Soil Sciences

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    Governing the soil: natural farming and bionationalism in India
    (Springer Nature, 2022-07-08) Fitzgerald, Ian Carlos; Millner, Naomi; Ginn, Franklin
    This article examines India’s response to the global soil health crisis. A longstanding centre of agricultural production and innovation, India has recently launched an ambitious soil health programme. The country’s Soil Health Card (SHC) Scheme intervenes in farm-scale decisions about efficient fertiliser use, envisioning farmers as managers and soil as a substrate for production. India is also home to one of the world’s largest alternative agriculture movements: natural farming. This puts farmer expertise at the centre of soil fertility and attends to the wider ecological health of soils. Despite emerging as a mode of resistance to dominant agricultural systems, natural farming is now being delivered in increasingly bureaucratic ways by India’s state governments. This article offers Himachal Pradesh as a case study in how the soil is governed, drawing on 38 semi-structured interviews with scientists, agricultural officers, non-governmental organisation leaders, and activists. Rather than assess approaches to soil health according to their ecological bottom line, we examine the differing forms of knowledge, expertise and ‘truth’ in the SHC and Natural Farming approaches. Our analysis reveals discontinuities in how farmers are imagined, as well as continuities in how quasi-spiritual language combines in a bionationalist project, positing assumptions about the correct arrangement of life in nationalist terms. We point to a shift toward hybrid and pick-and-mix approaches to soil health, as farmers and their organisers are increasingly invested with the capacities to combine multiple options. We see a fracturing of expertise and the opening up of epistemic pluralism in responses to the soil fertility crisis.
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    Means and ways of engaging, communicating and preserving local soil knowledge of smallholder farmers in Central Vietnam
    (Springer Nature, 2022-03-03) Huynh, Ha T. N.; Lobry de Bruyn, Lisa A.; Knox, Oliver G. G.; Hoang; Hoa T. T.
    Increasing interest in farmers’ local soil knowledge (LSK) and soil management practice as a way to promote sustainable agriculture and soil conservation needs a reliable means to connect to it. This study sought to examine if Visual Soil Assessment (VSA) and farmer workshops were suitable means to engage, communicate and preserve farmers’ LSK in two mountainous communes of Central Vietnam. Twenty-four farmers with reasonable or comprehensive LSK from previously studied communes were selected for the efficacy of VSA and farmer workshops for integrating LSK into a well-accepted soil assessment tool (VSA). In field sites chosen by the farmers, VSA was independently executed by both farmers and scientists at the same time. Close congruence of VSA scores between the two groups highlighted that farmers could competently undertake VSA. Farmers’ VSA score was compared with their perception of field’s soil quality. For the majority of farmers’ perception of soil quality was consistent to their VSA score (62.5%), while the remainder perceived their soil quality was lower than their VSA score. For most farmers their assessment of soil quality using VSA valued their LSK, and the two measures were well aligned. Soil colour and presence or vulnerability to erosion were common soil characteristics mentioned by farmers and affected the final VSA score. Farmers’ participation in VSA and workshops strengthen farmers’ confidence in their LSK and provided guidance on the impact of their soil management on soil improvement and conservation.
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    Microbial necromass carbon and nitrogen persistence are decoupled in agricultural grassland soils
    (Springer Nature, 2022-05-13) Buckeridge, Kate M.; Mason, Kelly E.; Ostle, Nick; McNamara, Niall P.; Grant, Helen K.; Whitaker, Jeanette
    Microbial necromass is an important component of soil organic matter, however its persistence and contribution to soil carbon sequestration are poorly quantified. Here, we investigate the interaction of necromass with soil minerals and compare its persistence to that of plant litter in grassland soils under low- and high-management intensity in northwest England. During a 1-year laboratory-based incubation, we find carbon mineralization rates are higher for plant leaf litter than root litter and necromass, but find no significant difference in carbon persistence after 1 year. During a field experiment, approximately two thirds of isotopically-labelled necromass carbon became mineral-associated within 3 days. Mineral-associated carbon declined more rapidly than nitrogen over 8 months, with the persistence of both enhanced under increased management intensity. We suggest that carbon mineralisation rates are decoupled from carbon persistence and that necromass carbon is less persistent than necromass nitrogen, with agricultural management intensity impacting carbon sequestration in grasslands.
