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1.
Cluster analysis and principal component analysis (PCA) have been used for the interpretation of dry sieving data. Chernozems from the treatments of long-term field experiments with different land-use patterns— annually mowed steppe, continuous potato culture, permanent black fallow, and untilled fallow since 1998 after permanent black fallow—have been used. Analysis of dry sieving data by PCA has shown that the treatments of untilled fallow after black fallow and annually mowed steppe differ most in the series considered; the content of dry aggregates of 10–7 mm makes the largest contribution to the distribution of objects along the first principal component. This fraction has been sieved in water and analyzed by PCA. In contrast to dry sieving data, the wet sieving data showed the closest mathematical distance between the treatment of untilled fallow after black fallow and the undisturbed treatment of annually mowed steppe, while the untilled fallow after black fallow and the permanent black fallow were the most distant treatments. Thus, it may be suggested that the water stability of structure is first restored after the removal of destructive anthropogenic load. However, the restoration of the distribution of structural separates to the parameters characteristic of native soils is a significantly longer process.  相似文献   

2.
The water stability of typical chernozems was studied, as well as the content and composition of the labile humic substances (LHSs) in the structural units of perennial experiment treatments: Corg was 4.68% on an unmown steppe (fallow), 3.55% under continuous winter wheat without fertilizers, and 2.92 and 2.78% in two treatments of permanent black fallow. It was shown that the water stability of the chernozem??s structure depended on the land use; it deteriorated in the following series: fallow > winter wheat > permanent fallow. No clear relationship was found between the content of Corg in the aggregates obtained by dry sieving and the size of these aggregates. At the same time, the content of Corg in the water-stable aggregates was shown to increase with their size. A positive correlation between the size of the water-stable aggregates and their content of LHSs was found for the unmown steppe and continuous winter wheat treatments.  相似文献   

3.
The hydrologic regimes of arable chernozems were simulated for two plots located within a watershed. For the last fifty years continuous corn monoculture was practiced in one plot, and permanent bare fallow was practiced in the other plot. Carbonates are detected from a depth of 140–160 cm under corn and from 70–80 cm under bare fallow. The objective of the simulation study was to test the validity of the hypothesis that the shallower depth to carbonates under bare fallow is related to carbonate rise due to changes in the hydrologic regime of bare soil compared to soil under vegetation. Mathematical modeling using the HYDRUS-1D software and the FAO56 method confirmed that the hydrologic regimes of arable chernozems within the two plots are different. The soil water content under bare fallow is generally higher than that under corn. The downward soil water fluxes for the two plots are comparable. The upward soil water fluxes under bare fallow significantly exceed those under corn and affect a thicker soil layer. The changes in the hydrologic regimes of chernozems under bare fallow favor the upward movement of carbonates through both the direct transfer by upward water fluxes and the diffusion of ions.  相似文献   

4.
Eurasian Soil Science - Indicators of the microbiological activity of virgin (mixed forest and forb–grassy meadow) and arable (permanent black fallow, permanent barley crop, field crop...  相似文献   

5.
The light clayey typical chernozems were studied on the fields of a long-term experiment on continuous fallowing performed by the Kursk Research Institute of Agroindustrial Production. The experiment was initiated in 1964. It includes the following variants: bare fallow, fallow with NPK application, fallow with manure application, idle land, and cropland under traditional cereal rotation. The fundamental physical properties of the chernozems, such as the particle-size distribution, the aggregate-size distribution, the water stability of the aggregates, the specific surface (as determined by the methods of the equilibrium desorption of water vapor and nitrogen), the mechanical stability of the air-dried aggregates, and the penetration resistance have not changed significantly under the impact of fertilizers and manure application. At the same time, reliable changes have taken place in the physicomechanical properties of the chernozem, including, in particular, the strength of the aggregates and the dependence of the penetration resistance on the water content. This attests to changes in the structural bonds between the soil particles under the impact of the fertilizers. An exponential equation describing the dependence of the penetration resistance on the soil’s water content in the range from the liquid limit to the plastic limit has been suggested. The analysis of the approximation parameters of this equation shows that the application of manure increases the dilatant characteristics of the chernozem and lowers its penetration resistance at the given water content. Reliably higher values of the penetration resistance have been found in the soil of the cropland, which may be related to the somewhat coarser soil texture in this experimental variant.  相似文献   

