Soil CEC Research Articles

A Comparative Effect of Sustainable Materials on the Immobilization, Geochemical Fractions, Bioaccumulation, and Translocation of Ni in Smelter- and Mine-Polluted Soils

The present study holds significant implications, as it aims to investigate the comparative effect of biochar, zeolite, and bentonite minerals on the stabilization of Ni fractions, bioaccumulation, translocation indices, and the reduction in their absorption by pakchoi in smelter- and mine-contaminated soils. The results, which are of great interest, showed that the maximum fresh and dry biomasses of pakchoi were observed up to 28.21 and 18.43% for smelter-polluted soil and 61.96 and 67.90% for mine-contaminated soil amended with zeolite compared to the control. Applying zeolite increased pakchoi chlorophyll SPAD values 1.17-fold in smelter soil and 1.26-fold in mine-polluted soil. The highest Ni immobilization in smelter and mine soil was observed at 76.8 and 85.38% with the application of bentonite, which increased soil pH and CEC. The application of biochar, bentonite, and zeolite reduced the Ni residual, oxidizable, and acid-soluble fractions, but biochar and bentonite increased the reducible fraction of Ni in smelter soil. The highest reduction in Ni in the shoot and root was noted as 82.08 and 68.28% of smelter-polluted soil and 77.25 and 89.61% of mine-polluted soil with bentonite compared to control soil. Overall, it has been concluded that biochar, zeolite, and bentonite can be successfully used to mitigate the Ni concentration in smelter- and mine-polluted soil and reduce uptake by vegetable crops.

Partial substitution of phosphorus fertilizer with iron-modified biochar improves root morphology and yield of peanut under film mulching.

Peanut production is being increasingly threatened by water stress with the context of global climate change. Film mulching have been reported to alleviate the adverse impact of drought on peanut. Lower phosphorus use efficiency is another key factor limiting peanut yield. Application of iron-modified and phosphorus-loaded biochar (BIP) has been validated to enhance phosphorus utilization efficiency in crops. However, whether combined effect of film mulching and BIP could increase water use efficiency and enhance peanut production through regulating soil properties and root morphologies needs further investigation. A two-year (2021-2022) pot experiment using a split-plot design was conducted to investigate the effects of phosphorus fertilizer substitution using BIP on soil properties, root morphology, pod yield, and water use of peanut under film mulching. The main plots were two mulching methods, including no mulching (M0) and film mulching (M1). The subplots were four combined applications of phosphorus fertilizer with BIP, including conventional phosphorus fertilizer rates (PCR) without BIP, P1C0; 3/4 PCR with 7.5 t ha-1 BIP, P2C1; 3/4 PCR with 15 t ha-1 BIP, P2C2; 2/3 PCR with 7.5 t ha-1 BIP, P3C1; 2/3 PCR with 15 t ha-1 BIP, P3C2. The results indicated that regardless of biochar amendments, compared with M0, M1 increased soil organic matter and root morphology of peanut at different growth stages in both years. In addition, M1 increased peanut yield and water use efficiency (WUE) by 18.8% and 51.6%, respectively, but decreased water consumption by 25.0%, compared to M0 (two-year average). Irrespective of film mulching, P2C1 increased length, surface area, and volume of peanut root at seedling by 16.7%, 17.7%, and 18.6%, at flowering by 6.6%, 19.9%, and 29.5%, at pod setting by 22.9%, 33.8%, and 37.3%, and at pod filling by 48.3%, 9.5%, and 38.2%, respectively (two-year average), increased soil pH and organic matter content during peanut growing season, and increased soil CEC at harvest. In general, the M1P2C1 treatment obtained the optimal root morphology, soil chemical properties, WUE, and peanut yield, which increased peanut yield by 33.2% compared to M0P1C0. In conclusion, the combination of film mulching with 7.5 t ha-1 BIP (M1P2C1) effectively improved soil chemical properties, enhanced root morphology of peanut, and ultimately increased peanut yield and WUE.

The impact of combined application of biochar and fertilizer on the biochemical properties of soil in soybean fields.

