Content Of Exchangeable Bases Research Articles

Estimation of Carbon Stocks in Soils of Forest Ecosystems as a Basis for Monitoring Climatically Active Substances

The eluvozems and soddy eluvozems on two-layer deposits dominating in the soil cover of the Zvenigorod biostation of Moscow State University contain, on average, 65–83 t/ha of organic carbon in the litter and a meter-deep layer of mineral strata. Carbon stocks are minimal in the soddy eluvozem of the complex spruce forest (59–68 t/ha), which is characterized by a lighter granulometric composition, and reach 76–92 t/ha in the soils of the birch–spruce and complex pine–spruce forests. At the same time, 3.3–5.8 t C/ha or 4–9% of the total organic carbon reserves are concentrated in the litter, and 64–69% in the upper mineral layer (0–20 cm). Different levels and profile distribution of organic carbon reserves in soils are determined by lithological and granulometric features and the nature of vegetation. The contribution of water-extractable organic carbon compounds to their total content in the upper mineral horizons of soils does not exceed 1.3–1.8%, microbial carbon, 1.7–2.4%. In acidic light loamy soils, the enrichment in calcium and potassium, the cation exchange capacity, the content of exchangeable bases, and the degree of saturation can serve as indicators of the content and reserves of organic carbon at the ecosystem level. The relationship with the content of finely dispersed fractions and oxalate-extractable Al and Fe is manifested to a lesser extent due to the similar origin and properties of soils. The variability of organic carbon stocks in soils is determined to the greatest extent by its content, the influence of which decreases with depth. Accounting for spatial heterogeneity, field measurements of the density and proportion of fine earth, and correct analytical determinations are essential components of the assessment of carbon stocks in soils of forest ecosystems as part of a national monitoring system for carbon pools and greenhouse gas fluxes under development.

Estimation of Carbon Stocks in Soils of Forest Ecosystems as a Basis for Monitoring the Climatically Active Substances

—The eluvozems and soddy eluvozems on two-layered deposits dominating in the soil cover of the Zvenigorod Biostation of Moscow State University, contain, on average, 65–83 t/ha of organic carbon in the organic layer and the upper meter of mineral strata. Carbon stock is minimal (59–68 t/ha) in the coarser-textured soddy eluvozem of the spruce forest and reaches 76–92 t/ha in soils of birch–spruce and pine–spruce forests. Organic layers store 3.3–5.8 t C/ha or 4–9% of the total soil organic carbon stock; the upper mineral layer (0–20 cm) stores 64–69%. Different levels and profile distribution of organic carbon in soils are determined by lithological and textural features of the soil profiles and by the nature of vegetation. The contribution of water-extractable organic carbon to the total organic carbon content in the upper mineral horizons does not exceed 1.3–1.8%; the contribution of microbial carbon is 1.7–2.4%. In acidic loamy soils, the enrichment in calcium and potassium, the cation exchange capacity, the content of exchangeable bases, and the degree of base saturation can serve as indicators of the content and stocks of organic carbon at the ecosystem level. The relationship with the content of clay fractions and oxalate-extractable Al and Fe is manifested to a lesser extent due to the similar origin and properties of soils. The variability of organic carbon stocks in soils is largely determined by its content, the influence of which decreases with depth. Accounting for spatial heterogeneity, field measurements of the soil bulk density and proportion of fine earth, and correct analytical determinations are essential components of the assessment of carbon stocks in soils of forest ecosystems as a part of the national monitoring system for carbon pools and greenhouse gas fluxes.

