Applied and Environmental Soil Science

Soil organic carbon (SOC) is a crucial carbon reservoir that needs to be monitored for deforestation and forest degradation. The top one-meter layer of soil contains around 1500–1600 Pg of carbon. Assessing the SOC pool is essential for understanding the soil system’s carbon sequestration potential (CSP) as a mitigation strategy and determining whether it acts as a source or sink for atmospheric CO₂, depending on the level of saturation. However, there are limited studies on SOC in Nepal’s forests. This research aims to assess SOC variation in the Shuklaphanta National Park in Nepal. It focuses on determining SOC according to depth and analyzing the variation of SOC among the core area of the national park, grasslands, and buffer zone community forests (CFs) and identifying the factors that contribute to the variation in soil carbon across different land uses. The study was conducted using a systematic sampling method with a sampling intensity of 6.59% on 180 soil samples taken from permanent plots set up by the Forest Resource Assessment (FRA) Nepal. The analysis was based on SOC estimated up to the depth of 0–10, 11–20, and 21–30 cm using a modified Walkley–Black wet oxidation method. The study also analyzed contributing factors affecting soil carbon such as vegetation, forest fire, rate of forest resource use, and different soil properties like pH and bulk density. The study found that the mean SOC% up to the depths of 0–10 cm, 11–20 cm, and 21–30 cm was 2.08, 0.98, and 0.68, respectively, in forest areas. Mean SOC% in grasslands was found to be 1.7, 1.68, and 1.87 in 0–10, 11–20, and 21–30 cm, respectively, and in community forests, it was found to be 1.3, 0.98, and 0.58 in 0–10, 11–20, and 21–30 cm, respectively. Similarly, the vertical mean SOC in tC⋅ha⁻¹ (0–30 cm) was found to be 41.75 tC·ha⁻¹ in the core area of the national park, 46.64 tC·ha⁻¹ in grassland, and 37.50 tC·ha⁻¹ in CFs. The study also found that there was variation in SOC with depth and that most of the SOC was concentrated in the topsoil in the core area of the national park and buffer zone community forests. Deep layers of SOC were found in grasslands, core area of the national park, and CF in decreasing order. The study implies that the national park has enormous potential to recapture atmospheric CO₂ into the soil. Participating in the sustainable management of the national park can enhance the soil quality and help meet strategies to mitigate climate change. Factors such as vegetation cover, fire, bulk density, and vegetation type were found to be promising for SOC concentration.

A process called bioremediation can be used to turn abandoned mining sites into useful agricultural land. An alternative to enhancing the quality of the ex-siltstone mining soil so that it can be used again as agricultural land is the application of biocompost fertilizer. This study intends to investigate how biocompost might enhance the ex-siltstone mining soil’s quality in incubation treatments. The composition of biocompost used in this study is ingredient I: (a) cow manure = 50%; (b) chicken manure = 30%; (c) sand = 10%; (d) bacteria (bioactivator) = 10%; ingredient II: ingredient I is mixed with cow manure in a composition ratio of 1 : 2. The ex-mining soils were gathered in the ex-cement mining region of Lhoknga Subdistrict, Aceh Besar District (5.45°N, 95.2°E). Incubation experiments were conducted in incubation pots (approximately 5 kg per pot) that were randomly placed in a greenhouse using a 4 × 4 factorial completely randomized design (CRD) with three replications. The first factor is the ratio of ex-siltstone mining soil : biocompost, which consists of four levels of comparison: control (ex-mining soil not incubated), 1 : 1 (50 : 50), 1 : 2 (33 : 67), and 1 : 3 (25 : 75). The second factor is the incubation period, which has four levels: 0, 2, 4, and 6 weeks with 48 experimental units. Indicators of the impact of biocompost on the physical and chemical quality of ex-siltstone mining soil were examined. The result shows that bioremediation of ex-siltstone mining soil with biocompost application improves the quality of ex-siltstone mining soil by decreasing bulk density and permeability and also increasing porosity, decreasing soil pH from alkaline to neutral, and increasing soil organic C, total N, available P, and total K. The incubation period of ex-siltstone mining soil influences the changes and dynamics of the soil’s chemical properties.

The assessment of the distribution of soil physicochemical properties provides basic information for our understanding of the soils to grow crops and sustain forests and grasslands. The changes in soil physicochemical properties along elevational gradients were studied in a less accessible Sida Forest, southern Ethiopia. Hence, the present study was conducted to assess the distribution of soil physicochemical properties along the elevational gradients and to evaluate the fertility status of the soil. Data on soil physicochemical properties were collected from five points (four from each corner and one from the center) of the main plot. A pit of 20 cm × 20 cm was dug at a depth of 0–30 cm and a kilogram of composite soil samples was brought to the Wolkite Soil Testing Laboratory for physicochemical analysis. The results revealed that the physicochemical properties of the collected soil samples show a significant correlation with elevation changes. Sand had a significantly negative correlation and variation with elevation; it decreases as elevation increases with the rate of correlation (r = −0.44, ). However, silt had a nonsignificantly positive (r = 0.20, ) correlation to the elevation, while clay had a significantly positive correlation to elevation, and it increases as elevation increases with the rate of correlation coefficient (r = 0.40, ). Soil OC, OM, TN, CEC, and exchangeable Mg²⁺ had significant positive correlation to the elevation; they increase as elevation increases with the rate of correlation coefficient (r = 0.42, ), (r = 0.41, ), (r = 0.44, ), (r = 0.34, ), and (r = 0.27, ), respectively. While BD, pH, EC, Av. P, exchangeable Ca²⁺, and exchangeable K⁺ had a nonsignificant negative correlation to the elevation, they decrease as elevation increases with the rate of correlation (r = −0.70, ), (r = −0.20, ), (r = −0.05, ), (r = −0.04, ), (r = −0.04, ), and (r = −0.053, ), respectively. This study attempted to provide information on the impact of elevation on soil’s physicochemical properties. Given that, the soil’s physicochemical properties exhibit variation with elevation changes.

