Soil & Tillage Research最新文献

In the coastal plain region of the United States, conservation agriculture practices are being implemented to improve soil health, minimize environmental impacts, and improve farm profitability. Common practices include cover cropping and conservation tillage using strip tillage, minimal tillage, or no tillage. However, the soil response to specific combinations of conservation tillage and cover crop rotations remains poorly quantified. The objective of this research was to evaluate changes in soil properties from different combinations of conservation management. Four tillage systems – conventional, strip, minimal, and no tillage – and three winter cover rotations – fallow, winter cash crop, and high-biomass cover crop – were tested in a split-plot design. Bulk density, depth to a root-restrictive layer, soil carbon concentration, soil carbon stock, field-saturated hydraulic conductivity, and yield were measured over a seven-year period. Bulk density and field-saturated hydraulic conductivity showed greater temporal variation in the strip tillage and conventional tillage practices. Depth to root-restrictive layer was consistently highest in the strip and minimal tillage treatments, which both included implements designed to alleviate subsoil compaction. Treatments that combined conservation tillage with a winter cover (i.e., cash crops or high-biomass cover crops) had greater increases in soil carbon concentrations and carbon stock. Summer cash crop yield was significantly increased following the high-biomass cover crop treatment in 2 out of the 7 years. Altogether, soil carbon showed a more consistent response to conservation management than the other soil properties, which tended to show greater variability based on the time since disturbance (e.g., tillage). Conservation management practices therefore need to be consistently applied for multiple years in order to improve soil properties such as bulk density and saturated hydraulic conductivity.

Cultivation of maize (Zea mays L.) can emit significant greenhouse gases (GHGs) due to root respiration, soil organic matter decomposition, and fertilizer losses in a tropical environment. Our objective was to examine the effect of tillage (conventional tillage [CT], minimum tillage [MT], and no-tillage [NT]), N fertilization rate (0, 90, and 120 kg N ha⁻¹), and manure application rate (0, 5, and 10 Mg ha⁻¹) on CO₂, N₂O, and CH₄ emissions under maize in two growing seasons (July-October 2018 and May-August 2019) in southwest Nigeria. We measured CO₂, N₂O, and CH₄ fluxes using the static chamber method and soil temperature and water content weekly, global warming potential (GWP), maize yield, and greenhouse gas intensity (GHGI). The CO₂ and N₂O fluxes peaked immediately following planting, fertilization, and intense precipitation, with most fluxes concentrated at 2–6 wk after planting. The CH₄ flux showed little change throughout the duration of the study. Cumulative CO₂ and N₂O fluxes were greater for CT and MT than NT, but cumulative CH₄ flux was greater for MT than CT and NT. Higher N fertilization rate increased N₂O and CH₄ fluxes. The GWP was greater for CT than MT and NT and greater for 90 than 0 kg N ha⁻¹. Maize yield was greater for MT than CT and NT and increased with higher N fertilization rate. The GHGI was lower for MT than CT and lower for 120 than 0 and 90 kg N ha⁻¹. Because of overall lower maize yield, MT with reduced N ferilization rate in split applications may be needed to reduce GHG emissions while sustaining yield in the sandy soils of southwest Nigeria.

Preventing water erosion is crucial for maintaining ecosystems and ensuring food security, necessitating a comprehensive understanding of the spatial and temporal patterns of water erosion and its underlying drivers. In the context of global warming, analyzing the impacts of land use dynamics and climate change on water erosion contributes to effective land management and sustainability of both industry and agriculture. This study aims to analyze the spatial distribution of water erosion in the western Songnen Plain from 1990 to 2020 using the Revised Universal Soil Loss Equation (RUSLE), with a focus on assessing the impacts of land use and climate on water erosion. The results revealed a 7.1 % increase in the area experiencing water erosion above light levels in the western Songnen Plain. The hotspots for water erosion were located in the southeast and northwest of the study area. The rapid expansion of farmland and land salinization, leading to reduced vegetation cover and soil property deterioration, were the main causes of intensified water erosion in the region before 2000. Although water erosion was slightly alleviated after 2000, the further expansion of farmland, the worsened water erosion intensity in alkaline land and frequent extreme weather still posed serious threats to water erosion in the study area. Water erosion was positively correlated with temperature and dry/wet alternation events, including frequency, duration, and severity. In addition, land use type was the main factor influencing the heterogeneous distribution of water erosion in the western Songnen Plain, whose interaction with dry/wet alternation events had the strongest explanatory power. Therefore, this study calls for the implementation of soil and water conservation measures to mitigate the impacts of land cultivation, salinization, and climate change on water erosion.

