Variation In Soil pH Research Articles

Soil pH influences the organic acid metabolism and exudation in cluster roots of Protea species from the Mediterranean-type fynbos ecosystem, Western Cape, South Africa

In nutrient-poor ecosystems, certain plant families have evolved specific adaptations for phosphate acquisition, namely cluster roots or proteoid roots. Cluster rooted species have a unique suite of adaptations that enable them to survive in nutrient poor ecosystems, such as the Fynbos biome of South Africa. The Fynbos biome has heterogeneous soils which caused radiation of varying soil pH within small localised areas. Previous studies on cluster rooted species ignored the possibility that cluster root functioning may differ at varying soil pH levels and soil types. Therefore, two native Fynbos protea species, Protea cynaroides (L.) L. and Protea obtusifolia H.Buek ex Meisn. were compared to assess the impact of different soil pH levels on organic acid metabolism and exudation in cluster rooted species. Our results show that cluster roots of the acidic-soil grown P. cynaroides is more effective and more efficient than that of the alkaline-soil grown P. obtusifolia. Our findings indicated that the mechanisms for P acquisition vary greatly, depending on substrate and plant organ type. This suggested that the metabolism of each species is adapted to specific soil pH and that these species have evolutionary adapted their P acquisition mechanisms for these extreme soils. The limited nutrient availability and variation in soil pH South African soils has led to various localised adaptations for cluster rooted species.

Response of spatiotemporal variability in soil pH and associated influencing factors to land use change in a red soil hilly region in southern China

Abnormal changes in soil acidity and alkalinity impact regional food security and sustainable development of terrestrial ecosystems, especially under land use change. The regulation of soil acidity and alkalinity requires a clear understanding of soil pH variability and its influencing factors under regional land use change. This study explored the patterns of soil pH variability under land use change between 1984 and 2018 in a red soil hilly region (Xunwu County, Jiangxi Province) in southern China. We identified the key factors influencing regional spatiotemporal variability in soil pH and analyzed the response of soil pH variability to land use change. The results showed that the mean pH values of surface soil samples in 1984 (n = 595) and 2018 (n = 580) were 5.35 and 5.05, respectively. The soil pH change between the two periods ranged from −0.91 to 0.32, with a mean value of −0.30. In total, 91.72% of the study area showed an acidification trend from 1984 to 2018. The spatiotemporal variability in soil pH was influenced by elevation, slope, distance to rivers, changes in distance to roads, and changes in the nitrogen fertilizer application rate. The main land use conversion modes were cropland and forest transferred to garden and other land. The soil pH decreased in 15 of 16 conversion modes of cropland land, garden, forest, and other land, whereas a pH increase of 0.32 occurred under conversion from cropland to garden. Changes in distance to roads, changes in the nitrogen fertilizer application rate, and slope played a dominant role in soil pH variability under land use change. This study provides fundamental data for the formulation of soil acidity and alkalinity control measures, which in turn contributes to regional improvement of agricultural production stability and sustainable development.

Comparative Study of Abiotic Stress Factors on GC-MS-Detected Phytoconstituents of Aloe greatheadii var: davyana Using Heat Map and Hierarchical Clustering Dendrogram.

Aloe greatheadii var. davyana or spotted aloe is indigenous to South Africa and widely distributed in the northern provinces. The plant has a vast ethnopharmacological application which is mostly attributed to its phytochemical content. The aim of the study was to examine the effect of abiotic stress factors on the plant's phytochemical content. The phytochemical content of A. greatheadii hexane extracts from four different provinces (Limpopo, Mpumalanga, Gauteng, and North West), harvested from the wild at varied altitudes, rainfall patterns, and soil types, was examined using gas chromatography-mass spectra (GC-MS). The phytochemical content of hexane extracts from the four South African provinces was analysed using heat map analysis and hierarchical clustering dendrogram. The phytochemical content of A. greatheadii hexane extracts was composed of fatty acids, alkanes, benzene, carboxylic acids, ketones, phytosterols, and vitamins. Eicosane, henicosane, and [(2S)-2-[(2R)-4-hexadecanoyloxy-3-hydroxy-5-oxo-2H-furan-2-yl]-2-hydroxyethyl] hexadecanoate were the only compounds detected in all samples from the four provinces. The concentration levels of 2-(((2-ethylhexyl)oxy)carbonyl) benzoic acid, beta-sitosterol, tritetracontane, and ethyl 13-methyltetradecanoate were closely related and expressed a low clustering distance amongst the samples. Variations in soil pH, soil type, and rainfall patterns were detected and differed in the four provinces. The different abiotic stress factors affected the biochemical pathways for the different compounds, with conditions in Gauteng being less favourable for many of the compounds detected. Abiotic stress factors have shown to influence phytochemical biochemical pathways and quantity. Aloe greatheadii plants can be selected based on location seemingly due to the variations that persist in their phytochemical content.

Rapid colorimetric methods for analysis of pH, extractable aluminium and Colwell phosphorus in soils

Context Analytical procedures and technologies for soil analyses can be prohibitively expensive for small laboratories and researchers in developing countries. There is a need for low cost and high-throughput methods for assaying pH, extractable aluminium and phosphorus when conducting field trials on acid soils. Aims We investigated methods to develop rapid yet inexpensive colorimetric assays for the assay of pH, extractable aluminium and Colwell phosphorus in soil extracts. Methods We developed a colorimetric method to measure soil pH enabling pH to be quantified in a high-throughput assay. Similarly, two existing methods for extractable aluminium and Colwell P were modified for high throughput assays also using microtiter plates. Key results All three methods yielded linear relationships when using absorbance to quantify the parameters with the high throughput methods. Furthermore, there was a strong correlation between pH values of the soil samples obtained with the colorimetric assay and pH values measured with a glass electrode. Conclusions We demonstrated that the rapid assays for all three methods can be implemented to characterise field sites through the mapping of distributions for extractable Al, Colwell P and pH. Implications The high-throughput methods described here will be useful for researchers who conduct field trials to map variations in soil pH, soluble Al and Colwell P. Although the focus of the current work was on acid soils, the colorimetric pH and Colwell P methods can also be applied to non-acid soils.

