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The variation in the soil microbial community composition over time was assessed at monthly time steps for 1 year in three neighboring Mollisols spanning a drainage gradient. This was done to distinguish between natural oscillations in the community composition versus lasting adaptations to environmental factors such as soil water availability. To isolate soil water availability as a controlling factor, we selected three soils sharing the same soil order (fine‐silty, superactive Argixerolls/Argialbolls); slope (0%–1%); temperature regime (mesic); moisture regime (xeric); and land use history (continuous grassland for the past 10 years) but differing in drainage class (well‐drained vs. moderately well‐drained vs. poorly drained). Changes in microbial diversity were quantified by monitoring the bacterial community at monthly intervals for 1 year. Within individual soils, α‐diversity varied little with season and drainage classes. Despite the three soils experiencing the same climate regime and vegetation/land use, they exhibited distinct community composition and turnover, which we attribute to differences in moisture availability across drainage and seasons. We posit that a seasonal recurring drop in soil redox potential induced by seasonal water saturation in the poorly drained soil is the most probable cause setting the microbial community of that soil apart from those in the better drained soils. Our investigation suggests that not all indicators of microbial diversity share the same sensitivity to seasonal and drainage‐related soil moisture variations. Core Ideas: Seasonal moisture fluctuations have a small effect on bacterial phylogenetic diversity.Phylogenetic diversity may increase with improved drainage.Impacts of seasonal saturation on the microbial community persist year‐round.Responsiveness to seasonal moisture fluctuations can influence the viability of microbial abundance as a bioindicator. [ABSTRACT FROM AUTHOR]

We used mid‐infrared (MIR) spectra (4000–600 cm−1) to identify and classify soil orders and soil horizons from 102 pedons across five soil orders (Alfisols, Entisols, Mollisols, Spodosols, and Histosols). The soils were analyzed for texture, total carbon, pH, and elemental properties. Random forest models were used to group the spectra of master horizons (O, A, E, B, and C), B horizons (Bs, Bt, and Bw), and the five soil orders. The prediction accuracies for the master horizons and B horizons were 0.81 and 0.89, respectively. The Kappa coefficient was 0.71 for the prediction of master horizons and 0.73 for the prediction of B horizons. The soil orders had an overall accuracy of 0.73 and a Kappa coefficient of 0.64. Histosols exhibited unique absorption characteristics at 2930 and 2860 cm−1 that differed distinctly from mineral soils. The MIR spectra accurately distinguished the O horizons. The spectral curve of topsoil of Spodosols was comparable to the O horizons. Spodosols under forest had A horizons with high organic matter and were classified accurately. Entisols (Psamments) displayed absorption peaks associated with sand, facilitating their differentiation from the other soil orders. The model struggled to discern subtle differences among some soil orders, and identification is hampered if soils undergo irreversible changes upon drying. However, our results showed that MIR spectra can be used for effectively identifying and classifying soil orders as well as soil horizons. Core Ideas: Mid‐infrared (MIR) spectra measured from 102 pedons across nine regions in Wisconsin.Unique adsorption characteristics in MIR spectra reflected pedogenetic features and horizons.MIR spectra and random forest machine learning correctly identified soil horizons and orders.Master horizons were classified with an accuracy of 0.81 and B horizons with an accuracy of 0.89.Soil orders were classified with an accuracy of 0.73. [ABSTRACT FROM AUTHOR]

The extent to which cover crops (CCs) accumulate soil organic carbon (SOC) in the entire soil profile is still unclear. We measured SOC, permanganate oxidizable C (POX‐C), and particulate organic matter (POM) concentrations down to 60‐cm soil depth in early [2–3 week before corn (Zea mays L.) planting]‐ and late‐terminated (at corn planting) winter rye (Secale cereale L.) CCs in rainfed and irrigated no‐till continuous corn systems in the U.S. Corn Belt after 10 years. CCs increased SOC stock and SOC, POX‐C, and POM concentrations but only in the irrigated system in the upper 5‐cm depth. Late‐terminated CC increased SOC concentration by 4.710 ± 3.501 g kg−1 and accumulated SOC at 0.207 ± 0.145 Mg C ha−1 year−1. It increased POX‐C and POM concentrations, on average, by 1.194 times. CCs likely increased SOC in the irrigated system by producing more biomass (2.247 ± 0.370 Mg ha−1) than in the rainfed system (0.949 ± 0.338 Mg ha−1). At least 2 Mg ha−1 of CC biomass may be needed to increase SOC. Because winter CCs often produce <1 Mg ha−1 of biomass when typically planted late and terminated early, extending the CC growing window by terminating CCs at or after crop planting (planting green) may boost CC biomass and SOC accumulation, although high‐C soils or Mollisols, such as our study soils (>22 g C kg−1), may limit SOC gains. We submit CCs would sequester more SOC in low‐C, eroded, and low‐fertility soils. Overall, winter rye CCs minimally alter soil C in the soil profile in no‐till continuous corn systems after 10 years. Core Ideas: Late‐terminated cover crop (CC) accumulates 0.207 ± 0.145 Mg C ha−1 year−1 at one of two sites but only in the top 5 cm of the soil profile.CCs may not accumulate soil C if they produce <2 Mg biomass ha−1.Early‐terminated CC (2–3 weeks before corn planting) does not accumulate soil C due to low biomass production.Extending CC growing window by terminating CC at or after corn planting can favor gains in total SOC and labile C.CCs minimally alter soil C in the soil profile in no‐till continuous corn systems after 10 years. [ABSTRACT FROM AUTHOR]