Increasing crop diversity and nitrogen (N) fertilizer application have been identified as effective strategies for enhancing productivity and soil organic carbon (SOC) storage in agroecosystems. However, the impact of these management practices on soil inorganic carbon (SIC) in agroecosystems remains unclear. At present, we evaluated the effects of maize/faba bean intercropping, N application rates, and inoculation rhizobia of faba bean on SIC in the top 20 cm of soil depth using a 13-year crop diversity field experiment. Our results showed that the soil total carbon (TC) content increased significantly by 5.9 % and 7.0 % compared to faba bean monoculture and maize monoculture, respectively, after 13 years of continuous intercropping. Intercropping increased the pedogenic carbonate (PIC) content by 36.7 %, resulting in an 8.9 % higher SIC content compared to faba bean monoculture. Additionally, intercropping significantly reduced the dissolution of lithogenic carbonate (LIC) by 17.5 %, leading to a 7.6 % higher SIC content compared to maize monoculture. The formation of PIC was associated with an increase in soil available cations especially Ca²⁺ in intercropping. The conservation of LIC was related to the higher soil available Mg²⁺ in intercropping than monoculture. Faba bean inoculated with rhizobia significantly decreased SIC content due to soil acidification after 13 years of continuous cropping. Intercropping also significantly increased SOC and C3-derived SOC content compared to maize monoculture and increased C4-derived SOC content compared with faba bean monoculture. Soil organic carbon showed a positive correlation with SIC across all cropping systems, and the SOC fractions could affect the neoformation of PIC and dissolution of LIC. Our results demonstrate that intercropping can increase SIC content, which further promotes soil carbon sequestration. This study highlights the significance of increasing crop diversity on cropland carbon sequestration and provides practical implications for mitigating carbon emissions.

Particulate organic matter (POM) decomposition is influenced by soil pore structure, and the volume loss associated with POM decomposition might also promote the generation of new pores. However, the interaction between POM decomposition and soil pore structure remains unclear. Therefore, the objective of this study was to explore this interaction during straw decomposition. A 57-day soil incubation experiment was conducted using ¹³C-labelled maize straw in both Shajiang black soil and Fluvo-aquic soil, with two bulk densities (1.2 g/cm³, T1.2 and 1.5 g/cm³, T1.5). The loss of POM volume and the changes in soil pore structure, both before and after the incubation experiment, were quantified using X-ray micro-computed tomography (μCT). The results showed that there was a significantly greater volume loss of POM in Shajiang black soil (POM volume loss: 58.2–75.0 %) compared to Fluvo-aquic soil (34.0 %). Within the Shajiang black soil, decomposition of POM and the release of respired ¹³CO₂ were notably higher in the soil from the T1.2 treatment compared to the T1.5 treatment (P<0.05), while no significant difference was observed in Fluvo-aquic soil. Image-based porosity and mean pore distance emerged as primary determinants of POM variations in Shajiang black soil. Furthermore, our results underscore the positive role of pores ranging from 50 to 300 μm in diameter (Ø) in facilitating rapid POM decomposition, as evidenced by a higher ¹³CO₂ release. In Shajiang black soil, POM decomposition increased the porosity of 100–200 μm, 200–300 μm, and >300 μm Ø pores by 26.2 %, 51.8 % and 82.9 %, respectively, in the T1.2 treatment (P<0.05), and 50–100 μm Ø pores by 24.7 % in the T1.5 treatment (P<0.05). Our findings emphasize the significance of 100–300 μm Ø pores in gas transport and fresh POM decomposition, highlighting the pivotal role of POM decomposition in shaping soil pore structure.

Soil organic carbon (SOC) is not a single and uniform entity, therefore understanding SOC fractions, particularly particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), offers valuable insights into SOC dynamics. However, traditional laboratory measurements of SOC fractions are labor-intensive and costly. Therefore, leveraging rapid and cost-effective soil spectroscopy holds significant promise for addressing this challenge. While previous studies have concentrated on predicting SOC fractions using mid-infrared (MIR) spectroscopy, the potential of visible and near-infrared (VNIR) spectroscopy remains relatively unexplored, especially for tropical soils. To fill this gap, we evaluated six machine learning approaches, including three global models (Cubist, random forest (RF), partial least squares regression (PLSR)) and three local models (memory-based learning fitted by applying partial least squares regression (MBL-PLSR) and Gaussian process local regressions (MBL-GPR), non-linear memory-based learning (N-MBL)), for predicting POC and MAOC (g C kg⁻¹ soil) based on a regional soil VNIR spectral library (224 samples) from lateritic red soil in the tropical region of Guangdong Province, China. We also assessed the impact of variable selection on improving model performance by iteratively evaluating and removing insignificant predictor variables to determine the optimal number of predictors. The results showed that: (1) MBL-PLSR and N-MBL demonstrated commendable predictive performance, attaining coefficients of determination (R²) of 0.73 and 0.72 for POC, and 0.53 and 0.55 for MAOC on the validation set, respectively, outperforming Cubist and PLSR; (2) variable selection simplified predictive models by identifying the best spectral bands, leading to improved predictive accuracy for both POC (R² increased from 0.68 to 0.73) and MAOC (R² increased from 0.49 to 0.55); (3) the overall predictive performance of VNIR spectroscopy was higher for POC (R² of 0.73) compared to MAOC (R² of 0.55), while MAOC could be predicted more accurately by subtracting POC predictions from SOC observations (R² of 0.73). The favorable predictive accuracy underscores VNIR spectroscopy's viability for POC predictions. Additionally, MAOC can be well predicted by subtracting the predicted POC from the measured SOC. The outcomes of this study offers valuable insights for predicting SOC fractions using VNIR spectroscopy.

