The Effect of Anaerobic Digestate on the Soil Organic Carbon and Humified Carbon Fractions in Different Land-Use Systems in Lithuania

The most important component of agricultural system are soils as the basis for the growth of plants, accumulation of water, plant nutrients and organic matter. The main task of our research was to ascertain changes in soil organic carbon (SOC) and mobile humified carbon fractions in digestate-treated soils. We have performed three field experiments using the same design on two soil types in 2019–2020. We studied the fertilization effects of different phases of digestate on Retisol and Fluvisol. Fertilization treatments: control; separated liquid digestate 85 kg ha−1 N; and 170 kg ha−1 170 N; separated solid digestate 85 kg ha−1 N; and 170 kg ha−1 N. We have found a greater positive effect on the increase in SOC because of the use of the maximum recommended fertilization rate of the solid digestate. The content of mobile humic substances (MHS) tended to increase in grassland and crop rotation field in digestate-treated soil. In our experiment, maximum concentration of SOC was found in 0–10 cm soil layer, while in the deeper layers the amount of SOC, MHS and mobile humic acids proportionally decreased. We concluded, that long-term factors as soil type and land use strongly affected the humification level expressed as HD (%) in the soil and the highest HD was determined in the grassland soil in Fluvisol.

Development Trend and Stability Analysis of Creep Landslide With Obvious Slip Zone Under Rainfall-Taking Xinchang Xiashan Basalt Slope as an Example

The creep slope is a dynamic development process, from stable deformation to instability failure. For the slope with sliding zone, it generally creeps along the sliding zone. If the sliding zone controlling the slope sliding does not have obvious displacement, and the slope has unexpected instability without warning, the harm and potential safety hazard are often much greater than the visible creep. Studying the development trend of this kind of landslide is of great significance to slope treatment and landslide early warning. Taking Xiashan village landslide in Huishan Town, Xinchang County, Zhejiang Province as an example, the landslide point was determined by numerical simulation in 2006. Generally, the landslide is a typical long-term slow deformation towards the free direction. Based on a new round of investigation and monitoring, this paper shows that there are signs of creeping on the surface of the landslide since 2003, and there is no creep on the deep sliding surface. The joint fissures in the landslide area are relatively developed, and rainfall infiltration will soften the soft rock and soil layer and greatly reduce its stability. This paper collects and arranges the rainfall data of the landslide area in recent 30 years, constructs the slope finite element model considering rainfall conditions through ANSYS finite element software, and carries out numerical simulation stability analysis. The results show that if cracks appear below or above the slope’s sliding surface, or are artificially damaged, the sliding surface may develop into weak cracks. Then, the plastic zone of penetration is offset; In the case of heavy rain, the slope can unload itself under the action of rainfall. At this time, the slope was unstable and the landslide happened suddenly.

Sloping land use affects the complexity of soil moisture and temperature changes in the loess hilly region of China

Various land use types have been implemented by the government in the loess hilly region of China to facilitate sustainable land use. Understanding the variability in soil moisture and temperature under various sloping land use types can aid the ecological restoration and sustainable utilization of sloping land resources. The objective of this study was to use approximate entropy (ApEn) to reveal the variations in soil moisture and temperature under different land use types, because ApEn only requires a short data series to obtain robust estimates, with a strong anti-interference ability. An experiment was conducted with four typical land use scenarios (i.e., soybean sloping field, maize terraced field, jujube orchard, and grassland) over two consecutive plant growing seasons (2014 and 2015), and the time series of soil moisture and temperature within different soil depth layers of each land use type were measured in both seasons. The results showed that the changing amplitude, degree of variation, and active layer of soil moisture in the 0–160 cm soil depth layer, as well as the changing amplitude and degree of variation of soil temperature in the 0–100 cm soil layer increased in the jujube orchard over the two growing seasons. The changing amplitude, degree of variation, and active layer of soil moisture all decreased in the maize terraced field, as did the changing amplitude and degree of variation of soil temperature. The ApEn of the soil moisture series was the lowest in the 0–160 cm soil layer in the maize terraced field, and the ApEn of the soil temperature series was the highest in the 0–100 cm layer in the jujube orchard in the two growing seasons. Finally, the jujube orchard soil moisture and temperature change process were more variable, whereas the changes in the maize terraced field were more stable, with a stable soil moisture and temperature. This work highlights the usefulness of ApEn for revealing soil moisture and temperature changes and to guide the management and development of sloping fields.

Complex Variable Solution for Stress and Displacement of Layered Soil with Finite Thickness

The static problem of a layered isotropic elastic body is a very useful research subject in relation to the analysis and design of foundation works. Due to the complexity of the problem, there is no analytical solution to the problem so far. This study provides an efficient analytical approach to accurately calculate the displacement and stress fields of the soil. The constraints of bedrock on soil, different soil layer thickness and the shear stress of the foundation on soil were all taken into account in the analysis. In this study, each layer is regarded as an isotropic elastomer with infinite width, and the layers are in complete contact. By using conformal mapping, each layer is mapped to a unit circle, and the two complex potential functions are expanded into Taylor series with unknown coefficients. These unknown coefficients are obtained by satisfying boundary conditions and continuity conditions. The boundary and continuity conditions were verified in this paper. As a validation step, we compared the analytical results for the settlement with the results of the ANSYS numerical simulations and found good agreement. Parametric analyses were also carried out to investigate the influence of different distribution forms of base pressure on surface settlement, and the effects of layered properties on the surface settlement and stress field.

