Mining wastes of the Russian North-West: microbiological prerequisites of reclamation

Russian North-West is the region with extremely high diversity of superficial mining wastes, deposited in form heaps and hills. These substrata are potentially dangerous for environments and. therefore, should be reclaimed. One of the most effective way of utilization of mineral wastes is to incorporate them to natural processes of revegetation and to initialize the priming of initial soil formation process. Thus, we have investigated microbial processes in very initial superficial ecosystems of numerous heaps of pre quaternary materials of former abandoned and recently explored quarries. The research question of this study: what groups of microorganisms we do have on the surface of mining mineral wastes and are we able to qualify their role in further recycling of mineral waste to natural processes, including pedogenesis and ecogenesis of terrestrial ecosystems. The great variation of taxonomy composition of microbiome composition was revealed. At the same time, some phylums of microorganisms were dominant in all revegetated heaps investigated - Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidetes, Chloroflexia, Verrucomicrobia. They could be considered as a core components of very initial soil microbiome. Primary data have showed the increasing of microbial biodiversity with timing rate of waste exposure on surface.

Imaging local soil kinematics during the first days of maize root growth in sand

Maize seedlings are grown in Hostun sand with two different gradings and two different densities. The root-soil system is imaged daily for the first 8 days of plant growth with X-ray computed tomography. Segmentation, skeletonisation and digital image correlation techniques are used to analyse the evolution of the root system architecture, the displacement fields and the local strain fields due to plant growth in the soil. It is found that root thickness and root length density do not depend on the initial soil configuration. However, the depth of the root tip is strongly influenced by the initial soil density, and the number of laterals is impacted by grain size, which controls pore size, capillary rise and thus root access to water. Consequently, shorter root axes are observed in denser sand and fewer second order roots are observed in coarser sands. In all soil configurations tested, root growth induces shear strain in the soil around the root system, and locally, in the vicinity of the first order roots axis. Root-induced shear is accompanied by dilative volumetric strain close to the root body. Further away, the soil experiences dilation in denser sand and compaction in looser sand. These results suggest that the increase of porosity close to the roots can be caused by a mix of shear strain and steric exclusion.

Implications of Hysteresis on the Horizontal Soil Water Redistribution after Infiltration

Although soil water redistribution is critical for a number of problems, a rather limited study of this process has been reported up to now and especially as regards the implications of hysteresis on horizontal soil water redistribution after infiltration. To this end, a thorough theoretical and numerical investigation of the redistributed soil water content profiles formed after the cessation of a horizontal infiltration is presented. A number of different initial soil water contents before the initiation of the horizontal infiltration and different infiltration depths were analyzed using the HYDRUS-1D software package considering the appropriate hysteretic wetting and drying curves. The effect of neglecting hysteresis was also investigated for the same conditions. The main wetting and drying boundary curves of the studied porous medium and the hydraulic conductivity at saturation were experimentally determined. The theoretical and numerical analysis indicated that the form of the redistributed soil water content profiles in the presence of hysteresis was similar to the original infiltration profile independently of whether the initial soil water content was taken on the boundary wetting or drying curve and independently of the porous medium type. Specifically, in a relatively short time after the initiation of the redistribution process, the magnitude of the soil matrix head gradient tended to zero due to hysteresis, and this resulted in an insignificant soil water movement, although the soil water content and the hydraulic conductivity values were still high. In addition, the redistribution proceeded at a faster rate than the smallest depth of infiltration water prior to the redistribution, and it was faster during the early stages of the redistribution. Accordingly, hysteresis is important for the simulation of horizontal soil water redistribution as it is, for example, in the case of localized irrigation systems’ design and management.

Soil test based fertilizer prescriptions under integrated plant nutrient management system for carrot in an Inceptisol

A field experiment was conducted at Agricultural Research Farm, Banaras Hindu University, Varanasi in an Inceptisol during rabi 2020-21 to develop a targeted yield equation for carrot crop. After developing three levels of fertility gradient with respect to available NPK in soil, the main experiment was conducted by taking carrot as a test crop. Initial soil data, carrot yield and NPK uptake by carrot crop were used for obtaining four important basic parameters, viz., nutrients required to produce a quintal of carrot roots (NR%), contribution of nutrients from fertilizers (CF%), contribution of nutrients from soil (CS%) and contribution of nutrients from organic matter (%C-OM). It was found that 0.65, 0.11 and 0.83 kg of N, P2O5 and K2O, respectively were required for producing one quintal carrot yield. The per cent contribution of nutrients from soil, fertilizer and FYM were 45.33, 65.91 and 67.26 for N; 58.45, 67.86 and 108.12 for P2O5 and 5.54, 3.35 and 10.53 for K2O, respectively. The ready reckoner for fertilizer doses with NPK alone and integrated use of NPK and FYM was also made using developed basic parameters for varying soil test values and desired yield targets of carrot yield.

Microscale evidence of the role of water during the emplacement of mass flows in glacial environments

Microscale analysis of unlithified glacial soils can provide far greater detail regarding their depositional and deformation histories than can be obtained from macroscale studies alone. This paper presents the results of three detailed case studies which examine the processes occurring during overriding and emplacement of mass flows in glacial environments: (i) laminated soils deposited in a proglacial lake setting at Heinabergsjökull, Iceland; (ii) a channelised, ice-marginal to submarginal mass flow at Whitburn (County Durham), England; and (iii) a mass flow exposed at Carstairs, Central Scotland which was emplaced in a glaciofluvial to glaciolacustrine setting. Microscale evidence from all three sites is combined to develop a conceptual model of the role played by water during mass flow; from the initial soil disruption under and/or in front of an advancing mass flow, to the formation of a basal shear zone facilitating mass flow transport and emplacement, through to the decoupling of the flow from the underlying substrate as a result of the injection of fluidised soil along its base. The development of these detachments during mass flow has the potential to increase the velocity of the flow and its run out distance, increasing the potential impact of these geohazards.Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes