Plow Layer Research Articles

Assessing the capability of Sentinel-2 time-series to estimate soil organic carbon and clay content at local scale in croplands

The use of remote sensing data methods is affordable for the mapping of soil properties of the plowed layer over croplands. Carried out in the framework of the ongoing STEROPES project of the European Joint H2020 Program SOIL, this work is focused on the feasibility of Sentinel-2 based approaches for the high resolution mapping of topsoil clay and organic carbon (SOC) contents at the within-farm or within-field scales, for cropland sites of contrasted climates and soil types across the Northern hemisphere. Four pixelwise temporal mosaicking methods, using a two years-Sentinel-2 time series and several spectral indices (NDVI, NBR2, BSI, S2WI), were developed and compared for i) pure bare soil condition (maxBSI), ii) driest soil condition (minS2WI), iii) average bare soil condition (Median) and iv) dry soil conditions excluding extreme reflectance values (R90). Three spectral modeling approaches, using the Sentinel-2 bands of the output temporal mosaics as covariates, were tested and compared: (i) Quantile Regression Forest (QRF) algorithm; (ii) QRF adding longitude and latitude as covariates (QRFxy); (iii) a hybrid approach, Linear Mixed Effect Model (LMEM), that includes spatial autocorrelation of the soil properties. We tested pairs of mosaic and spectral approaches on ten sites in Türkiye, Italy, Lithuania, and USA where soil samples were collected and SOC and clay content were measured in the lab. The average RPIQ of the best performances among the test sites was 2.50 both for SOC (RMSE = 0.15%) and clay (RMSE = 3.3%). Both accuracy level and uncertainty were mainly influenced by site characteristics of cloud frequency, soil types and management. Generally, the models including a spatial component (QRFxy and LMEM) were the best performing, while the best spatial mosaicking approaches mostly were Median and R90. The most frequent optimal combination of mosaicking and model type was Median or R90 and QRFxy for SOC, and R90 and LMEM for clay estimation.

First application of plutonium in soil erosion research on terraces

The spatial distributions of 239+240Pu and 137Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion. The activity concentrations of 239+240Pu and 137Cs in the surface soils of the paddy fields were in the range of 0.089–0.734 and 1.80–7.88 mBq/g, respectively. The activities of 239+240Pu and 137Cs showed very similar distribution trends, first increasing and then decreasing with increasing elevation. The 240Pu/239Pu atom ratios in the surface soils ranged from 0.162 to 0.232. The activities of 239+240Pu and 137Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth. The mean soil erosion rates of Longji Rice Terraces estimated by 239+240Pu and 137Cs tracer methods were 5.44 t/(ha·a) and 5.16 t/(ha·a), respectively, which demonstrated that plutonium can replace 137Cs as an ideal tracer for soil erosion research in the future. Landform features are the main factors affecting the distribution of plutonium and 137Cs as well as soil erosion in the Longji Rice Terraces.

If Sand Interlayer Acts Better than Straw Interlayer for Saline Soil Amelioration? A Three-Year Field Experiment

An addition of straw interlayer in the 0.40 m soil depth could effectively reduce salt accumulation in the surface soils by regulating water fluxes, thus mitigating the salt stress to the crop growth and development. However, the positive effects of straw interlayer were weakened with straw decomposition, and whether we could use sand (an indecomposable substance) instead of straw for saline soil amelioration still needs further investigation. Therefore, a three-year field experiment was established with straw and sand interlayers, as well as with no interlayer as a control. Straw interlayer demonstrated an increase of 4.85~13.10% of water content, while the sand interlayer increased 12.41~16.48% of water content in the soil layer of 0–0.40 m depth comparing to the control. Salt contents were lowered by 10.69~17.01% in the same soil layer of the straw interlayer and lowered by 7.00~7.59% in the sand interlayer treatment after irrigation. Data also shows that irrigation significantly increased water content and lowered salt accumulation in the soil plough layer, thus increasing the sunflower emergence rate of 10.49~13.54% in the straw interlayer treatment and 12.53~14.78% in the sand interlayer treatment, respectively. Both the straw interlayer and sand interlayer treatments effectively reduced the evaporation of groundwater and established a beneficial plough layer with a lower salt accumulation throughout the sunflower growth period. At harvesting stage, the evaporation fluxes of salt in the straw interlayer and sand interlayer treatments were significantly lower than that in the control treatment. Lower salt accumulation conferred a beneficial promotion for the growth of sunflower, while the grain yields in the straw interlayer treatment were increased by 8.67% in 2018, 11.00% in 2019 and 17.37% in 2020 compared to the no-interlayer soil, respectively. However, the low water content in the soil layer of 0–0.40 m depth in the sand interlayer treatment inhibited the growth of sunflower, resulting in a significant decrease in the seed yields. It is worth noting that the precipitation effectively alleviated water stress on the sunflower at the middle and late growth stage in the sand interlayer treatment. This study suggests that a maize straw burial of 0.05 m thickness at a depth of 0.40 m soil layer could be used as an effective tillage practice that could improve the distribution of water and salt in saline soils.

