ENERGY-SAVING PREPARATION OF THE SOIL FORPLANTING HOPS

At present, the preparation of the soil for the hop plant with machines of traditional hop production technology is unrealistic, since there are no more hops and no one is producing them. In this regard, a progressive technology for growing hops and promising machines for them, including for energy-saving tillage for hops, have been proposed. As the main cultivation, two-strip soil cultivation was used for rows of hops with a combined subsoiler-drener developed at the Chuvash State Agrarian University. Moreover, loosening is carried out with the simultaneous introduction of liquefied litterless manure with a dose of 100-120 t / ha to the subsurface zone from 0.20 to 0.60 m. In the soil, liquefied litterless manure fills the drainage canal and the soil pores adjacent to the canal, activates the activity of microorganisms and soil biochemical processes. Row loosening with a combined machine allows to reduce the energy consumption of processing by 57% compared to continuous plowing with plantation plows and to exclude the operation of applying bedding manure with subsequent moldboard embedding. As a pre-planting soil preparation, cultivation with combined stubble cultivators of the KST-3,8 type and its analogues with the incorporation of crushed green manure (up to 75%), high-quality leveling and crumbling of the soil is proposed. Stirring and leveling of the field surface is provided by afrontal discs behind the last row of flat-cut tines, crumbling - by a ribbed roller. The maneuverability of such a cultivator in the cramped conditions of the hop is taken into account. Replacement of plowing operations with general purpose plows and subsequent leveling by a cultivator allows an additional 45-50% reduction in the energy intensity of pre-planting soil cultivation. The main energy source in the main tillage is the tractor BTZ-243k

Morphological and physico-chemical properties of Cryosoils in the Bulgarian antarctic base on Livingston island, Antarctica

Under the global climatic changes and anthropogenic impacts on the environment, information about characteristics and specific features of soils in remote regions as Antarctica is valuable and could be used as references. This study focuses on the analyses of original data about the physico-chemical composition and micromorphological structure of Cryosols, collected in 2019 from the sampling area of the Bulgarian Antarctic Base “St. Kl. Ohridski” located on Livingston Island, Antarctica. The studied Cryosols are moderately acidic with slow and incomplete transformation of organic residues. The organic carbon content is low, except for soils formed under the influence of an ornithogenic factor. The mezo- and micromorphological observations show a predominance of the mineral phase, weakly affected by weathering processes. Many soil pores and voids are observed, which facilitates water-air and intra-soil exchange during the short Antarctic summer. The analyses showed an evidence for the connection of the processes of soil formation of Cryosols in the region with the pulsating degradation of the glaciers.

Effects of grass type on hydraulic response of the three-layer landfill cover system

Soil column tests were conducted to investigate the effects of grass type on water infiltration in a three-layer landfill cover under drying and wetting conditions. Five soil columns were prepared, including one bare, two Bermuda grass-planted and the other two vetiver-planted. During the drying period, the suction of vetiver-planted soil column was the largest, while that of bare case was the lowest. During the wetting period, the infiltration rate shows a bimodal form due to the contrasting hydraulic properties of different soil layers. The infiltration rate of vetiver-planted soil column was the lowest, followed by Bermuda grass-planted and bare cases. Correspondingly, the vetiver-planted soil column retained the maximum suction and the deepest ponding depth during rainfall. This was likely due to the larger leaf area and deeper roots of vetiver than those of Bermuda grass, thus inducing the maximum initial suction by root water uptake before rainfall and reducing the water permeability by root occupations of soil pores. These results show that vetiver is more effective than Bermuda grass to reduce water percolation through the three-layer landfill cover.

Experimental Study on Early Age Characteristics of Lime-GGBS-Treated Gypseous Clays under Wet–Dry Cycles

Gypseous soils are capable of presenting ground construction challenges to civil and geotechnical engineers due to their unpredictable deformation characteristics. These undesirable responses are sometimes caused by environmental changes in moisture content due to temperature variations, fluctuation of underground water table, surface water, and gypsum content. Hence, the adoption of effective and economical means of stabilising gypseous soils is imperative. This study’s focus is on the early age strength and microstructural characteristics of gypseous soils treated with lime and GGBS. Treated and untreated gypseous soils with 5%, 15%, and 25% gypsum content were subjected to wet–dry cycles while investigating unconfined compressive strength (UCS), water absorption, pH, microstructural changes, and swell. The analysis of the results shows that at zero cycle, the UCS of the untreated gypseous soils increases from 0.62 to 0.79 MPa and swell decreases from 69 to 23%, respectively, as gypsum content increases. However, upon subjection to wet–dry cycles, the UCS reduced from 0.16 to 0.08 MPa at the end of the sixth cycle due to dissolution of gypsum within the soil pores which reduced the strength. The result also shows that gypsum content increases water absorption and reduces the pH of the untreated gypseous soils because of the neutral pH of gypsum. Furthermore, lime-GGBS-treated gypseous soils maintained a higher pH after six wet–dry cycles compared to untreated gypseous soils due to the high pH of lime and the increase in calcium content which improved bonding. In addition, microstructural analysis using SEM indicated early age precipitation of cementitious compounds (CSH) for increasing strength of lime-GGBS-treated gypseous soils compared to untreated gypseous soils.