华西雨屏区植被恢复对紫色土酸化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 华西雨屏区植被恢复对紫色土酸化的影响 DOI: 10.5846/stxb202102220488 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 内江师范学院科研启动费项目（18B10）；四川省教育厅重点项目（17ZA0223） Effect of vegetation restoration on Purple soil acidification in rainy area of Western China Author: Affiliation: Fund Project: Neijiang Normal University Research Start-Up Funds;Key Projects of the Education Department of Sichuan Province 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:退耕还林是控制水土流失、恢复森林植被和改善生态环境的重要举措。植被恢复进程中会发生土壤酸化，进而影响植物生长，厘清不同还林树种对土壤酸化的影响程度及作用机制有助于更好地评估退耕还林工程的整体生态效益。以华西雨屏区紫色土坡耕地（玉米）为对照，分析了退耕20a后柳杉纯林、柳杉-光皮桦混交林、慈竹林和茶园土壤pH的变化及其垂直分异。结果表明：玉米地、慈竹林、茶园、混交林和柳杉纯林0-50 cm土壤pH平均值分别为5.66、5.55、5.12、5.03和5.00，相较于玉米地，柳杉纯林、混交林和茶园土壤pH值显著下降（P<0.01），土壤酸化严重。相较于玉米地土壤pH值的均匀分布，植被恢复不同类型人工林pH值随土壤深度的增加而增加，10-50 cm土壤pH值（4.89-5.90）显著高于0-10 cm土壤pH值（4.72-5.21）（P<0.01），表层土壤酸化最明显。土壤pH值与土壤有机质含量呈极显著负相关，而与风化指数Na/K比值呈显著正相关，有机质含量和Na/K比值共同解释了土壤pH值变化的53.9%，表明植被恢复引起的土壤有机质积累与长石类矿物风化是驱动紫色土酸化的重要过程。通过对紫色土人工林酸化特征及其过程的揭示，可为华西雨屏区森林生态系统恢复及其管理提供科学依据。 Abstract:The Chinese Grain for Green Project is crucial for controlling water and soil erosion, rehabilitation forest vegetation, and improvement of the environment. Soil acidification could be induced during the vegetation restoration, which has a negative impact on plant growth. It is important to clarify the degrees and mechanisms of the influences of reforestation species on soil acidification in order to achieve a better ecological benefit of the Grain for Green Project. In this study, we used the Purple soil of sloping farmland (planted Zea mays) as control group (SF) in rainy area of western China, and analyzed the changes and profile distribution of soil pH value after a 20-year farmland to artificial forestland with plant species of Cryptomeria fortune (CF), Cryptomeria fortune & Betula luminifera (MF), Neosinocalamus affinis (NA) and Camellia sinensis (CS). Results showed that the weighted average value of soil pH in the top 50 cm was 5.66 for SF, 5.55 for NA, 5.12 for CS, 5.03 for MF, and 5.00 for CF. Soil pH value of CF, MF and CS decreased significantly compared with SF (P<0.01), and these soils exhibited severe acidification. In addition, vegetation restoration increased the degree of vertical variations of soil pH for SF that showed a uniform profile distribution. By contrast, soil pH for artificial forests exhibited greater profile differentiations. Soil pH values (4.89-5.90) of the 10-50 cm layer for different artificial forests were significantly higher (P<0.01) than those (4.72-5.21) of the 0-10 cm layer suggesting that soil acidification was most intense for the top 10 cm. There were significantly negative correlations between soil pH value and soil organic matter content, while significantly positive correlation between soil pH value and Na/K ratio of weathering index was observed. 53.9% of the variation for soil pH was explained by soil organic matter content and Na/K ratio, indicating that the acidification of Purple soil in this area were driven by the accumulation of soil organic matter during the process of returning farmland to forests and sorts of feldspar weathering. By revealing the acidification characteristics and its processes for Purple soil, this study provides a scientific basis for future vegetation restoration and ecosystem management in rainy area of western China. 参考文献 相似文献 引证文献

Spatial prediction of soil organic matter in Adingnigon (Benin) using Bayesian Maximum Entropy (BME)

Demographic pressure and climate change have heavily affected soil fertility. Proper soil management requires the understanding of the spatial variation of soil properties. In this study, Bayesian maximum Entropy (BME) was used to explore the variation of soil pH and soil organic matter (SOM) at Adingningon (Benin) using 106 soil samples. The predicting maps indicated a lower concentration (0.6 to 0.8g/kg) of SOM toward the center and pH mostly around 5.8 to 6.5 with lower error variance, suggesting an acidic soil. This results provide useful information for managing soil fertility to improve crop yields.\\

