The formation of the agrogenic typical chernozem profile in the Ukrainian forest-steppe after plowing virgin steppe and fallow soils

The data on the changes in the physicochemical, biological, and agrochemical properties of a loamy-clayey typical chernozem after plowing a 40-year-old Fallow (for six cycles of a cereal-beet rotation) and a sandy-loamy typical chernozem (for eighteen cycles of a five-course rotation) under different intensities of their use are presented. The major role of the mineral and organic fertilizers and the methods of their application have been revealed in the formation of the humus profile, the acid-base characteristics, and the agrophysical and agrochemical properties.     

The influence of land use and fallow period on the properties of two calcareous soils in the humid tropics of southern Mexico

Calcareous soils are common in the humid tropics of Mexico, but little is known about their productivity and resistance to changes in land use. The influence of land use and duration of fallow on physical and chemical properties were investigated in (a) a loamy Rendzina (at Site A) rich in organic matter and limited in depth by calcareous gravel, and (b) a deeper Calcaric Phaeozem (at Site B) with a more clayey texture throughout. Plots at different successional stages within farmers' shifting cultivation systems were selected on both soils: cropland/young fallow (zero years fallow length), shrub-fallow and tree-fallow at Site A, and cropland/young fallow and forest at Site B. Changes in soil properties suggested a process of recovery with fallow length, in which organic matter, total N and CEC increased with time. The increase in organic matter was remarkably large, on average 0.5–0.6% per year. The Rendzina contained more organic matter than the Calcaric Phaeozem, probably because of its greater carbonate content, which is presumed to protect organic matter against decomposition. The differences in soil properties were mostly greater over time than between treatments.     

Biological activity of soddy-pale-podzolic soils under coniferous-deciduous forest parks in the city of Mogilev

The physicochemical properties, enzymatic activity, number and biomass of soil microorganisms was determined by direct microscopic methods in the anthropogenically changed loamy sandy-loamy soddy-pale-podzolic soils under forest parks (the city of Mogilev) with the predominance of meadow-weed plants in the ground cover. The urban environment had a more toxic influence on the biological activity of the soils than recreation. A more intense transformation of the litter substrate and accumulation of biogenic elements was revealed in the old-plowed sandy loamy soils under the urban coniferous-deciduous plantations as compared to these processes in the soils of the recreational pine forests in the vicinity of Mogilev.     

The influence of different land management practices on the transformation of humic acids in heavy loamy soddy-podzolic soils of the Cis-Urals region

The elemental composition and structure of humic acids were studied in heavy loamy soddy-podzolic soils of the Cis-Urals region under different land management practices. The humic acids in the soil of the long-term clean fallow, overgrown fallow (abandoned plot), and crop rotation plots differed in their composition and properties. The humic acids in the soils of the crop rotation with the regular application of manure and of the overgrown fallow were enriched in the components of both their central (nuclear) and peripheral parts. Such a structure ensured the active participation of humic acids in the carbon cycle with the simultaneous preservation of the soil’s fertility.     

Geographical features of the distribution and renewal of easily decomposable organic matter in virgin and arable zonal soils of European Russia

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.     

The influence of fires on the properties of forest soils in the Amur River basin (the Norskii Reserve)

The influence of forest fires on the properties of taiga brown, gley taiga brown, and alluvial bog soils widespread in the area of the Norskii Reserve (the Amur River basin) was studied. During several years after the fire, the humus content increased, especially in the soils subjected to fires of high intensity. In the soils of steep slopes, the humus content decreased due to damage to the forest vegetation and activation of lateral runoff after the fire. As a rule, in the soils subjected to fire, the C ha-to-C fa ratio increased and correlated with the fire intensity. Some relationships between the forest fires and the acid-base properties of the soils were revealed. After the fires, the pH values often became higher. The stronger the fire, the higher the pH values. The stony soils differed from the other ones, since the reaction of their upper horizons turned out to be more acid after the fires. The analysis of the authors’ and literature data showed that the pyrogenic changes of some soil properties have been poorly studied and need further investigation, including their geographical aspects.     