6.
青海省东部山区旱作农田土壤团聚体特征研究   总被引：1，自引：0，他引：1  
比较了青海省东部山区垂直梯度分布的三种旱作农田土壤(黑钙土、栗钙土、灰钙土),在0~60 cm土层的不同粒级土壤风干团聚体和水稳性团聚体含量间的差异,并结合其它土壤质量指标(有机质、粘粒)对不同土壤结构和抗侵蚀能力进行了综合评价。结果表明,>0.25mm风干团聚体、>0.25mm水稳性团聚体含量和土壤有机质含量与土壤类型间有密切关系。均表现为黑钙土>栗钙土>灰钙土。黑钙土和栗钙土的土壤有机质含量与>0.25mm水稳性团聚体间存在显著正相关关系(P<0.05),灰钙土则无明显相关性;三种土壤粘粒含量与>0.25mm风干团聚体和0.25mm水稳性团聚体含量间无明显相关性。各项指标综合比较,三种土壤抗侵蚀能力大小为:黑钙土>栗钙土>灰钙土。  相似文献   

7.
Eurasian Soil Science - Changes in the macro-, meso-, and micromorphological properties of plowed migration-mycelial chernozems (Haplic Chernozems) after their conversion into permanent unmanaged...  相似文献   

8.
Rheological parameters of humus horizons from typical chernozems under different land use—on a virgin land (unmown steppe) and under an oak forest, long-term black fallow, and agricultural use—have been studied by the amplitude sweep method with an MCR-302 modular rheometer at water contents corresponding to swelling limit and liquid limit. From the curves of elastic and viscous moduli, the ranges of elastic and viscoelastic (plastic) behavior of soil pastes—as well as that of transition from viscoelastic to viscous behavior—have been determined. It has been shown that the rheological behavior is largely determined by the content of organic matter, which can act as a binding agent structuring the interparticle bonds and as a lubricant in the viscous-flow (plastic) state of soil pastes. Soil samples enriched with organic matter (virgin land, oak forest, forest belt) have a more plastic behavior and a higher resistance to loads. Soil samples with the lower content of organic matter (long-term fallow, plowland) are characterized by a more rigid cohesion of particles and a narrower range of load resistance. Soil pastes at the water content of liquid limit have a stronger interparticle cohesion and a more brittle behavior than at the water content of swelling limit. Methodological aspects of testing soil pastes at the constant sample thickness and the controlled normal load have been considered. For swelling soil samples, tests under controlled normal load are preferred.  相似文献   

9.
The physical properties of ordinary chernozems and meadow-chernozemic soils under different land management practices (maple, larch, birch, and pine sections of the shelterbelts; continuous (since 1959) fallow; and arable field (since 1952)) were studied in the Kamennaya Steppe. The soils had favorable physicochemical properties, light clayey texture, and high microaggregation independently from the type of land management. The long-term impact of the shelterbelts improved the soil structure in the upper part of the humus horizon: the content of agronomically valuable aggregates increased, the content of coarse aggregates (>10 mm) decreased, the aggregation coefficient increased by 3.7–4.3 times, and the water stability of the aggregates became by 8–12% higher. The soils under the shelterbelts were characterized by minimum values of the bulk density and solid phase density and by maximum values of the total, active, and air porosities. At the same time, no considerable differences between water reserves in the studied range of soils were detected. The ratio of the optimum productive water range to the active (productive) water range (OPWR/AWR) within the upper soil meter varied from 0.42–0.44 to 0.45–0.54. This points to changes in the character of perched water: the content of intra-aggregate capillary-perched water decreases, and content of film perched water increases down the soil profile.  相似文献   