Exogenous carbon (C) input may induce priming effects, leading to the loss of soil organic C (SOC) by accelerating the decomposition of native soil organic matter (SOM), while also replenishing SOC through various mechanisms. However, the net C balance resulting from priming and replenishment of SOC under long-term nitrogen (N) fertilization and its stoichiometric regulation mechanisms remain largely undetermined. Soils subjected to 11 years of different N applications were used to investigate the net C balance following the addition of exogenous ¹³C-labeled glucose. The retention of glucose-derived C exceeded the loss of C caused by the priming effect, resulting in a positive net C balance, albeit attenuated by historical N application (ranging from 25.9 to 36.9 μg C mg⁻¹ SOC). The application of increasing historical N levels resulted in a decrease in soil C:N imbalance and an increase in soil N:phosphorus (P) imbalance, as well as an increase in TER_C:N and TER_C:P. This suggested that the C and/or P limitations of soil microbial communities were intensified with increased N availability. Soil nutrient stoichiometric imbalance and available resource stoichiometry directly influenced the threshold element ratio, which in turn impacted glucose mineralization, subsequently affecting the net C balance. Collectively, our results provided solid evidence that labile C input could lead to a positive net C balance, which diminished with increased historical N application and was primarily regulated by soil C:N:P stoichiometry. This study highlights the significant implications for the soil C turnover and sequestration under long-term N application management in agroecosystems.

Soil structure development can be described with tensile and shear processes as well as the further stabilization of interparticle bonds by hydraulic, chemical, biological, and physicochemical processes. The related shrink, swell or stress strain processes, as well as organic bindings and biological glueing processes, however, define the rigidity limits of soil structure and soil functions, which also coincide with defined boundaries that can be applied in modelling approaches. Aggregate formation due to volume separation occurs in soils depending on these interactions and undergo further strengthening or weakening processes with consequences for their rigidity. The goal of this review is to document these processes with corresponding results and to discuss some consequences for global change impacts on, e.g., plant growth and yield or mechanical strength. It is obvious that the hydraulic and mechanical processes have become neglected to some extent in the study of soil structure formation and aggregation, which caused remaining research gaps identified in this review. Consequently, there is an urgent need for a more precise determination of the rigidity limits of soils under various land use and climatic conditions to better predict or model climatic impacts but also the effect of soil management changes or amelioration impacts.

Understanding the large-scale spatial distribution characteristics of gully development dynamics, particularly over long periods, can help in accurately identifying areas with severe gully erosion and is thus crucial for targeted gully prevention and rehabilitation efforts. This study aimed to investigate the long-term dynamics of permanent gullies on cropland in the Songnen typical black soil region (SBR), which is the most important commercial grain production area in China, covering an area of 212,000 km². For this purpose, 998 sampling units were selected using the systematic sampling method. Based on Corona KH-4B images from 1970 and Google images from 2018, all gullies within each sampling unit were visually interpreted. In the past 50 years, the number of permanent gullies on cropland in SBR increased by 24.55 %, but the average linear density of gullies in the cropland sampling unit decreased from 0.47 to 0.45 km·km⁻² because the average lengths of gullies decreased from 285.90 m to 233.15 m. While 50.50 % of gullies found in 1970 disappeared from the images of 2018, more gullies formed and were widespread in the east part of the study area characterized by a topography of rolling hills. In particular, 66.70 % of gullies were active, including all newly formed gullies and 16.28 % of long-standing gullies (LSGs), and the average gully retreat rate of LSGs was 0.53 m·yr⁻¹, with active LSGs grew at a rate of 3.26 m·yr⁻¹ on average, indicating the severity of gully erosion and limited effectiveness of efforts made to control gully erosion in the black soil region of China. The threat of gully erosion is more serious in the eastern part of SBR, with 44.69 % of cropland suffering gully erosion and 66.14 % of the gullies being active. Moreover, the trend of increased gully erosion in the centre and the west requires further attention. The findings highlight the need for studies on more effective and targeted measures for gully control and their wide application in order to ensure the sustainable utilization of the valuable black soil resources.

Although data regarding the effect of different types of synthetic biochar on plant performance and physical and chemical characteristics of soil is widely available, the effect of natural biochar in this respect is not well known, so far. The purpose of this research was to investigate the effect of 650-million-years old natural biochar at three application levels of 0 %, 2.5 % and 5 % by weight on yield parameters of quinoa plant and the soil water retention characteristic curve in sandy loam, loam, and clay textural classes. The results showed that the application of 5 % natural biochar to the loam soil increased the thousand seed weight by 8 %, but adding 2.5 % of biochar to the sandy loam soil increased biological yield by 2 %, and in loam soil increased root volume by 409 %, compared to the control. The results of the physical parameters of the soil showed that the application of biochar in three soil textures caused an increase in moisture content at the field capacity (1.8 %-11.22 %), a decrease in macropores in the range of 10–46 %, and an increase in micropores in the range of 0.2–10 % in three soil textures. Therefore, it can be concluded that the potential of natural biochar storage affected the physical properties of the soil and increased soil water retention while improving important soil functions.