European Journal of Soil Science最新文献

Promoting food security, fostering economic growth, and building resilience to climate change are crucial priorities in Africa, where the health and fertility of soils play a key role. Raising awareness about soil-related issues and finding potential solutions are vital for addressing the complex interplay of factors affecting soils across the African continent. This paper is written in three parts. The first part highlights and discusses the current problems which include soil erosion, desertification, nutrient imbalances, acidity, salinization, deforestation, and soil compaction. The second part highlights the effects of the identified causes on soil and agricultural productivity, and human health, which included but was not limited to loss of fertile land and biodiversity, increased carbon dioxide and other greenhouse gas (GHG) emissions, nutrient depletion, loss of ecosystem services, malnutrition, and other human health issues. The third part proffers potential solutions to tackle soil degradation in Africa. Some of the suggested solutions include afforestation of degraded land, integrated landscape management that involves innovative soil fertility and rangeland management, and effective soil conservation measures to combat erosion. Strengthening policy implementation at regional and country levels, such as awareness creation, education, and community engagement on soils as the basis of human existence, is also crucial. We concluded that no single solution fits all while addressing soil degradation in Africa, but integrated approaches that promote sustainable soil management, such as conservation agriculture, crop rotation, agroforestry, afforestation, organic farming, and community engagement, would have a significant impact in resolving the menace of soil degradation.

The bacterial phoD gene encoding alkaline phosphatase (ALP) plays a crucial role in the mineralisation of organic phosphorus (Po) to inorganic phosphorus (Pi). The purpose of this study was to explore the association between soil P fractions and the phoD-harbouring bacterial community. Based on a long-term P fertilisation experiment in calcareous soil on the Loess Plateau (started in 2014), this study analysed the results of treatments including four P fertilisation rates: 0, 60, 120 and 180 kg P₂O₅ ha⁻¹ (denoted as P0, P60, P120 and P180, respectively). The abundance and community structure of the ALP-encoding gene (phoD) were analysed by PCR amplification and high-throughput sequencing, and the soil P fractions were measured using Hedley sequential fractionation approach. The majority of soil P was present in the form of HCl-Pi, and P fertilisation significantly increased the contents of Resin-P, NaHCO₃-Pi, NaHCO₃-Po, NaOH-Pi, NaOH-Po and HCl-Pi in soil. The ALP activity and phoD gene abundance in the P120 and P180 treatments were significantly less than those in the P0 and P60 treatments: P180 decreased by 14.52% and 46.83% compared with P0, respectively. ALP activity was positively correlated with pH, but negatively correlated with the contents of Resin-P, NaHCO3-Pi, NaHCO3-Po and NaOH-Pi. P fertilisation decreased the relative abundance of the genera Streptomyces, Bradyrhizobium and Rhizobacter. Sinorhizobium had the highest abundance in low-P (P60) soil and played an important role in improving ALP activity and bacterial community network stability. P fertilisation significantly affected the community assembly processes of phoD-harbouring bacteria, with high-P input promoting stochastic processes in soil. Soil microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP) contents significantly affected the abundance of phoD, while pH and MBP contents significantly affected the composition of the phoD bacterial community. ALP activity was significantly correlated with phoD gene abundance, which played a key role in promoting Po turnover and improving soil P availability. The decrease in soil pH and the increase of MBC and MBP contents caused by long-term P fertilisation influenced the activity of ALP by regulating phoD gene abundance and community composition, thereby inhibiting the mineralisation of Po.

To accurately predict soil organic carbon (SOC) stocks under a changing climate, models must properly integrate soil hydrological controls. In Northwest Europe, prolonged droughts are expected, during which capillary moisture transport may help maintain topsoil moisture. At present, the importance of capillary moisture supply for topsoil moisture during dry summers remains uncertain, and so it is not clear if account thereof during SOC stock simulation is needed. This study aimed to determine whether a ~2-m deep groundwater table supplies moisture to topsoil during a dry summer and its effect on SOC mineralisation in six croplands across common textures (loamy sand, (sandy) loam and silt loam) in Flanders. We adopted a novel approach by installing repacked topsoil columns in situ within the plough layer, with or without a gravel layer below to act as a hydraulic barrier. In the loamy sand and (sandy) loam soils, groundwater tables of up to 2.3-m depth appeared too deep to affect topsoil through capillary moisture transport in our setup since topsoil was even slightly wetter in the gravel treatment, likely due to impeded downward water redistribution following rainfall. This artefact could be avoided with deeper barrier placement. In contrast, in the silt loam fields with groundwater tables up to 2-m depth, soil at a 15-cm depth was significantly wetter (25% volumetric water content (VWC) and a matric suction of −405 cm water height (WH)) when upward water transport was unobstructed compared to when it was blocked by the gravel barrier (18% VWC and −445 cm WH) during a 1-month drought period with very limited rainfall (5.8 mm). Surprisingly, this moisture increase via capillary rise did not enhance C mineralisation. Apparently, in these silt loam soils, C mineralization did not strongly depend on moisture, whereas in the coarser loamy sand soil, temporal moisture fluctuations had a greater impact on C mineralisation. This suggests that if capillary rise were to reach the topsoil, for instance with shallower groundwater, it could potentially influence C mineralisation. However, further research is needed to confirm this effect. Overall, whether groundwater moisture supply significantly impacted topsoil moisture and C mineralisation could only be evaluated in the silt loam croplands. Nonetheless, the proposed hydraulic barrier, with a recommended deeper installation, offers a promising tool for further testing conditions where capillary wetting may influence SOC dynamics.