Physico-chemical Characterization of the Soils of New Localities of Côte d’Ivoire: Case of the Departments of Man (West) and Toumodi (Centre)

In order to assess the suitability of soils for rubber cultivation in the departments of Man and Toumodi, two new rubber-growing areas, a study was carried out to evaluate the physical, physico-chemical and chemical characteristics of soils under rubber trees (Hevea brasiliensis). The methodology used consisted of a physical description of twelve soil pits, coupled with chemical analyses of the soil samples taken. The pedological profiles carried out revealed that these soils belong mainly to the Ferralsol class with distinctive characteristics, except for those of Kimoukro (Toumodi) which belong to the Cambisol class. The Toumodi soils, of silty-clay-sandy texture, are provided with coarse elements (≥30 p.c) with good internal drainage in the surface horizons. More or less deep, depending on the topographical position, Toumodi soils are slightly acidic (pH = 6) and less supplied with nitrogen and exchangeable bases. The soils of Man, on the other hand, have a sandy-clay texture, with more than 30 p.c. of clay from the surface to the depths. The bulk density (Da = 1.6 ≥ 1.5 g/cm3) was higher for the soils of this locality compared to those of Toumodi (Da = 0.8 ≤ 1 g/cm3). The soils of Man, which are less rich in nitrogen and carbon, are more acidic (pH = 5.4). Exchangeable base contents and CEC are high, mainly in the upper surface horizons.

Irrigation with treated wastewater in humid regions: Effects on Nitisols, sugarcane yield and quality

Treated wastewater (TWW) reuse for crop irrigation has been developing in recent decades in areas hampered by severe water shortages. However, in humid conditions, the agronomic impacts of supplementary irrigation are less and poorly documented. On the island of Réunion, we measured sugarcane yield and quality on a Nitisol over 2 years by providing 2600 mm of TWW or irrigation water (control) as a supplement to the 3500 mm rainfall. Meanwhile, with the same TWW, irrigation water (IW) and rainfall inputs, we monitored leachates and soil under controlled conditions without plants. Sugarcane yield, Brix degree, fiber and sucrose contents were similar between the TWW and control plots each year. The leachate pH and electrical conductivity at 60 cm depth showed marked differences between the TWW and control modalities. Similarly, after a constant increase in chloride, sulfate, potassium and sodium contents, or breakthrough curves for calcium and magnesium, the concentrations of these elements under the TWW modality were stable from 12 pore volumes (PV), except for calcium which was stable from 16 PV. At the end of the experiment, the hydraulic conductivity and organic carbon contents did not show any significant change, while the pH of soils that had received TWW and of the control soil was higher overall than the pH of the initial soil. The dynamics of the major elements in leachates at 65 cm depth were consistent with the input concentrations and the variations in exchangeable base contents in the soil at the end of the experiment. However, potassium and mineral nitrogen had accumulated in the soil profile while there were low concentrations in the leachate. The TWW quality and quantities provided, uptake by plants, competition for adsorption or leaching, and the pedoclimatic context, could therefore: (i) explain the absence of negative agronomic impact, and (ii) highlight the benefits of irrigation with TWW in humid environments to supplement water requirements and fertilize intensive crops.

Comparative Analysis of Properties of Particleboards Made from Corn Cobs at Varying Proportions of Clay Soil

Particles of dried corn cobs were employed for manufacture of cement bonded particleboards. Two types of clay soil (red and white) were used as supplement with cement to manufacture cement bonded particleboards. The production of the boards was done at varying proportions of 50/50/0, 50/40/10, 50/30/20, 50/20/30, 50/10/40 and 50/0/50 for (corn/cement/clay) in weight to weight basis while the other considerable production factors like nominal density and curing agent percentage remained constant at 1.30 g/cm3 and 3%. The chemical composition of the soil such as pH, organic carbon, organic matter, total nitrogen, and exchangeable bases were determined. Its impact on physical and mechanical properties such as density, water absorption, thickness swelling, modulus of rupture and modulus of elasticity were also investigated The results of the analysis of variance shows that all considerable production factors for the cement bonded particleboards were significant at 5% level of probability except clay soil type for density. The results show that cement bonded particleboard made of red clay soil with higher content of exchangeable bases proves better outstanding performance in density, strength and dimensional properties than the white clay soil. Among the cement bonded particleboards made at varying proportions. It was discovered that boards of 50/20/30 (corn/cement/clay) had better strength properties than others. Also, the boards made at the proportions of 50/40/10, 50/10/40 and 50/30/20 (corn/cement/clay) were better dimensionally stabled in moisture exposure but weak in strength. The outcome of this study may serve as a guideline for any manufacturer who intends to use clay soil as supplement for production of particleboards.
 Keywords: Cement, particleboard, clay soil, corn cobs, strength, variance

