hydragric Anthrosols (Sodic Arenic). The experiment was carried out over a period of 1 year from May 2014 to July 2015 inside a plastic film house. Saturated electrical conductivity (EC_e) and exchangeable sodium percentage (ESP) values of soils in gypsum treatment and gypsum with rice straw treatment then reached the desalinization criteria (EC_e = 4.0 dS m^?1, ESP = 15%) after the five or six pore volumes leaching cycles. However, in spite the 10 pore volumes leaching cycles in control and rice straw alone treatment, the values did not reach the desalinization criteria. The results showed that effectiveness of improvement of sodicity and salinity in coastal reclaimed tidal land soils was in the order of gypsum = gypsum + rice straw > rice straw = control. Our study has shown that gypsum alone treatment or gypsum with rice straw treatment in a coastal reclaimed tidal land soils improves their physicochemical characteristics.     

Replacement of soil and soil-forming materials by loose tipping in reclamation to woodland

Abstract. Four experiments studying ground preparation for the restoration of disturbed land to a woodland cover are described. They provide consistent evidence to suggest that methods of soil replacement which minimize compaction are preferable to conventional methods followed by deep ripping to relieve compaction induced in the placement operation. In addition, soil loosening using an excavator is more effective than that achieved by ripping. The research supports modern guidance which advocates 'loose tipping' as the best method of ground preparation for a woodland or forestry after-use on sites reclaimed after dereliction or mineral extraction.     

Amelioration of saline–sodic soil with mildly saline water in the Songnen Plain, northeast China

Abstract. The saline–sodic soils of the dryland Songnen Plain in northeast China are only slowly permeable to fresh water because of their large content of montmorillinite clay and sodium bicarbonate. Use of slightly saline groundwater containing adequate dissolved calcium and magnesium for leaching and reclamation can potentially prevent dispersion of the clay soil particles during treatment. Amelioration was evaluated using shallow, mildly saline groundwater to irrigate sorghum–corn rotations in a two-year field experiment. After two growing seasons during which a total of 400 mm of leaching water was applied, in addition to some supplemental irrigation water, the average electrical conductivity (EC_e) of the top 1.2 m of the soil profile decreased from 14.5±3.5 to 2.7±0.2 dS m⁻¹, and the sodium absorption ratio (SAR_e) decreased from 35.3±4.1 to 10.1±2.5 (meq L⁻¹)^0.5. The soil physical properties were improved: infiltration rate with mildly saline groundwater increased from 12.1 to 42 mm h⁻¹. Salinity changes in the top 1.2 m of soil layers after 700 mm of leaching produced no further improvement. Crop yields produced on plots undergoing amelioration increased by 64–562% compared with the rainfed control. The improved soil conditions after leaching resulted in 59–548% greater crop yields.