Suitability of Image Analysis in Evaluating Air and Water Permeability of Soil

A comprehensive understanding of the water and air permeability of soil is necessary for modelling the transport properties which depend on soil structure. We aimed to evaluate the suitability of image analysis to estimate gas and liquid transport in soil using resin-impregnated soil blocks. The soil texture, TOC, density, porosity, air capacity (VV), air permeability (logAP), and the saturated hydraulic conductivity (logKS) of a Cambisol developed from loess were measured. To characterise the pores, using the soil structure images, we determined the macroporosity (AA), index of soil pore-network growth rate, percolation number (lognPER), length of pore path/unit area (PLA), and relative volume of pores overlapping top and/or bottom edge of the image (VTB). logKS and logAP related to morphometric parameters of soil structure derived from the image analysis. The main factor controlling the soil’s infiltration was the total volume of soil pores (VV and AA). AA, PLA, VTB, and lognPER were equally useful for characterising the soil pore system. These results will contribute to more accurate estimations of gas and liquid transport in soils and allow to obtain historical hydraulic properties and model long-term trends in the soil water regime based on the existing collections of thin sections and polished blocks.

The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the Associated Microscopic Mechanism

To better understand and analyze the unsaturated stability of loess filling body, it is necessary to study the changes in suction stress before and after the drying-wetting cycles. In this study, the SWCC of compacted loess before and after drying-wetting cycles was tested using the filter paper method. Then, the suction stress was calculated and the microstructure of the loess sample was determined by the SEM and NMR. The results showed that the drying-wetting cycles had an important influence on the SSCC and microstructure of compacted loess. The change in suction stress before and after the drying-wetting cycles can be well explained by the loess microstructure. The drying-wetting cycles did not significantly change the basic trend of the compacted loess’s SSCC, but it increased the porosity and the dominant pore diameter of loess, and reduced the suction stress under the same matric suction. The main significant change in suction stress with matric suction occurred within the range of the dominant soil pores. The larger the dominant pore diameter, the smaller the suction stress under the same matric suction. In addition, this study proposes a new method for calculating suction stress based on the PSD parameters.

ANALISIS PERMEABILITAS TANAH LAPISAN ATAS DAN BAWAH DI LAHAN KOPI ROBUSTA

Coffee (Coffea sp.) is one of the leading commodities in Indonesia for it has a high economic value. In Bangelan Village, Malang Regency, there is a company that manages robusta coffee commodity. The land was converted into a coffee plantation from forest land. The conversion of forest land into a coffee plantation caused the decreasing number of total soil pores lower than the forest land. This will make it difficult for water to absorb into the soil. This research was conducted in Afdeling Besaran, PT. Perkebunan Nusantara XII Kebun Bangelan to elucidate the value of soil permeability and the nature of the relationship between them. The result of this research indicated that the permeability of the soil on each land map unit was in the category of fast permeability class and slightly fast permeability class. The highest soil permeability value was found on land map unit 2 at the 56 years average age of coffee robusta field, with each depth of 6.03 cm hour-1, 7.95 cm hour-1, and 7.82 cm hour-1. Soil permeability is influenced by soil porosity, sand and silt with a positive correlation way. In addition, aggregate stability, soil bulk density and clay also significantly affected the soil permeability with a negative correlation way. Permeability affected the production of robusta coffee plants with a positive correlation way of 16.09%.

The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the associated Microscopic Mechanism

In order to better understand and analyze the unsaturated stability of loess fillings, it is necessary to study the changes in suction stress before and after the drying-wetting cycles. In this study, the soil-water characteristic curve (SWCC) of compacted loess before and after drying-wetting cycles was tested using the filter paper method. Then, the suction stress was calculated and the microstructure of the loess sample was determined by the scanning electron microscope（SEM）and nuclear magnetic resonance (NMR). The results showed that the drying-wetting cycles had an important influence on the suction stress characteristic curve (SSCC) and microstructure of compacted loess. The change in suction stress before and after the drying-wetting cycles can be explained by the loess microstructure. The drying-wetting cycles did not significantly change the basic trend of the compacted loess's suction stress, but it increased the porosity and the diameter of the dominant pore (i.e., the inter-aggregate pore) of the sample, and reduced the suction stress when the same matrix suction was applied. The main significant change in suction stress with matrix suction occurred within the range of the dominant soil pores. The larger the diameter of the dominant pore, the smaller the suction stress under the same matrix suction. In addition, this study also proposes a new method for calculating suction stress based on the pore size distribution（PSD） parameters, which is more convenient than traditional calculation methods based on SWCC parameters.