Limed Soil Research Articles

Study on the strength characteristics and microscopic mechanism of sewage sludge ash modified lime soil

The large amount of sewage sludge ash (SSA) generated by incineration treatment of sewage sludge each year can seriously pollute the environment, and there is an urgent need to seek an effective resource utilization method for SSA treatment. SSA has the significant pozzolanic activity, and can be used as an auxiliary cementitious material. For that, SSA was adopted to modify lime soil in this work. The strength characteristics of SSA modified lime soil (SLS) were investigated by conducting unconfined compressive strength test and unconsolidated-undrained triaxial compression test, and X-ray diffraction (XRD) test and scanning electron microscopy (SEM) test were conducted to investigate the mineral composition, microstructure and porosity of SLS. It is observed that the unconfined compressive strength (UCS) increases first and then decreases with increasing SSA content in the range of 0–20 %, and reaches the maximum value while SSA content is 15 %, which increases by 25 % at the curing age of 28 days comparing to the specimen without SSA. Additionally, the triaxial strength and cohesive force both have the same change law as UCS with SSA increasing, and 15 % can be used as the optimal content of SSA to modify lime soil. The added SSA can promote the pozzolanic reaction, and more hydration products fill the specimen porosity so that the specimen strength can be improved. Furthermore, the porosity of SLS decreases first and then increases with SSA content increasing, and there is a linear relationship between the porosity and strength of SLS. Finally, a simple function is proposed, which can simulate the quantitative relationship between UCS and the triaxial strength with satisfying accuracy. Generally, the research results can be used as a reference for the application of SSA in soft soil foundation treatment.

Diurnal, and seasonal dynamics in essential oil content and composition of cultivated Helichrysum italicum (Roth) G. Don

Helichrysum italicum from the Asteraceae family is a small odorous shrub that is distributed in the Mediterranean region different altitudes. However, the species was not naturally found in the flora of Türkiye. Cultivation interest in H. italicum has grownsince its cosmetic and pharmaceutical usage. In the present study, H. italicum plants (seedlings were obtained from the same source) were cultivated in Hatay (Mediterranean, 149 m altitude) and Uşak (Continental, 906 m altitude) cities of Türkiye. Harvestings were done in the spring and autumn, at three different hours of the day (09.00, 13.00, and 18.00) in both locations. Soil samples were analyzed to determine some soil properties in both locations. Harvested aerial plant samples were evaluated for essential oil content and composition with three replicates. The experimental field soils' pH values were similar, however there were differences in the ratio of soil lime and macro-microelements. The essential oil content varied between 0.29 and 0.59% in all examined variables. Generally, neryl acetate and α-pinene were found as a main component in all essential oils. Neryl acetate contents ranged between 8.07 and 36.66%, while α-pinene content was found between 13.93 and 31.18%. In the spring harvest, harvesting in the evening produced higher neryl acetate in the continental environment, whereas harvesting at any time of day did not affect the amount of neryl acetate in the Mediterranean climate. In the autumn harvest in the Mediterranean environment, the neryl acetate content was higher in the morning harvest, while neryl acetate content in autumn was comparatively low in the continental climate. Examining the seasons has shown that, in a Mediterranean environment, harvest time is not very significant, but in a continental climate, spring harvest could be favored.

Influencia de enmiendas calcáreas sobre el rendimiento y calidad para fritura de la papa variedad Bicentenaria

The quality of potatoes for processing depends on varietal, environmental and crop management factors, and the consumption of potato products has increased.The objective of the research was to determine the effect of calcareous amendments on the production and frying quality of potatoes potato cv. Bicentenaria under high Andean conditions. The research was carried out in the rural community of Canín at Checras district (Lima) altitude of 3880 masl. The climate of the locality is humid and cold, with an annual rainfall of 800 mm and acid soils (pH 5.0) of sandy-clay texture. Five liming treatments and a control without liming were applied to the soil (agricultural lime 500 kg ha-1 and carbonatite 500, 1000, 1500 and 2000 kg ha-1). Agronomic and biochemical characteristics of the tuber were evaluated and sensory analysis was performed for potato frying. Data were analyzed statistically and the Scott-Knott test was used to compare treatment means. Liming with carbonatite 1500 kg ha-1 statistically outperformed the other treatments in tuber weight and was similar to the control; treatment with carbonatite 1000 kg ha-1 had a greater effect on mean tuber weight. The treatments with agricultural lime or carbonatite significantly reduced (p <0.05) the glucose content in the tuber with respect to the control. Sensory tests were significant for liming treatments for chip color. Soil liming influenced some agronomic characteristics and biochemical parameters of the tuber, as well as the sensory evaluation of potato chips.