Heilongjiang Province is a major soybean production area in China. To improve soil structure and increase soybean yield, this study examined the effects of combined biochar and chemical fertilizer application on the biochemical properties of soil in a maize-soybean rotation system. The research were conducted from 2021 to 2022 at Heshan Farm Science Park in Heilongjiang Province, this field plot experiment utilized two soybean varieties, Heihe 43 (a high-protein variety) and Keshan 1 (a high-oil variety). In 2021, two plots with similar fertility levels were selected for planting soybeans and maize. In 2022, a maize-soybean rotation was implemented with five treatments: conventional fertilization (CK), increased biochar+reduced fertilizer 1 (F1+B), reduced fertilizer 1 (F1), increased biochar+reduced fertilizer 2 (F2+B), and reduced fertilizer 2 (F2). The study systematically analyzed the effects of combined biochar and chemical fertilizer application on soil chemical properties and microbial characteristics. Over 2 years, results showed that combined application effectively improved soil chemical traits. Compared to conventional fertilization (CK) and reduced fertilization (F1, F2), t he combined application of biochar and chemical fertilizer (F1+B, F2+B) increased soil pH, EC and the absolute value of zeta potential of soil surface, the CEC of soil significantly increased by 15.6-44.3%, the soil surface charge density and the soil surface charge quantity significantly increased by 16.4-73.5%. The combined application of biochar and chemical fertilizer also effectively enhanced the abundance and diversity of soil microbes. Dominant bacterial groups in soybean field soils under different treatments included Actinobacteria, Acidobacteria, Chloroflexi, and Proteobacteria; while dominant fungal groups were Ascomycota, Basidiomycota, and Mortierellomycota. Alpha and Beta diversity analyses revealed that the F1+B treatment significantly enhanced the species richness and diversity of bacteria and fungi in the soil, increasing the proportion and evenness of dominant and beneficial genera.

Industrial by-products (ferrous sulfate minerals and stone powder) can serve as amendments to remediate Cd-As paddy soil, alleviating Cd-As accumulation in rice

Our previous research has shown that industrial by-products such as ferrous sulfate mineral and stone powder as amendments can remediate Cadmium (Cd) and arsenic (As) soil. However, their role in the soil-rice system is unknown. Therefore, this article explored the effects of the combined use of industrial by-products and commercial conditioners on the accumulation of Cd-As in weakly alkaline and acidic soil-rice systems. Potted experiments shown that SL (stone powder+ferrous sulfate mineral) and SLW (stone powder+ferrous sulfate mineral+Weidikang conditioner) could reduce the availability of Cd-As in soil by adjusting soil pH and CEC, increase iron film content on the root surface, strengthening the “barrier” for fixing Cd-As. Brown rice Cd was lower than the national food safety standard of 0.20 mg kg−1 (GB2762–2022). 1 % SLW could reduce brown rice As from 1.24 mg kg−1 to 0.83 mg kg−1. The results of field experiments confirmed the conclusion of pot experiments. SL and SLW not only reduced the accumulation of Cd-As in rice but also significantly increased rice yield by 16.58 % and 11.68 %, respectively. Compared to the two types of conditioning agents sold in the market, the material costs have been reduced by 79.1 % -86.5 % and 12.4 % -43.3 %, respectively. In summary, this study demonstrates that ferrous sulfate minerals and stone powder could efficiently remediate Cd-As pollution in paddy soil under different acid-base conditions, providing an application example for the resource utilization of industrial by-products for the remediation of Cd-As pollution in paddy soil.

The Effect of Anaerobic Composting Method of Coffee Waste on The Growth of Robusta Coffee Seedlings (Coffea canephora L.)