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    Thresholds in aridity and soil carbon-to-nitrogen ratio govern the accumulation of soil microbial residues
    (Springer Nature, 2021-11-18) Hao, Zhiguo; Zhao, Yunfei; Wang, Xia; Wu, Jinhong; Jiang, Silong; Xiao, Jinjin; Wang, Kaichang; Zhou, Xiaohe; Liu, Huiying; Li, Jia; Sun, Yuxin
    Microbial moribunds after microbial biomass turnover (microbial residues) contribute to the formation and stabilization of soil carbon pools; however, the factors influencing their accumulation on a global scale remain unclear. Here, we synthesized data for 268 amino sugar concentrations (biomarkers of microbial residues) in grassland and forest ecosystems for meta-analysis. We found that soil organic carbon, soil carbon-to-nitrogen ratio, and aridity index were key factors that predicted microbial residual carbon accumulation. Threshold aridity index and soil carbon-to-nitrogen ratios were identified (~0.768 and ~9.583, respectively), above which microbial residues decreased sharply. The aridity index threshold was associated with the humid climate range. We suggest that the soil carbon-to-nitrogen ratio threshold may coincide with a sharp decrease in fungal abundance. Although dominant factors vary between ecosystem and climate zone, with soil organic carbon and aridity index being important throughout, our findings suggest that climate and soil environment may govern microbial residue accumulation.
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    Urban Soil Pollution by Heavy Metals: Effect of the Lockdown during the Period of COVID-19 on Pollutant Levels over a Five-Year Study
    (MDPI, 2023-03-20) Papadimou, Sotiria G.; Kantzou, Ourania-Despoina; Chartodiplomenou, Maria-Anna; Golia, Evangelia E.
    When residents of Volos, a city in central Greece, are trying to recall their daily life after the end of the quarantine due to COVID-19, the soil pollution survey provided valuable insights, which are compared with a 4-year study carried out in that area before the pandemic period. Using appropriate indices, namely contamination factor (CF), pollution load index (PLI), geo-accumulation index (Igeo), ecological risk factor (Er), and potential ecological risk index (RI), and using geostatistical tools, maps were constructed for each metal (Cu, Zn, Pb, Ni, Cd, Co, Cr, Mn). Variations in the values of the contamination indices showed a significant redistribution in pollutant load from areas previously polluted by high vehicle traffic and the activities of the main port to the residential areas, where the habitants have their homes and playgrounds. The study showed that Cu, Zn, Pb, and Co concentrations increased during the pandemic period by 10%, 22.7%, 3.7%, and 23.1%, respectively. Ni’s concentration remained almost constant, while Cd, Cr, and Mn concentrations were decreased by 21.6%, 22.2%, and 9.5%, respectively. Fluctuations in the concentrations and corresponding contamination and ecological indices of the elements can serve as a means for highlighting potential sources of pollution. Therefore, although the pandemic period created anxiety, stress, and economic hardship for citizens, it may prove to be a valuable tool for investigating the sources of pollution in urban soils. The study of these results could potentially lead to optimal ways for managing the environmental crisis and solve persistent problems that pose risks to both the soil environment and human health.