Prediction of soil organic matter using Landsat 8 data and machine learning algorithms in typical karst cropland in China

Soil organic matter (SOM) is crucial for karst ecosystems, affecting cropland health, climate change mitigation, and rocky desertification control. However, there are limited research on cropland SOM prediction in karst areas with complex topography and diverse microclimates. Here, we compared the performance of four machine learning algorithms—random forest (RF), support vector regression (SVR), multilayer perceptron regression (MLP), and gradient boosting regression trees (GBRT)—for predicting cropland SOM in a typical karst landform area in 2019. Our results indicated that the GBRT model achieved the highest prediction accuracy with an R² of 0.69, MAE of 2.19 g/kg, RMSE of 3.37 g/kg, and LCCC of 0.82. Using the GBRT model and spatial data on climate, topography, and remote sensing, we predicted SOM for each 30 m × 30 m grid cell. The analysis revealed higher SOM content in the northeastern and southwestern regions and lower content in the central area, ranging from 13.95 to 47.81 g/kg, with an average of 27.16 g/kg. Lime soil had the highest SOM content, while purple soil had the lowest. Paddy fields showed significantly higher SOM than dry land. Over the past 40 years, SOM content has slightly increased, while its spatial distribution has remained stable.

Effect of Phosphorus and Magnesium Fertilizers on Mineral Nutrition and Yield of Winter Wheat depending on Liming of Sod-Podzolic Soil

In long-term field experience on strongly acidic, poorly cultivated sod-podzolic soil, high efficiency of phosphorus fertilizers combined with magnesium and liming in the cultivation of winter wheat of the Moskovskaya 56 variety was revealed. Under these conditions, the content of nitrogen, phosphorus and magnesium in plants in the flowering phase increased. Improving the mineral nutrition of plants in this case provided the highest yield (75.3 c/ha), exceeding the background level of nitrogen-potassium fertilizers by 2.7 times, the payback of mineral fertilizers (NPK) increased by 2.5 times, reaching 16.7 kg/kg. The use of phosphorus fertilizers on highly acidic soil increased yields by 65% at 27.5 c/ha against the background of nitrogen-potassium fertilizers. On calcified soil with a slightly acidic reaction of the medium, the yield from the use of phosphorus fertilizers increased by 19% compared to the background of 58.1 kg/ha. Yield increases when using magnesium fertilizers against the background of full fertilizer (NPK) decreased as soil acidity decreased and were significant: on medium acidic soil – 4.9 and slightly acidic – 6.1 c/ha. At the maximum yield of winter wheat, due to the use of phosphorus and magnesium fertilizers and a decrease in the acidity of sod-podzolic soil, the removal of nutrients by the winter wheat harvest increased: nitrogen – by 3.5, phosphorus – 3.7, potassium and magnesium – 3 times.

Effect of Low Molecular Weight Organic Acids and Liming on Phosphorus Adsorption in Acidic Tea Soils in the Black Sea Region, Türkiye

ABSTRACT Agricultural productivity is significantly hindered by the limited availability of phosphorus in acidic soils due to the presence of aluminum and iron phosphates. Soil liming is commonly employed to enhance soil fertility. However, modifying the pH might also impact the interactions involving existing soil organic matter, leading to changes in the effective concentrations of competing low-molecular-weight acids (LMWOACs) participating in phosphorus adsorption. This study explored the impacts of citric, oxalic, and malic acids in acidic soils from tea cultivation regions within the Eastern Black Sea. These soils had undergone various levels of liming and were incubated for 15 months to assess their effects on phosphorus (P) adsorption in 7 acidic soils. The experimental sorption data were utilized to calculate the soil Langmuir and Freundlich adsorption parameters. In addition, the influences of organic acids and liming levels on the Freundlich and Langmuir model parameters were subjected to ANOVA analysis. The findings indicated that citric acid demonstrated the highest efficiency in diminishing phosphorus adsorption among the tested organic acids, followed by oxalic and malic acids. Three carboxyl groups (−COOH) in citric acid facilitated the formation of more complexes with adsorbed phosphorus on the soil surface. Furthermore, the 100% LR ratio of liming notably decreased phosphorus adsorption, especially in the lower end of the isotherms. Therefore, it can be concluded that the combination of LMWOACs and liming treatments could be used to overcome P deficiency in acid soils with very high P sorption ability.