Inventory and assessment of pH in cropland and grassland soils in Germany#

AbstractBackgroundSoil pH is one of the key factors affecting soil fertility. For optimal plant growth on agricultural land, suitable liming management is recommended. The basis of appropriate soil pH management in agriculture is provided by recommendations on site‐specific optimum pH ranges and lime application.AimsThis study determined the current variability of soil pH of cropland and grassland in Germany, analysed the factors associated with this variability, evaluated pH management on German agricultural land and developed a national map of current pH values in agricultural soils.MethodsThe study mainly focused on the topsoil layers of 2197 cropland sites (0–30 cm) and 812 permanent grasslands sites (0–10 cm) in the German Agricultural Soil Inventory, but reports soil pH (CaCl2) down to 50 cm. Random forest models were applied to identify environmental and management factors related to soil pH and develop a map of pH values in agricultural topsoils in Germany. The current pH status of the sampled sites was classified in accordance with German lime requirement recommendations.ResultsThe soil pH of both land‐use types showed a bimodal distribution, with peaks at pH 6.1 and 7.3 for cropland and pH 5.0 and 7.1 for grassland. Soils with pH &lt;5 were mainly found on sandy soils in northern Germany and acidic parent material in southern Germany. Alkaline soils predominated in central and southern Germany on loess and carbonate‐rich material. The carbonate content was the major factor explaining soil pH variability, but its effect was restricted to pH values &gt;6. Only 35.4% of the cropland sites and 23.9% of the grassland sites were within the recommended optimum pH range. The percentage of sites below the recommended pH range was greater for grassland than for cropland (52.0% and 41.0%, respectively).ConclusionsSoil pH of German agricultural land is influenced by natural factors and pH management. The first national inventory of soil pH showed that many agricultural soils exhibited pH values lower than those recommended. More conscientious pH management could help improve soil fertility and crop yield. This should be based on the regular topsoil pH analysis conducted by most farmers every five years, together with the determination of plant‐available potassium and phosphorus in soils.

Soil organic matter and clay zeta potential influence aggregation of a clayey red soil (Ultisol) under long-term fertilization

The effect of soil organic matter (SOM) on aggregation of variably-charged red soils (Ultisol) through clay zeta potential is not fully understood. Therefore, the objectives of this study were to investigate the SOM effect on the clay zeta potential and soil aggregation after fertilization. Soils under 17 years of fertilization (manure, NPK + straw, NPK, and control (CK) were adjusted by KCl solution to reach varying soil pH and concentration in order to determine clay zeta potential, cations, and aggregate size distribution. The SOM content and C-functional groups by 13C-NMR analysis were also determined. Results showed that the negative zeta potential displayed a bell-shaped pattern with increasing concentration of KCl, but displayed different amplitude of variation among treatments. Manure had the highest zeta potential value and its degree of variation in relative to the value at KCl concentration of 0.1 mol L−1 (19%), NPK + straw and NPK treatments were similar, and CK was the least. Greater negative zeta potential for manure treatment was attributed to higher SOM content, aromatic-C functional groups, and their greater concentrations of Ca2+ and Mg2+ than did the CK. As a result, higher SOM and clay zeta potential yielded in less release of amount of soil particles (< 10 μm) (r = − 0.46*) and enhanced water stable macroaggregates for manure instead of NPK + straw. Long-term manure fertilization would be suggested as a conservation practice for red soil due to its increase in soil aggregate stability and negative zeta potential in subtropical climate.

Divergent Patterns and Spatial Heterogeneity of Soil Nutrients in a Complex and Dynamic Savanna Landscape

AbstractMany grassy ecosystems around the world are experiencing woody encroachment. These woody encroachers often cause nutrient enrichment in the plant‐soil environment, potentially facilitating their growth and reproduction. However, studies of encroachment effects on nutrient distributions have been confined to a few major elements (e.g.,N, and P) and limited in spatial extent. We analyzed 19 elements in dominant plants and in georeferenced soils across a subtropical savanna landscape experiencing woody encroachment to quantify their spatial patterns and elucidate drivers responsible for these patterns. We found divergent patterns of spatial heterogeneity of these elements in surface soils across this complex landscape. Nutrient accumulation and redistribution underneath woody canopies occurred in a subset of elements (i.e., N, P, S, Ca, Cu, and Sr). Though some of these elements are not necessarily growth‐limiting, they do occur in higher concentrations in woody compared to herbaceous plants. Distributions of the other elements were closely related to spatial variation in soil pH, clay content, and slope rather than to woody encroachment. Our nuanced spatial sampling approach and analysis reveal significant variation in nutrient distributions in response to woody encroachment, and illustrate the role of landscape patterns in mediating ecosystem processes. These changes in the concentrations and distributions of key essential nutrients broaden our understanding of the biogeochemical consequences of woody encroachment, and provide new insights regarding the significance of long‐term vegetation dynamics in dryland ecosystems.

