Soil & Tillage Research最新文献

Soil aggregates, which are the basic units of soil structure, play an important role in the carbon cycle of ecosystems. The pore characteristics of aggregates influence soil organic carbon sequestration. However, studies on SOC mechanisms in aggregates have been limited to Mollisols. This study was conducted as a long-term experiment established in 2004 with a corn-soybean rotation in Mollisols. There are three treatments, including rotary tillage without straw return (conventional tillage, CT), subsoiling without straw return (reduced tillage, RT), and no tillage with straw return (NT). The soil pore size distribution, shape parameters, extracellular enzymes activity, and carbon mineralization were measured. The results showed that 15-year no tillage and reduced tillage increased the total porosity and proportion of larger pores, but significantly decreased the proportion of smaller pores in situ soil columns. Conventional tillage exhibited the most complex pores because of the highest pore fractal dimension (2.75–2.90), anisotropy (0.366–0.516), and the lowest sphericity (5.1–28.7). As for the soil columns filled with > 2 mm aggregates, reduced tillage significantly increased the pore connectivity by 3.02–3.62 %, whereas no tillage had no effect. The structural equation modelling indicated that in soil columns filled with > 2 mm aggregates, pore shape parameters, particularly connectivity and anisotropy, positively influenced the activities of β-glucosidase and β-xylosidase directly, and positively affected soil carbon mineralization by influencing extracellular enzymes activity indirectly. The findings emphasize the importance of pore shape parameters effect on soil carbon sequestration, and will be helpful in comprehending the microscopic mechanisms of soil carbon sequestration in > 2 mm aggregates.

Long-term sustainability of intensive cropping systems in tropical soils depends on strategies to reconcile grain output, cover crops to maximize biomass yield for soil mulching, and maintaining soil organic carbon (SOC). In this study, we evaluated spatiotemporal constraints underpinning the diversification from soybean (Glycine max (L.) Merr.) monoculture under conventional tillage (CT) or no-tillage (NT) and soybean in succession with maize (Zea mays L.) double cropping (NTS3) to the use of millet (Pennisetum glaucum L., NTS1) and brachiaria (Brachiaria ruziziensis (R.Germ. & Evrard) Crins, NTS2) in successions or millet, crotalaria (Crotalaria spectabilis Roth.), and maize+brachiaria in rotations in a 12-year field experiment in an Oxisol. We quantified total grain output, total biomass production, and SOC contents and stocks (0–40 cm depth). Over 12 years, cumulative grain output under the double cropping (NTS3) was 135.0 Mg ha⁻¹, with soybean-maize proportions of 35–65 %. Thus, the successions NTS1 and NTS2 would reduce maize grain output relative to NTS3 (7.3 Mg ha⁻¹ year⁻¹). Under the rotations, reduction in soybean and maize grain output relative to NTS3 was about 1.4 and 4.1 Mg ha⁻¹ year⁻¹, respectively. Biomass production under NTS3 was 12.0 Mg ha⁻¹ year⁻¹ but reached 15.7 Mg ha⁻¹ year⁻¹ under the rotation including summer soybean (1st and 2nd years) and off-season crotalaria (1st year) or maize+brachiria (2nd year), and only brachiaria (3rd year). Under this rotation, changes in SOC stocks were +2.0 Mg ha⁻¹ year⁻¹ for the 0–40 cm depth layer, whereas under NTS3 it was +1.4 Mg ha⁻¹ year⁻¹, relative to the native Cerrrado. For soybean monoculture under CT or NT changes in SOC were about −0.5 Mg ha⁻¹ year⁻¹ relative to the native Cerrado. Overall, despite the reduced total grain output, the rotation system proposed may be critical to reconcile sustainable food security, soil protection by mulching and SOC maintenance in agricultural Cerrado soils.