Experimental study on improving the performance of imitation earthen site soil in carbon dioxide environment

This study aims to explore the performance of lime-treated soil for repairing the lime soil of the earthen city wall of Kaifeng and to standardize the construction technology of lime-treated soil. The research comprehensively considered factors such as carbonation time, lime particle size, aging conditions, and lime content, and conducted various tests and analyses including triaxial mechanical properties, surface crack analysis, particle size distribution, pH measurement, composition analysis, and electron microscopy on different samples. The results indicate that the significant effect of high-concentration CO2 carbonation enhances the chemical reactions of lime soil, and an appropriate carbonation process can strengthen the bonding and density between soil particles. Under the maintenance condition of 5 % CO2, with increasing carbonation time, the crack ratio, average crack length, and average crack width of the samples decreased. Cohesion and internal friction angle of the samples exhibited an initial increase followed by a decrease, while shear strength of the samples increased by 22.93 %–75.09 %. The lime particle size has a critical impact on the formation of cracks in lime soil. With increasing lime particle size, the crack ratio, average crack length, and average crack width of the samples increased. Cohesion and internal friction angle of the samples gradually increased with increasing lime content. The increase in crack ratio, average crack length, and average crack width during natural curing of lime-treated soil samples was proportional to the lime content. Appropriate carbonation time, smaller lime particle size, and curing conditions with 5 % CO2 contribute to improving the particle size distribution of lime-treated soil samples, reducing surface cracks, and enhancing performance. However, prolonged carbonation may lead to larger lime particle size, resulting in rough and loose particles, disorganized arrangement of CaCO3 crystals, and the inability to form a cross-linked network skeleton, causing a reduction in shear strength of the samples. These research findings provide important theoretical basis and construction technology guidance for the application of lime-treated soil combined with CO2 carbonation in repairing earthen city walls.

Comparing the Effects of Lime Soil and Yellow Soil on Cadmium Accumulation in Rice during Grain-Filling and Maturation Periods.

The karst area has become a high-risk area for Cadmium (Cd) exposure. Interestingly, the high levels of Cd in soils do not result in an excessive bioaccumulation of Cd in rice. Carbonate rock dissolution ions (CRIs) could limit the accumulation and translocation of Cd in rice. CRIs can become a major bottleneck in the remediation and management of farmlands in karst areas. However, there is limited research on the effects of CRIs in soils on Cd accumulation in rice. The karst area of lime soil (LS) and the non-karst areas of yellow soil (YS) were collected, and an external Cd was added to conduct rice cultivation experiments. Cd and CRIs (Ca2+, Mg2+, CO32-/HCO3-, and OH-) in the rice-soil system were investigated from the grain-filling to maturity periods. The results showed that CRIs of LS were significantly higher than that of YS in different treatments. CRIs of LS were 2.05 mg·kg-1 for Ca2+, 0.90 mg·kg-1 for Mg2+, and 42.29 mg·kg-1 for CO32- in LS. CRIs could influence DTPA Cd, resulting in DTPA Cd of LS being lower than that of YS. DTPA Cd of YS was one to three times larger than that of YS. Cd content in different parts of rice in YS was higher than that of LS. Cd in rice grains of YS was one to six times larger than that of LS. The uptake of Cd from the soil during Filling III was critical in determining rice Cd accumulation. CRIs in the soil could affect Cd accumulation in rice. Ca2+ and Mg2+ had significant negative effects on Cd accumulation of rice at maturity and filling, respectively. CO32-/HCO3- and OH- had significant negative effects on DTPA Cd in soil.