10.
Temporal changes of eroded soils in the southern Cis-Ural region (Republic of Bashkortostan) depending on their agricultural use during the period from 1975 to 2011 were studied. In the northern foreststeppe zone, the development of erosion processes was retarded upon the use of soil-saving management practices and grain-fallow-grass crop rotations. In slightly eroded light gray forest soils (Eutric Retisols (Cutanic)), the thickness of humus-accumulative horizons and the content of humus increased; the conversion of cropland into permanent fallow was found to be the most efficient measure to control soil erosion. In podzolized chernozems (Luvic Greyzemic Chernic Phaeozems) and typical chernozems (Haplic Chernozems) of the Cis-Ural steppe, the content of humus in the plow layer under grain-row crop rotation and classical soil management decreased, especially in moderately eroded soils. The development of water and wind erosion on slopes depended on the slope shape: the texture of soils at different degrees of erosion on slopes with free runoff became coarser by one gradation after 35 years; in the presence of linear obstacles in the lower part of slopes, the content of fine fractions in moderately and strongly eroded soils increased.  相似文献   

11.
为探究轮作休耕模式对红壤坡耕地团聚体稳定性及有机碳含量的影响,通过田间试验设置了休闲地、玉米单作、玉米-豌豆-玉米和玉米-苕子-玉米4个处理,分析了不同种植模式下土壤团聚体稳定性及有机碳含量,结果表明:(1)不同种植模式下土壤机械稳定性和水稳定性团聚体组成均以≥0.25 mm粒径占比最高,机械稳定性团聚体占比在80.68%以上,水稳定性团聚体达到了77.05%以上,且≥0.25 mm团聚体所占比例大小顺序为:休闲地>玉米-豌豆-玉米>玉米-苕子-玉米>玉米单作。(2)根据不同团聚体稳定指数(MWD,GMD,R0.25和PAD)显示,休闲地的团聚体稳定性最好,与玉米单作之间差异显著,且休闲地和玉米轮作两种模式下团聚体稳定性均优于玉米单作。(3)玉米单作土壤团聚体有机碳含量最低,玉米轮作和休闲地能显著提高有机碳含量,并且玉米-苕子-玉米轮作效果最优; ≥0.25 mm粒径范围的团聚体储存的有机碳含量最高。(4)通过对土壤水稳性团聚体稳定指数与有机碳含量的相关性分析表明,4个不同团聚体稳定指数与有机碳含量都呈极显著正相关关系,与R0.25相关程度最高。研究结果可为试验区域坡耕地水土流失防治提供理论依据。  相似文献   

12.
The analysis of long-term (since 1947) data on the water content of the upper 3-m-thick layer in the Streletskaya Steppe chernozems under annual mowing showed that the weather changes during the last decades (from 1972–1973 to 2005–2006) resulted in an increase in the soil wetting depth during the fall-winter-spring period and the frequency of the percolation, a decrease in the water consumption from the 150- to 300-cm layer during the growing season, and a decrease in the water deficit in the fall. Therefore, the total water content of the steppe chernozems increased, although to a significantly lesser degree than that found for the steppe plot with a succession of woody-shrub vegetation. In a perennial fallow, the water content of the soil layer also increased. The water supply of the 0- to 160-cm layer of chernozems under winter wheat and corn underwent no significant changes.  相似文献   