KERAGAAN VARIETAS PADI SAWAH DI LAHAN MARGINAL LAMPUNG

Acid dry land in the experimental garden Taman Bogo, East Lampung including the classification of Ultisol acil, and generally ultisol acid soils can be used as representative for acid soils in Indonesia. Characteristic of ultisol soil, among others: sour soil reaction (low pH <5.5), high aluminium content, high P fixation, exchangeable base contents and low exchange capacity (CEC), iron and manganese content close to poisonning, sensitive erosion and poor biotic elements. Acid dry land in Indonesia is directed in supporting the improvement of land resources, Display/ Show window and visitor plot development of acid dry land management technology, implemented to accelerate the process of superior technology transfer such as fertilizer technology and the use of organic materials, conservation, reclamation and land rehabilitation, as well as superior varieties in acid dry land. Show window dan visitor plot development of dry land management technology in Taman Bogo experimental garden is a means of discussion and communication between researchers, extension workers, farmers and local policy makers.

Genesis of sandstone-derived soils in the Cerrado of the Piauí State, Brazil

This study characterized the morphological, physical and chemical attributes of sandstone-derived soils at the Cerrado of the Piauí State, Brazil, in order to identify evolutionary standards. The study was carried out with five representative soil profiles identified as P1-RY (Typical Flavic Psychotic Neosol - Aquents), P2-PA (Typical Dystrophic Yellow Argisol - Alfisol), P3-RL (Fragmentary Litholic Distrophic Neosol - Psammenit), P4-RQ (Typical Ortic Quartzenetic Neosol - Orthents) and P5-PV (Typical Dystrophic Red Argisol - Ultisol). Soil samples were submitted laboratory analysis described morphologically. In general, the soils presented high sand content, low pH, low content of exchangeable bases and low cation exchange capacity (CEC). Organic matter governed the CEC in most cases, suggesting dependence of organic matter in the supply of charges. These soils showed a low degree of weathering, but with iron of high crystallinity. Thus, the relief and the parent material are the major important soil-forming factors at the Cerrado of the Piauí State. Moreover, these soils are young, with the soils from the Piauí Formation being more evolved. However, the sandstones from the Canindé Group apparently are providing lithological secondary minerals for the soil.

Soil quality decrease over 13 years of agricultural production

Soils are a key issue in the management of global environmental changes and food supply. The goal of this work was to characterize the soil changes that were promoted by agriculture in Uruguay in the period 2002–2014. We analysed the association between pH, Ca2+, Mg2+, K+, Na+ and soil organic carbon (SOC) and its tendency through the years of soil analysis database 2002–2014 that belong to Experimental Station Alberto Boerger INIA La Estanzuela (Colonia, Uruguay). During the study period, the average soil pH, SOC, and exchangeable base content across the archive sample set were reduced. The exchangeable K+ content decreased by 0.04 mmol kg−1 year−1 with the increase in grain production. The SOC decreased by 0.43 mg (g year)−1 even when most agricultural activity followed a no-tillage system. A reduction of 0.02 units of pH per year also occurred. If these changes continue in the future, agricultural soils will significantly decrease their food production potential, and will not be adequate for sustainable crop production.

Why copper and zinc are ineffective in reducing soil urease activity in New Zealand dairy-grazed pasture soils