Multi-Factor Orthogonal Experiments and Enhancement Mechanisms of Unconfined Compressive Strength of Soda Residue Cement Lime Soil

In order to study the effects of soda residue content, particle size, moisture content, and curing age on the unconfined compressive strength (UCS) of soda residue cement lime soil (SRCLS), a 4-factor, 4-level orthogonal experimental design was employed in this study. Different conditions of SRCLS UCS and their impacts were tested and analyzed. The internal microstructure and hydration products of SRCLS were studied using SEM and XRD to explore the strengthening mechanism of SR in SRCLS. The results indicate that as the soda residue content gradually increased, SRCLS UCS initially increased and then decreased, with a maximum increase of up to 67%. With increasing soda residue particle size and moisture content, the UCS of SRCLS gradually decreased. The optimized mix ratio was determined to be soda residue:cement:lime:soil = 3%:3%:6%:100%, with the soda residue dried naturally and an ideal particle size of 0.15 mm. The factors influencing the unconfined compressive strength (UCS) of SRCLS, in order of importance, are curing age, soda residue content, moisture content, and particle size of SR. Among these, curing age and soda residue content have a significant impact on the UCS. An adequate amount of SR can act as a fine aggregate filler, replace lime, promote cement hydration, and enhance chloride ion binding. This improves the grading of SRCLS materials and facilitates the formation of cementitious products from AFm, AFt, and Friedel’s salt, resulting in denser and stronger SRCLS materials. The research findings provide a reference for the mix design of SRCLS and the large-scale utilization of waste soda residue.

Assessment of Management Practices to Prevent Soil Degradation Threats on Lithuanian Acid Soils

An assessment of soil characteristics pertaining to their suitability for agricultural use in general is necessary to reverse the declining trend of soil quality and to ensure sustainable agriculture. The aim of this study was to determine the soil resistance (SRI) and degradation indices (SDI) under different agrotechniques and to find out whether management-induced changes are large enough to reduce soil degradation. The study was based on the comparison of physicochemical data of 3 long-term experiments conducted in the western part of Lithuania. Changes in soil properties over the past 20 years (1999–2019) have been determined. The most commonly used measures in Lithuania, such as soil liming, manuring, residue maintenance, and tillage, were selected for the analysis. The analysis carried out showed that the soil, which was fertilized with manure, had a higher value of soil quality parameters compared to natural Retisol: organic matter (by 0.53 percentage points), total nitrogen (by 0.04 percentage points), and the available amounts of phosphorus (by 69 mg/kg) and potassium (by 6.6 mg/kg). The assessment of the relative annual change in SOC content revealed that long-term soil manuring has significant SOC sequestration capability. Among the soil management techniques examined, it appeared that the greatest relative annual change (0.47 g kg−1yr−1) in SOC content was noted in manured soil. The results indicate that the higher degradation, and resistance values were observed in acid soil (pH 4.2), where liming was applied, indicating greater sensitivity to degradation. Based on analyzed indices, the agricultural practices ranked as: manuring > residue management > reduced tillage > liming. The lowest SRI values were obtained for low level of nutrients (from −0.11 to 0.89), organic carbon (from −0.72 to −0.49), and pH (from −0.25 to –0.1), indicating that these properties are more sensitive to applied agricultural practices compared to others. All these findings provide information for promoting better soil management, soil protection, land use planning, and the planning of remedial measures, especially in the most afflicted areas.

Lime and Gypsum Rates Effects in New Soybean Areas in the Cerrado of Matopiba, Brazil