Coffee is one of the plantation commodities that has significant economic value. A factor that needs to be considered in coffee plant cultivation is good planting media composition. This study aims to determine the effect of planting media composition on the growth of robusta coffee seedlings. This study used a Completely Randomized Design with treatments M0= Soil: 100%, M1= Soil: 50% + Coffee Husk Compost: 25% + Rice Husk: 25%, M2= Soil: 25% + Coffee Husk Compost: 50% + Rice Husk: 25%, M3= Soil: 25% + Coffee Husk Compost: 25% + Rice Husk: 50%. The analyses conducted were compost analysis and initial and post-incubation soil analysis. Observation data were analyzed using the F test followed by DNMRT at the 5% level. The research results show that the provision of coffee husk compost and rice husks affects the chemical properties of the soil and the growth of coffee seedlings. The planting media composition of Soil: 25% + Coffee Husk Compost: 50% + Rice Husk: 25% proved to increase the pH of the planting media from 5.5 to 6.6, increase in total N-value from 0.2% to 0.5%, available P from 18.6 ppm to 38.5 ppm and the soil CEC from 7.6 me/100g to 36.6 me/100g. This planting media composition also makes it possible to enhance the growth of robusta coffee seedlings in plant height, stem diameter, number of leaves, leaf width, and root volume. Thus, this planting media composition is a suitable medium for the growth of robusta coffee seedlings.

Remediation Mechanism of Chitosan-modified Biochar on Cd-contaminated Farmland Soil and Its Effect on Bacterial Community

To explore the remediation mechanism of chitosan-modified biochar （passivator） on Cd-contaminated farmland soil, pot experiments were conducted to determine the effects of passivator on soil physical and chemical properties, ryegrass biomass, enzyme activity, and the response of soil bacterial diversity and structure. The results showed that when the amount of passivating agent was increased from 0.5% to 3%, the content of available Cd in soil was significantly decreased compared with that in the control, and the above-ground and subsurface biomass of ryegrass was increased by 1.08-1.56 times and 1.00-1.68 times, respectively. The enrichment and running coefficients were reduced by 6.15%-30.00% and 10.42%-31.25%, respectively. The correlation analysis results showed that soil pH, CEC, SOM, AN, AP, and AK were significantly negatively correlated with DTPA-Cd, indicating that the application of a passivating agent promoted the passivation of Cd in soil by changing the physical and chemical properties of soil. High-throughput sequencing results showed that the application of the inactivation agent changed the structure and diversity of the soil bacterial community, which was manifested as a significant decrease in α diversity, significant isolation of bacteria between different treatment groups, and an increase in the relative abundance of beneficial bacteria such as Sphingomonas and Blastococcus. Moreover, the activities of soil urease and cellulase increased, whereas the activities of sucrase and catalase decreased with the addition of a passivator. This study provides a theoretical basis and technical reference for the application of modified biochar in the remediation of Cd-contaminated farmland soil.

The Effect of C-Organic Sediment and Litter Carbon Estimation on Fertility and Site Health in Lampung Mangrove Center

Subsurface carbon storage reflects the fertility of mangrove sites. Site fertility has implications for site health. The aims of this study, among others, are to determine the content of C-organic sediments, determine the litter carbon content, and understand the effect of C-organic and litter carbon on on-site health (soil pH and CEC). The stages of research, among others, are sediment and litter sampling on the observation plot, analysis of sediment and litter samples in the laboratory, calculation of litter carbon by dry weight, and fertility analysis of site health using multiple linear regression analysis with a significant threshold of 95%. Based on the results of the study, the highest C-organic content was observed in cluster plot 3 (CL3); the highest increase in litter carbon was at CL2, and there was a significant effect between site fertility (C-organic) and site health (pH). The pH and carbon play a role in the mobility of compounds that form organic materials. Factors influencing on-site carbon health conditions include waste production, organic material, temperature, tree species, pollution, and climate. Sediment conditions affect sigh in organic matter and the health of the site. The results of this research can illustrate the fertility and health conditions of sites inmangrove forests, so regulations can be formulated to prevent damage to mangroves.