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    Silica and Biochar Amendments Improve Cucumber Growth under Saline Conditions
    (MDPI, 2023-03-12) Al-Toobi, Manar; Janke, Rhonda R.; Khan, Muhammad Mumtaz; Ahmed, Mushtaque; Al-Busaidi, Waleed M.; Rehman, Abdul
    Rapidly increasing salinization of arable land is a major threat to crop production globally, and the soil of regions with arid environments, such as Oman, are more prone to this menace. In this work, two complementary studies were carried out to evaluate the effect of soil amendments on soil physicochemical properties and growth of cucumber seedlings. In the first study, high- and low-saline soils were used with or without perlite. The amendments tested included mango wood biochar, silica, and biochar + silica, while no amendment was taken as the control. The second study included two cucumber cultivars and irrigation water with two salinity treatments, along with the same four soil amendments. The results showed that soil amendment with biochar alone or with silica enhanced the soil organic matter and NO3, P, and K concentration, while silica amendment substantially enhanced the soil Si level in both studies. Saline soil and irrigation water inhibited seedling emergence and plant growth in both experiments. However, the addition of biochar and silica alone or in combination increased the cucumber seedling dry weight from 39.5 to 77.3% under salt stress compared to the control. Likewise, silica and biochar + silica reduced the sap Na accumulation by 29–31.1% under high salinity. Application of biochar under high salinity resulted in 87.2% increase in sap K. Soil amendments with biochar and silica or their combination have the potential to reduce the adverse effect of salt stress on cucumber.
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    Soil Health Assessment and Management Framework for Water-Limited Environments: Examples from the Great Plains of the USA
    (MDPI, 2023-03-02) Ghimire, Rajan; Thapa, Vesh R.; Acosta-Martinez, Veronica; Schipanski, Meagan; Slaughter, Lindsey C.; Fonte, Steven J.; Shukla, Manoj K.; Bista, Prakriti; Angadi, Sangamesh V.; Mikha, Maysoon M.; Adebayo, Olufemi; Strohm, Tess Noble
    Healthy soils provide the foundation for sustainable agriculture. However, soil health degradation has been a significant challenge for agricultural sustainability and environmental quality in water-limited environments, such as arid and semi-arid regions. Soils in these regions is often characterized by low soil organic matter (SOM), poor fertility, and low overall productivity, thus limiting the ability to build SOM. Soil health assessment frameworks developed for more productive, humid, temperate environments typically emphasize building SOM as a key to soil health and have identified the best management practices that are often difficult to implement in regions with water limitations. This study reviewed existing soil health assessment frameworks to assess their potential relevance for water-limited environments and highlights the need to develop a framework that links soil health with key ecosystem functions in dry climates. It also discusses management strategies for improving soil health, including tillage and residue management, organic amendments, and cropping system diversification and intensification. The assessment of indicators sensitive to water management practices could provide valuable information in designing soil health assessment frameworks for arid and semi-arid regions. The responses of soil health indicators are generally greater when multiple complementary soil health management practices are integrated, leading to the resilience and sustainability of agriculture in water-limited environments.
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    Toward Soil Nutrient Security for Improved Agronomic Performance and Increased Resilience of Taro Production Systems in Samoa
    (MDPI, 2023-03-02) Antille, Diogenes L.; Macdonald, Ben C. T.; Uelese, Aleni; Webb, Michael J.; Kelly, Jennifer; Tauati, Seuseu; Stockmann, Uta; Palmer, Jeda; Barringer, James R. F.
    A progressive decline in soil fertility in taro (Colocasia esculenta L., Schott) production systems has contributed to reduced crop productivity and farm profitability, and is recognized to be a threat to soil nutrient and food security in Samoa. Evidence based on three years of field experimentation showed that appropriate nutrient budgeting is required to reduce soil nutrient deficits and mitigate soil organic carbon loss. Balanced crop nutrition coupled with appropriate crop husbandry can significantly improve productivity and narrow yield gaps. A framework to guide nutrient recommendations for taro production systems is presented and discussed. This framework proposes that recommendations for N be derived from the yield-to-N response function (from which the most economic rate of N can be estimated) and that for other nutrients, namely P, K, Ca, and Mg, recommendations be based on replacement. The replacement strategy requires the development of soil nutrient indexes, which can be used to define the long-term nutrient management policy at the field scale. This long-term policy is informed by soil analyses, and it will determine whether existing soil nutrient levels are to be maintained or increased depending on the focus (productivity, profitability, environmental protection). If soil nutrients were already at an agronomically satisfactory level, their application may be omitted in some years to help reduce crop production costs, improve use efficiency, and ensure environmentally safe levels in soil are not exceeded.