High rates of limestone have been increasingly utilized in newly converted areas for grain production in agricultural frontier regions to expedite the short-term correction of soil fertility, leading to compensatory yields. However, there is a lack of information about different doses of lime and gypsum for soils in the Cerrado of Matopiba, especially in the state of Piauí, Brazil. The aim of this study was to evaluate the effects of doses of lime and gypsum in newly converted areas for soybean production in the Cerrado of Southwest Piauí. The study was carried out in the 2019/2020 and 2020/2021 crop years, on yellow Oxisol soil, in a randomized block design and treatments following a 5 × 4 factorial: five lime rates (0, 5, 10, 15, and 20 t ha−1) and four gypsum rates (0, 1, 2 and 4 t ha−1), with four replicates. The standard lime and gypsum rates were 5 t ha−1 and 1 t ha−1, respectively. Soil fertility attributes (0.0–0.2, 0.2–0.4, and 0.4–0.6 m), nutritional status of plants, and soybean yield were measured. The increases in grain yield using a lime rate of 10 t ha−1 were 18% and 12% in the 2019/2020 and 2020/2021 crop years, respectively. High lime rates provide a reduction in the concentrations of P, K, and cationic micronutrients in soil, thereby reducing leaf contents of macro- and micronutrients in soybean plants. Concentrations of Ca, Mg, and S in subsurface layers were raised to proper levels, similar to those recommended for topsoil (0.0–0.2 m). The use of gypsum and lime in newly converted areas for soybean cultivation provides quick improvement in soil chemical conditions and reduction in acidity components. The application of 10 t ha−1 of lime improved the soil chemical environment in the Matopiba region the short time available for chemical reactions to occur, allowing soybean cultivation in newly converted areas of Cerrado into agriculture.

ОТЗЫВЧИВОСТЬ КАРТОФЕЛЯ НА УДОБРЕНИЕ НА ДЕРНОВО-ГЛЕЕВЫХ ПОЧВАХ

It was experimentally established that potato yields increased from increasing a single dose of NPK to a triple dose, which resulted in the highest yield (22.7 t/ha, which is 9.0 t/ha more than the control, or 65.7 %). The equivalent variants N2P2K2 and manure+NPK were almost equal in yield (21.0 and 21.2 t/ha). Due to liming of the soil, the yield increased by 1.7 t/ha or 12 %. The dry matter content in tubers in the fertilized variants decreased by 0.6-1.6% relative to the control, and starchy content also decreased by 0.35-2.25 % (17.3 % in the control). At the same time, the accumulation of protein increased by 0.17-0.34% and vitamin C by 0.1-3.6 mg%. The best option in terms of the amount of starch and vitamin C was manure + NPK. According to it, the payback of fertilizers was also the highest - 41.0 kg/kg a.i., in second place was N1P1K1+lime (33.5 kg/kg a.i.). With an increase in the level of fertilization, the payback of fertilizers consistently decreased from 24.3 to 16.2 kg/kg a.i. Conventionally, net income from fertilizers increased, and the profit per ruble spent decreased as the level of fertilization increased. Judging by the last indicator, the option manure + NPK was economically more profitable, for which the bioenergy coefficient was also the highest (4.48 units). In the conditions of the forest-meadow zone when cultivating potatoes, liming of acidic sod-gley soils is quite effective.

The Effect of Manganese and Sulfur Applications on the Rocket (Eruca vesicaria subsp. Sativa) Plant Grown in Lime Soils

Due to the high lime and pH in the soil, sulfur and micro element deficiencies are observed in green vegetable plants. Rocket, one of the green vegetables and a member of the Brassicaceae family, is widely produced in our country. It is noteworthy that rocket is grown by producers almost everywhere and that this plant grown in our region also has a deficiency of microelements. For this reason, in this study were investigated that the sulfur and manganese requirement of rocket, which is one of the vegetable plants grown in Konya calcareous soil, and the effect of the interaction between these two elements on plant growth and yield. In our study, sulfur (S) fertilizer was applied in three doses (0- 40- 80 kg S da-1) and manganese (Mn) fertilizer in three doses (0- 1- 2 kg Mn da-1) was applied to the rocket plant. The experiment was carried out in the greenhouse conditions according to the randomized plots factorial design. At the end of the experiment, the average leaf height, chlorophyll SPAD value, plant fresh weight, plant height and plant Mn concentration did not differ with different doses of fertilizer applications in the rocket plant. On the other hand, the sulfur concentration in the plant and soil increased significantly with sulfur fertilization (p

Calcium alginate−biochar composite promotes nutrient retention, enzyme activity, and plant growth in lime soil