Aims: Application of cattle manure could improve soil fertility by increasing the stability of soil organic carbon (SOC), however, the extent of this effect might depend on the soil layer. This study aims at evaluating the differences in SOC chemistry between topsoil and subsoil caused by cattle manure addition. Methods: Here, a 90-day pot experiment was used to investigate the SOC chemical structure (13C-NMR and FTIR), as well as microbial community composition (PLFA), with cattle manure amended in topsoil (T1M) and subsoil (T2M) and without manure in topsoil (T1) and subsoil (T2). Results: Application of cattle manure significantly increased SOC, total nitrogen (TN) contents and plant biomass either in topsoil or subsoil. The alkyl C/O-alkyl C (A/OA) ratio of T1M was lower than that of T1, while T2M was greater than that of T2, indicating the SOC of T1M decomposition was delayed but of T2M was promoted. The A/OA ratio of T2M was greater than that of T1M, indicating the decomposition degree of SOC of T2M was greater. The fungi/bacterial PLFA ratio, G+/G− PLFA ratio and fungi PLFA were lower in T2M than T1M. RDA analysis demonstrated that O-alkyl C was negatively associated with bacterial and G- PLFA, especially Gemmatimonadetes and Acidobacteria, while positive correlation with fungi PLFA. However, the alkyl C was negatively associated with fungi PLFA, especially Basidiomycota. Conclusions: The subsoil with cattle manure added promoted bacterial consumed labile C, especially Gemmatimonadetes and Acidobacteria. Therefore, the subsoil with cattle manure added had a higher decomposition degree of SOC when compared with the topsoil with cattle manure added, improving the stability of SOC. [ABSTRACT FROM AUTHOR]

The temperature sensitivity (Q10) of soil organic C (SOC) decomposition is an important parameter to predict C dynamics under climate change. Given that SOC is mainly protected by aggregates and minerals, differentiating the Q10 of the two C fractions helps to explain bulk soil C dynamics. In the present study, we collected agricultural soils from adjacent paddy and upland areas in mid‐temperate (Mollisols) and subtropic (Ultisols) regions of China. We employed density fractionation to separate aggregate‐protected and free mineral‐associated C fractions of soil samples and determined the Q10 of SOC and the two C fractions at 15 and 25°C incubated conditions. Results showed that the Q10 of SOC for Mollisols were lower than that for Ultisols, with an exception of aggregates in upland soils. Aggregate‐protected C had lower Q10 than free mineral‐associated C, except in the upland Mollisols. The Q10 of SOC was negatively correlated with the proportion of C protected in aggregates, whereas it was positively correlated with the proportions of mass or C of free minerals. Given that the mass and C proportion of aggregates in bulk soils of Mollisols were 271% and 80% higher than of Ultisols, respectively, the SOC of Mollisols exhibited lower Q10 than Ultisols. Therefore, stronger soil aggregation and higher proportion of aggregate‐protected C contributed to the lower temperature sensitivity of SOC in Mollisols. Consequently, agricultural practices aimed at promoting soil aggregation will alleviate SOC loss under future global warming scenarios. [ABSTRACT FROM AUTHOR]

Long term tillage in mollisol of Northeast China has led to an inhomogeneous distribution of soil organic matter content. Biochar, a carbon material, changes the soil carbon pool and physical-chemical characteristics after adding to the soil. However, the mechanism remains unclear for the relation between the soil organic matter level and biochar amount. So, the soil physical and chemical properties and soybean growth in a two-year pot experiment were detected at three levels of soil organic matter and three biochar additions (0, 1% and 10%). The difference was found in two biochar application rates. The 1% biochar addition had no positive effect on the soil chemical properties based the two-year experiment. However, 10% biochar application significantly increased the soil water content (8.0%-39.7%), the total porosity (9.7%-21.3%), pH (0.26-0.84 unit), organic matter content (89.0%-261.2%), and the available potassium content (29.0%-109.1%). The biomass of soybean increased by 19.4%-78.1% after biochar addition, yet, the soil bulk density reduced at the range of 12.6%-26.0% by 10% biochar addition. Only the 100-grain weight was correlated to the interaction of biochar and the native soil organic matter. All the indicators showed that the interaction between biochar and soil organic matter level was weak in mollisol. The effects of biochar on the physical-chemical properties relied on its amount. When biochar is applied to the soil, the amount of biochar should be considered rather than the native soil organic matter level. [ABSTRACT FROM AUTHOR]

Since Chernozems are among the most fertile soils in the world, the study of their degradation is of great interest. However, the microstructure and composition of the soil organic matter (SOM) in eroded Chernozems have not yet been sufficiently studied. We studied the SOM and aggregate states of eroded Chernozems using the example of two catenas with arable Haplic Chernozems in the Kursk region of Russia. In the plow horizons (the part of the soil most susceptible to water erosion), we determined the mean-weighted aggregate diameter (MWD), structure and water stability coefficients (SC and WS; dry and wet sieving, respectively), soil organic carbon (SOC) content, and SOM composition and content (qualitative and quantitative micromorphological analyses, respectively). It was shown that with an increase in the degree of erosion, the content of SOC decreased significantly, according to both chemical and micromorphological methods of evaluation. No significant relationships were found between the degree of erosion and the indicators of the structure (except for WS, which was significantly lower in non-eroded Chernozem than in slightly and moderately eroded soils). With the increasing degree of erosion, the humus state of these soils deteriorates at the microlevel, the intensity of humification decreases, the depth of the appearance of assimilated biogenic aggregates with finely dispersed calcite in the profile increases, the structure is destroyed, lumpy aggregates form, and the proportion of planar voids increases. The downslope transport of the soil solid phase under the impact of erosion is accompanied by the accumulation of the transformation products of carbohydrates in the Chernozems in the lower part of the catena. In the Chernozems located in the transit position of the slope, the composition of SOM is characterized by the predominance of lipids and nitrogen-containing compounds. Our unique results contribute to a deeper understanding of the formation of structure and water resistance in eroded soils. [ABSTRACT FROM AUTHOR]