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    Experimental Warming of Typically Acidic and Nutrient-Poor Boreal Soils Does Not Affect Leaf-Litter Decomposition of Temperate Deciduous Tree Species
    (MDPI, 2023-02-06) Bélanger, Nicolas; Chaput-Richard, Clémence
    Ongoing rapid climatic changes are expected to modify the structure, composition, and functioning of forest ecosystems. Studying the influence of such changes on biogeochemical processes is thus crucial for a fuller understanding of forest response to climate change. In a temperate forest of Quebec, Canada, we emulated climate change by warming the acidic, nutrient-poor, and dry soils of two mixedwoods by 3 to 4 ◦C using heating cables. Leaf-litter mass loss of the local red maple, sugar maple, large-tooth aspen, and American beech were monitored to assess the ability of these tree species to condition boreal soils in the context of their northward migration under climate change. We hypothesized that decomposition rates of all leaf-litter types would be decreased equally by warming due to a drying effect of the soil and its surface, which is detrimental to microbial biomass and activity. Our results suggest differences in decomposition rates between tree species as follows: sugar maple > red maple ≥ American beech = large-tooth aspen. There was no indication of a slower turnover in these marginal soils compared to other studies conducted on typical hardwood soils. Moreover, no difference in litter mass loss was detected between treatments, likely due to a drying effect of the soil warming treatment. Results imply that climate change has a marginal influence on leaf-litter dynamics of temperate tree species on soils that are typical of the boreal forest. However, some variables that could play an important role on litter decomposition in the context of climate change were not measured (e.g., plant phenology, understory composition and density, microbes) and thus, uncertainties remain. The soil drying effect by warming also needs to be further documented and modeled. The study year was characterized by significant periods of water stress but was not considered an exceptional year in that regard. It would be relevant to test for leaf-litter dynamics during dry and wet summers and verify again our initial hypothesis of decreased leaf-litter decomposition rates due to soil warming/drying.
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    Natural and Anthropogenic Sources of Cadmium in Cacao Crop Soils of Santander, Colombia
    (MDPI, 2023-02-06) Joya-Barrero, Valentina; Huguet, Carme; Pearse, Jillian
    Elevated cadmium (Cd) levels in cacao products have been detected in a major cacao producing region of Colombia, with concentrations well above those permitted for export and posing a potential threat to human health. Geochemical and petrographic analyses of fertilizer, soil and rocks from three farms were used to determine the origin of Cd. Parent rocks were the main source of the Cd in soils, while organic fertilizer may have further contributed to elevated metal content in one farm. High Cd levels in the organic fertilizer were most likely due to bioaccumulation, since it was sourced from animals in the same area. Even though the soil pH range, elevated OM content and the presence of Mn and K diminish bioavailability, the extremely high Cd content in soils results nonetheless in significant uptake by the plants and subsequent accumulation in cocoa beans. Traditional methods to reduce Cd adsorption, such as the addition of calcium, will not be effective in this case. Instead, the selection of cacao species that are naturally low accumulators and amendment with soil microorganisms with mineralization and biotransformation capabilities, as well as testing of fertilizers before application, could all be cost-effective solutions to reduce Cd in the final product.
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    Conservation Agriculture as a Sustainable System for Soil Health: A Review
    (MDPI, 2022-11-23) Rodríguez, Belén Cárceles; Durán-Zuazo, Víctor Hugo; Rodríguez, Miguel Soriano; García-Tejero, Iván F.; Ruiz, Baltasar Gálvez; Tavira, Simón Cuadros
    Soil health is a term used to describe the general state or quality of soil, and in an agroecosystem, soil health can be defined as the ability of the soil to respond to agricultural practices in a way that sustainably supports both agricultural production and the provision of other ecosystem services. Conventional agricultural practices cause deterioration in soil quality, increasing its compaction, water erosion, and salinization and decreasing soil organic matter, nutrient content, and soil biodiversity, which negatively influences the productivity and long-term sustainability of the soil. Currently, there are many evidences throughout the world that demonstrate the capability of conservation agriculture (CA) as a sustainable system to overcome these adverse effects on soil health, to avoid soil degradation and to ensure food security. CA has multiple beneficial effects on the physical, chemical, and biological properties of soil. In addition, CA can reduce the negative impacts of conventional agricultural practices on soil health while conserving the production and provision of soil ecosystem services. Today, agricultural development is facing unprecedented challenges, and CA plays a significant role in the sustainability of intensive agriculture. This review will discuss the impact of conservation agricultural practices on soil health and their role in agricultural sustainability.