Changes in the structure of soil microbial biomass under fallow

The number and biomass of various groups of microorganisms in fallow soils is greater as compared to plowed soils. The microbial biomass in all fallow and plowed soils is dominated by fungal mycelium (from 90% in the top horizons to 97% in the lower ones). The part of spores in the fungal biomass is higher in plowed soils (from 9% in the top horizons to 4% in the lower ones) as compared to fallow soils (3.5?C6%). The fallow soils are characterized by the greater part of prokaryotic microorganisms in the biomass, and the reserves and structure of the microbial biomass are more similar to those in the undisturbed soils. These characteristics changed during a ten-year-long period in a soddy-calcareous soil and during a 25-year-long period in a leached chernozem.     

Changes in the physical properties of soils in the Kamennaya Steppe under the impact of shelterbelts

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.     

Changes in amino acid enantiomers and microbial performance in soils from a subtropical mountain oasis in Oman abandoned for different periods

An important feature of maintaining the agricultural stability in millennia-old mountain oases of northern Oman is the temporary abandonment of terraces. To analyse the effects of a fallow period on soil microbial performance, i.e. microbial activity and microbial biomass, samples of eight terrace soils abandoned for different periods were collected in situ, assigned to four fallow age classes and incubated for 30 days in the laboratory after rewetting. The younger fallow age classes of 1 and 5 years were based on the records of the farmers recollections, the two older fallow age classes of 10–20 and 25–60 years according to the increase in the d -to- l ratio of valine and leucine enantiomers. The increase in these two ratios was in agreement with that of the d -to- l ratio of lysine. The strongest relationship was observed between the increase in the d -to- l ratio of lysine and the decrease in soil microbial biomass C. However, the most stringent coherence between the increase in fallow age and soil properties was revealed by the decreases in cumulative respiration and net N mineralisation rates with decreasing availability of substrate to soil microorganisms. During the 30-day incubation following rewetting, relative changes in microbial activity (respiration and net N mineralisation) and microbial biomass (C and N) indices were similar in the eight terrace soils on a fallow age-class-specific level, indicating that the same basic processes occurred in all of the sandy terrace soils investigated.     

Postagrogenic transformation of organic matter in soddy-podzolic soils

In the chronological sequence of postagrogenic soils, the restoration of the original differentiation of the soil profile and its horizons proceeded with different rates depending on the fallow age and the horizon depth. The layer sampling (at 5-cm intervals) showed that the plow horizon began to differentiate into a system of subhorizons in all the fallow soils. The zonal pedogenesis showed clear signs of manifestation already in the 15-year-old fallow. The upper part of the former plow horizon in the 15- and 60-year-old fallows under herbaceous plants was transformed into a soddy horizon, while a postagrogenic soil 90 years old already developed under a zonal type of vegetation and approached the control soil in its morphological features. The content and reserve of carbon in the soils showed a stable tendency of increasing (especially in the upper part of the plow horizon) during the entire postagrogenic period under study. The water permeability of the soils gradually increased and approached that of the virgin soil. However, the compacted subsurface horizon (the plow pan) disappeared only after 90 years. The assessment of the physicochemical properties of the soils and the structural and functional parameters of the humic acids indicated the expansion of the layer differentiation primarily within the homogeneous plow horizon. From the elemental analysis and 13C NMR spectroscopy data, the degree of aromaticity in the molecular structure of the humic acids gradually decreased, and the aliphatic part developed with the age of the fallow.     

亚热带典型地貌下旱地和水田可溶性有机物化学组成特征

阐明亚热带典型地貌下旱地与水田土壤可溶性有机物(DOM)化学组成差异可为农田土壤DOM稳定性评价提供理论依据。研究采用XAD-8树脂分组和热裂解气质联用仪(Py-GCMS)技术,分析比较休闲期、耕作期亚热带喀斯特山区、丘陵区及平原湖区旱地和水田土壤DOM化学组成特征。结果表明:休闲期,亲、疏水性可溶性有机碳(DOC)含量以水田(10.2、33.4 mg/kg)显著高于旱地(4.15、12.8 mg/kg),耕作期无显著性差异。与休闲期相比,耕作期水田亲、疏水性DOC含量均显著降低,而旱地亲、疏水性组分DOC含量在两个时期间保持相对稳定。休闲期旱地和水田土壤DOM中有机酸相对比例分别为31.9%、35.6%,耕作期显著降至17.9%、20.0%(P0.05)。脂类相对比例趋势与有机酸相反,旱地和水田土壤DOM中脂类相对比例在休闲期分别为55.0%、49.5%,耕作期显著增至70.1%、62.9%(P0.05)。Adonis分析表明,亲、疏水性DOC含量在旱地和水田、休闲期和耕作期差异显著(P0.05);DOM化学组成在不同时期(休闲期和耕作期)及地貌(喀斯特山区和丘陵区、丘陵区和平原湖区)差异显著(P0.05)。Random Forest分析表明,有机酸和脂类参与微生物代谢过程,在休闲期和耕作期差异显著(P0.05);芳香化合物作为DOM稳定性组分,在不同地貌区差异较大(P0.05)。总体上,田间条件下水田DOC比旱地DOC对时期响应更敏感,且土壤DOM中微生物代谢相关组分(有机酸、脂类)和稳定性组分(芳香族化合物)在不同时期及地貌区的差异性不同,这对评价旱地和水田土壤DOM稳定性及土壤有机碳积累具有一定的参考意义。     