Effects of Urbanization Intensity on Glomalin-Related Soil Protein in Nanchang, China: Influencing Factors and Implications for Greenspace Soil Improvement

Glomalin-related soil protein (GRSP) is a stable and persistent glycoprotein secreted by arbuscular mycorrhizal (AM) fungi that plays important roles in sequestering soil organic carbon (SOC) and soil quality improvement. Rapid urbanization has led to serious greenspace soil disturbances, resulting in soil degradation. However, few researches have examined the effects of urbanization on GRSP and its influencing factors. In this study, impervious surface area (ISA) was selected as an indicator of urbanization intensity. A total of 184 soil samples were collected from the 0-20 cm soil layer in the Nanchang greenspace, China (505 km2). The GRSP content, soil properties, urban forest characteristics, and land-use configuration were determined and investigated. The results showed that total GRSP (TG) and easily extractable GRSP (EEG) averages were 2.38 and 0.57 mg·g-1, respectively. TG and EEG decreased by 16.22 % and 19.68 %, respectively, from low to heavy urbanization areas. Linear regression analysis revealed a negative correlation between SOC and GRSP/SOC. SOC decreased from 39.9 to 1.4 mg·g-1, while EEG/SOC and TG/SOC increased by about 17 % and 34 %, respectively, indicating the important contribution of GRSP to the SOC pool. Pearson and redundancy analysis showed that GRSP was positively correlated with soil SOC, P, N, vegetation richness, and tree height but negatively correlated with pH, bulk density, and impervious area. The partial least squares path model (PLS-PM) further showed that urbanization affected soil properties, forest characteristics, and land use factors leading to GRSP changes. This study revealed the effects and key influencing factors of urbanization on GRSP. In the future, urban greenspace soil improvement can be considered from the new perspective of enhancing GRSP soil content.

Application of Corn Straw and Woody Peat to Improve the Absorption and Utilization of 15N-Urea by Maize

Increasing nitrogen fertilizer use efficiency has become an environmental and economic demand in order to minimize losses of nitrogen and maximize the output from nitrogen added. The application of organic amendments with N fertilizers could be proposed as an important economic and environmental practice for improving N fertilizer use. A two-year field experiment was carried out using the 15N tracer technique to study the impact of corn straw and woody peat application on uptake and utilization of N fertilizer by maize plant. Three treatments were set up: CK (15N labeled urea alone), CS (15N labeled urea + crushed corn straw) and WP (15N labeled urea+ crushed woody peat). The results showed that, as compared to CK, both straw and peat treatments led to (i) an increase in yield of maize, 15N urea utilization rate, and residual 15N urea remained in soil by 11.20% and 19.47%, 18.62% and 58.99%, 41.77% and 59.45%, respectively, but (ii) a decrease in the total loss rate by 6.21% and 16.83% (p < 0.05), respectively over the two seasons. Moreover, the significantly highest effect was recorded with woody peat application rather than that with corn straw. Our study suggests that corn straw and woody peat can be used as organic fertilizers to increase maize yields, promote nitrogen fertilizer balance sheet, reduce the leaching of N fertilizer into the subsurface soil layer, and facilitate the further absorption and utilization of soil residual nitrogen. Therefore, the application of humified organic material play a crucial role in N utilization efficiency enhancement.

Exploitation of neighbouring subsoil for nutrient acquisition under annual-perennial strip intercropping systems

Little is known of how the deep root systems of perennial crops contribute to deeper and better resource use when intercropped with annuals in arable fields. Therefore, we aimed at measuring the capacity of perennial deep roots, alfalfa (Medicago sativa L.) and curly dock (Rumex crispus L.) to access the nutrient source located under the neighboring annuals at 1.0 and 2.5 m of soil depth. Alfalfa and curly dock were able to access the tracer-labelled source placed at a distance under the annual crop strips. As a result, the reliance on deeper soil layer for nutrient uptake under intercroppings became greater compared with sole-croppings. Combination of an annual cereal (winter rye) and a perennial legume (alfalfa) with contrasting root systems exhibited higher resource complementarity compared with intercroppings having similar root systems or absence of legumes. Our results demonstrated that the deep-rooted perennials when intercropped with annuals can induce vertical niche complementarity, especially at deeper soil layers. This was assumed to be due to the vertically stratified root activity between the crop components, however, the magnitude of the effects depended on choice of crop combinations, and on types of tracers. Future studies should include estimates such as relative yield total and land equivalent ratio to quantitatively determine the effects of resource acquisition under annual-perennial intercropping in arable fields.

Deep tillage reduces the dependence of tobacco on AMF and promotes the growth of tabacco(Nicotiana tabacum L.) in dryland

The traditional shallow tillage method makes the soil quality declining, and affects the efficiency of agricultural production. Taking the conventional rotary tillage(12 cm) as the control, Yunyan 87 as the test variety, and the soil type of the test site is paddy soil, we studied the effects of deep tillage(Subsoiling 30 cm) on soil nutrients, arbuscular mycorrhizal fungi (AMF) and tobacco（Nicotiana tabacum L.）growth. The results showed that deep tillage increased the contents of organic carbon, available phosphorus(AP) and available potassium(AK) in 20 ~ 40 cm soil layer. The community of AMF was changed by deep tillage. Glomus, the dominant genus in both group, increased significantly in the soil after deep tillage. The colonization rate of AMF was lower than that of conventional rotary tillage. Deep tillage was beneficial to the growth of tobacco in the middle and late stages. Root growth and nutrient content of tobacco increased. Deep tillage significantly improved the output value of tobacco. It can be seen that deep tillage is conducive to improving soil fertility, promoting the vigorous growth of root, reducing the dependence of tobacco on AMF, and promoting the high quality and yield of tobacco in drylands of Hunan.