The yields realized under rice-wheat rotation are generally low in the geographical regions prone to B deficiency and a sound B application schedule recommendation is required for the sustainable yields and enhanced soil fertility. The effect of different B application schedules involving different dosages and frequency of B application was investigated on yields and B nutrition of rice-wheat rotation and changes in the chemical fractions of B in soil in six years field study carried out on a sandy loam (Typic hapludoll). Based on the average grain yields of rice and wheat during the period of experimentation, application of 1.5 kg B as borax ha−1 to rice crop on alternate years was the profitable practice for mollisols as it gave an average yearly production of 5.51 t of rice grain and 4.28 t of wheat grain ha−1. The average concentration of B in flag leaves and grains of rice was much lower compared to wheat crop. The recommended schedule of B application to rice-wheat rotation resulted in a Benefit: Cost ratio of 11: 1 and also maintained the optimum level of B in soil. Most of the added B markedly increased specifically bound (0.05 M KH2PO4 extractable), ammonium oxalate (pH 3.3) extractable fractions followed by residual and organically bound fraction in the soil. [ABSTRACT FROM AUTHOR]

Purpose: To clarify the effects of maize straw retention combined with reduced fertilization and urease/nitrification inhibitors on the accumulation and leaching potential of mineral N in the deep soil profile of no-tillage agroecosystem. Methods: A 15N-tracing micro-plot experiment was conducted with four treatments (NPK, traditional NPK fertilization; NPKS, NPK with maize straw retention; RNPKS, NPKS with 20% fertilizer-N reduction; and RNPKSI, RNPKS with inhibitors application) in the Mollisol of Northeast China. We analyzed fertilizer-N transformation dynamics in different soil N pools, quantified the fertilizer N use efficiency in crops, and evaluated fertilizer-derived nitrate leaching losses throughout the complete maize growing period. Results: Our analyses revealed that, compared to the NPK treatment, NPKS, RNPKS, and RNPKSI remarkably reduced the accumulation of urea-derived mineral-N during maize seedling stage by enhancing the transformation of urea-N into fixed NH4+-N and organic-N pools, both of which could be quickly released for maize uptake following the extension of crop growth periods. At the maize ripening stage, soil NO3−-N and 15N-labeled urea-derived NO3−-N, which migrated vertically to a depth of 80–100 cm, were significantly reduced by treatments of RNPKS and RNPKSI without minimizing crop yields when compared with NPK. Conclusion: Our results suggest that combining maize straw retention with reduced fertilization and the application of urease/nitrification inhibitors can be efficient management practices for lowering urea N leaching risk, improving N use efficiency, and maintaining or even increasing crop yields by enhancing soil N retention and supply in the croplands of Northeast China. [ABSTRACT FROM AUTHOR]

Mollisols are highly fertile soils and function as significant carbon reservoirs. However, determining their ages and formation processes is challenging due to extensive pedoturbation, which undermines conventional dating methods. Here, we employed luminescence, a light‐sensitive property of minerals widely used in geological dating, to investigate and quantify soil mixing. We analyzed over 2,400 luminescence ages of individual K‐feldspar grains from a Mollisol profile in Northeast China, and for the first time, we were able to determine the intensity of pedoturbation in the Mollisol profile over the past 50,000 years. The results showed that the current pedoturbation can penetrate to a depth of approximately 80 cm, with the intensity decreasing with depth. By identifying a significant intensification in historical pedoturbation, we inferred that the paleoenvironment might be suitable for the formation of Mollisols 16,400 years before present. Plain Language Summary: Mollisols, also known as a type of black soils, are highly fertile soils characterized by a thick, dark surface layer rich in soil organic matter. Mollisols are not only crucial for food security but also serve as a significant carbon pool. To predict the future evolution of these valuable soil resources, it is important to understand when and how they formed. However, due to intensive mixing by animals, plants, and freeze‐thaw processes, it is challenging to accurately obtain soil ages using traditional dating methods that rely on undisturbed sedimentation layers. Here, we utilized luminescence, a light‐sensitive property of minerals, to address the challenge of soil mixing. We analyzed more than 2,400 luminescence ages of individual K‐feldspar grains from a Mollisol profile in Northeast China. The results showed that the upper 80 cm of the soil body is currently mixed, with the mixing intensity being most intense at the soil surface and decreasing with depth. Additionally, we observed evidence of historical soil mixing over the past 50,000 years. The intensity of soil mixing increased around 16,400 years ago. We infer that the paleoenvironment might be favorable for forming Mollisols since then. Key Points: Single‐grain luminescence was used to quantify the intensity of pedoturbation in the Mollisol profile over the past 50,000 yearsDust accumulation fostered the formation of the thick, dark, humus‐rich surface layer of the Mollisol profileThe formation processes of the Mollisol profile were traced back to 16,400 years before present [ABSTRACT FROM AUTHOR]

Background Aims Methods Results Conclusion There are no extractable boron (B) thresholds for maize (Zea mays L.) in Mollisols determined by field calibrations.Our objectives were to: (1) explore maize grain yield response to B fertilization, (2) calibrate the soil hot water extractable B (HW‐B) as a predictor of maize response to B fertilization under field conditions, and (3) assess the contribution of clay, pH, and soil organic matter (SOM) as predictive variables of maize response to B fertilization.We conducted 53 field trials with 2 treatments: with and without B fertilization. At all sites, we measured clay, SOM, pH, and HW‐B at a 0–20 cm depth.Maize grain yield ranged from 5.34 to 17.35 Mg ha−1. Grain yield response to fertilization was observed in 6 out of 53 sites (11.3%). In responsive sites, average grain yield response was 1.0 Mg ha−1. Multiple regression models to predict yield response to B addition that included soil, pH, and SOM only explained 19% of the variability. The critical soil HW‐B concentration threshold was 0.78 mg kg−1, correctly diagnosing 79% of the site‐years.The critical threshold for maize B levels resulting from our field study is the first of its kind in Mollisols. This threshold will improve the identification of soils deficient in B. [ABSTRACT FROM AUTHOR]