Impact Of Seawater Intrusion Bund On Soil & Water Conservation Along The Coastal Line Of Poonakary, Sri Lanka

Abstract Saltwater intrusion into coastal aquifers is reported at coastal region of Poonakary, Kilinochchi district. A sea water intrusion bund was constructed by United Nations Development Programme in 2015 to reduce the issues with seawater intrusion. This study aimed to measure the variations of soil salinity and pH before (2015), just after (2016) and three years after (2018) the construction of bund and to identify the impacts of seawater intrusion bund on soil, water quality and crop improvement in the area. The study was conducted in three selected Grama Niladari Divisions of Poonakary, during July to September period in 2018. Soil samples were collected from 30 locations at different sampling depths and the locations were recorded by using GPS and fifteen water samples were collected to measure the water quality parameters and the values compared with WHO standards. A questionnaire survey was conducted to assess the crop improvement in the selected locations. When comparing the soil pH in 2016 and 2018, at all depths except 60cm, changes were highly significant and at 60 cm, it was significant. The Soil EC during 2016 and 2018 revealed that, at 15cm, 30cm and 60cm the changes were significantly different and at 45cm it was not significantly differ due to hardpan formation. A considerable improvement in the water quality and yield improvement of paddy were observed. The study reveals that, the seawater intrusion bund can be considered as a potential permanent solution for seawater intrusion at Poonakary.

The Susceptibility of Pea (Pisum sativum L.) to Simulated Mesotrione Residues as Affected by Soil pH Manipulation

Variations in soil pH have been shown to affect mesotrione adsorption, which in turn, may have an impact on crop susceptibility. Therefore, a greenhouse experiment was conducted to evaluate the effect of simulated mesotrione residues on pea crop grown in the typical agricultural soil (gleysol) of north-western Croatia. The soil pH was manipulated to obtain neutral (pH 7.0) and acidic (pH 5.0) values. Simulated mesotrione residues were 1.1, 2.3, 4.5, 9.0, 18, 36 and 72 g a.i. ha−1. Crop visual injuries as well as reductions in chlorophyll fluorescence and aboveground dry biomass were higher at pH 7.0 than at pH 5.0. With increasing mesotrione residues, the reductions in chlorophyll fluorescence ranged from 38.8% to 89.7% at pH 5.0 and from 63.7% to 99.3% at pH 7.0. Compared to chlorophyll fluorescence, the reductions in dry biomass were smaller and ranged from 49.2% to 96.8% at pH 7.0 and from 32.0% to 82.6% at pH 5.0 for the mesotrione residues from 1.1 to 72 g a.i. ha−1. These results indicate that soil pH is an important factor determining the susceptibility of pea crop to simulated mesotrione residues.

A meta-analysis of soil microbial and physicochemical properties following native forest conversion

The conversion of natural forest to artificial vegetation may deplete nutrients and thus affect the soil quality. However, little is known about synergetic changes of microbial and physicochemical dynamics in soils after natural forest conversion and their implications. In the current study, we synthesized the responses of soil microbial and physicochemical properties in the uppermost soil layer (<20 cm) following natural forest conversion, as reported in 51 published studies (127 sites). Our results showed that the response ratios of soil moisture, soil microbial carbon and nitrogen, bacteria, fungi, enzymatic activities, soil organic carbon, total carbon, total nitrogen, NO3–, total phosphorus, available phosphorus, cations (K+, Mg2+ and Ca2+), and cation exchange capacity (CEC) overall declined following natural forest replacement. In contrast, natural forest conversion caused significant increases in soil bulk density, soil pH and NH4+. Reductions of microbial carbon, organic carbon and total nitrogen in soil were independent of revegetation type, but variations in soil pH, available phosphorus and fungi were correlated to land use. Soil CEC reduction increased soil pH, allowing soils to retain NH4+, which promoted fungal growth. Moreover, natural forest replacement led to the loss of soil cations in regions of higher precipitation. Revegetation practices led to greater consumption of soil microbial and chemical nutrients and produced “harder” soils (increased soil compaction and decreased moisture content) in warmer regions. Stand age influenced ratios of soil carbon to nitrogen and ratios of bacteria to fungi following natural forest conversion. Altogether, our study suggests that natural forest conversion results in decreased soil microbial and chemical fertility, and desirable soil properties are more likely to be lost in warmer regions and over time as global climate warming exacerbates, which in turn may potentially damage ecosystem sustainability.