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    Effects of improved pigeonpea fallows on biological and physical soil properties and their relationship with maize yield
    (Springer Nature, 2021) Musokwa, Misheck; Mafongoya, Paramu L.
    Declining soil properties have triggered lower maize yields among smallholder famers in South Africa. Legume trees such as pigeonpea can be used as improved fallows to replenish degraded soils. The objectives of the study were to: (1) examine the effects of improved pigeonpea fallows on enhancing biological, physical soil properties and maize yield responses and (2), analyze the relationship of maize grain yield to biological and physical soil properties after improved pigeonpea fallows at Wartburg, South Africa. Pigeonpea fallows were established in 2015/16 season and terminated in 2017 and subsequently maize was planted. A randomized complete block design replicated three times was used with five treatments: continuous sole maize without fertilizer (T1), natural fallow then maize (T2), pigeonpea + grass—pigeonpea then maize (T3), maize + pigeonpea—pigeonpea then maize (T4), two-year pigeonpea fallow then maize (T5). Improved pigeonpea fallows increased maize yields through improvement in soil macrofauna species abundance, richness and diversity, aggregate stability, infiltration rate. Pigeonpea fallows increased maize yield by 3.2 times than continuous maize without fertilizer. The maize grain yield (3787 kg ha−1), was the highest on two-year pigeonpea fallows while continuous maize without fertilizer had the least (993 kg ha−1). There was a significant positive correlation between soil macrofauna indices and physical soil properties to maize yields. Smallholders who have limited access to fertilizers can sustainably use improved fallows to restore degraded soils to achieve higher maize yields in South Africa.
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    Comparison of bacterial communities in roots of selected trees with and without summer truffle (Tuber aestivum) ectomycorrhiza
    (Sciendo (De Gruyter), 2021-06-08) Siebyła, Marta; Szyp-Borowska, Iwona
    In this study, we examined the effect of the presence of mycorrhiza and ascomata of summer truffle (Tuber aestivum) on the bacterial composition of roots from small trees growing in selected sites of the Nida Basin. Qualitative DNA sequencing methods such as Sanger and next-generation sequencing (NGS) were used. The Sanger method revealed different bacterial species compositions between the samples where summer truf fle ascomata was recorded and control samples. Five genera of bacteria could be distinguished: Bacillus, Erwinia, Pseudomonas, Rahnella and Serratia, among which the most numerous were Pseudomonas (Gammmaproteobacteria class) at 32.9%. The results obtained by the NGS method also showed differences in species composition of the bacteria depending on the study sample. Seven genera of bacteria were distinguished: Rhizorhabdus, Methylotenera, Sphingomonas, Nitrosospira, Streptomyces, Methyloceanibacter and Niastella, which dominated in roots from the truffle sites. Telmatobacter, Roseiarcus, Granulicella, Paludibaculum, Acidipila, Acidisphaera and Aliidongia dominated in roots from the control sites. With the NGS method, it is possible to identify the microbiome of a whole root, while only a root fragment can be analysed by the Sanger method. These results extend the scope of knowledge on the preferences of certain groups of bacteria associated with truffles and their influence on the formation of ascomata in summer truffles. Our results may also be useful in selecting and monitoring sites that promote ascomata of Tuber aestivum.