Effects of Organic and Inorganic Fertilizers on Soil Properties of Lowland Rice on Vertisols of Fogera District, Northwestern Ethiopia

Declining land productivity due to low soil fertility status as a result of continuous cultivation, inadequate use of organic and inorganic fertilizers is a major cause for decline crop productivity. Hence, a field experiment was conducted at Fogera National Rice Research and Training Center (FNRRTC) during the 2021 cropping season to determine the effects of integrated use of farmyard manure (FYM) and nitrogen fertilizer on soil properties and yield of lowland rice on the vertisols of Fogera district. The treatments were factorial combination of three levels of FYM (0, 5, and 7.5 t ha<sup>-1</sup>) and four levels of Nitrogen (0, 46, 92, and 184 kg ha<sup>-1</sup>). The experiment was arranged in a randomized complete block design (RCBD) with three replications. Representative soil samples were collected at a depth of 0-20 cm before treatment application and after crop harvest, and analyzed following the standard laboratory procedures. All collected soil data were analyzed by using SAS software (version 9.4). After crop harvest the results showed that soil pH, OC, TN, CEC, Exc. K, Ca, Mg and Av.P were significantly (p<0.01) affected by the main effects of FYM. The combined applications of FYM and N fertilizer also significantly (p<0.01) affected CEC, OC and Exc.Mg. The highest soil CEC, OC and Exc.Mg were recorded from the combine effects of 7.5 t/kg with 92 kg/ha. From the results of this experiment, it could be concluded that combined application of FYM and inorganic N fertilizers improved the chemical and physical properties, which may lead to enhanced and sustainable production of rice in the study area.

Annual Flood Phenomenon and Fertility Status of Rice Soil in The Coastal Area of Bengkulu

[ANNUAL FLOOD PHENOMENON AND FERTILITY STATUS OF RICE SOIL IN THE COASTAL AREA OF BENGKULU]. The rice fields in Rawa Makmur Village were agricultural land that was affected by annual floods. Soil fertility status is important for increasing the productivity of paddy. The research aimed to get the fertility status of soil affected by annual flood disasters, evaluating and mapping the distribution of soil fertility status at the research location. The methods used in this research include survey and soil testing methods at the Soil Science Laboratory, Faculty of Agriculture, Bengkulu University. Further evaluation of soil fertility status is in accordance with technical instructions from the Soil Research Center, Bogor (1995). This research was conducted in June – August 2023. The soil CEC value from each sampling point was classified as high with values ranging from 28.15 me/100 g - 39.83 me/100 g. The base saturation value in the study was classified as very low to moderate with values ranging from 11.49% - 40.08%. Soil organic C at the research location from each sampling point was classified as moderate to very high with values ranging from 2.42% - 5.97%. The soil phosphorus content at the research locations observed was classified as very low to low with values ranging from 2.69 mg/100 g – 12.11 mg/100 g. The soil potassium content at each sample point at the research location observed was classified as very low with values ranging from 0.14 mg/100 g – 1.43 mg/100 g. The research results show that the flood phenomenon has a significant impact on soil fertility. The soil fertility status at the research location is classified as low. Soil fertility parameters which are limiting factors in the status of soil fertility in Rawa Makmur Village are phosphorus, potassium and pH. So it is necessary to add P and K fertilizer to improve the soil fertility status.

Perubahan Sifat Kimia Tanah Tercemar Merkuri Dengan Berbagai Modifikasi Pemberian Biochar Dan Tanaman Akar Wangi (Vetiveria zizanioides (L.)

This research aims to determine changes in the chemical properties of mercury-contaminated soil with various modifications in the application of biochar and vetiver grass (Vetiveria zizanioides (L.). This research uses an experimental method with an ex-situ remediation approach which was carried out from October 2023 to January 2024 at greenhouse. Sampling of mercury-contaminated soil was carried out on former traditional gold mining land in Segubuk Hamlet, Kuang Village, Taliwang District, West Sumbawa Regency. Soil sampling was carried out at 13 locations determined by purposive sampling and carried out using a soil drill soil (pH H2O, C-organic and CEC) as well as analysis of the total concentration of mercury (Hg) in the soil before and after the experiment. The results showed that the application of biochar alone and biochar planted with vetiver grass (Vetiveria zizanioides (L.) had a significant effect) on changes in soil chemical properties and is effective in reducing the concentration of mercury (Hg) in the soil. Biochar application can improve soil chemical properties by increasing pH, organic C, and soil CEC. On the other hand, the release of H+ ions from the carboxyl functional group (-COOH) in biochar has the opportunity to form complexes with heavy metal ions so that it can reduce their concentration in the soil.