Performance of linear mixed models and random forests for spatial prediction of soil pH

Digital soil maps describe the spatial variation of soil and provide important information on spatial variation of soil properties which provides policy makers with a synoptic view of the state of the soil. This paper presents a study to tackle the task of how to map the spatial variation of soil pH across Zambia. This was part of a project to assess suitability for rice production across the country. Legacy data on the target variable were available along with additional exhaustive environmental covariates as potential predictor variables. We had the option of undertaking spatial prediction by geostatistical or machine learning methods. We set out to compare the approaches from the selection of predictor variables through to model validation, and to test the predictors on a set of validation observations. We also addressed the problem of how to robustly validate models from legacy data when these have, as is often the case, a strongly clustered spatial distribution. The validation statistics results showed that the empirical best linear unbiased predictor (EBLUP) with the only fixed effect a constant mean (ordinary kriging) performed better than the other methods. Random forests had the largest model-based estimates of the expected squared errors. We also noticed that the random forest algorithm was prone to select as “important” spatially correlated random variables which we had simulated.

Effect of pH on metal mobility in the soil

pH is a parameter that can be used to estimate the mobility of chemical elements in the soil and can be used to measure the level of toxicity and soil pollution. The purpose of this study is to prove how far the influence of pH on metal mobility in the soil. Method that used in this study, 35 samples each 1 kg were taken from the soil profile in Cilengsi Bogor and then dried at room temperature. From each sample 20 grams were taken for pH and Eh measurements. The result of this study that the analysis showed a significant correlation between pH and Eh with r = 0.888. Although the samples are heterogeneous or come from different soils, there is still a positive correlation between metal concentration and pH (pH-Mn = 0.12; pH-Cd = 0.0058; pH-Pb = 0.39). This means that for homogeneous samples, the correlation between pH-metals will be more significant. Eh and soil pH variations depends on the activity and decomposition of carbon by plants and microorganisms. Therefore, it can be ideally be concluded that the topsoil Eh is higher than the bottom Eh. The aerobic-anaerobic boundary is at around 300 mV.

Global patterns and drivers of alpine plant species richness

AbstractAimAlpine ecosystems differ in area, macroenvironment and biogeographical history across the Earth, but the relationship between these factors and plant species richness is still unexplored. Here, we assess the global patterns of plant species richness in alpine ecosystems and their association with environmental, geographical and historical factors at regional and community scales.LocationGlobal.Time periodData collected between 1923 and 2019.Major taxa studiedVascular plants.MethodsWe used a dataset representative of global alpine vegetation, consisting of 8,928 plots sampled within 26 ecoregions and six biogeographical realms, to estimate regional richness using sample‐based rarefaction and extrapolation. Then, we evaluated latitudinal patterns of regional and community richness with generalized additive models. Using environmental, geographical and historical predictors from global raster layers, we modelled regional and community richness in a mixed‐effect modelling framework.ResultsThe latitudinal pattern of regional richness peaked around the equator and at mid‐latitudes, in response to current and past alpine area, isolation and the variation in soil pH among regions. At the community level, species richness peaked at mid‐latitudes of the Northern Hemisphere, despite a considerable within‐region variation. Community richness was related to macroclimate and historical predictors, with strong effects of other spatially structured factors.Main conclusionsIn contrast to the well‐known latitudinal diversity gradient, the alpine plant species richness of some temperate regions in Eurasia was comparable to that of hyperdiverse tropical ecosystems, such as the páramo. The species richness of these putative hotspot regions is explained mainly by the extent of alpine area and their glacial history, whereas community richness depends on local environmental factors. Our results highlight hotspots of species richness at mid‐latitudes, indicating that the diversity of alpine plants is linked to regional idiosyncrasies and to the historical prevalence of alpine ecosystems, rather than current macroclimatic gradients.