Precompression stress, compression index, and swelling index are used for characterizing the compressive behavior of soils, and are essential soil properties for establishing decision support tools to reduce the risk of soil compaction. Because measurements are time-consuming, soil compressive properties are often derived through pedotransfer functions. This study aimed to develop a comprehensive database of soil compressive properties with additional information on basic soil properties, site characteristics, and methodological aspects sourced from peer-reviewed literature, and to develop random forest models for predicting precompression stress using various subsets of the database. Our analysis illustrates that soil compressive properties data primarily originate from a limited number of countries. There is a predominance of precompression stress data, while little data on compression index or recompression index are available. Most precompression stress data were derived from the topsoils of conventionally tilled arable fields, which is not compatible with knowledge that subsoil compaction is a serious problem. The data compilation unveiled considerable variations in soil compression test procedures and methods for calculating precompression stress across different studies, and a concentration of data at soil moisture conditions at or above field capacity. The random forest models exhibited unsatisfactory predictive performance although they performed better than previously developed models. Models showed slight improvement in predictive power when the underlying data were restricted to a specific precompression stress calculation method. Although our database offers broader coverage of precompression stress data than previous studies, the lack of standardization in methodological procedures complicates the development of predictive models based on combined datasets. Methodological standardization and/or functions to translate results between methodologies are needed to ensure consistency and enable data comparison, to develop robust models for precompression stress predictions. Moreover, data across a wider range of soil moisture conditions are needed to characterize soil mechanical properties as a function of soil moisture, similar to soil hydraulic functions, and to develop models to predict the parameters of such soil mechanical functions.

On-time and accurate estimation of the soil nitrogen mineralization rate (SNMR) is critical for nitrogen (N) management and protecting the environment. This study evaluated the performance of a visible-to-near-infrared reflectance (vis-NIR) spectroscopy for predicting SNMR for four texture groups. A total of 62 topsoil samples were collected from 17 management zones distributed over four fields and incubated with seven destructive sampling events. Samples were analysed for total mineral N (NH₄⁺+NO₃^–) content and scanned using a vis-NIR sensor simultaneously at each of the seven-sampling times. Four partial least squares regression models were calibrated and validated for four textural groups (groups- 1– 4) identified over the United State Department of Agriculture (USDA) texture triangle. Prediction accuracies indicated that vis-NIR sensor was moderately to highly accurate for predicting SNMR, while observing variable accuracies across texture groups. The highest accuracy was obtained for group 1 (sandy-loam; coefficient of determination, R² = 0.90; root mean square error, RMSE = 0.04 mg N kg⁻¹ soil day⁻¹), successively followed by group 2 (mostly loam; R² = 0.80, RMSE = 0.05 mg N kg⁻¹ soil day⁻¹) group 4 (mostly silt; R² = 0.66, RMSE = 0.08 mg N kg⁻¹ soil day⁻¹), and group 3 (silt-loam; R² = 0.44, RMSE = 0.08 mg N kg⁻¹ soil day⁻¹). Variable importance in projection score revealed that the key spectral bands to predict SNMR were in 2150 – 2260 nm and 2470 – 2480 nm, resembling the key bands associated with soil organic compounds and clay minerals. In-advance texture information required for soil stratification is regarded a limitation of the proposed approach. In conclusion, vis-NIR holds potential for a rapid estimation of SNMR when samples are stratified into similar texture groups in advance, however, confirmatory research will be needed to validate the current findings for soils from different origin and under different management.

This article presents a review of the equipment used in the process of determining the mechanical strength of soil, in particular with regards to the vertical loads applied. Here, devices incorporating the bevameter approach, i.e. medium and large-scale testers, are discussed. The bevameter technique is described in detail, along with the most common mathematical models relating to the vertical pressure applied to the soil and its compaction. The paper also highlights important phenomena for this type of experiment, such as the scale effect, wall effect, multipass effect, and slip sinkage effect. The article presents the reasons for which plate testers are currently the most commonly used tester type for soil penetration tests for the purpose of terramechanics, including the Next Generation NATO Reference Mobility Model that is currently under development. Investigations towards the influence of the penetration rate on soil penetration are also addressed. Furthermore, the authors also present a selection of their own results of currently ongoing research on the subject of potential influence of the plate grouser on plate sinkage. The results already obtained have made it possible to identify phenomena that are not taken into account in the current research methods, in turn resulting in the development of an innovative plate tester for investigating the sinkage of the running gear components of machines and vehicles in fragmented media.