Appropriate mechanized straw returning and tillage sowing techniques were effective means to optimize soil physical properties and enhance agricultural productivity, as well as important measures for the conservation and restoration of mollisols region in Northeast China. Under the condition of full-scale maize straw returning, four mechanized tillage and sowing modes were set, including plough tillage and sowing (PTS), combined tillage and sowing (CTS), no-tillage and sowing (NTS), and no-tillage and sowing with straw mulching (NTSM). In 2020 and 2021, the study investigated the effects of different mechanized tillage and sowing modes on soil physical properties, soybean yield and economic benefits. The results showed that during the pod-setting and pod-filling period of soybean, the NTS and NTSM treatments exhibited better effects on deep soil insulation and shallow soil moisture retention, the soil physical structure of PTS and CTS treatments were relatively ideal. Compared with PTS and CTS treatments, NTS and NTSM treatments significantly increased soil gravimetric water content (SWC) by 2.35% to 7.98% in the 5-15 cm soil layer and increased soil temperature (ST) by 3.94% to 10.42% in the 2535 cm soil layer (p<0.05), significantly increased soil bulk density (SBD) by 2.98% to 6.72% and significantly reduced soil total porosity (STP) by 3.88% to 6.53% in the 5-25 cm soil layer, and significantly reduced soil gas phase ratio by 8.26% to 6.27% at the 15-25 cm soil layers, which caused soil three-phase ratio (STPR) of PTS and CTS treatment in 15-25 cm soil layer were relatively ideal. The soybean yield of NTSM treatment in 2020 was not significantly different from PTS and CTS treatment (p>0.05), the soybean yield of NTSM treatment in 2021 significantly increased by 7.30% and 5.84% over PTS and CTS treatments, respectively. And the average annual profit per unit area of NTSM treatment increased by 12.84%, 12.41% and 8.57% compared with PTS, CTS and NTS treatments, respectively. Therefore, it was recommended to combine NTSM technique with PTS or CTS technique in a maize-soybean rotation system in mollisols region. The research results provided reference for the selection of appropriate mechanized tillage and sowing techniques in Northeast China's mollisols region and had important guiding significance and practical value for the construction of rational plow layers and the implementation of conservation tillage. [ABSTRACT FROM AUTHOR]

This work aimed to evaluate the capacity of anaerobically mineralized nitrogen (AN) within large (ANLM), small (ANSM), and total macroaggregates (ANTM) to predict grain yield, aboveground biomass, and total nitrogen (N) content of wheat (Triticum aestivum L.) plants as compared to AN in bulk soil (ANBS). Eight fields with non-N-fertilized wheat on Mollisols of the southeastern Argentinean Pampas were studied. Soil ANBS, ANLM, ANSM, and ANTM, and wheat grain yield, aboveground biomass, and plant total N content were determined. The ANLM, ANSM, and ANTM were positively related to grain yield, aboveground biomass, and plant total N content (R²=0.34-0.65). The relationships between ANBS and all those crop variables showed similar predictive capacity. Therefore, AN within macroaggregates was not a better indicator of soil nitrogen supply capacity than ANBS. [ABSTRACT FROM AUTHOR]

Managing carbon input from crop straw in cropland ecosystems could increase soil organic carbon (SOC) sequestration to achieve C neutrality and mitigate climate change. The complexity of the chemical structures of crop residue largely affects SOC sequestration. Fungi communities play an important role in the degradation of crop residues. However, the relationship between the fungal community composition and the chemical structures of crop residues remains unclear and requires further investigation. Therefore, a 120-day incubation experiment was conducted in Mollisols in Northeast China to investigate the decomposition processes and dynamics of maize straw stem (ST), leaf (LE) and sheath (SH) residues using 13C-NMR spectroscopy. Additionally, the microbiomes associated with these residues were analyzed through high-throughput sequencing to explore their relationship. Our results showed that the alkyl C contents in all treatments exhibited increases ranging from 15.1% to 49.1%, while the O-alkyl C contents decreased, ranging from 0.02% to 11.2%, with the incubation time. The A/OA ratios of ST, LE and SH treatments were increased by 23.7%, 43.4% and 49.3% with incubation time, respectively. During the early stages of straw decomposition, Ascomycota dominated, and in the later stage, Basidiomycota were predominant. The class of Sordariomycetes played a key role in the chemistry transformation of straw tissues during decomposition. The keystone taxa abundances, Fusarium_kyushuense, and Striatibotrys_eucylindrospora, showed strong negative correlations with di-O-alkyl C and carbonyl-C content and positive correlations with the β-glucosidase and peroxidase enzyme activity, respectively. In conclusion, our study demonstrated that the keystone taxa play a significant role in regulating the chemical structures of straw tissues, providing a better understanding of the influence of residue quality on SOC sequestration. [ABSTRACT FROM AUTHOR]

Background: Grain legumes are considered as an important group of food crops that can play a vital role to address national food and nutritional security and also tackle environmental challenges. They are known as the basis for an ecologically-sound, farmerfocused agricultural development effort and an important component of sustainable farming systems. Biofertilizers, being a cheap and environment friendly source of plant nutrients assume a special significance in supplying the plant nutrients under the present context of indiscriminate use and high costs of chemical fertilizers. Biofertilizers could be a good alternative to supplement the chemical fertilizers. Methods: A field experiment was carried out at Pantnagar in Mollisols during 2017-18 and 2018-19 to study the performance of Rhizobium sp. and plant growth promoting rhizobacteria (PGPR) inoculation in mungbean on productivity, soil health and economics. Result: A pronounced effect of biofertilizers application in mungbean was observed on the root nodulation, yields, nutrient uptake and soil health. Co-inoculation of Rhizobium and PGPR significantly increased the nodule number, nodule dry weight, plant dry weight, grain yield, straw yield, N and P uptake in mungbean and improved soil health over the no inoculation. The study suggested that combined application of PGPR and Rhizobium sp. in mungbean is better than Rhizobium sp. alone in increasing crop yields, soil health and farmer's profit. [ABSTRACT FROM AUTHOR]