Effect of coffee husk biochar and inorganic NP fertilizer on soil properties, growth and yield of potato (Solanum tuberosum L.) on acidic soil of southwest Ethiopia

Soil acidity and low soil fertility due to nutrient leaching coupled with low inorganic fertilizer usage is a major cause of low crop yields across Southwest Ethiopia. Recently, biochar potential to improve soil fertility has gained significant attention but there are limited studies on the use of biochar in combination with inorganic fertilizers. A field experiment was, therefore, conducted to investigate the effect of combined application of biochar and inorganic NP nutrient on soil physicochemical properties, growth and yield of potato in Andiracha district, Southwestern Ethiopia. The experiment was laid out in randomized complete block design (RCBD) and replicated three times. The treatment consisted of four levels of biochar rates (0, 2.5, 5 and 7.5 t ha−1) and four fertilizer rates of (0, 75,100 and 125% of recommended N P rates). Data were analyzed using SAS version 9.3 Software. Analysis of variance showed that combined application of biochar and inorganic NP fertilizer had highly significant (p < 0.01) effect on days to flowering, stem number, plant height, total leaf area, total dry biomass, marketable tuber number per hill and harvest index and significant (p < 0.05) effect on marketable tuber weight and total tuber weight ha−1. Combined application of 7.5 ton ha−1 biochar with 165 kg N and 60 kg P ha−1 resulted highest tuber yield (42.64 t ha−1), that increased yield by 28.99% compared with recommended NP fertilizer alone (165 kg N ha−1 and 60 kg P ha−1), and by 76.6% compared to the control. The increase was mainly attributed to the improvement in soil physico-chemical properties especially soil pH, CEC, organic matter, total N and available P which is a reflection of increase in soil fertility. Consequently, it was determined that the best course of action for potato production in the area was to apply 7.5 tons of biochar ha−1 together with 165 kg N and 60 kg P ha−1. Therefore, the study recommends adoption of low cost biochar production techniques and capacity building to ensure satisfactory knowledge of biochar use and its adoption by potato growers for soil fertility management and enhanced crop productivity.

The Effect of Remediation of Soil Co-Contaminated by Cu and Cd in a Semi-Arid Area with Sewage Sludge-Derived Biochar

In this study, biochar derived from sewage sludge was applied to remediate Cu and Cd co-polluted soil in semi-arid areas for the first time, in which the effects of biochar on the improvement of soil physicochemical and biological properties as well as the immobilization of Cu and Cd were investigated. Soil water holding capacity increased by 0.22–2.74%, soil CEC increased by 0.52–4.06 units, soil SOM content increased by 1.41–5.97 times, and urease and catalase activities increased by 0.012–0.032 mg·g−1·24 h−1, 0.18–2.95 mg H2O2·g−1, but soil pH increased only slightly by 0.69 units after biochar application. In addition, although the total content of these two metals in the soil increased with the use of biochar, the content of DTPA-Cu and Cd decreased by −0.128–0.291 mg/kg, 0–0.037 mg/kg, with the increase in biochar application, and the content of acid-soluble Cu in the soil decreased from 27.42 mg/kg to 3.76 mg/kg, the mobility and bioavailability of these two metals in the soil decreased. Finally, the complexation of organic functional groups with the soil dominates the immobilization process of metals, especially Cu. These findings suggest that biochar from sewage sludge can effectively improve soil quality and remediate heavy metal-contaminated soils in semi-arid regions. Meanwhile, the use of sludge-based biochar for the remediation of contaminated soils also provides a new method for the safe disposal of sewage sludge and a new way for sustainable development. In subsequent studies, methods such as modification are recommended to improve the efficiency of sludge-based biochar for the removal of Cu and Cd.