The increased focus on soil quality (SQ) aims to conserve land resources and arrest land degradation. However, there are several unknowns regarding which indicators can most effectively indicate specific SQ outcomes and ecosystem functioning. For the first time, this study aims to integrate the soil morphological properties and earthworm population with physical and chemical properties and propose a comprehensive soil quality index (SQI_w) to evaluate SQ across a land-use – soil type – climate gradient. Soil profile data (n = 47) covering semi-arid, sub-humid, and humid climates, three soil types (Inceptisols, Vertisols, and Alfisols) and three major land-use systems (grassland, plantation, and annual field crops) were used in this study. As a novel approach, we used a combination of expert opinion and principal component analysis to select 12 soil quality indicators (five morphological, two physical, three chemical, and two biological properties) and developed four thematic SQ indices, viz., morphological quality index (SQI_m), physical quality index (SQI_p), chemical quality index (SQI_c), and biological quality index (SQI_b) from the respective SQ indicators using the weighted additive index method. The thematic SQ indices were integrated to create SQI_w for surface and subsurface soils. The SQI_m showed a strong relationship with SQI_p and SQI_c and a moderate relationship with SQI_b, indicating that the thematic SQ indices can be employed to evaluate soil quality in resource-limited regions or countries. The SQI_w differentiated the effects of climate, soil type, and land use management on soil quality and showed a strong correlation with crop yield, enabling the comparison of production systems. The integration of the earthworm population to SQI_w is a crucial advancement in SQ assessment, and the SQI_m adds a new dimension. The proposed SQI_w could be a potential precursor for emerging consensus towards a generalised and comprehensive SQI, which can be effectively used for SQ monitoring across varied land use, soil types, and climate regions.

Drip irrigation with alternate use of surface water and groundwater (ADI) has been widely applied in arid regions to relieve the effects of heat stress on crop growth. However, the heat dynamics under ADI are still unclear, especially concerning the impacts of ADI on daily and seasonal fluctuations of soil temperature (T_s). Thus, a two-year experiment was carried out during 2019–2020 in the Jiuzhuang comprehensive saving-water experimental station to continuously monitor soil water content (SWC) and T_s variations. Moreover, the HYDRUS (2D/3D) software was used to simulate T_s fluctuations under various evaluated scenarios involving a) surface water irrigation (SW), b) groundwater water irrigation (GW), c) alternate use of groundwater and surface water irrigation (1G1S), d) two groundwater irrigations and one surface water irrigation (2G1S), and e) three groundwater irrigations and one surface water irrigation (3G1S). The result showed that the HYDRUS (2D/3D) software could precisely simulate soil water content and T_s dynamics under all irrigation treatments, with the root mean square error of 0.01–0.06 cm³ cm⁻³ and 1.25–1.57 °C for SWC and T_s in the verification period, respectively. Apparent spatial-temporal differences in diurnal T_s fluctuations under different ADI treatments were found, especially in the 5 cm soil depth. In general, T_s decreased in response to an increase in the frequency of groundwater irrigation. The lowest T_s occurred in the 3G1S treatment under different ADI treatments. The average T_s in both years under 3G1S was 12.2 % lower than under SW and 4.4 % higher than under GW. However, the highest T_s occurred in the 1G1S treatment under different ADI treatments. Average T_s in both years under 1G1S increased by 8.6 % and 15.4 % compared to 2G1S and 3G1S, respectively. Meanwhile, the difference in T_s fluctuations under different ADI treatments during daytime was substantially higher than during nighttime. The largest area (1271.8 cm²) of “moderate T_s” (20–22 ℃) occurred in the 2G1S treatment. Moreover, the longest “optimal T_s” duration occurred for the 22.5 mm irrigation depth under 2G1S. Therefore, the irrigation depth of 22.5 mm and the 2G1S treatment is recommended as the optimal irrigation strategy in this region.

Prescribed fire (slash and burn) tends to impede the sustainable functionality of soil in agricultural systems. However, the use of amendment has a potential to reverse these negative effects. Prescribed fire is still used by farmers in Nigeria for land preparation before planting. This has continued to increase soil degradation in Nigeria with no agronomic activities that could ameliorate this effect in view. This study therefore examined the influence of prescribed fire and grass mulch on selected soil physical properties and organic carbon immediately after burning, and the potential of amendment to improve the soil properties negatively affected by fire. The prescribed fire treatments consisted of 200 °C and 500 °C fire intensities using Megathyrsus maximus (a large perennial bunch of grass that is dominant in the study area) as the fuel and also served as the grass mulch. Cured poultry manure at 7.5 t ha⁻¹ was combined with urea at 40 kg N ha⁻¹ and applied as a combined amendment while a single dose of urea was applied at 80 kg N ha⁻¹ as an inorganic amendment. The experiment was carried out across three cropping seasons on maize (Zea mays L.) in 2019 and 2020. Soil water repellency (SWR), bulk density (D_b), soil unsaturated hydraulic conductivity (K_unsat), water stable aggregates (WSA), soil strength (SS), and soil organic carbon (SOC) were determined immediately after burning and three months after amendments were applied. Data obtained were subjected to analysis of variance and means separated using the Duncan multiple range test at p≤0.05. Results showed that prescribed fires increased SWR by an average of 50.1 and 62.7 % for 200 °C and 500 °C intensities, respectively compared with the control. Three months later, the SWR was reduced by 25.9 % and 62.3 % for 200 °C and 500 °C, respectively when no amendment was added. Notably, the addition of sole urea and cured poultry manure + urea reduced the SWR by 50 % and 48.5 %, respectively in the 200 °C intensity, and 62.2 % and 62.7 % in the 500 °C intensity, respectively. Also, K_unsat was reduced by an average of 49.6 and 62.2 % by 200 °C and 500 °C intensities, respectively just after burning. However, it was not improved three months after the prescribed fires despite the applied amendments. The prescribed fire of 200 °C and grass mulch had no significant influence on OC just after the fire. Also, amendments did not significantly improve OC three months after prescribed fire. Therefore, the non-improvement of other soil properties, after the applied amendments, showed that further study is required to determine the required rate of the applied amendments that will significantly improve other soil properties negatively affected by prescribed fire in agricultural soils.