Ecological study on the dynamics of soil organic matter and its related properties in shifting cultivation systems of Northern Thailand

Abstract

There is a large number of hill people in northern Thailand, who practices shifting cultivation. In order to analyze the soil ecological problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the authors carried out comparative studies on the dynamics of organic matter and its related properties in soils both in the traditional shifting cultivation systems adopted by Karen people and more intensive upland farming practiced by Thai and Hmong people in the area. The contents of organic matter and available N in the surface 10 cm layers of soil from the fields continuously cultivated were lower than those in soils under prolonged fallow (more than 10 y) or natural forest. Based on the rate of soil respiration, the amount of organic matter decomposed within 1 y was estimated to reach nearly 10% of that stored in the upper 50 cm layers of the soil profile in the upland crop fields. These results indicate that the organic matter-related resources markedly decreased under continuous cropping. The contents of C, N, and P in the microbial biomass of the surface 10 cm layers of soil ranged from 0.37 to 2.09 mg C g^?l soil, from 22.7 to 188 µg N g^?l soil, and from 6.1 to 65.7 µg P g^?l soil, respectively. Since the contents of microbial C, N, and P in the surface soils were generally higher under prolonged fallow and natural forests than in the fields continuously cultivated, the microbial activity and/or the amounts of C, N, and P available for biological activity seemed to have declined under continuous upland farming. The incubation experiment to assess the N mineralization pattern showed two remarkable characteristics: 1) there was an initial time lag until active mineralization of N occurred in the soils from young fallow forest and 2) the soil burning effect was observed after burning in the fields under prolonged fallow. The active process of nitrification after N mineralization was always associated with a sharp fall in soil pH, suggesting that soil acidification was promoted and basic cations were lost from the soils. In conclusion, rapid deterioration of the soil organic matter-related properties in cropping fields can be considered to be one of the ecological reasons why upland fields must be returned to fallow again a few years after forest reclamation in traditional shifting cultivation systems. Therefore, in alternative farming systems with more intensive land use, it is essential to apply organic materials into soils to decrease the rate of soil degradation, or to improve the soil fertility, in avoiding soil acidification along with nitrification.     

Changes in the organic matter forms in chernozems of the Kamennaya Steppe under different land uses, locations, and hydromorphism degrees