Simultaneous removal of ammonium, phosphate, and phenol via self-assembled biochar composites CBCZrOFe3O4 and its utilization as soil acidity amelioration

ABSTRACT High concentrations of ammonium, phosphate, and phenol are recognized as water pollutants that contribute to the degradation of soil acidity. In contrast, small quantities of these nutrients are essential for soil nutrient cycling and plant growth. Here, we reported composite materials comprising biochar, chitosan, ZrO, and Fe3O4, which were employed to mitigate ammonium, phosphate, and phenol contamination in water and to lessen soil acidity. Batch adsorption experiments were conducted to assess the efficacy of the adsorbents. Initially, comparative studies on the simultaneous removal of NH4, PO4, and phenol using CB (biochar), CBC (biochar + chitosan), CBCZrO (biochar + chitosan + ZrO), and CBCZrOFe3O4 (biochar + chitosan + ZrO + Fe3O4) were conducted. The results discovered that CBCZrOFe3O4 exhibited the highest removal percentage among the adsorbents (P < 0.05). Adsorption data for CBCZrOFe3O4 were well fitted to the second-order kinetic and Freundlich isotherm models, with maximum adsorption capacities of 112.65 mg/g for NH4, 94.68 mg/g for PO4 and 112.63 mg/g for phenol. Subsequently, the effect of CBCZrOFe3O4-loaded NH4, PO4, and phenol (CBCZrOFe3O4-APP) on soil acidity was studied over a 60-day incubation period. The findings showed no significant changes (P < 0.05) in soil exchangeable acidity, H+, Mg, K, and Na. However, there was a substantial increase in the soil pH, EC, available P, CEC, N-NH4, and N-NO3. A significant reduction was also observed in the available soil exchangeable Al and Fe (P < 0.05). This technique demonstrated multi-functionality in remediating water pollutants and enhancing soil acidity.

Natural colonizers effectively restore heavy metal polluted wasteland

In India, ∼30% of total land is degraded due to pollution, salinization, and nutrient loss. Change in soil-quality at urban waste-dumping site prior and after cow-dung amendment was compared with control agriculture soil. The soil at waste-dumping site had elevated pH, EC, temperature and lowered OC and NPK concentrations when compared to control. Polymetallic pollution of Cr, Cd, Pb, and Ni beyond permissible limits was obtained. Cow-dung amendment restored soil physicochemical properties at the waste-dumping site, with increasing soil moisture, CEC and OC; however, a slight change in soil bulk-density and heavy-metal concentration post-amendment was noted. The seven natural colonizers present at the waste-dumping site accumulated more metals in roots than shoots. Datura innoxia had maximum bioaccumulation of Cr, Calotropis procera of Cd and Ni and Parthenium hysterophorus of Pb in roots. All these plants had Bioacccumulation factor (BAfroot )>1 and translocation factor (Tf) <1 for Cd and serve as its phytostabilizer except Calotropis procera which had BAfroot >1 and Tf >1 and is identified as a phytoextractor for Cd. Cow-dung amendment alone appeared to be insufficient and additionally the revegetation of natural colonizers is recommended for effective reduction in heavy metal load and improving overall soil health at wasteland. Such eco-restoration may also minimize risks to biodiversity in India.

Pb(II) and chlortetracycline immobilization and economy of biologically amended coastal soil

To study the pollutants immobilization and economy of biologically amended coastal soil, Alternanthera philoxeroides biomass (Bm), biochar (Bc), and dodecyldimethyl betaine (BS) modified Bc (BS-Bc) were used to amend coastal soil from Jialing, Fu, and Qu River. A runoff experiment was used to simulate the longitudinal migration and morphological changes of Pb(II) and chlortetracycline (CTC) in each amended coastal soil, and the economy of pollutants immobilization by different amended coastal soil were compared. The equilibrium time of Pb(II) and CTC in each amended coastal soil ranked in the order of BS-Bc-amended > Bc-amended > Bm-amended > unamended coastal soil. The average Pb(II) and CTC flow rate in different amended coastal soils presented an opposite trend with the equilibrium time. Pb(II) and CTC content all reduced with the increasing runoff length. Under the same soils, the content changes presented Bm and Bc amended > unamended > BS-Bc amended. CEC and clay content of coastal soils were the key factors affecting Pb(II) and CTC immobilization. The immobilization mechanisms were electrostatic attraction, ion exchange, surface precipitation, and complexation to Pb(II) and ion exchange and complexation to CTC. The economy of Pb(II) and CTC immobilization ranged from 0.5 to 9.0 and from 1.0 to 5.4 mg/¥, and coastal soil amended by BS-Bc had practical application value and high economy.