The discovery of complete ammonia oxidizers (comammox) challenged our cognition of the nitrification process. Ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB) and comammox can carry out soil autotrophic nitrification process together. However, the differentiation of the ecological niche of three types of ammonia oxidizers in different environments has not been fully discovered. In this study, a typical black soil collected from northeast China was adjusted to different pH (original and adjusted pH were 4.29 and 7, respectively) and NH4+-N concentrations (weekly adding and without adding 100 mg NH4+-N kg− 1 soil). The activities of AOA, AOB and comammox were examined using DNA stable isotope probing approach with 13CO2, the phylogenetic information of active ammonia oxidizers was detected by high-throughput sequencing. The results showed that niche differentiation of AOA, AOB and comammox in black soils differed with soil pH. AOA dominated the nitrification process in acidic soils, while AOA, AOB and comammox Clade A taken part in the nitrification process in neutral soils. Among them, AOB showed strong activity in the soils with the high N treatment. The active AOA mainly belonged to Nitrososphaera in acidic and neutral soils. The active AOB and comammox Clade A mainly belonged to Nitrosospira and Clade A.2 in neutral soils, respectively. Taken together, the results highlighted the significance of canonical ammonia oxidizers in nitrification process of black soils, and comammox Clade A played an active role in neutral condition. [ABSTRACT FROM AUTHOR]

Soil fertility diagnosis often omits subsoil measurements, impacting precision. Our objective was to compare the vertical distribution of nitrate and sulfate in agricultural Mollisols. Both anions were measured in 34 Mollisols of the Pampean region (Argentina) sampled to 160‐cm depth at 20 cm intervals. Nitrate exhibited a continuous downward trajectory, with maximum values at 0–20 cm (12.7 mg N kg−1) and minimum values at 140–160 cm (3.3 mg N kg−1). Sulfate displayed a sinuous pattern, with a minimum at 60–80 cm (3 mg S kg−1). The 60–160/0–160 cm concentration ratio was 42% for nitrate and 60% for sulfate, indicating greater topsoil stratification for nitrate. Predicting deep‐layer nitrate concentrations from topsoil data was more accurate than for sulfate. This poses a challenge for assessing soil S bioavailability, as subsoil sulfates go undetected in conventional sampling. Core Ideas: Nitrate content consistently decreased from the shallowest to the deepest soil layer.In contrast, sulfate exhibited a sinuous trajectory, with minimum values at 60–80 cm.Compared to sulfates, the stratification toward the topsoil was 35% higher for nitrates.Sulfates in the upper layers failed to predict sulfate concentrations in deep layers.Nitrate at 20–60 cm was an acceptable predictor of subsoil nitrate (60–160 cm). [ABSTRACT FROM AUTHOR]

Soil quality decline can adversely affect ecosystem health and land productivity, with soil-dwelling mesofauna considered to potentially fulfill vital functions in accurately predicting these outcomes. However, the current state of research reveals a gap concerning the relationships between soil quality decline and soil-dwelling mesofauna in the Mollisols Region. For a more profound understanding of this issue, we conducted a comprehensive investigation of soil-dwelling mesofaunal communities in the different agricultural lands of the Mollisols Region. In this study, soil-dwelling mesofauna were collected, and 11 soil properties were determined following standard procedures, with soil quality levels quantified by utilizing soil quality index (SQI). Our results revealed that there was a gradient of soil quality across the different agricultural lands, which were divided into five levels, including very strong, strong, medium, weak, and very weak. Subsequently, this investigation provided empirical evidence that the decline in soil quality had implications for soil-dwelling mesofaunal communities in agricultural lands of the Mollisols region. A consistent decrease in the density of soil-dwelling mesofauna was observed with the decline of soil quality. In contrast, a greater richness was observed in areas with relatively weaker soil quality, suggesting that the consequences of soil quality decline on soil-dwelling mesofauna were not exclusively negative. Various taxa of soil-dwelling mesofauna exhibited varying degrees of response to the decline in soil quality. Oribatida was overwhelmingly dominant in the sampling fields with medium soil quality, and most Entomobryidae were found in agricultural lands with very weak soil quality. During soil quality decline, soil nutrients were observed to correlate positively with the density of soil-dwelling mesofauna. Overall, the outcomes of this investigation carry significance for comprehending how soil quality decline relates to soil-dwelling mesofauna, and can provide valuable ecological insights for formulating biodiversity guidelines targeted at preserving soil resources in the Mollisols region. [ABSTRACT FROM AUTHOR]