Study of the Effects of Different Agronomic Practices on Inorganic Carbon in the Plough Layer of Dryland Field: A Meta-Analysis

Soil inorganic carbon (SIC) is an essential component of the soil carbon pool and plays a vital role in the global carbon cycle and climate change. However, few studies have examined the effects of different agronomic practices on the SIC content. This paper aims to study the effects of different agronomic practices on the SIC content in the 0- to 40-cm soil layer of dryland fields; the innovations are intended to explore the relative importance and synergistic effects of different agronomic practices on the SIC content of the plough layer of dryland fields. We screened out 136 peer-reviewed articles worldwide from 1990–2022, with a total of 2612 valid data pairs, using meta-analysis to assess the effects of different agronomic practices on the SIC content of the plough layer of dryland fields. Compared to conventional tillage (CT), both no-tillage (NT) and plastic film mulching (PM) were able to increase the SIC content in the 0- to 40-cm soil layer of dryland fields. NT increased the SIC content by 15.07 ± 3.48%, while PM gradually increased SIC accumulation as the soil layer deepened, with the greatest increase in SIC content in the 30- to 40-cm soil layer at 11.61 ± 5.89%. When organic manure application (M) and straw return mulching (SM) were applied, the SIC content in the 0- to 40-cm soil layer of dryland fields showed a non-significant reduction trend, with the largest changes in SIC content in the 0- to 10-cm soil layer, at 5.23 ± 2% and 4.69 ± 3.53% reductions, respectively. No-tillage straw return (NTS) significantly increased the SIC content in the 0- to 40-cm soil layer of dryland fields by 77.34 ± 5.6%, which was significantly higher than the independent effects of NT and SM, showing a more substantial synergistic effect. Different agronomic practices have different effects on the SIC content of dryland fields in the 0- to 40-cm soil layer, with NTS > NT > PM > SM > M. Among practices, NTS, NT and PM can increase the SIC content of the plough layer of dryland fields; in particular, NTS can increase the SIC content of 0- to 40-cm in dryland fields to the greatest extent through a synergistic effect. At the same time, SM and M showed an insignificant reduction effect.

Hygienic assessment of new pesticides migration from soil into the lower atmospheric air layer

Annotation. A great danger to the environment and the health of the population is the release of chemical substances of technogenic origin, in particular plant protection products into the atmospheric air. The aim of the study was to evaluate the hazard of harmful inhalation impact on the human body of new pesticides: triazolone herbicide amicarbazone, tricetone herbicide bicyclopyrone, and carboxamide fungicide pydiflumetofen, during their migration from soil to the lower atmospheric air layer. Mathematical modeling of the process of evaporation of the studied pesticides from soil to the atmospheric air was carried out and comparison of the maximum achievable concentrations with the average lethal concentration during acute inhalation exposure and hygienic standards in the air environment. Experimental study of the behavior of amicarbazone, bicyclopyrone, and pydiflumetofen in the "soil - atmospheric air" system was carried out in laboratory conditions. The concentrations of the studied substances in the air were determined by the method of high - performance liquid chromatography. It was established that amicarbazone, bicyclopyrone, and pydiflumetofen are non - volatile under saturated vapor pressure and Henry's law constant, and low - risk by the coefficient of possible inhalation poisoning. Acute inhalation poisoning as a result of evaporation from the soil into the lower atmospheric air layer is unlikely. The maximum achievable concentrations of the studied pesticides that can form in the air as a result of evaporation from the soil are significantly lower than their hygienic standards in the working zone. The migration levels of the studied substances from soil to the lower atmospheric air layer depend on their initial concentrations and the type of soil: bicyclopyrone and pydiflumetofen migrate more intensively from sandy soil than from leached chernozem. Threshold concentrations in the soil according to the air – migration indicator of harmfulness: amicarbazone – 0.05 mg/kg, bicyclopyrone – 1.0 mg/kg and pydiflumetofen – 1.2 mg/kg are formed in the plow layer of soil when researched pesticides are introduced according to 1th, 20th and 20th maximum consumption rates. The “soil - atmospheric air” system is not a leading link to the migration of the studied pesticides in the environment. The obtained results were used in the substantiation of hygienic standard of amicarbazone, bicyclopyrone and pydiflumetofen in soil.