Micronutrients copper (Cu) and zinc (Zn) have the potential to inhibit soil urease activity (UA) and reduce ammonia (NH3) emissions over long duration (8–12 weeks) but have not been tested for reducing NH3 losses from cattle urine deposited in dairy-grazed pasture soils. The objective of this study was to assess the effectiveness and longevity of Cu and Zn in reducing soil UA, for the use of these metals to reduce NH3 emissions from deposited urine by grazing cattle. A series of experiments were conducted to (i) assess the relationship between inherent Cu and Zn status and soil UA of New Zealand dairy-grazed pasture soils, (ii) determine the impact of Cu and Zn addition to pasture soils on soil UA and (iii) investigate how soil organic carbon (C) and other C-related textural and mineralogical properties such as clay content and cation exchange capacity influence the effectiveness of added Cu and Zn in reducing urea hydrolysis. The results showed significant positive correlations of soil total C and total nitrogen (N) with soil UA. However, there were no significant negative correlations of soil UA with inherent Cu and Zn levels. Similarly, addition of Cu and Zn to soil did not significantly reduce soil UA. However, when Cu was added to two different soil supernatants there was a significant reduction in hydrolysis of urea applied at 120 and 600 mg urea-N kg–1 soil. Additions of Zn achieved negligible or small reductions in urea hydrolysis after 120 and 600 mg urea-N kg–1 soil applications to soil supernatants. This result suggests that Cu can inhibit soil UA and urea hydrolysis in soil supernatants with potentially low C, clay and cation exchangeable base contents. However, the interaction of bioavailable Cu with labile soil organic C and clay particles leads to its inactivation, resulting in ineffectiveness in organic C-rich pasture soils. Although most of the added Zn did not complex and remained bioavailable, the observed levels of bioavailable Zn had limited effect on soil UA.

Spatial variability of selected soil properties in relation to land use and slope position in Gelana sub-watershed, Northern highlands of Ethiopia

Land degradation resulting from land-use changes and soil erosion has been a serious environmental problem in Ethiopia. This study addressed the effects of land use and slope position on soil physical and chemical properties in the Gelana sub-watershed, Northern highlands of Ethiopia. A total of 63 soil samples were collected and analyzed using a two-way ANOVA. Results showed that clay, soil pH, soil organic matter, total nitrogen, cation exchange capacity, and exchangeable base contents of the cultivated land were significantly (p < 0.001) lower than those of the forest land, while soil bulk density, available phosphorous, and percentage base saturation were higher for cultivated land than forest land. In general, soil fertility declines as land use changes from forest to grazing and cultivated lands. Sand, clay, bulk density, soil pH, organic matter, total nitrogen, carbon:nitrogen ratio, available phosphorous, cation exchange capacity, exchangeable cations, and percentage base saturation showed significant variation due to slope position differences. Therefore, the study reinforces the need for integrated watershed management for sustainable agricultural production in the study area.

The impact of clearcutting in boreal forests of Russia on soils: A review

Data on the impact of tree logging in boreal forests of Russia on soils are systematized. Patterns of soil disturbances and transformation of microclimatic parameters within clearcutting areas are discussed. Changes in the conditions of pedogenesis in secondary forests are analyzed. It is suggested that the changes in forest soils upon reforestation of clearcutting areas might be considered as specific post-logging soil successions. Data characterizing changes in the thickness of litter horizons and in the intensity of elementary pedogenic processes, acidity, and the content of exchangeable bases in soils of clearcutting areas in the course of their natural reforestation are considered. The examples of human-disturbed (turbated) soil horizons and newly formed anthropogenic soils on clearcutting areas are described. It is suggested that the soils on mechanically disturbed parts of clearcutting areas can be separated as a specific group of detritus turbozems.

Effects of Biochar on the Emissions of Greenhouse Gases from Sugarcane Residues Applied to Soils

The sugar and bioethanol industry generate large amounts of filter cake and vinasse, residues that are applied to sugarcane fields as conditioners and organic fertilizers. However, these may be significant sources of greenhouse gases emissions to the atmosphere. This study assessed the impact of sugarcane straw biochar on the emissions of CO2, CH4and N2O promoted by filter cake and vinasse applied to soil, and its effects on the chemical properties and bacterial communities of a Typic Hapludox and a Quartzipsamment. A laboratory incubation was conducted for 100 days with both soils under five treatments: vinasse and filter cake amendment (FV), plus biochar at 10 (FV + B10), 20 (FV + B20) and 50 (FV + B50) Mg·ha-1, and a control. Soil pH, available P and exchangeable base contents increased with biochar added to sandy soil. Mineral N decreased with biochar addition to both soils. The FV treatment increased CO2 emissions by 5-fold and 2.4-fold in sandy and clayey soils, respectively, compared to the control. Moreover, FV +B10 increased CO2 emissions by 4% and 6.4% in sandy and clayey soils, respectively, compared to FV. Cumulative N2O emissions in FV were 537% and 125% higher in sandy and clayey soils, respectively, compared to the control. Nevertheless, increasing biochar amendment rates reduced N2O emissions from 24% to 34% in sandy soil, and from 14% to 56% in clayey soil. CH4 emissions were negligible. The effects of filter, vinasse and biochar amendments on soil amelioration were closely related to its buffering capacity. Temporal changes on bacterial community structure were more pronounced in the sandy soil compared to clayey, and indicated that N2O emission mitigation in clayey soil was directly related to biotic mechanisms, while abiotic mechanisms caused by biochar played a more important role in mitigating N2O emissions in sandy soil.