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    Liming alkaline clay soils: effects on soil structure, nutrients, barley growth and yield
    (Taylor & Francis Group - Informa UK Limited, 2022-07-04) Gunnarsson, Anita; Blomquist, Jens; Persson, Lars; Olsson, Åsa; Hamnér, Karin; Berglund, Kerstin
    Liming before cultivation of sugar beets is favourable even on alkaline soils but knowledge of response in other crops is lacking. Therefore, effects of ground limestone (GL) and structure lime (SL1 slaked lime or SL2 mix of ground limestone and slaked lime) were evaluated in southern Sweden on soil structure, growth and nutrient concentration in barley under four fertilisation strategies 1.5–2 years after application. All lime products increased aggregate stability, but with variations between locations. A lower proportion of large aggregates was found in both limed treatments, and a higher proportion of small aggregates in SL. In barley, grain yield was unaffected while shoot numbers and biomass in first node stage increased for GL and biomass increased further for SL. Structure lime increased potassium concentration in plants in first node stage, due to more potassium in the product. Both lime types increased molybdenum concentration. Ground limestone reduced zinc concentration compared with no liming. Finer seedbed tilth and increased aggregate stability may explain increased biomass for GL. Higher potassium content in SL might be a further explanation. No interactions between liming and fertilisation were found. In conclusion, on the soil types studied, no change of fertilisation strategy is needed due to liming.
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    Mitigating phosphorus leaching from a clay loam through structure liming
    (Taylor & Francis Group - Informa UK Limited, 2022-11-01) Norberg, Lisbet; Aronsson, Helena
    Phosphorus (P) losses from clay soils can be mitigated by introducing measures for improving soil structure. These include structure liming, where a mixture of CaO or Ca(OH)2 and CaCO3 is added to the soil. In a field experiment with separately tile-drained plots on a clay loam in Sweden, we examined the effects of structure liming on leaching of total-P, phosphate P (PO4-P) and total nitrogen (N) during three years after initial application. The treatments included two application rates (8 and 16 t ha−1) of a common product in comparison with a control (no lime). Effects of structure liming emerged during the second and third year after application, with 45 and 38% lower total-P leaching than in the unlimed control. A significant effect of the application rate was found in the third year. Nitrogen leaching and crop yield were not affected. As expected, soil pH raised following structure lime addition. Measurements of aggregate stability did not confirm the reduction in P leaching, indicating that it is important to measure P concentrations in drainage water directly when assessing the effect of structure liming.
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    Exploring structural sediment connectivity via surface runoff in agricultural lands of Finland
    (Taylor & Francis Group - Informa UK Limited, 2022-10-26) Tähtikarhu, M; Räsänen, T; Oksanen, J; Uusi-Kämppä, J.
    Spatial information on the distribution of erosion areas and sediment transport pathways within agricultural landscapes is limited. Thus, we assess structural sediment connectivity via surface runoff by using a digital elevation model (2 × 2 m2) and RUSLE-based erosion estimates to compute index of connectivity (IC) and sediment delivery estimates. The variables were analyzed within and between two topographically contrasting subcatchments. We found greater spatial variability of IC within a subcatchment than between the subcatchments. The majority of field parcel areas (65%–97%) were structurally connected to adjacent open ditches and streams. Areas with high erosion estimates also tended to be structurally well-connected, both at the pixel (Pearson r = 0.58–0.63) and parcel scale (r = 0.49–0.67). The IC model was not highly sensitive to parameter variations. In contrast, the magnitude of sediment delivery estimates was highly sensitive to parameter variations. However, based on the high rank correlation (Spearman rs > 0.95) between computed sediment delivery estimates, the tool provided consistent information on potentially high sediment delivery areas. More empirical data and dynamic model applications could be applied to improve the accuracy of the estimates. The method provides a feasible tool to generate open data on connectivity.