Does soil thinning change soil erodibility? An exploration of long-term erosion feedback systems

Abstract. Soil erosion rates on arable land frequently exceed the pace at which new soil is formed. This imbalance leads to soil thinning (i.e. truncation), whereby subsoil horizons and their underlying parent material become progressively closer to the land surface. As soil erosion is a selective process and subsurface horizons often have contrasting properties to the original topsoil, truncation-induced changes to soil properties might affect erosion rates and runoff formation through a soil erosion feedback system. However, the potential interactions between soil erosion and soil truncation are poorly understood due to a lack of empirical data and the neglection of long-term erodibility dynamics in erosion simulation models. Here, we present a novel model-based exploration of the soil erosion feedback system over a period of 500 years using measured soil properties from a diversified database of 265 agricultural soil profiles in the UK. For this, we adapted the Modified Morgan–Morgan–Finney model (MMMF) to perform a modelling experiment in which topography, climate, land cover, and crop management parameters were held constant throughout the simulation period. As selective soil erosion processes removed topsoil layers, the model gradually mixed subsurface soil horizons into a 0.2 m plough layer and updated soil properties using mass-balance mixing models. Further, we estimated the uncertainty in model simulations with a forward error assessment. We found that modelled erosion rates in 99 % of the soil profiles were sensitive to truncation-induced changes in soil properties. The soil losses in all except one of the truncation-sensitive profiles displayed a decelerating trend, which depicted an exponential decay in erosion rates over the simulation period. This was largely explained by decreasing silt contents in the soil surface due to selective removal of this more erodible particle size fraction and the presence of clayey or sandy substrata. Moreover, the soil profiles displayed an increased residual stone cover, which armoured the land surface and reduced soil detachment. Contrastingly, the soils with siltier subsurface horizons continuously replenished the plough layer with readily erodible material, which prevented the decline of soil loss rates over time. Although our results are limited by the edaphoclimatic conditions represented in our data, as by our modelling assumptions, we have demonstrated how modelled soil losses can be sensitive to erosion-induced changes in soil properties. These findings are likely to affect how we calculate soil lifespans and make long-term projections of land degradation.

Tillage-Depth Verification Based on Machine Learning Algorithms

In an analysis of the penetration resistance and tillage depth of post-tillage soil, four surface-layer discrimination methods, specifically, three machine learning algorithms—Kmeans, DBSCAN, and GMM—and a curve-fitting method, were used to analyze data collected from the cultivated and uncultivated layers. Among them, the three machine learning algorithms found the boundary between the tilled and untilled layers by analyzing which data points belonged to which layer to determine the depth of the soil in the tilled layer. The curve-fitting method interpreted the intersection among data from the fitted curves of the ploughed layer and the un-ploughed layer as the tillage depth. The three machine learning algorithms were used to process a standard data set for model evaluation. DBSCAN’s discrimination accuracy of this data set reached 0.9890 and its F1 score reached 0.9934, which were superior to those of the other two algorithms. Under standard experimental conditions, the ability of DBSCAN clustering to determine the soil depth was the best among the four discrimination methods, and the discrimination accuracy reached 90.63% when the error was 15 mm. During field-test verification, the discriminative effect of DBSCAN clustering was still the best among the four methods. However, the soil blocks encountered in the field test affected the test data, resulting in large errors in the processing results. Therefore, the combined RANSCA robust regression and DBSCAN clustering algorithm, which can eliminate interference from soil blocks in the cultivated layer and can solve the problem of large depth errors caused by soil blocks in the field, was used to process the data. After testing, when the RANSCA and DBSCAN combined method was used to process all samples in the field and the error was less than 20mm, the accuracy rate reached 82.69%. This combined method improves the applicability of discrimination methods and provides a new method of determining soil depth.