Variation of the chemical composition of Pyrenean oak (Quercus pyrenaica Willd.) heartwood among different sites and its relationship with the soil chemical characteristics

This work presents the results of a study on the variation of the chemical composition of Pyrenean oak (Quercus pyrenaica Willd.) heartwood among different sites and its relationship with the soil chemical characteristics. The chemical characteristics of the heartwood are quantified in terms of proximate and ultimate analysis, calorific value and ash composition. Subsequently, the relationship between the wood chemical characteristics and the soil characteristics was also examined. The results showed no significant differences between the wood chemical characteristics from different sites. There are, however, significant differences between trees from the same site regarding the wood ash content, the calorific value and the contents of nitrogen and hydrogen. Strong correlations were observed between the heartwood ash contents of BaO, MnO, CuO and TiO2 and the soil nitrogen, phosphorous and potassium and the soil exchangeable base contents.

Dynamics of selected soil properties under four land uses in Arsamma watershed, Southwestern Ethiopian Highlands

Land-use change from natural ecosystem to agriculture is a critical environmental challenge in the highlands of Ethiopia. This study was designed to assess dynamics of selected physico-chemical soil properties under four land-use types. Forty-two soil samples were collected from the top 20 cm depth of forestland, multistory canopy coffee farm, coffee monoculture, and annual cropland. Two-way ANOVA and Tukey’s post hoc test were used to analyze the data. Forest soil contained significantly (p < 0.05) higher silt, organic matter, total nitrogen, exchangeable calcium, and exchangeable magnesium content than annual cropland. The pH value in annual cropland was significantly (p < 0.01) lower than in forestland. Decreasing patterns of organic matter, total nitrogen, exchangeable base contents, and cation exchange capacity were observed, sequentially, in soils of forest, multistory canopy coffee, coffee monoculture, and annual crops. The soils were strongly acidic regardless of land uses. Application of integrated soil fertility management to annual cropland, scaling up of multistory canopy coffee farm, and application of organic fertilizers to coffee soil could alleviate the problem of soil fertility deterioration resulting from land-use change from natural ecosystem to agricultural land use.

Physical and Chemical Properties of Cultivated Peat Soils in Four Trial Sites of ICCTF in Kalimantan and Sumatra, Indonesia

The large distribution of peat soils in Indonesia have important role in carbon stock and greenhouse gas emission which contribute to global warming issue. The objective of this study was to characterize physical and chemical properties of cultivated peat soils in four trial sites of Indonesia Climate Change Trust Fund (ICCTF) in Central Kalimantan, South Kalimantan, Riau and Jambi Provinces to provide a baseline data by a greenhouse gas emission study. Detailed soil observations were conducted using grid system with spacing of 25 × 50 m. A total of 16 representative peat soil profiles consisting of 74 soil samples of horizons were selected for laboratory analyses. The results showed that peat maturity varied from hemic to sapric in the surface layers and hemic in the subsurface layers, except in Site-2 that was fibric. The peat thickness ranged respectively from 5.4 to 7.0 m in Site-1 and Site-3, and from 0.5 to 2.5 m in site-2 and site-4, and all overlying fine-textured mineral soil (substratum). Depth of water table varied from 10 to 30 cm in Site-2 and Site-4, and from 30 to 70 cm in Site-1 and Site-3. Fiber content ranged from 13 to 57% and increased with depth indicating the peat was less decomposed. The bulk density was very low (0.07-0.24 g cm-3) and negatively correlated to fiber content (r = 0.74 for Kalimantan and r = 0.66 for Sumatra). The ash content was low (0.1-8.5%) and negatively correlated to organic carbon content (r = 0.89 for Kalimantan and r = 0.65 for Sumatra). Soil CEC was high and positively correlated to organic carbon content (r = 0.86 for Kalimantan and r = 0.93 for Sumatra). These soils showed very acid reaction (pH 3.3-4.7), low content of exchangeable bases and total P2O5 and K2O (HCl 25%). Based on these properties, the peat soils were grouped as oligotrophic ombrogenous peat. The estimated carbon stock for all the trial sites with total extent of 22.58 ha was 57,282 Mg C. The variation of thickness, maturity, and water table depth will imply to the magnitude of carbon reserves and greenhouse gas emissions. [How to Cite: Hikmatullah and Sukarman. 2014. Physical and Chemical Properties of Cultivated Peat Soils in Four Trial Sites of ICCTF in Kalimantan and Sumatra, Indonesia. J Trop Soils 19: 131-141. Doi: 10.5400/jts.2014.19.3.131]