The level of sediment deposited in the Lake Ziway is increasing through time as a result of soil erosion, and eventually the depth of the lake has decreased. Therefore, the objective of the study was to assess farmers’ perception of soil erosion and the conservation measures to the surrounding areas of Lake Ziway in the central Rift Valley of Ethiopia. The survey was made using purposive sampling techniques. The survey has considered the 14 Kebeles from the 3 districts adjacent to the lake. From each Kebele, 10 respondents were selected randomly. Totally, 140 respondents were selected from the community. The descriptive statistic was used to compare the dependent variables. The majority of respondents (92.2%) have observed the presence of soil erosion in the study area. The hillsides and slope areas are the major sources of soil erosion, according to 80% of the respondents. The respondents that have identified the most and least susceptible soils to erosion by their textural classes are sand soil (Biyyo Chirecha) (57.1%) and soft clay soil (Biyyo Bole) (1.4%), respectively. The soil erosion is increasing in their cultivated land and surrounding areas. The study has found that most of the respondents (86.5%) are participating in soil and water conservation activities. Leucaena leucocephala, Faidherbia albida, Azadirachta indica, and Schinus molle are the dominant tree species planted in the study area for soil and water conservation purposes. In conclusion, there is heavy soil loss due to erosion on cultivated land from the upland which directly deposited to Lake Ziway as sediment which decreases the lake depth. The study recommends that appropriate soil and water conservation measures and land management should be implemented on erosion prone areas in the Lake Ziway watershed with full participation of all stakeholders including the local farmers.

There are various challenges that limit crop productivity in developing countries like Ethiopia. Lack of accessible plant nutrients in proper quantity as well as form to plants is an important determinant of reducing agricultural productivity. In this regard, a trial was conducted at Shela Borkoshe on the land owned by the farmer in Sodo Zuriya District, Wolaita Zone, Southern Ethiopia over the planting seasons of 2019 to 2020 with the aim of identifying the appropriate rates of blended nitrogen, phosphorus, sulfur, boron (NPSB), and potassium (K) fertilizer in maize production. The treatments, which were assessed using a factorial randomized complete block design with three replications, comprised of four rates of blended NPSB (0, 50, 100, and 150 kilograms/hectare) and four rates of K (0, 30, 60, and 90 kilograms/hectare K₂O). Agronomic traits leaf area, LAI, ear length, seeds per row, seeds per ear, TSW, biomass as well as grain produce have been significantly varied due to NPSB by K fertilizer rates interactions. The highest leaf area (9886.20 ± 343.95 cm²), LAI (7.78 ± 0.26), ear length (32.58 ± 1.46 cm), TSW (160.67 ± 4.85 g), biomass (14941 ± 200.92 kilograms/ha), and grain output (7544 ± 119.49 kilograms/ha) have been attained by combining 150 kilograms/ha NPSB and 90 kilograms/ha K fertilizer rate. Following this, maximum quantity of seeds per row (44.88 ± 1.67) and seeds per ear (705.87 ± 25.61) have been attained from combination of 150 kilograms/ha NPSB and 60 kilograms/ha K fertilizer rates. Economic analysis revealed that maximum net profit (1491 Dollar/ha) and marginal rate of return (MRR) 1196.67% have been achieved from combining 150 kilograms/ha NPSB and 60 kilograms/ha K fertilizer rates. This investigation revealed that the combination of the NPSB fertilizer level of 150 kilograms/ha and 60 kilograms/ha K fertilizer showed superior performance with higher grain yield and economic return over other treatments. Therefore, a combined application of 150 kilograms/ha NPSB with 60 kilograms/ha K fertilizer rates could be recommended for maize production in the study area and similar agro-ecologies.

The characterization of soil landscapes is becoming increasingly important for making decisions regarding site-specific agriculture systems and soil management. This study was initiated for the purpose of identifying landscape-scale spatial soil variation using a toposequence model so that site-specific fertilization could be achieved. According to the finding, the soils were shallow to very deep in depth, moderately acidic to moderately alkaline in soil reaction, nonsaline in salinity, and clay to sandy loam in texture. The soils were found very low to low levels in most soil nutrients, very low to very high levels of base saturation, and deficient in zinc but have adequate levels of iron, copper, and manganese. The soil exchange complex was mainly dominated by Ca and Mg where the order of occurrence was Ca > mg > K > Na. The CEC values were in high to very high range. Following the field survey and soil analytical results, five main reference soil groups of the World Soil Resource Base—Leptosols (56%), Luvisols (8.5%), Fluvisols (14.4%), Vertisols (13%), and Cambisol (8.2%)—were identified and mapped. Leptosols cover the largest landmass of the watershed and mostly found at the summit and hill back slopes. On the other hand, Luvisols, Fluvisols, Vertisols, and Cambisols were found on the middle and foot slopes. According to the findings, the variation in soil source indicating that topography is the primary pedogenic element in the formation of the soil in the watershed that was under research. Therefore, having local-scale-specific soil information can assist the site-specific application of soil nutrients and amendments based on spatial variability which is tailored to the soil requirements.