Decoupling of soil nitrogen and phosphorus dynamics along a temperature gradient on the Qinghai-Tibetan Plateau

Responses of soil nitrogen (N) and phosphorus (P) dynamics to global warming have received much attention. However, there are a lot of uncertainties. Given that a large-scale field investigation along a temperature gradient can provide deep insight into the long-term effect of climate warming, we conducted a soil sampling along a temperature gradient across a 1500-km transect on the Qinghai-Tibetan Plateau. To minimize the interference of the collinearity between temperature and precipitation on the temperature patterns of soil N and P dynamics, the sampling was performed along the 400 mm isohyet. We wanted to clarify the alterations of soil N and P dynamics in response to increasing temperature when the precipitation effect was minimized. Soil N content and N storage decreased, whereas soil P content and P stocks were stable with increasing temperature, leading to a decreased soil N:P ratio along the temperature gradient. This means that soil N and P dynamics are decoupled under the condition of increasing temperature. Soil N dynamics were associated with the variations in soil organic matter content, silt content, pH and vegetation type, and the effect of temperature on soil N dynamics was mainly through the influence of temperature on soil organic matter content. Soil P dynamics were related to the changes of soil silt content, precipitation, vegetation and soil type. Our results suggest that global warming may negatively affect soil N dynamics, but have no or only a small effect on soil P dynamics, and at the same time may cause the ecosystem to change from P limited to N limited.

Contrasting effects of microbial fertiliser and organic fertiliser on soil bacterial community in coal mine dump of Inner Mongolia

ABSTRACT Knowledge about fertiliser limitation to soil microbes is crucial for exploring microbial community succession and ecosystem functions. In this study, an experiment was conducted to promote ecological restoration by different treatments of organic fertiliser (OF), microbial fertiliser (MF) and non-fertiliser (CK) in a coal mine dump. We investigated microbial community structure using high-throughput sequencing. Soils under OF and MF treatment showed distinct community structures with highly bacterial α-diversity due to the variation of soil pH and organic matters (SOM). Of those, the community dissimilarity between OF and CK was higher. The DistLM analysis indicated that SOM and available nitrogen (AN) significantly influenced microbial community structure. Furthermore, functional annotation by the FAPROTAX revealed that the functional groups associating with C, N, and S cycling increased significantly under OF and MF treatment, but decreased that associated with parasites or symbionts. Compared with MF, the functional groups with OF treatment varied greatly. However, the function groups including nitrogen_fixation, hydrocarbon_degradation and methanotrophy were significantly improved under the MF treatment, which have an important implication for soil quality and microbial growth. It was concluded that MF treatment could improve microbial community structure and enhance potential ecosystem function in coal mine dump soils.

Antarctic Water Tracks: Microbial Community Responses to Variation in Soil Moisture, pH, and Salinity

Ice-free soils in the McMurdo Dry Valleys select for taxa able to cope with challenging environmental conditions, including extreme chemical water activity gradients, freeze-thaw cycling, desiccation, and solar radiation regimes. The low biotic complexity of Dry Valley soils makes them well suited to investigate environmental and spatial influences on bacterial community structure. Water tracks are annually wetted habitats in the cold-arid soils of Antarctica that form briefly each summer with moisture sourced from snow melt, ground ice thaw, and atmospheric deposition via deliquescence and vapor flow into brines. Compared to neighboring arid soils, water tracks are highly saline and relatively moist habitats. They represent a considerable area (∼5–10 km2) of the Dry Valley terrestrial ecosystem, an area that is expected to increase with ongoing climate change. The goal of this study was to determine how variation in the environmental conditions of water tracks influences the composition and diversity of microbial communities. We found significant differences in microbial community composition between on- and off-water track samples, and across two distinct locations. Of the tested environmental variables, soil salinity was the best predictor of community composition, with members of the Bacteroidetes phylum being relatively more abundant at higher salinities and the Actinobacteria phylum showing the opposite pattern. There was also a significant, inverse relationship between salinity and bacterial diversity. Our results suggest water track formation significantly alters dry soil microbial communities, likely influencing subsequent ecosystem functioning. We highlight how Dry Valley water tracks could be a useful model system for understanding the potential habitability of transiently wetted environments found on the surface of Mars.