Plow layer management during the fallow season can enhance the wheat productivity and resource utilization in a semi-arid region

The soil quality is poor in the arid areas of Northwest China and planting green manure can improve the soil quality but it also increases the soil water consumption. Straw mulching in the wheat (Triticum aestivum L.) fallow season can improve the soil water content. It is unclear whether green manure can be planted in addition to straw mulching to improve the soil water content and quality. Therefore, a field experiment was conducted in the semi-arid area of the Loess Plateau in China from 2009 to 2017 with the following treatments; (1) traditional bare land in fallow season after plowing (CK), (2) no-tillage with straw mulching (NTSM), (3) and no-tillage with straw mulching and planting soybean as green manure (NTSGM). We determined the effects of these three treatments on the soil water, nutrients, and wheat productivity. Compared with CK, the average soil water contents in 0–100 cm soil depth increased by 11.1% and 3.6% under NTSM and NTSGM, respectively, during the soybean full bloom stage, and by 13.06% and 6.6% before wheat sowing. Compared with CK, the decomposition of green manure increased the NO3–-N contents in the 0–100 cm soil depth by 6.6% and 5.3% under NTSGM before wheat sowing and after harvesting, respectively, and NTSM and NTSGM significantly improved the soil nutrients, microbial biomass contents, and enzyme activities. The superior soil quality and water content under NTSM and NTSGM increased the fertilizer uptake and partial factor productivity. Compared with CK, the average precipitation storage efficiency, water use efficiency during the whole year, biomass, and wheat yield were 32.6%, 23.2%, 16.2%, and 21.6% higher under NTSGM, respectively. Therefore, NTSGM is an effective method for improving the soil water storage and NO3–-N contents before sowing wheat, as well as the water use efficiency, soil quality, utilization of nutrients, and wheat productivity in semi-arid areas of the Loess Plateau.

Soil organic carbon under conservation agriculture in Mediterranean and humid subtropical climates: Globalmeta‐analysis

AbstractConservation agriculture (CA) is an agronomic system based on minimum soil disturbance (no‐tillage, NT), permanent soil cover, and species diversification. The effects of NT on soil organic carbon (SOC) changes have been widely studied, showing somewhat inconsistent conclusions, especially in relation to the Mediterranean and humid subtropical climates. These areas are highly vulnerable and predicted climate change is expected to accentuate desertification and, for these reasons, there is a need for clear agricultural guidelines to preserve or increment SOC. We quantitively summarized the results of 47 studies all around the world in these climates investigating the sources of variation in SOC responses to CA, such as soil characteristics, agricultural management, climate, and geography. Within the climatic area considered, the overall effect of CA on SOC accumulation in the plough layer (0–0.3 m) was 12% greater in comparison to conventional agriculture. On average, this result corresponds to a carbon increase of 0.48 Mg C ha−1 year−1. However, the effect was variable depending on the SOC content under conventional agriculture: it was 20% in soils which had ≤ 40 Mg C ha−1, while it was only 7% in soils that had > 40 Mg C ha−1. We proved that 10 years of CA impact the most on soil with SOC ≤ 40 Mg C ha−1. For soils with less than 40 Mg C ha−1, increasing the proportion of crops with bigger residue biomasses in a CA rotation was a solution to increase SOC. The effect of CA on SOC depended on clay content only in soils with more than 40 Mg C ha−1and become null with a SOC/clay index of 3.2. Annual rainfall (that ranged between 331–1850 mm y−1) and geography had specific effects on SOC depending on its content under conventional agriculture. In conclusion, SOC increments due to CA application can be achieved especially in agricultural soils with less than 40 Mg C ha−1and located in the middle latitudes or in the dry conditions of Mediterranean and humid subtropical climates.HighlightsThe results of 47 studies were quantitively summarized by using a meta‐analysisSOC accumulation due to CA was 12% greater compared to conventional agricultureSOC increment due to CA can reach 20% in soils having less than 40 Mg C ha−1The impacts of pedo‐climatic factors and agronomic management practices were studied