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    Soil carbon under arable and mixed dairy cropping in a long-term trial in SE Norway
    (Taylor & Francis Group - Informa UK Limited, 2022-03-10) Riley, Hugh; Henriksen, Trond Maukon; Torp, Torfinn; Korsaeth, Audun
    Soil organic carbon (SOC) was studied at 0–45 cm depth after 28 years of cropping with arable and mixed dairy rotations on a soil with an initial SOC level of 2.6% at 0–30 cm. Measurements included both carbon concentration (SOC%) and soil bulk density (BD). Gross C input was calculated from yields. Averaged over all systems, topsoil SOC% declined significantly (−0.20% at 0–15 cm, p = 0.04, −0.39% at 15–30 cm, p = 0.05), but changed little at 30–45 cm (+0.11%, p = 0.15). Declines in topsoil SOC% tended to be greater in arable systems than in mixed dairy systems. Changes in BD were negatively related to those in SOC%, emphasizing the need to measure both when assessing SOC stocks. The overall SOC mass at 0–45 cm declined significantly from 98 to 89 Mg ha−1, representing a loss of 0.3% yr−1 of the initial SOC. Variability within systems was high, but arable cropping showed tendencies of high SOC losses, whilst SOC stocks appeared to be little changed in conventional mixed dairy with 50% ley and organic mixed dairy with 75% ley. The changes were related to the level of C input. Mean C input was 22% higher in mixed dairy than in arable systems.
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    How 75 years of rubber monocropping affects soil fauna and nematodes as the bioindicators for soil biodiversity quality index
    (Taylor & Francis Group - Informa UK Limited, 2022-02-23) Panklang, Phantip; Thaler, Philippe; Thoumazeau, Alexis; Chiarawipa, Rawee; Sdoodee, Sayan; Brauman, Alain
    Natural rubber consumption has led to the expansion of rubber (Hevea brasiliensis) plantations which affects the deforestation and ecosystem. However, no study of the long-term effect of rubber plantations on soil biodiversity has been carried out yet. This study aimed to assess the long-term impact of continuous rubber monocropping on soil biodiversity, focusing on soil macrofauna and nematode diversity. Three successive rubber rotations at young and old ages were compared with the adjacent forest in Suratthani province, Thailand. Soil biodiversity quality index was calculated from a set of indicators which were combined into a single score to present a functional assessment of the gradient of disturbance. The results showed three negative effects on soil biodiversity (i) the biodiversity quality index immediately declined after deforestation (ii) the old age rubber plantations had a lower soil biodiversity as the nematodes were a main driver of diversity in the young plantation, and (iii) similarly, for the soil chemical properties, the long-term effect of rubber chronosequence evidenced deterioration in the third rotation. Therefore, two rotations of rubber plantation (around 50 years) seemed to be the maximum length of rubber monocropping in terms of soil biodiversity recovery.
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    Spatial variability of soil organic matter and total nitrogen and the influencing factors in Huzhu County of Qinghai Province, China
    (Taylor & Francis Group - Informa UK Limited, 2022-02-03) Zhang, Bicheng; Niu, Lele; Jia, Tianzhong; Yu, Xianhua; She, Diao
    The soil organic matter (SOM) and soil total nitrogen (STN) is a significant concern in Qinghai–Tibet Plateau, China. This study analysed the spatial distribution of SOM and STN and determined their influencing factors to support the conservation of cultivated soil and development of sustainable agricultural strategies in the Plateau. In total, 120 soil samples were collected from the 0–20-cm soil layer in Huzhu County, Qinghai Province. Traditional statistical and geostatistical methods were used to analyse the spatial distribution of SOM and STN; a geographical detector (GeoDetector)was used to explore the factors influencing the spatial variation. The SOM and STN concentrations were 6.92–44.57 and 0.52–2.54 g/kg, respectively. The Cokriging interpolation map showed a similar spatial distribution pattern for SOM and STN concentrations, which decreased from the northeast to southwest directions in the study area. GeoDetector results revealed that the three primary factors influencing the spatial variability of SOM and STN were soil type, annual accumulated precipitation and elevation, with their explanatory power ranging between 38.4% and 59.5%. Two-factor interactions enhanced the explanatory power of the spatial variability of SOM and STN. The research results provide a reference for conservation tillage and precision agriculture.