Soil acidity status in the vicinity of the Severonikel copper-nickel industrial complex, Kola Peninsula

The physicochemical properties of soils exposed to emissions from the Severonikel industrial complex (one of the largest sources of SO2 and heavy metals in northern Europe) for 70 years were studied. The results showed that even after the long-term impact of heavy SO2 emissions, the \(pH_{H_2 O}\), the content of exchangeable bases, and the base saturation remained at the medium and high levels inherent to undisturbed soils of the region studied. An exclusion was the illuvial horizon of the podzols, where a relative reduction of the \(pH_{H_2 O}\) (at the level of low values of the natural variation) was revealed. At the same time, the hydrolytic acidity and cation exchange capacity in most samples of podzols, peat eutrophic, and mountain soils in the zone exposed to emissions (local zone) were also reduced. This fact is explained by indirect effects of the emissions: the gradual decrease in the organic matter content in the soils due to the destruction of the vegetation, the absence of fresh plant falloff, the development of erosion, and the disturbance of the hydrological regime of the soils and landscapes.

Soil Fertility under Improved and Conventional Management Practices in Sanga, Kavrepalanchowk District, Nepal

A study was carried out to compare the fertility of soils under improved soil management practice with that of prevailing conventional practice and to assess the farmers’ perception on the improved practice in the upland farming system. The study was carried out in Nasikasthan Sanga of Kavrepalanchok district of Nepal. Soil samples were collected from fields under improved conventional practice. Samples were taken at 0-15 and 15-30 cm depths and were analyzed for various physico-chemical properties to compare the fertility status of the soils under both the practices. Altogether 68 farmers were interviewed to have information on farming practices and information pertinent to improved soil management practice being adopted by them. Results from soil physico-chemical analysis showed higher fertility of soils under improved practice in terms of more favorable pH level, contents of exchangeable bases, available phosphorus and soil organic matter compared to prevailing conventional soil management practice. Moreover, majority of the farmers believed that soil fertility and physical condition of their upland soils had improved and that the productivity of major upland crops had also increased after the adoption of improved soil management practice. Improved practice could play an important role in the sustainable management of upland soils in the mid hills of Nepal. It is however, desirable to conduct long-term research to further ascertain the effect of the practice on soil fertility of different soil types and land uses.Nepal Agric. Res. J. Vol. 9, 2009, pp. 27-39DOI: http://dx.doi.org/10.3126/narj.v9i0.11639