Новобиксентеевский клад металлических изделий конца VI – VII вв. в Нижнем Прикамье

The article covers the treasure trove of bronze jewelry found by the employees of LLC “Archeology of the East European Plain” in 2022 when determining the boundaries of the Novobiksenteevsky settlement located in the Lower Kama region (Iksko-Belsky interfluve). On the southern borderline of the settlement, on the plowed surface with the help of metal search devices 32 objects were identified, which were located in a compact group on the area of about 11×7 m. On the spot of the greatest concentration of findings, a 3×2 m-sized soil pit was dug, in the plowed layer of which ten more valuable findings were identified just as well. While conditioning the mainland surface numerous traces of modern mechanical plow knives designed for deep plowing and their impact were revealed. Thus, we assume that as a result of agricultural labour on this allocated site, the treasure was turned out of the ground, which according to the materials of the Novobiksenteevsky settlement, coincides with the main complex of this monument and can be dated back to the end of the VI – VII centuries. Novobiksenteevsky treasure is represented by 42 items. It includes noisy and wheel-shaped suspensions, fragments of hryvnia, belt linings, various under-layings and fragments of other metal products. The items of the found treasure have never been registed in the early medieval antiquities of Zakamye. The closest analogies come from the monuments of the Vyatka, Sylva and Cheptsy river basins, as well as the Upper Kama Region, which belong to the Yemanayevskaya, Nevolinskaya, Polomskaya and Lomovatovskaya cultures. Based on the listed analogies, the time of placing the Novobiksenteevsky treasure into the ground can be approximately related to the end of the VI – VII centuries. For most of the items of the found treasure the identification of chemical composition using X-ray analysis was held, which made it possible to assign the main types of metals and alloys. The metal composition of the Novobiksenteevsky treasure is also typical for bronze articles of the Kama region cultures of the VI–VII centuries.

Optimization of multifunctional powing unit parameters

Technology of soil moldboard plowing with a reversible plow with the simultaneous the main mineral fertilizer application, as well as additional crumbling of plowed layer and leveling the field surface, is substantiated. Using the modeling of operation process of complex plowing unit, its optimal parameters and operating modes are substantiated. Feature of the structural and technological scheme of the proposed unit is the use of reversible high-speed plow PSK with a reinforced frame structure, with a low energy intensity of the plowing process due to the elimination of plow land-sides, with devices for crumbling furrow slice and leveling field surface with simultaneous mineral fertilizer application. Incorporation and application of fertilizers into the soil without a break in time improves operation quality and reduces costs. Block diagram of algorithm for optimizing parameters and modes of proposed multifunctional plowing unit operation is presented and dependence of tractor engine power on its mass is approximated. Mathematical model and algorithm for optimizing the parameters and modes of complex unit operation have been developed, using as an optimization criterion, the minimum value of total energy consumption for the performance of operation process with a working speed limit of up to 15 km/h, plow working width of up to 6 m, plow specific resistance coefficient of up to 80 kN/m2, plowing depth of up to 0.3 m, fertilizer hopper capacity up to 4 m3, furrow length of up to 2 km. The K-701 tractor has been adopted as a power unit. At the minimum value of the optimization criterion, the following parameters have been substantiated: plow width, working speed, fuel consumption, performance, power unit tractive effort, traction power, fertilizer hopper capacity. Dependences of optimization criterion on the unit parameters and modes of its operation have been obtained.