Soil nutrients loss in karst area is an urgent eco-environmental problem. To control soil erosion and improve soil quality, calcium alginate−rice straw biochar composite (CA−MRB300) was prepared by embedding method. The retention mechanisms of soil nutrients onto CA−MRB300 were explored through batch adsorption experiments of soil nutrients, soil column leaching experiments combined with the analysis of physicochemical properties and soil enzyme activity. The effects of CA−MRB300 and its co-application with fertilizer on plant growth were investigated by a pot experiment. The results suggested that CA−MRB300 effectively retained PO43− and NO3− in lime soil mainly through surface precipitation and physical adsorption. The addition of CA−MRB300 increased the activities of alkaline phosphatase, urease, and sucrase in lime soil. Increased activity of urease accelerated the hydrolysis of urea to NH4+ in lime soil. Compared to a low proportion, a high proportion of CA−MRB30 was more likely to lead to the loss of K+. Moreover, the application of CA−MRB300 alone was more beneficial to the growth of soybean than the co−application of CA−MRB300 with fertilizer. This study indicates that CA−MRB300 has a great potential for application in retaining nutrients and promoting crop growth in lime soil.

Study on the Characteristics and Influencing Factors of Selenium Content in Soil of Western Hubei Province, China

Mastering the distribution of selenium in soils is vital for the development of selenium-enriched industries. This study focuses on Xintang Township in Enshi City, western Hubei Province, known for its selenium-rich soils, analyzing 2,469 soil samples to understand selenium distribution and its influencing factors. Key findings include: 1. Selenium content in surface soils ranges from 0.14 to 25.74 mg/kg, with an average of 0.81 mg/kg, and 86.23% of the area has selenium-rich soils. 2. Soil selenium content is significantly influenced by the parent material, especially soils from the Permian black rock series, showing higher selenium levels with an enrichment factor of 3.74. 3. Soil type impacts selenium distribution, with yellow lime soil and brown lime soil showing high enrichment factors of 3.94 and 2.62, respectively.

Is agricultural lime a profitable investment for African smallholders? Evidence from Rwanda

Soil acidity is a major constraint to crop production in tropical regions. Although agricultural lime is one option to remediate acid soils, there is limited information on the potential returns on investments to liming by smallholders. Using survey data collected from 261 households in Rwanda, we estimated the crop-specific yield response to lime application and associated financial benefits. The estimated average yield gain from lime ranged from 941 kg/ha to 1 579 kg/ha for Irish potato, 562 kg/ha to 709 kg/ha for maize, and 453 kg/ha to 520 kg/ha for beans. With the existing lime and farmgate crop prices, reliable returns on investment from lime were observed for Irish potato, while applying lime to maize and bean was only profitable at a 50% lime price subsidy. As maize and beans are the major staple crops in Rwanda, the subsidy for ag-lime use in improving crop productivity is highly justifiable. The results inform policy decisions in considering market-oriented crops and subsidies when promoting agricultural lime in acid soils under smallholder conditions.

Improving an agroforestry system with livestock in southern Brazil

Agroforestry systems hold significant environmental and cultural value but are yet to receive economic valorisation. In southern Brazil there is a centuries old agroforestry system called Caíva which is classified as a silvopastoral system, combining native trees, cattle herds and pastures. Caívas occupy significant land area and contribute to priceless forest conservation, maintaining rare and threatened trees, but challenges of legal insecurity, low economic yield and ineffective management are threatening the preservation of caívas. To address these challenges, the Agricultural Research and Rural Extension Company of Santa Catarina State (Epagri) began conducting research in 2006 to develop technologies that would increase productivity while maintaining forest cover. Their technology has shown promising results, increasing animal production by up to 400% while still maintaining the tree stratum and active forest regeneration. Epagri’s technologies are based on five activities: the selection of adapted perennial pastures, planting improved pastures without soil disturbance, soil liming and annual fertilisation, rotational grazing, and overseeding with ryegrass and clover during the autumn/winter period. By adopting Epagri's technologies, caíva owners can increase their income, maintain active forest regeneration, and ensure legal certainty over their properties. These strategies are primarily applicable to open and very open caívas, and it is recommended that other types of caívas be used for the preservation and provision of ecosystem services. Research on caivas improvement has shown multiple benefits, emphasising the importance of continued investment in research and development, to further valorise agroforestry systems. It is essential, however, to balance these productive improvements with the maintenance of permanent preservation areas and mixed ombrophilous forest landscapes.