13.
陈曦  王改玲  刘焕焕  殷海善  樊文华 《土壤》2021,53(2):375-382
为探究不同撂荒年限土壤结构及有机碳分布特征,试验选取黄土高原吕梁山自然撂荒1、2、3、5、10、15、20 a枣园土壤为研究对象,以清耕作业下的枣园土壤为对照(CK),利用干筛和湿筛法测定并分析各样地0～20 cm土层中土壤团聚体稳定性、团聚体有机碳与土壤总有机碳含量及其相关性。结果表明:撂荒初期,土壤团聚体含量呈波动变化趋势,撂荒3 a后土壤水稳性大团聚体含量(0.25 mm团聚体含量,R_(0.25))及团聚体平均重量直径(MWD)、几何平均直径(GMD)随撂荒年限的增加逐步提高。20 a撂荒地土壤水稳性大团聚体含量占团聚体总量的69.6%,较CK提高了55.2个百分点。土壤总有机碳、团聚体有机碳含量随撂荒年限的延长均呈先降低后增加的趋势,撂荒20 a土壤总有机碳含量达最大值7.88 g/kg;团聚体有机碳含量随团聚体粒径的减小呈先增加后降低的特点,主要集中于1～0.25 mm团聚体内。不同撂荒年限土壤中机械稳定性大团聚体有机碳对土壤总有机碳的贡献率为54.3%～82.2%,较CK(29.3%)提高25.0～52.9个百分点;水稳性大团聚体有机碳对土壤总有机碳的贡献率为17.7%～71.8%,除撂荒1 a和3 a土壤外,其他样地均高于CK (21.1%)。水稳性团聚体MWD、R_(0.25)与土壤总有机碳含量极显著相关(P0.01);水稳性团聚体GMD与土壤总有机碳含量显著相关(P0.05);水稳性团聚体R_(0.25)与2～1、1～0.25和0.25 mm水稳性团聚体有机碳含量极显著相关(P0.01),与5～2 mm团聚体有机碳含量显著相关(P0.05)。可见,撂荒恢复促进了土壤有机碳及水稳性团聚体有机碳含量的提高,从而提高了团聚体的稳定性。  相似文献   

14.
东北黑土区冻融作用对黑土水稳性团聚体的影响   总被引：3，自引：0，他引：3  
Soil aggregate stability,an important index of the physical characteristics of a soil,can provide a good indication of a soil’s erodibility,and deserves special consideration in regions with cold climate.The objective of this study was to study the effect of freeze-thaw on soil water-stable aggregates in the black soil region of Northeast China.Samples of a typical black soil in the region were collected to measure water-stable aggregates after freeze-thaw under different conditions(i.e.,initial moisture contents,freezethaw cycles and freezing temperatures)by wet-sieving into eight particle size groups(10,10–6,6–5,5–3,3–2,2–1,1–0.5,and0.5–0.25 mm).Freeze-thaw had the most effect on aggregate stability when the samples had an initial moisture content of 400 g kg-1.The water-stable aggregates of the four larger particle size groups(5,5–3,3–2,and 2–1 mm)reached a peak stability value,but those of the two smaller particle size groups(1–0.5 and 0.5–0.25 mm)reached a minimum value when the soil moisture content was 400 g kg-1.Water-stable aggregates of the four larger particle size groups decreased while those of the two smaller particle size groups increased with the increase of freeze-thaw cycles.As temperatures fell,the water-stable aggregates of the four larger particle size groups decreased while those of the two smaller particle size groups increased.  相似文献   

15.
The tendency and type of quantitative changes in the main characteristics of the water permeability of automorphic (typical and ordinary) chernozems in the central part of the Russian Plain have been studied in the system of virgin soil (long-term fallow), rainfed plowland, and irrigated plowland. It is shown that irrigation exerts the most pronounced adverse effect on the water permeability of chernozems. The revealed causes of unfavorable changes in the water permeability of chernozems in the region are related to their agricultural use.  相似文献   

16.
A method is presented for assessing the distribution of enzymatic activity inside and outside of water-stable aggregates. Two samples of water-stable aggregates >1 mm have been isolated from dry aggregates of 1–2 mm. To determine the enzymatic activity, a substrate has been added to one of the samples without disaggregation; the other sample has been preliminarily disaggregated. Enzymatic activity within waterstable aggregates has been assessed from the difference between the obtained results under the supposition that the penetration of substrate within the water-saturated aggregates is hampered, and enzymatic reactions occur only at the periphery. The levels and distributions of enzymatic (peroxidase, polyphenol oxidase, and catalase) activities in water-stable aggregates of soddy-podzolic soils under forest and plowland and typical chernozems of long-term field experiments have been studied. The peroxidase, polyphenol oxidase, and catalase activities of water-stable aggregates vary from 6 to 23, from 7 to 30, and from 5 to 7 mmol/(g h), respectively. The ratio between the enzymatic activities inside and outside of soil aggregates showed a higher dependence on soil type and land use, as well as on the input of organic matter and the structural state, than the general activity level in water-stable aggregates.  相似文献   