The density of the structure of dark gray podzolized soil under different tillage systems under crop rotation

The results of studies on the influence of tillage systems on the density of the structure of dark gray podzolized soil under crops in a four-field short-rotation crop rotation (winter rape – winter wheat – corn for grain – spring barley) in the stationary field experiment of the Institute of Agriculture of the Western Polissia of the National Academy of Sciences of Ukraine during 2016 are shown. – 2020. In the experiment, three tillage systems were studied (shelf by 20–22 cm, shallow by 10–12 cm, surface by 6–8 cm) against the background of mineral fertilizers N128P90K120 kg/ha of the crop rotation area. It was determined that at the time of spring germination and spring weeding of winter crops under the shelf system of soil cultivation, a plow layer was formed under the crops of the crop rotation, which was characterized by a compaction density close to the optimum – 1.06–1.33 g/cm3. Under no-shelf tillage under crop rotation, the 0–30 cm soil layer was differentiated by compaction density into the upper loose 0–10 cm layer with a density of 1.13–1.24 g/cm3 and compacted to 1.30–1.41 g/cm3. The lowest soil compaction density was in winter wheat, spring barley, and corn crops under the shelf and shallow tillage systems in soil layers of 0–10 cm and 10–20 cm, where it was, respectively, in the range of 1.06–1.19 g/cm3 and 1.17–1.25 g/cm3. Noticeably, the density of the soil compaction increased during crop rotation during surface tillage under winter rape in the soil layer of 10–20 cm to 1.36 g/cm3 and in the soil layer of 20–30 cm to 1.47 g/cm3. The compaction density under the surface tillage system under winter rape in the 20–30 cm soil layer increased by 0.14 g/cm3, compared to the wormwood tillage system for this crop. The system of shelf and shallow soil cultivation in crop rotation creates better conditions for optimizing the agrophysical fertility indicators of dark gray podzolized soil and provides the highest crop yield in crop rotation, compared to the surface 6–8 cm system, and made it possible to obtain yields of 6.80 and 6.32 respectively t/ha of winter wheat 5.19 and 4.99 of spring barley 11.25 and 11.33 of corn and 2.97 and 3.05 t/ha of winter rapeseed. From the application of surface tillage to a depth of 6–8 cm, the yield of winter wheat decreases by 1.45 t/ha, spring barley by 1.69 corn by 3.66 t/ha and winter rapeseed by 0.30 t/ha compared with a shelf tillage system. Key words: compaction density, tillage, shelf, shal-low, surface, productivity, crop rotation.

Combining Multitemporal Sentinel-2A Spectral Imaging and Random Forest to Improve the Accuracy of Soil Organic Matter Estimates in the Plough Layer for Cultivated Land

Soil organic matter (SOM) is vital for assessing the quality of arable land. A fast and reliable estimation of SOM is important to predict the soil carbon stock in cropland. In this study, we aimed to explore the potential of combining multitemporal Sentinel-2A imagery and random forest (RF) to improve the accuracy of SOM estimates in the plough layer for cultivated land at a regional scale. The field data of SOM content were utilized along with multitemporal Sentinel-2A images acquired over three years during the bare soil period to develop spectral indices. The best bands and spectral indices were selected as prediction variables by using the RF algorithm. Partial least squares (PLS), geographically weighted regression (GWR), and RF were employed to calibrate spectral indices for the SOM content, and the optimal calibration model was used for the mapping of the SOM content in arable land at a regional scale. The results showed the following. (1) The multitemporal image estimation model outperformed the single-temporal image estimation model. The estimation model that utilized the optimal bands and spectral indices as prediction variables usually had better accuracy than the models based on full spectral data. (2) For the SOM content estimates, the performance was better with RF than with PLS and GWR in almost all cases. (3) The most accurate SOM estimation in the case area was achieved by using multitemporal images from 2018 and the RF calibration model based on the optimal bands and spectral indices as prediction variables, with R2val (coefficient of determination of the validation data set) = 0.67, RMSEval (root mean square error of the validation dataset) = 2.05, and RPIQval (ratio of performance to interquartile range of the validation dataset) = 3.36. (4) The estimated SOM content in the plough layer for cultivated land throughout the study area ranged from 16.17 to 36.98 g kg−1 and exhibited an increasing trend from north to south. In the current study, we developed a framework that combines multitemporal remote sensing imagery and RF for the SOM estimation, which can improve the accuracy of quantitative SOM estimations, provide a dynamic, rapid, and low-cost technique for understanding soil fertility, and offer an early warning of changes in soil quality.