The soils of the Kamennaya Steppe (Voronezh oblast) were studied. The rate of changes in the contents of C_org and the particular forms of organic matter (labile, microbial, and stable) were revealed in the quasi-natural soils of the fallows and shelterbelt and in the arable soils (rainfed farming for 12, 55, 85, and 115 yrs and irrigated farming for 40 yrs) of different positions on the watersheds and slopes. The effect of the increased soil moistening in the recent decades was also studied. In the upper 50 cm of the fallow soils that were not plowed since 1882, the relative C_org accumulation in the recent 30 yrs has amounted to 5%. The soils of the shelterbelt planted in 1903 were similar to the fallow soils. As compared to the soil of the unmown fallow, the C_org loss from the 1-m soil layer under the shelterbelt and the 12-year-old cropland were less than 9%; the losses from the plowed soils (used for 55–115 yrs) were 21–27% on the watersheds and 37–46% on the slopes. In the first decade, the rate of the Corg losses in the 0- to 20-cm layer of the cultivated chernozem was 120 g C/m². With the increasing duration of the soil plowing (from 55 to 115 yrs), the C_org losses decreased from 45 to 28 g C/m² per yr in the watershed soils and from 51 to 35 g C/m² per yr in the soils on the slopes. The maximum loss of C_org was found for the soils on slopes, waterlogged soils, and irrigated soils. In the slope soils, the C_org loss due to erosion was 9–18% of the total. In the upper horizons of the old agrogenic soils, compared to the soil of the unmown fallow, the C_ha/C_fa increased, since the content of fulvic acids (FA) faster decreased than that of the humic acids (HA); the C content of the nonhydrolyzable residue was reduced. The slope and waterlogged soils differed from the watershed soils in the smaller amounts of HA and FA and in the greater content of humin carbon. In the 0- to 20-cm layer of the soils studied, the rate of the basal respiration (BR) was 0.2–0.5 μg C/g soil per h, the content of the microbial biomass (C_micr) was 326–1073 μg C/g, and the share of C_micr amounted to 1.0–1.9%. These values were minimal in the irrigated soil and maximal in the fallow ones. A high correlation coefficient (r = 0.88–0.92) was found between the C_micr content and the BR, between the contents of C_org and HA, and between the contents of C_org and mobile C. The correlation coefficient between the contents of C_org and FA and C_org and humin C was 0.67.     

Assessment of soil quality in different ecosystems (with soils of Podolsk and Serpukhov districts of Moscow oblast as examples)

The values of the soil-ecological index and microbiological parameters (the carbon of microbial biomass C_mic, its ratio to the total organic carbon C_mic/C_org, and basal respiration) were determined for the soddy-podzolic, soddy-gley, bog-podzolic, meadow alluvial, and gray forest soils under different land uses (forest, fallow, cropland, and urban areas) in the Podolsk and Serpukhov districts of Moscow oblast (237 and 45 sampling points, respectively). The soil sampling from the upper 10 cm (without the litter horizon) was performed in September and October. To calculate the soil-ecological index, both soil (physicochemical and agrochemical) and climatic characteristics were taken into account. Its values for fallow, cropland, and urban ecosystems averaged 70.2, 72.8, and 64.2 points (n = 90, 17, and 24, respectively). For the soils of forest ecosystems, the average value of the soil-ecological index was lower (54.4; n = 151). At the same time, the micro-biological characteristics of the studied forest soils were generally higher than those in the soils of fallow, cropland, and urban ecosystems. In this context, to estimate the soil quality in different ecosystems on the basis of the soil-ecological index, the use of a correction coefficient for the biological properties of the soils (the C_mic content) was suggested. The ecological substantiation of this approach for assessing the quality of soils in different ecosystems is presented in the paper.     

Dynamics of denitrification and ammonification activities in the abandoned and intensely cultivated gray forest soils (Tula oblast)

The results of experimental study of daily dynamics of denitrification activity and the activity and population density of ammonifiers in the abandoned (converted to long-term fallow) and intensely cultivated gray forest soils (Luvic Retic Greyzemic Phaeozems (Aric)) are discussed. The potential denitrification activity in the arable soil is higher than that in the fallow soil, whereas the actual denitrification activity in the arable soil is lower. Data on the dynamics of ammonification do not show reliable differences between the activities of ammonifiers in the arable and fallow soils, though the number of ammonifying bacteria is considerably higher in the arable soil. Differences in daily dynamics of the numbers of ammonifiers in the fallow and arable soils are shown.     

Influence of soil properties on the population and activity of geophagous earthworms after five years of bare fallow

Many soil properties influence earthworm populations and activity. To determine which properties are of significance, a broad collection of soils was investigated. Samples from these different soils were kept bare at one site in large plots (3 Mg soil per plot) to liminate crop and weather interference and to isolate the dominating mechanisms of earthworm effects. Earthworm density, biomass, and tunnelling activity were assessed after 5 years of bare fallow. All earthworm parameters varied strongly. Earthworms increased soil respiration by their tunnelling activity, and in turn increased microbial activity and propagated the loss of organic C. Earthworm abundance ranged from 12 to 274 m^-2 and was about 10 times greater than on cropped soils. The range in abundance was mainly caused by variations in the numbers of juveniles. The average soil moisture content was the only soil property among the many properties investigated that was consistently correlated with earthworm abundance and biomass. Even after 5 years of bare fallow with almost no addition of fresh plant biomass and with little water loss by plant transpiration, the earthworm population was controlled by water stress and not by food stress. We therefore conclude that high water consumption by productive crops may degrade the habitat for geophagous earthworms.     