Estimating the spatiotemporal variations and driving factors of farmland soil organic carbon density (SOCD) is of great significance for enhancing soil carbon sequestration capacity. Herein, a large region of complex topography was targeted, which includes hill–mountain, valley–basin, and plain–platform. Based on the massive amounts of sampling data (57,254 measured values) and a large-scale soil map of 1:10,000 (371,976 polygonal patches), the gravity center migration model and gray correlation model were used to quantify the spatiotemporal variations and driving factors of farmland SOCD. The results indicated that the farmland soils in the study area had dual functions of carbon source and sink during 1982–2018, of which 45.50 % and 54.50 % were identified as carbon source and sink, respectively. Specifically, the SOCD for the entire study area, its hill–mountain, and valley–basin increased from 2.79 kg m⁻², 2.97 kg m⁻², and 3.06 kg m⁻² to 2.87 kg m⁻², 3.06 kg m⁻², and 3.14 kg m⁻², respectively, with 0.08 kg m⁻² carbon sequestrations and a northeast migration direction for the SOCD gravity center (angle: 21.94°, 23.56°, and 18.82°; distance: 1.56 km, 2.73 km, and 3.20 km). There was a smaller increase of 0.07 kg m⁻² in SOCD for the plain–platform from 2.38 kg m⁻² (1982) to 2.45 kg m⁻² (2018), and the SOCD gravity center migrated to the southwest with an angle of −172.46° and a distance of 1.84 km. Thus, the spatiotemporal variations of farmland SOCD in various landforms varied greatly. Over the past 36 years, SOCD variations were driven by a combination of intrinsic soil factors and external factors such as human disturbance. However, the driving effects of these factors on the landforms of hill–mountain, valley–basin, and plain–platform were quite different in size and order. Therefore, we suggest that topography must be considered when formulating policies to improve soil carbon sequestration, and priority should be given to landform-specific SOCD variation and the factors contributing to them.

The stability and chemical composition of SOM are related to the changes of the proportions of old and young SOM. However, there are few studies that investigated the effects of no-tillage (NT) on the stability, chemical composition, and sources of SOM. In this study, the effects of 9-years of NT on the contents of total, thermally labile and stable SOM, their chemical composition and the contributions from C₃ and C₄ plants were determined. Before application of NT, the field has been used for C₄ maize cultivation under conventional tillage (CT) management about 80 years after initial C₃ grassland reclamation. Soil samples were collected in the 0–20 cm soil profile. Under NT treatment, the contents of total SOC, thermally labile and stable SOC, and C₄-SOC decreased with soil depths. However, they were greater in the 0–10 cm layers than that in the 10–20 cm layer under CT. The contents of C₃-SOC showed no change with depths under both of tillage treatments. NT had greater contents of total SOC, C₄-SOC, thermal-labile SOC, and C₄-SOC_{thermal-labile} than CT in the 0–5 cm layer, but lower in the subsoil layers. The contents of C₃-SOC_{thermal-labile} decreased in the 0–5 cm layer under NT. The alkyl-C and O-alkyl-C were the main fractions of thermal-labile SOM and aromatic-C was the dominant fraction of thermal-stable SOM. C₄-SOC (young SOC) was significantly positively correlated with alkyl-C and O-alkyl-C and negatively correlated with aromatic-C. Our results indicated that: (1) compared with continuously CT, applying NT resulted in SOC accumulation in the surface layer, (2) more maize residue input increased the new thermally labile and stable SOM yet lead to decrease the C₃-SOC_{thermal-labile} under NT, (3) the contributions of C₃ and C₄-direved SOM determined the chemical compositions of various SOM pools.