Mollisols region of China is a ballast stone of Chinese food security. In this study, 484 soil organic carbon (SOC) data points from the documented soil surface (0–20 cm) samples in the typical Chinese Mollisols region were selected. The regional soil fertility was divided into high, medium, and low levels based on the SOC content from the long‐term positioning fertilization stations in Shenyang, Harbin, and Hailun of Northeast China. Furthermore, the regional SOC balance point (SOCb) model was built driven by the factors of annual mean temperature, annual precipitation, annual effective accumulative temperature, the ratio of precipitation and temperature, soil clay content, and pH. Using geographic information systems (GIS) interpolation method, the regional mean SOCb and SOC sequestration potential (SOCsp) at the SOCb's status were simulated to be 40.10 g kg−1 and 10.71 kg m−2, respectively. Moreover, the SOC content increased (SOCc) and the SOC sequestration capacity increased of medium‐ or low‐fertility soil were evaluated by GIS subtraction. Consequently, the means of SOCc in medium‐ and low‐fertility soils could be 16.88 g kg−1 and 26.79 g kg−1, respectively. Furthermore, the means of SOCsp in medium‐ and low‐fertility soils could be 4.30 kg m−2 and 7.43 kg m−2, respectively. The sensitivity analysis of this model showed that the high SOCb area was distributed in study region with low temperature, dry, high clay content, and low pH. The results provide an actual perspective on estimating regional SOCsp and soil fertility promotion target induced by the different soil fertility levels. Core Ideas: A soil organic carbon (SOC) balance point concept was innovatively put forward.The SOC sequestration potential of typical Chinese Mollisols region was estimated based on the SOC balance point.Both regional SOC content increased and sequestration capacity increased were estimated. [ABSTRACT FROM AUTHOR]

Although Mollisols are renowned for their fertility and high-productivity, high carbon (C) losses pose a substantial challenge to the sustainable provision of ecosystem services, including food security and climate regulation. Protecting these soils with a specific focus on revitalizing their C sequestration potential emerges as a crucial measure to address various threats associated with climate change. In this study, we employed a modeling approach to assess the impact of different fertilization strategies on crop yield, soil organic carbon (SOC) stock, and C sequestration efficiency (CSE) under various climate change scenarios (baseline, RCP 2.6, RCP 4.5, and RCP 8.5). The process-based SPACSYS model was calibrated and validated using data from two representative Mollisol longterm experiments in Northeast China, including three crops (wheat, maize and soyabean) and four fertilizations (no-fertilizer (CK), mineral nitrogen, phosphorus and potassium (NPK), manure only (M), and chemical fertilizers plus M (NPKM or NM)). SPACSYS effectively simulated crop yields and the dynamics of SOC stock. According to SPACSYS projections, climate change, especially the increased temperature, is anticipated to reduce maize yield by an average of 14.5% in Harbin and 13.3% in Gongzhuling, and soybean yield by an average of 10.6%, across all the treatments and climatic scenarios. Conversely, a slight but not statistically significant average yield increase of 2.5% was predicted for spring wheat. SOC stock showed a decrease of 8.2% for Harbin and 7.6% for Gonghzuling by 2,100 under the RCP scenarios. Future climates also led to a reduction in CSE by an average of 6.0% in Harbin (except NPK) and 13.4% in Gongzhuling. In addition, the higher average crop yields, annual SOC stocks, and annual CSE (10.15-15.16%) were found when manure amendments were performed under all climate scenarios compared with the chemical fertilization. Soil CSE displayed an exponential decrease with the C accumulated input, asymptotically approaching a constant. Importantly, the CSE asymptote associated with manure application was higher than that of other treatments. Our findings emphasize the consequences of climate change on crop yields, SOC stock, and CSE in the Mollisol regions, identifying manure application as a targeted fertilizer practice for effective climate change mitigation. [ABSTRACT FROM AUTHOR]

Long-term application of chemical fertilizer poses an environmental threat to belowground ecosystems. However, the impact of nitrogen (N) or phosphorus (P) fertilizers on soil biodiversity and the conditions of soil food web remains largely unknown. Soil nematodes are the most abundant multicellular soil animals and serve as excellent bioindicators of soil. Here, we investigated soil nematode communities and food web structure in a long-term experiment with different application rates of N and P fertilizers in northeast China. The application of N and P fertilizers increased the abundance of bacterivores but suppressed the abundance of omnivores and predators. The abundance of bacterivores exhibited an increasing trend, while that of omnivores and predators showed a decreasing trend with increasing rates of N and P fertilizers. Plant parasites displayed a decreasing trend in response to N fertilizer, but not to P fertilizer. N and P fertilizers also altered nematode functional guild composition, with N fertilizer increasing the abundance of Ba1, and P fertilizer increasing the abundance of Fu2 and Ba3. Nonmetric multidimensional scaling (NMDS) analysis revealed apparent successions of nematode communities from no fertilizer soils to high rates of N or P fertilizer soils at both the genus and functional guild levels. Furthermore, N and P fertilizers resulted in different nematode communities. In terms of nematode food web indices, N fertilizer increased the enrichment index (EI) but reduced the channel index (CI) and structure index (SI), whereas P fertilizer only reduced the SI value. High rates of N and P fertilizers increased the respired carbon of bacterivores but reduced the respired carbon of predators. Mantel tests revealed significant correlations between soil properties and the community composition of both fungivores and omnivores. Among all soil properties, available phosphorus (AP) had the greatest influence on the community structure of soil nematodes. Our findings indicate that N fertilizer has a powerful effect on nematode food web structure, while P fertilizer exerts a stronger effect on soil nematode community composition. [ABSTRACT FROM AUTHOR]