Acidification of European croplands by nitrogen fertilization: Consequences for carbonate losses, and soil health

Soil acidification is an ongoing problem in intensively cultivated croplands due to inefficient and excessive nitrogen (N) fertilization. We collected high-resolution data comprising 19,969 topsoil (0–20 cm) samples from the Land Use and Coverage Area frame Survey (LUCAS) of the European commission in 2009 to assess the impact of N fertilization on buffering substances such as carbonates and base cations. We have only considered the impacts of mineral fertilizers from the total added N, and a N use efficiency of 60 %. Nitrogen fertilization adds annually 6.1 × 107 kmol H+ to European croplands, leading to annual loss of 6.1 × 109 kg CaCO3. Assuming similar acidification during the next 50 years, soil carbonates will be completely removed from 3.4 × 106 ha of European croplands. In carbonate-free soils, annual loss of 2.1 × 107 kmol of basic cations will lead to strong acidification of at least 2.6 million ha of European croplands within the next 50 years. Inorganic carbon and basic cation losses at such rapid scale tremendously drop the nutrient status and production potential of croplands. Soil liming to ameliorate acidity increases pH only temporarily and with additional financial and environmental costs. Only the direct loss of soil carbonate stocks and compensation of carbonate-related CO2 correspond to about 1.5 % of the proposed budget of the European commission for 2023. Thus, controlling and decreasing soil acidification is crucial to avoid degradation of agricultural soils, which can be done by adopting best management practices and increasing nutrient use efficiency. Regular screening or monitoring of carbonate and base cations contents, especially for soils, where the carbonate stocks are at critical levels, are urgently necessary.

Potential of organic wastes typical of the Brazilian Amazon for fertilizer use in agriculture

Characterization of different organic wastes is essential to reveal alternative nutrient sources useful for agriculture. The objective of this work was to characterize a variety of organic wastes generated in the Brazilian Amazon in order to identify nutrient sources for potential use as organic fertilizers. Samples of nine different organic wastes from agricultural, livestock and forestry activities were collected in the state of Pará, Amazon region, Brazil. These samples were characterized using reference methods for analyses of organic fertilizers. Palm oil mill boiler ash was highly concentrated in P, K, Ca, and Mg and also highly alkaline, being considered a promising material for use as fertilizer and lime in acid soils. Palm oil mill decanter cake was the best N source; it also contained relevant amounts of K, S, and Zn. Cattle manure was more concentrated in N and oil palm empty fruit bunch in K. Residual eucalyptus charcoal was high in Ca but also in Na and Al. Oil palm fruit fiber, oil palm fruit shell, wood sawdust of the pile top, and wood sawdust of the pile slope were consistently poor in nutrients. All wastes presented low concentrations of As, Ba, Cd, Cr, Hg, Pb, and Se. This study identified organic wastes differing in prevalent nutrients for potential use as organic fertilizers. Such a difference could be explored in further studies by combining two or more wastes with complementary prevalent nutrients in order to better meet the nutritional requirements of different crops in the Brazilian Amazon.

Study on small strain characteristics and microscopic mechanism of rice husk ash modified lime soil

As a solid waste residue from rice husk combustion, rice husk ash (RHA) has volcanic ash activity. The application of RHA in lime soil can both realize the resource utilization of solid waste and improve the performance of lime soil. In this experiment, lime soil was modified by using rice husk ash (RHA). Following this, the dynamic characteristics of rice husk ash modified lime soil (RLS) were examined by a series of resonant column tests, which indicated the effects of confining pressure, RHA content, and age of curing on the small strain shear modulus G and damping ratio D of RLS. The micro-mechanisms of the RHA modified limestone soil were analyzed by using SEM, EDS, and TEM tests. The results show that: (1) The dynamic shear modulus G exhibits a growing pattern due to increasing confining pressure and curing age, but the damping ratio D indicates a contrary tendency. (2) The dynamic shear modulus G and the damping ratio D both show an increasing and then decreasing trend with RHA content increasing, and the optimal content of RHA can be seen as 4% according to the experimental data. (3) The added RHA led to generate a larger amount of hydration silicate hydrate on the surface of soil particles, and the hydration products tends to densify the soil by filling the pores between soil particles. The test results verified the feasibility of RHA modified lime soil applied to roadbed treatment, which is of great significance for the practical engineering.