17.
The size, number, and biomass of bacteria and microscopic fungi were studied in chernozems of different land uses (forest, fallow, pasture, and cropland), in paleosols under mounds of different ages in the territories adjacent to the background recent chernozems; and in the cultural layer of an ancient settlement of the Bronze Age, Early Iron Age, and Early Middle Age (4100–1050 years ago). The method of cascade filtration revealed that bacterial cells had a diameter from 0.1 to 1.85 μm; their average volume varied from 0.2 to 1.1 μm3. Large bacterial cells predominated in the soils of natural biocenoses; fine cells were dominants in the arable soils and their ancient analogues. The bacterial biomass counted by the method of cascade filtration was first found to be 10–380 times greater than that determined by luminescence microscopy. The maximal bacterial biomass (350–700 μg/g) was found in the soils of the birch forest edge (~80-year-old) and under the 80-year-old fallow. In the soils of the 15–20 year-old fallows and pastures, the bacterial biomass was 110–180 μg/g; in the arable soils and soils under the mounds, it was 80–130 and 30–130 μg/g, respectively. The same sequence was recorded in soils for the content of fungal mycelium and spores, which predominated over the bacterial mass. With the increasing age of the buried paleosols from 1100 to 3900 years, the share of the biomass of fungal spores increased in the total fungal and total microbial biomasses. In the cultural layer of the Berezovaya Luka (Altai region) settlement that had been functioning about 4000 years ago, the maximal biomass and number of fungal spores and the average biomass of bacteria and fungal mycelium comparable to that in the studied soils were revealed. In this cultural layer, the organic matter content was low (Corg, 0.4%), and the content of available phosphorus was high (P2O5, 17 mg/g). These facts attest to the significant saturation of this layer with microbial cenoses 4000 years ago and to their partial preservation up to now owing to the high concentration of ancient human wastes there.  相似文献   

18.
Specific features of the microbiological and enzymatic activity of chernozems are considered in genetically associated and technogenic series. The biological processes in chernozems follow the main soil-geographical regularities inherent to the Central Chernozemic region. The biological characteristics of the chernozems reflect the dynamic properties of the microorganisms habitat and are indicators of their technogenic degradation. Plowing of chernozems and their intense agricultural use is accompanied by changes in their biological activity. The disturbances revealed in the biosystem of the chernozems caused by plowing and fertilization were of a functional, i.e., reversible character. The changes in the intensity of the biochemical processes in the chernozems were observed only under the long-term application of fertilizers (for not less than 10 years). A single application of fertilizers caused temporary changes.  相似文献   

19.
A decrease in the depth of organic surface horizons (forest litters and steppe mats), the reserves of organic matter in them, and an increase in their renewal rate were noted for virgin and fallow soils when going from the southern taiga to the dry steppe zone. Zonal changes in the content and reserve of easily decomposable soil organic matter showed a similar tendency: these parameters regularly decreased from soddy-podzolic soils of the southern taiga to chestnut and light chestnut soils of the dry steppe. An exception from this series is provided by fallow chernozems of the steppe zone noted for the lowest content and reserve of labile organic matter in the series of soils studied. Similar, although less pronounced, tendencies were observed for the arable soils.  相似文献   

20.
We studied the physical properties of chernozems subjected to local waterlogging because of different reasons. The secondary soil hydromorphism resulted in insignificant changes in the soil’s texture related to some redistribution of the elementary soil particles by the particle-size fractions. The physical clay content somewhat increased in the lower part of the soil profiles (in the B2 and BC horizons) at the expense of the clay particles. The bulk density of the waterlogged soils somewhat increased, particularly in the B2 horizon. The regular soil waterlogging worsened the soil’s structural status with a decrease in the content of the silt-size aggregates and an increase in the content of the coarse blocky aggregates. The changes in the soil’s structure can be considered a diagnostic feature of the locally waterlogged chernozems. The water stability of the aggregates increased due to the higher contents of the major cementing agents, including the soil humus and carbonates.  相似文献   

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