Mollisols represent 29 % of agricultural land and they are considered to be one of the most fertile soils in the world. Here, we compare soil organic carbon (SOC) concentrations and pools of Mollisols for the globe, the USA and Poland, and review how differences are caused by climate, land use, and key environmental factors. Globally, the mean thickness of the A horizon in Mollisols is 50 cm. At 0–30 cm the mean SOC concentration is 2.3 %, SOC pool is 84 t ha−1, and clay content calculated at 0–50 cm soil depth is 21 %. Mollisols in the USA have an A horizon thickness of 36 cm and have a mean clay content of 27 % (0–50 cm). SOC concentrations are 2.0 and 1.7 % and SOC pools are 85 and 116 t ha−1 at 0–30 and 0–50 cm soil depth, respectively. Mollisols in Poland have SOC concentrations of 1.8 and 1.5 % at 0–30 and 0–50 cm soil depth, respectively, and lower clay content (17 %) at 0–50 cm depth. The SOC pool at 0–30 cm depth is 74 t ha−1 whereas it is 106 t ha−1 at 0–50 cm. At the global scale, the highest SOC concentrations and pools are in Mollisols from Eastern Europe (including Ukraine and Western Russia) and Asia, while the lowest SOC pools are found in Mollisols from South America. The Mollisols in Western and Central Europe and North America have similar SOC pools, although Mollisols in North America have higher SOC concentrations and lower A horizon thickness. Globally, the mean pH value of Mollisols is 7.1, and the pH is slightly lower in Mollisols of the USA (6.9 ± 0.9). The SOC concentrations and pools are strongly and positively correlated with clay content. Soil moisture and temperature regimes determine SOC concentration and pools in Mollisols, and higher SOC concentrations and pools are in Mollisols with frigid and frigid-cryic soil temperature regimes as well as aquic, xeric, and aridic soil moisture regimes. Mollisols under grassland have the largest SOC pools compared to those cultivated or under forest. The important environmental factors on SOC concentrations and pools in Mollisols worldwide are soil texture, land use, and soil temperature regime.

ABSTRACTConducting studies that focus on the alterations occurring in the soil microbiome within protection forests in the northeast plain is of utmost importance in evaluating the ecological rehabilitation of agricultural lands in the Mollisols region. Nevertheless, the presence of geographic factors contributes to substantial disparities in the microbiomes, and thus, addressing this aspect of influence becomes pivotal in ensuring the credibility of the collected data. Consequently, the objective is to compare the variations in soil physicochemical properties and microbial community structure within the understory of diverse shelterbelt species. In this study, we analyzed the understory soils of Juglans mandshurica (Jm), Fraxinus mandschurica (Fm), Acer mono (Am), and Betula platyphylla (Bp) from the same locality. We employed high-throughput sequencing technology and soil physicochemical data to investigate the impact of these different tree species on soil microbial communities, chemical properties, and enzyme activities in Mollisols areas. Significant variations in soil nutrients and enzyme activities were observed among tree species, with soil organic matter content ranging from 49.1 to 67.7 g/kg and cellulase content ranging from 5.3 to 524.0 μg/d/g. The impact of tree species on microbial diversities was found to be more pronounced in the bacterial community (Adnoism: R = 0.605) compared to the fungal community (Adnoism: R = 0.433). The linear discriminant analysis effect size (LEfSe) analysis revealed a total of 5 (Jm), 3 (Bp), and 6 (Am) bacterial biomarkers, as well as 2 (Jm), 6 (Fm), 4 (Bp), and 1 (Am) fungal biomarker at the genus level (LDA3). The presence of various tree species was observed to significantly alter the relative abundance of specific microbial community structures, specifically in Gammaproteobacteria, Ascomycota, and Basidiomycota. Furthermore, environmental factors, such as pH, total potassium, and available phosphorus were important factors influencing changes in bacterial communities. We propose that Fm be utilized as the primary tree species for establishing farmland protection forests in the northeastern region, owing to its superior impact on enhancing soil quality.IMPORTANCEThe focal point of this study lies in the implementation of a controlled experiment conducted under field conditions. In this experiment, we deliberately selected four shelterbelts within the same field, characterized by identical planting density, and planting year. This deliberate selection effectively mitigated the potential impact of extraneous factors on the three microbiomes, thereby enhancing the reliability and validity of our findings.

The maintenance of sustainability and quantification of soil health in the rice-wheat system in the Himalayan tarai region is of utmost importance, and a long-term study can properly demonstrate what needs to be done to achieve this. The current study was conducted after the completion of a 29-year crop cycle in the rice-wheat system in 2015 at Pantnagar. Since the beginning of the experiment in 1984, various NPK combinations with or without Zn and farmyard manure (FYM) applications were maintained in a fixed layout along with an absolute control plot without any external nutrition. FYM at 5mg ha-1 and Zn at 5 kg ha-1 were applied in only rice, and NPK-chemical fertilizers were applied both in rice and wheat. The results revealed that the application of N at 120 kg ha-1 + P at 40 kg ha-1 + K at 40 kg ha-1 + FYM at 5mg ha-1 + Zn at 5 kg ha-1 (NPK + FYM + Zn) resulted in the maximum attainment of long-term system productivity and the sustainable yield index (SYI), which were 22% higher than those with NPK application. NPK + FYM + Zn and NPK + FYM also improved the soil's overall physical, chemical, and biological parameters. Soil organic carbon, dehydrogenase activity, soil available P and K, phosphate solubilizing bacteria, and actinomycetes were found to be the most important soil quality parameters in Mollisols. From this study, it can be concluded that the application of the recommended NPK along with FYM and Zn can improve soil health and sustain the system productivity of the rice-wheat system in Mollisols of the Himalayan tarai region. [ABSTRACT FROM AUTHOR]