Effects of Deep Plowing with a Chisel Plow on Soil Physical Properties in the Subsoil and Drainage of the Plow Layer in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Effects of Deep Plowing with a Chisel Plow on Soil Physical Properties in the Subsoil and Drainage of the Plow Layer in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Effects of Land Reclamation on Soil Bacterial Community and Potential Functions in Bauxite Mining Area.

Studying the characteristics of microorganisms in mine reclamation sites can provide a scientific reference basis for mine land reclamation. Soils in the plough layer (0-20 cm) of the bauxite mine plots in Pingguo city, Guangxi Zhuang Autonomous Region, China, with different reclamation years were used as the research objects. The community structure of soil bacteria was analyzed with high-throughput sequencing technology. The results show the following: (1) Reclamation significantly increased the contents of soil nutrients (p < 0.05). (2) The relative abundances of Proteobacteria were high (22.90~41.56%) in all plots, and reclamation significantly reduced the relative abundances of Firmicutes (3.42-10.77%) compared to that in the control plot (24.74%) (p < 0.05). The relative abundances of α-proteobacteria generally increased while the reclamation year increased. The relative abundances of α-proteobacteria and γ-proteobacteria showed significant positive correlations with soil carbon, nitrogen, and phosphorus nutrients (p < 0.01). The relative abundance of Acidobacteria Group 6 showed significant positive correlations with soil exchangeable Ca and Mg (p < 0.01). (3) Bacterial co-occurrence network showed more Copresence interactions in all plots (50.81-58.39%). The reclaimed plots had more nodes, higher modularity, and longer characteristic path length than the control plot, and the keystone taxa changed in different plots. (4) The chemoheterotrophy and aerobic chemoheterotrophy were the most abundant functional groups in all plots (35.66-48.26%), while reclamation reduced the relative abundance of fermentation groups (1.75-11.21%). The above findings indicated that reclamation improved soil nutrients, changed the bacterial community structure and potential functions, and accelerated the microbial stabilization of the reclaimed soil.

An empirical model for prediction of topsoil deformation in field traffic

Agricultural topsoils are characterized by a heterogeneous mixture of structural units with a considerable difference in soil mechanical properties. Mechanistic modeling of compaction for this layer is challenging because of the need to parameterize model input parameters. This study quantified soil deformation during loading in semi-confined conditions and searched for drivers decisive for observed strains with no a priori assumptions of material properties. Undisturbed soil samples were collected in the plough layer of eleven sandy and loamy soils in Denmark. The samples were adjusted to either of the following matric potentials: − 30, − 50, − 75, − 100, − 160 and − 300 hPa (pF from ∼1.5 to ∼2.5). Cores at each water condition were loaded with an annulus covering one third of the soil surface at either of the following normal loads: 30, 60, 90, 120, 150, 180 kPa. Multiple regression was performed to estimate the best model describing the variation in soil compressibility. Measured strain, ε, decreased with increase in soil organic matter, bulk density and pF, but the effect of pF was affected by soil clay content. The model explained ∼84 % of the variation in data and predicted well measured strain for two independent data sets. The regression model is suggested for prediction of soil deformation of arable topsoils in field traffic. A procedure is described for the prediction, including calculation of the relevant stress based on loading characteristics.

The high accumulation of phosphorus in high-yield paddy soils: A new insight from cutans

Phosphorus (P) is a key limiting nutrient for crops. Oscillation of redox conditions usually induces formation of Fe-enriched cutans in the plow layer of paddy soils. This study investigated P biogeochemistry in the cutans, which were collected from high-yield paddy soils in Taihu Lake region, China. Mössbauer spectroscopy showed that the content of Fe3+ was eight times higher than Fe2+ in the cutans. Based on the evidences from XRD and wet chemical analysis, the enriched Fe in the cutans mostly existed as amorphous oxides, which owned high surface areas for P sorption. In addition, the cutans were composed of spherical particles with diameters of 20–130 μm under microscopy. Moreover , the particles showed evident “trench” structures on their top surface under SEM imaging. These features caused the cutans to retain three times higher P than that in the matrix soils. Furthermore, the cutans demonstrated both high microbial richness and community diversity, in contrast to the matrix soils. In particular, the abundance of phosphate-solubilizing fungi (with relatively highly competitive saprophytic ability) was also significantly promoted. Therefore, the cutans could be considered as hotspots of P accumulation in paddy soils. The subsequent enhancement of the available P would promote rice production.