English

With slash-and-burn agriculture, changes in soil properties occur, which could influence crop production and future soil fertility recommendations. The objectives of this study were to: Identify dynamic soil properties that could be used to monitor soil quality; evaluate residual effects of slash-and-burn; and establish P and K fertilizer equivalence values of ash from slash-and-burn. Each experimental site was divided into 3 blocks within which treatments were randomly allocated. Broadcast burning and pile burning were carried out as practiced by local farmers. Soil samples were collected before burning (control), immediately after burning (burned) and one year after burning and cropping (burned-cropped), hereafter referred to as treatments. Soil samples were analyzed following standard analytical methods. P and K fertilizer equivalence values of the soil tests immediately before burning and after one year cropping of burned land were established and compared. The most sensitive soil properties to slash-and-burn were coarse silt, fine silt, pH, organic carbon (OC), total N (totN), P, Ca, Mg, K, Na, exchange acidity, effective cation exchange capacity (ECEC) and base saturation (BS). Between 47 and 87% of increases in content of exchangeable bases and available P resulting from burning of forest vegetation cover is lost after one year of cropping positive. Benefits in soil P and K attributed to slash and burn agriculture after one year cropping in terms of fertilizer equivalence was between 1 to 18 kg P2O5&nbsp;and 22 to 76 K2O. P and K fertilizer recommendations for targeted crop yields based on the initial soil fertility status of the secondary forest in the humid forest zone of Cameroon should be 9 kg P2O5&nbsp;and 49 kg K2O less in the second year of cropping. &nbsp; Key words: Slash-and-burn, soil properties, humid forest zone, shifting cultivation, Southern-Cameroon.

Soil acid and exchange properties of red soil in hilly regions under different cropping patterns

Soil acid and exchange properties of red soil in hilly regions under continuous cropping of citrus,camellia and watermelon,under intercropping of citrus with camellia,grass,peanut or sweet potato,under intercropping of camellia with watermelon and under wasteland pattern in Yongzhou and Liuyang,Hunan Province were studied through field sampling and laboratory analysis.The results showed that soils under different cropping patterns were acidified seriously with pH value around 4.0 and showed low to middle fertility-preserving capacity with CEC being 8.7?10.96 cmol/kg,and soil with camellia intercropping showed comparatively stronger fertility-preserving capacity.Exchangeable acid and exchangeable Al3+ were both the lowest in citrus intercropping soil,thus the potential acid was the lowest;exchangeable base content and base saturation were both the highest in citrus intercropping soil,thus the fertility,fertility-preserving capacity and buffering capacity was the strongest.Exchangeable acid in the tested soils mainly existed in the form of exchangeable Al3+,accounting for 92.5%?95.1%,and the exchangeable base mainly existed in the form of exchangeable Ca2+ and Mg2+,accounting for 82.7%?91.8%.The difference of CEC content among soils under various cropping patterns was very significant,while there was no significant difference in soil pH,exchangeable acid,exchangeable Al3+,exchangeable K+,Na+,Ca2+ and Mg2+ contents under various cropping patterns.

No-till and cover crops shift soil microbial abundance and diversity in Laos tropical grasslands

Abstract Agricultural practices affect the physical and chemical characteristics of the soil, which in turn may influence soil microorganisms with consequences on soil biological functioning. However, there is little knowledge on the interactions between agricultural management, soil physicochemical properties, and soil microbial communities, notably in tropical ecosystems with few studies conducted in strongly weathered and acid soils. Here, we investigated the early effect of tillage and crop residues management on top soil physical, chemical, and microbial properties in an acid savannah grassland of northeastern Laos. We initiated a 3-year rotation of rice/corn/soybean under three no-till systems (NTs) distinguished by the cover crops associated prior to and with the main crops, and one conventional tillage-based system (CT). The effect of agricultural management was evaluated 2 years after land reclamation in reference to the surrounding natural pasture (PAS). Our results demonstrate that NTs improve soil physicochemical characteristics (aggregate stability, organic carbon, and cation exchange capacity) as well as microbial abundance (total biomass, bacterial and fungal densities). A significant discrimination of the genetic structure of soil bacterial community was also observed between NTs, CT, and PAS. Interestingly, bacterial abundance and diversity were differently influenced by soil environment changes: microbial density was affected by the quantity and diversity of crop residues, soil organic carbon, and exchangeable base contents, whereas soil bacterial genetic structure was mainly determined by exchangeable aluminum content, pH, cation exchange capacity, and C/N ratio. Altogether, our study represents one of the most complete environmental evaluations of agricultural practices in tropical agrosystems and leads to recommend no-till systems with high residue restitutions to improve the physical, chemical, and microbial properties of tropical acid soils and thus contribute to the sustainability of agriculture in these ecosystems.