Soils, vegetation, and climate of the southern Transural region in the Middle Bronze Age (by the example of the Arkaim fortress)

Paleosols of the unique fortress of Arkaim located in the steppe zone of the southern Transural region (Chelyabinsk oblast) were investigated. The dating of the buried soils was performed using the radiocarbon method. The time of building this archeological monument is the Middle Bronze Age (the Sintashta culture; the calibrated dating with 1σ confidence is 3700–4000 years ago). Seven pits of paleosols and ten pits of background ordinary chernozems were studied. The soils are loamy and sandy-loamy. The morphological and chemical properties of the buried and background ordinary chernozems are similar; they differ by the lower content of readily soluble salts in the paleosols as compared to the background ones. The sporepollen spectrum of the Arkaim paleosol is transitional from the steppe to the forest-steppe type. During the existence of this settlement, pine forests with fern ground cover grew, and hygrophytic species (alder and spruce) that nowadays are not recorded in the plant cover occurred. The main feature of the paleosols is the presence of pollen of xerophytic and halophytic herbaceous plants there. The few pollen grains of broad-leaved species testify to a higher heat supply as compared to the current one. Judging by the results of the spore-pollen and microbiomorphic analyses, the climate during the time of building the walls of the settlement was somewhat moister and warmer (or less continental) than the present-day climate. The duration of this period appeared to be short; therefore, soil properties corresponding to the changed environment could not be formed. They reflect the situation of the preceding period with the climatic characteristics close to the present-day ones.     

Degradation and restoration of soils in the Moscow River floodplain for the last fifty years

During a short-term recent period (about 50 years), many floodplains of the Nonchernozemic zone were used as meadows, croplands for growing row crops, or they were abandoned. This was done to supply the populations of industrial cities with vegetables. In this case, the agrotechnical, ameliorative, and some other measures applied were often incompatible with the properties of the floodplain soils and caused their degradation. Among these measures was the elimination of grasses in the crop rotation, the monoculture of row crops, inadequate irrigation inducing systematic waterlogging, and the wide use of heavy agricultural machines. The consequences of using such technologies were investigated by the authors; on these soils, row crop were grown for 30 years and, for the next 20 years, the soils were left under fallow. Based on the data obtained, methods for the floodplain soils’ protection against degradation are proposed.     

A comparison of sulphatase,urease and protease activities in planted and in fallow soils

Sulphatase, urease and protease activities were studied in 12 New Zealand topsoils over 5 months during which the soils were held at 10, 18 and 25°C in pots sown with perennial ryegrass and in pots left fallow.Sulphatase activity in the planted soils showed little significant change over the period of examination. In contrast, sulphatase activity in the fallow soils decreased significantly in almost every instance, the extent of the decrease becoming larger with increasing temperature. Urease behaved similarly to sulphatase, except that in the planted soils several significant increases in activity occurred. Protease activities proved to be very variable. Because of this few significant differences in protease activity were recorded, although it showed the same trends as the other two enzymes.It is suggested that temperature-dependent denaturation could have caused the decrease in enzyme activity in the fallow soils. Replacement of activity lost in this manner by enzymes liberated from plants and microorganisms, and by intracellular enzymes, may have been responsible for the maintenance or increase of activity in the planted soils.     

黄土高原丘陵区不同土地利用方式对土壤理化性质的影响

对晋西北黄土高原丘陵区持续利用30年的小叶锦鸡儿人工林、农田、杨树林、小叶锦鸡儿和杨树的混交林地以及撂荒地的土壤理化性状进行了研究。结果表明,不同土地利用方式对土壤理化性质影响很大。小叶锦鸡儿和杨树的混交林以及小叶锦鸡儿人工林可以降低土壤容重,提高土壤酶活性、有机质和全N含量,从而改善土壤肥力。混交林和小叶锦鸡儿人工林的土壤培肥作用高于杨树纯林。粗放的农业耕作措施提高土壤容重,降低土壤养分含量,使土壤退化。撂荒地一定程度上可以起到培肥土壤的作用。在黄土高原丘陵区,种植小叶锦鸡儿人工林以及小叶锦鸡儿和杨树的混交林是较好的生态重建和植被恢复方式。