Remediation effect of walnut shell biochar on Cu and Pb co-contaminated soils in different utilization types

Biochar, with its dual roles of soil remediation and carbon sequestration, is gradually demonstrating great potential for sustainability in agricultural and ecological aspects. In this study, a porous biochar derived from walnut shell wastes was prepared via a facile pyrolysis coupling with in-situ alkali etching method. An incubation study was conducted to investigate its performance in stabilizing copper (Cu) and lead (Pb) co-contaminated soils under different utilization types. The biochar effectively decreased the bioavailable Cu (8.5–91.68%) and Pb (5.03–88.54%), while increasing the pH, CEC, and SOM contents in both soils. Additionally, the results of sequential extraction confirmed that biochar promoted the transformation of the labile fraction of Cu and Pb to stable fractions. The mechanisms of Cu and Pb stabilization were found to be greatly dependent on the soil types. For tea plantation yellow soil, the main approach for stabilization was the complexation of heavy metals with abundant organic functional groups and deprotonation structure. Surface electrostatic adsorption and cation exchange contributed to the immobilization of Cu and Pb in vegetable-cultivated purple soil. This research provides valuable information for the stabilization of Cu and Pb co-contaminated soils for different utilization types using environmentally-friendly biochar.

Effects of Land uses on Soils Quality in Rwandan Central Plateau Agro-Ecological Zone

Conversion of land use from forest to agricultural uses modifies soil quality through physiochemical soil properties changes. This study was conducted in Rwanda’s central plateau agro-ecological zone to evaluate the effect of forest and agricultural land uses on soil quality. The study was conducted in 2020. Soil samples were collected at the top, middle and bottom positions of each of the two land uses. We analyzed soil bulk density, soil moisture content, soil pH, soil organic matter (SOM), total nitrogen (TN), available phosphorus (Av P), and CEC for each position of the land uses. Data were analyzed using ANOVA in GENSTAT version 13. The results revealed that soil properties were significantly affected by land use change. Analysis of variances (LSD&lt;0.05) results showed, however, that treatments were not significantly different within the same land use. The results showed that treatments from top position of forest lands had the highest mean values for soil organic matter and total N parameters with the respective mean values of 6.58 %, and 0.37 %. Treatments from middle position of forest lands had the highest mean values for soil moisture content and Av P parameters respectively with 23.60 % and 29.56 ppm. But, soil bulk density was high on top position of agricultural land with a mean value of 1.49 g/cm3. Land users are advised to apply crop and soil management techniques which maintain soil quality and productivity on agricultural lands.

Dynamics of Soil Physical and Chemical Properties under Different Current Land Use Types and Elevation Gradients in the Sala Watershed of Ari Zone, South Ethiopia

The dynamics of soil physical and chemical properties have been increasing due to inappropriate land use and unsustainable land management practices in Ethiopia. This study aims to assess the dynamics of selected soil physical and chemical properties under different current land use types and altitudinal gradients in the Sala watershed of Ari Zone in South Ethiopia. In the study area, analyzing and understanding the dynamics of soil physicochemical properties under different land use types play a vital role in sustainable soil productivity. Before collecting a soil sample, land use types and altitudinal variations were surveyed in the study watershed. Three random strata were selected from the watershed, and the major adjacent land use types in each stratum were identified across elevation gradients. A total of 30 composite soil samples were collected from different land uses and elevations using a zigzag sampling technique at 0–20 cm soil depth from upland (12), midland (9), and lowland (9). Laboratory results showed that most soil physical and chemical properties had poor ratings in the watershed area. All soil properties were significantly affected by land use types and elevation factors (P&lt;0.05), except for soil texture, TN, and CEC. Soil texture is highest in the upper and lower elevations of grazing land (61.3%) and shrubland (55.4%), while lowest in cultivated land (11.3%) and barren land (11.6%) at higher altitudes. The highest mean of soil texture was dominated by clay soil (55%) in shrubland followed by sand soil (50.30%) in the barren land and silt soil (20.06%) in cultivated land. Chemical soil properties (pH, SOM, TN, Av. P, Av. K, and CEC) were significantly varied under each land use type across altitudes. The results of this study showed that inappropriate land use and unsustainable agricultural practices had more significantly influenced the soil fertility status. Therefore, appropriate soil and water conservation measures should be implemented in the studied watershed to improve soil fertility and crop productivity.