Distribution and weathering characteristics of microplastics in paddy soils following long-term mulching: A field study in Southwest China

Agricultural plastic-film residues have been considered as one of the important sources of microplastics in the agroecosystem. However, limited researches were conducted on the accumulation of microplastics in long-term film-mulched paddy soil. This study aims to investigate the distribution and the weathering characteristics of filmy microplastics in a mulched paddy field (non-mulch, four years of mulched, and ten years of continuous mulched soil were investigated) in Southwest China. More than 50 % of the microplastics in the mulched soil were 1–3 mm, whereas the largest percentage of the microplastics in the non-mulched soil was <1 mm (55.3 %). Microplastic compositions in this field mainly consist of polyester (PES) and polyethylene (PE) (82.1 %). The abundance of microplastics increases with the film mulching time, which were 76.2 ± 18.4, 118.6 ± 44.8, and 159.6 ± 23.5 items kg−1 in soil with non-mulching, four years of mulching, and ten years of continuous mulching, respectively. The filmy microplastics accumulated annually in the plough layer is estimated at 18.1 million items ha−1. Weathering characteristics of filmy microplastics extracted from paddy soil were characterized using FTIR, SEM-EDS, AFM, and contact angle meter. The vinyl, carbonyl, and hydroxyl indices calculated from FTIR results showed that the degradation degree of microplastics incereased as mulching time rose; compared with commercial PE films, the oxygen-containing functional groups of soil-extracted PE films were increased. This study revealed the status of microplastic pollution in paddy soil with long-term mulching. It provided primary data and a scientific basis for further study on environmental behavior and ecological impacts of microplastics in agricultural soils.

Effects of soil redistribution by tillage on subsequent transport of pesticide to subsurface drains.

Tillage operations will change the distribution in soil for any pesticide residues still present from earlier applications. This redistributive effect of tillage has been neglected in the study of pesticide leaching behavior. This study reviews the literature to characterize this redistributive effect for different tillage operations and uses a pesticide leaching model to investigate the impact of redistribution on pesticide transport to subsurface drains which is a significant input route to surface water bodies. Inversion ploughing moves the majority of any residues of pesticide present at or near the soil surface into the bottom two-thirds of the plough layer, whereas non-inversion ploughing has only a limited redistributive effect. Incorporating this redistributive effect into model simulations resulted in large changes (typically 5-10-fold difference) in both the maximum concentration and total mass of pesticide transported to drains over the winter following cultivation. More intense cultivation decreased subsequent leaching for relatively mobile compounds (Koc ≤1000 mL g-1 ), but increased it for strongly sorbed pesticides (Koc ≥2000 mL g-1 ). The redistributive effect of soil tillage on pesticide residues can have a large effect on subsequent transport to subsurface drains. This effect has been neglected in the literature. Field research is required to validate the model simulations presented here, and consideration should be given as to whether the effect needs to be included within risk assessment procedures. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

UAV imaging and deep learning based method for predicting residual film in cotton field plough layer.

In this paper, a method for predicting residual film content in the cotton field plough layer based on UAV imaging and deep learning was proposed to solve the issues of high labour intensity, low efficiency, and high cost of traditional methods for residual film content monitoring. Images of residual film on soil surface in the cotton field were collected by UAV, and residual film content in the plough layer was obtained by manual sampling. Based on the three deep learning frameworks of LinkNet, FCN, and DeepLabv3, a model for segmenting residual film from the cotton field image was built. After comparing the segmentation results, DeepLabv3 was determined to be the best model for segmenting residual film, and then the area of residual film was obtained. In addition, a linear regression prediction model between the residual film coverage area on the cotton field surface and the residual film content in the plough layer was built. The results showed that the correlation coefficient (R2), root mean square error, and average relative error of the prediction of residual film content in the plough layer were 0.83, 0.48, and 11.06%, respectively. It indicates that a quick and accurate prediction of residual film content in the cotton field plough layer can be realized based on UAV imaging and deep learning. This study provides certain technical support for monitoring and evaluating residual film pollution in the cotton field plough layer.