Temporal Variations of Soil Organic Carbon and pH at Landscape Scale and the Implications for Cropping Intensity in Rice-Based Cropping Systems

Landscape scale assessment of temporal variations in soil organic carbon (SOC) contents and soil pH and the implications for long-term agricultural sustainability was determined using legacy datasets collected over two periods separated by 20 years: the 1990s and 2010s. Soil data on SOC and pH were categorized according to the prevailing land types (based on inundation as highland (HL), medium highland (MHL), and medium lowland (MLL)), and physiographic types (i.e., Himalayan Piedmont plain, Tista Floodplain and Barind tract/Terrace) to determine which variable or combination of variables was more influential in spatial and temporal changes of these properties. SOC contents in the physiographic types were generally found to be low, varying between 8 to 12 g/kg. While, SOC contents were significantly higher in MHL and MLL compared with HL that experienced less inundation. The change in SOC contents over 20 years was significant with a 14.5% increase of SOC. There was a greater influence of land type compared with physiography on SOC contents over time. Inundation land types and associated cropping intensity were considered likely to influence SOC of soils under rice-based cropping systems. Furthermore, the levels of soil pH decreased by 0.5 units over 20 years with an approximately 50% increase in soils within a pH category of 4.6–5.5. The majority of soil pH results shift from slightly acidic to strongly acidic in the intervening 20-year period between samplings. Soil acidification is potentially a combination of inefficient and excess use of ammonium-based fertilizers with higher application rates and low input from residues. We conclude that acidification may continue with more intensive land use. However, trends in SOC contents over time under certain combinations of physiography and land type either increased slightly or showed a significant loss and in the latter, specifically, the role of land management is not clear. The legacy datasets would be useful for monitoring spatial and temporal soil quality trends at a regional scale, but has limited capacity to capture field level variations in soil properties as data on smallholder cropping practice and management were not collected. Therefore, future research examining the role of management in SOC and pH dynamics at the field-scale would guide the use of fertilizers, crop residue management, and amelioration of acidic soil, to improve the sustainability of rice-based cropping systems in Bangladesh.

Impacts of Land Use Changes on Selected Soil Physical and Chemical Characteristics under Pineapple Cropping Systems in Matara District, the Low Country Wet Zone of Sri Lanka

The present paper investigated the impacts of land use change on physical and chemical characteristics of soil. A land, originally inhabited by native secondary forest, later converted to pineapple cultivation was selected for collection of representative soil samples from the 0-15 cm depth. A closely forest land was used as the reference. Soil texture, bulk density, aggregate stability, pH, total nitrogen, available soil P, exchangeable K and organic matter (OM) content were determined following standard methods. According to the results, significant variations in OM, soil pH, aggregate stability and available P were observed among forest and cultivated lands. The distribution of particle size revealed a decrease in larger particle size and an increase in smaller particle size following the conversion of natural forest to other land cover. Land use changes from forest to pineapple cultivation resulted in decreased aggregate stability, soil pH and organic matter content. The highest (17.3 mg kg-1) mean available P was recorded in the old pineapple land followed by forest land (15.0 mg kg-1) whilst the lowest in the new pineapple land (12.4 mg kg-1). However the values of bulk density, total nitrogen content and exchangeable K content of forest and cultivated lands were not significantly different (p ≤ 0.05). Based on the results, it can be concluded that regular monitoring of soil properties is essential to maintain soil health, enhance agricultural productivity and sustain agro-ecosystems.