Recent advances in hardware technology have enabled the development of handheld sensors with comparable performance to laboratory-grade near-infrared (NIR) spectroradiometers. In this study, we explored the effect of the uncertainty from the NeoSpectra Scanner Handheld NIR Analyzer (Si-Ware) on estimating farm-level soil organic carbon (SOC) stocks at three small farms in Massachusetts, USA. A field campaign conducted in Falmouth, MA, collected 192 soil samples from three farms at depths of 0–10, 10–20 and 20–30 cm. All samples were scanned both in the field at field moisture and under laboratory conditions after being dried and sieved. Samples were analysed for SOC via elemental analysis, while bulk density was determined after weighing the dry fine earth sampled with cylindrical cores in the field. Several strategies for spectral prediction were tested for estimating SOC content and bulk density (BD) using both moist and dry scans, including testing the application of prebuilt models from the Open Soil Spectral Library. Cubist was used to train all models, and conformal prediction was used to estimate the prediction intervals to one standard deviation. The Cholesky decomposition algorithm allowed us to consider the correlation between variables over the three depth layers during uncertainty propagation with Monte Carlo to come up with robust estimates of field-scale SOC stocks and uncertainty. This analysis revealed that spectroscopy predictions, although less precise, can detect the same statistical patterns in SOC stock across farms at a large cost savings compared with the traditional analytical methods.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous persistent organic pollutants that accumulate in soils because of their high affinity for soil organic matter (SOM). As these pollutants are toxic to humans and the environment, a better understanding of their fate in the environment is required. This study aimed to assess the PAH distribution within soils according to different soil fractions: the free particulate organic matter (fPOM), the occluded particulate organic matter (oPOM) and the mineral-associated organic matter (MaOM). PAH contents were measured in bulk soils and SOM fractions of alpine soils along an elevation gradient in the French Alps (Lautaret) from 1920 m to 2840 m a.s.l. A specific PAH distribution was identified, with highest PAH contents in the oPOM, followed by the fPOM, then the MaOM. Organic matter (OM) contents of each fraction can partly explain this distribution, but results of nuclear magnetic resonance (NMR) spectroscopy on fPOM and oPOM also highlighted a correlation between the PAH contents and the degree of decomposition of SOM. This indicates that the PAH distribution may be linked to the formation and transformation of fractions: (i) PAHs in the fPOM correspond to relatively recent deposits and mainly reflect the background contamination, (ii) in the oPOM are the PAHs that resist biodegradation during the transformation of fPOM into oPOM and accumulate in the oPOM; this accumulation may be further enhanced by the formation of aggregates. Finally, (iii) in the MaOM, the lower PAH contents can be explained by the different formation pathway of this fraction and its high degree of decomposition. As the PAH distribution may have an impact on their dynamics in soils, it should be taken into consideration in future research.

Globally speaking, academic research assumes that soils affected by water stagnation have a significant constraint, especially concerning their productivity and environmental benefits. In the surrounding landscape of northern Ávila Province (northern Spanish Central System), where many small farmers and livestock breeders of the region live, there are areas that are periodically flooded. This study examines the impact of hydromorphism on soil features and formation in La Moraña, a region with arkosic and aeolic sands; it also investigates the soil's role in sustainable waterlogged agro-silvopastoral development. The main land uses are agriculture, pastures or pine forests. The soils show acidic to alkaline reaction (pH 5.6 to 9.1), with sandy to loamy textures, and contain moderate to high levels of organic matter (1.7% to 8.0%) and total nitrogen (0.01% to 0.26%) contents. A moderate to medium cation exchange capacity (CEC) (3.13 to 15 cmol kg⁻¹) and high base saturation status (72% to 81%) were observed. In both soil groups (Cambisols and Arenosols), the predominant soil cations were Ca²⁺ (0.7 to 25.7 cmol kg⁻¹) and Na⁺ (0.19 to 9.5 cmol kg⁻¹), while K⁺ was present in minor amounts. Given the nature of the original material, although the carbonate content of the parent material lay below the detection limit, high carbonate contents greater than 25% were observed in certain horizons (Bkg of profiles 1 and 2). Weak gleization was observed in all profiles, with grey colours (light to dark) in the subsurface horizons, denoting some effects of iron reduction, resulting from a dual action of pluviometry and a practically flat topography; and occasionally flooding or water-table rise. In addition, hydromorphic conditions can also develop due to soil compaction. So, the major soil-forming processes are accumulation of organic matter and brunification in drained conditions. While litter formation in conditions of high moisture, and weak gleization against excessive moisture are the dominant processes. La Moraña's soils stay productive through agroforestry and crop rotations, preserving their potential despite their hydromorphic nature.