Soil Fertility Assessment and Mapping under Different Land Use Types along Toposequence at Danka Watershed in Dinsho Districts of Bale Highland Oromia, Southeastern Ethiopia

Soil fertility assessment and mapping bases, to increase fertilizer usage efficiency, decision-makers, planners, and soil management in undulating slopes farming of Ethiopian highlands like Bale Highland. The study aimed to assess and map soil fertility status along toposequence under different land use types at the Danka watershed of Dinsho District Bale Highland, Southeastern Ethiopia. Following the initial reconnaissance field survey, 54 composite soil samples were prepared from the three land use types (natural forest, grazing, and cultivated) at three slope positions lower (0 - 10%), middle (10 - 15%), and upper (15 - 30%) at a soil depth of 0 to 20 cm. Finally, the laboratory results were interpolated using the IDW interpolation technique in ArcGIS software 10.5 for the soil fertility status map and further analyzed using R software 4.1.1 Version for mean separation. The study findings indicate that the soil texture class of the study was loam to clay loam, clay loam, and clay to clay loam at the upper, middle, and lower slope positions, respectively. The finding revealed that the values varied from 5.81 – 6.66, 2.07 – 6.25%, 0.13 – 0.71%, 2.83 – 17.56 gm/kg, and 14.04 -38.80 cmol (+)/kg) for the soil pH, organic matter, total nitrogen, available phosphorus, and CEC, respectively. In this study, most of the soil fertility status of the Danka watershed was as follows: natural forest &gt; grassland &gt; cultivated land use types and lower slope &gt; middle slope &gt; upper slope positions. In conclusion, the main factors contributing to the area's declining soil fertility status were monocropping, total crop residue removal, soil erosion, nutrient leaching, and inadequate soil management. The results of the current study offer the basis for the work of farmers, planners, decision-makers, and other agriculture-related stakeholders. Integrated soil fertility management with biophysical soil conservation measures is advisable for cultivated land at all slope positions. Further, a study on slope position-based crop response fertilizer rating for agricultural precision and ensuring food security is recommended in undulating fields of the Danka watershed.

Effects of Slope Position on Soil Physicochemical Properties of Cultivated Land Use Type in Danka Watershed of Dinsho District, Bale Highland, Oromia, Southeast Ethiopia

Quantify and understand soil nutrient loss under different undulating topography farming bases for site-specific management and targeted fertilizer application rates. The study aimed to assess the effect of slope positions on soil physicochemical properties at the Danka watershed of Dinsho District Bale Highland, Southeastern Ethiopia. Consequent to the reconnaissance survey, soil samples were taken from the cultivated land use type in three replications at three different soil depths (0-0, 20-40, and 40-60 cm) and three slope positions (upper, middle, and lower), analyzed follow standard laboratory procedure and further analyzed using R software 4.1.1 version. The results showed soil physicochemical properties were significantly (P ≤ 0.05) influenced by the interaction between slope positions and soil depth. The results of soil physical properties varied from 1.29 -1.73 g cm-3, 2.47 – 2.74 g cm-3, 47.80 - 36.75%, 10.78 – 15.11%, 12.76 – 18.16%, and 4.06 – 8.16% bulk density, particle density, total porosity, FC, PWP, and AWHC, respectively. Selected soil chemical properties varied from 5.91 - 6.45, 0.64 - 3.20%, 0.04 - 0.25%, 1.14 - 5.60 gm/kg, and 10.24 - 37.24 cmol (+)/kg) soil pH, organic matter, total nitrogen, available phosphorus, and CEC, respectively. The values of exchangeable bases were concentration increased from the upper slope position toward the lower slope position and with increased soil depth. Soil micronutrients were increased with increased slope and decreased with increased soil depth. The lowest slope position had relatively better soil nutrient contents than other slope positions. It is advised that integrated soil fertility management, biophysical soil and water conservation, and slope-based, site-specific fertilizer rating for advance agricultural precision and ensure food security.