The spatial pattern of soil available nitrogen (AN) is the key reference for farmland fertilization however, it is still unclear how freeze–thaw cycles (FTC) altered the spatiotemporal heterogeneity of AN at the watershed scale. In this study, the geostatistical, traditional analysis and structural equation models were used to detect how topography, land management, and soil properties influence the spatiotemporal heterogeneity of AN in both before‐ and after FTCs of Mollisols of a watershed in Northeast China for three consecutive years. The results showed that AN decreased in >88% of areas of the watershed after FTCs, and the mean value significantly decreased by >7.6% (>10.4 mg kg−1) in 0–20 cm soil depth during 2016–2017 years and 2017–2018 years. The AN distribution, especially in the surface soil layer, tended to be aggregated after FTCs. The AN decreased in the areas near the areas of top slope position, while it tended to increase in areas of downslope position covered by forest although the total N decreased here after FTCs. The AN‐change (ANbefore FTCs minus ANafter FTCs) influenced by land use types was greater than slope steepness. The slope aspect as the key factor combined with slope steepness, slope position, and previous crops influenced the spatiotemporal heterogeneity of AN‐change after FTCs. The higher content of AN before FTCs accelerated more N loss during FTCs, and this process was mainly influenced by soil pH, nitrogen (N), and phosphorus. The N loss (5.7%) did not significantly alter the AN‐change after FTCs in the watershed. Generally, the spatial heterogeneity of AN‐change was mainly influenced by topography, land management, and soil properties (before FTCs) during FTCs in the watershed. In order to sustain a high level of AN, the mediation of N transformation and both vertical‐ and horizontal migration, caused by the dynamics of soil water potential and snowmelt erosion should be considered during FTCs. [ABSTRACT FROM AUTHOR]

Purpose: Soil erosion and deposition are natural occurrences that can greatly affect the functions of soil. Currently, soil erosion has become an important cause of soil degradation in the northeast China, which severely limits the sustainable development of agriculture. Therefore, understanding the effects of soil erosion and deposition on multiple soil ecosystem functions and soil microbial communities can facilitate a comprehensive assessment of their influence on soil quality and fertility of this region. Materials and methods: This study investigated the effects of soil erosion and deposition on microbial diversity and community in agroecosystems with Mollisols (black soil) at different sites of a slope in northeastern China. The study involves comparison of four slope sites with different erosion intensities and a deposition site. Firstly, a multifunctionality index was generated after determination of a number of soil physicochemical and microbiological parameters. Then, the soil bacteria were determined by 16 s rRNA gene sequencing technology. Finally, the above data were analyzed to investigate the relationship among microbial community characteristics, soil multifunctionality, and soil erosion and deposition. Results and discussion: Erosion reduces while deposition enhances soil multifunctionality and microbial diversity. Soil multifunctionality decreased from 0.52 (TS) to –0.83 (LS) and increased to 0.85 (FS). Erosion and deposition significantly changed the abundance of Desulfobacterota, Geobacteraceae, Methylomirabilota, and others, which may be related to soil physicochemical properties and hydrothermal conditions. Erosion reduced the complexity and stability of the co-occurrence network of bacteria, whose node and robustness respectively decreased from 540 and 0.1936 (TS) to 488 and 0.1881 (LS), and the vulnerability increased from 0.0006 (TS) to 0.0013 (LS). Moreover, the complexity and stability showed positive correlations with soil multifunctionality and microbial diversity. Overall, our results indicated that erosion and deposition can significantly affect soil multifunctionality and microbial diversity, which will further alter soil microbial communities and their functions. Conclusions: Soil degradation caused by soil erosion may be reflected not only by the reduction of soil nutrients and destruction of soil structure, but also by decreases in soil microbial diversity, network complexity, and stability. Soil degradation caused by erosion includes a decline in soil multifunctionality and microbial characteristics, both of which should be taken into account when treating and rehabilitating degraded soils caused by erosion. [ABSTRACT FROM AUTHOR]

Organo–mineral interactions have been regarded as the primary mechanism for the stabilization of soil organic carbon (SOC) over decadal to millennial timescales, and the capacity for soil carbon (C) storage has commonly been assessed based on soil mineralogical attributes, particularly mineral surface availability. However, it remains contentious whether soil C sequestration is exclusively governed by mineral vacancies, making it challenging to accurately predict SOC dynamics. Here, through a 400‐day incubation experiment using 13C‐labeled organic materials in two contrasting soils (i.e., Mollisol and Ultisol), we show that despite the unsaturation of mineral surfaces in both soils, the newly incorporated C predominantly adheres to "dirty" mineral surfaces coated with native organic matter (OM), demonstrating the crucial role of organo–organic interactions in exogenous C sequestration. Such interactions lead to multilayered C accumulation that is not constrained by mineral vacancies, a process distinct from direct organo–mineral contacts. The coverage of native OM by new C, representing the degree of organo–organic interactions, is noticeably larger in Ultisol (~14.2%) than in Mollisol (~5.8%), amounting to the net retention of exogenous C in Ultisol by 0.2–1.3 g kg−1 and in Mollisol by 0.1–1.0 g kg−1. Additionally, organo–organic interactions are primarily mediated by polysaccharide‐rich microbial necromass. Further evidence indicates that iron oxides can selectively preserve polysaccharide compounds, thereby promoting the organo–organic interactions. Overall, our findings provide direct empirical evidence for an overlooked but critically important pathway of C accumulation, challenging the prevailing "C saturation" concept that emphasizes the overriding role of mineral vacancies. It is estimated that, through organo–organic interactions, global Mollisols and Ultisols might sequester ~0.1–1.0 and ~0.3–1.7 Pg C per year, respectively, corresponding to the neutralization of ca. 0.5%–3.0% of soil C emissions or 5%–30% of fossil fuel combustion globally. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) plays an essential role in mediating community structure and metabolic activities of belowground biota. Unraveling the evolution of belowground communities and their feedback mechanisms on SOC dynamics helps embed the ecology of soil microbiome into carbon cycling, which serves to improve biodiversity conservation and carbon management strategy under global change. Here, croplands with a SOC gradient were used to understand how belowground metabolisms and SOC decomposition were linked to the diversity, composition, and co‐occurrence networks of belowground communities encompassing archaea, bacteria, fungi, protists, and invertebrates. As SOC decreased, the diversity of prokaryotes and eukaryotes also decreased, but their network complexity showed contrasting patterns: prokaryotes increased due to intensified niche overlap, while that of eukaryotes decreased possibly because of greater dispersal limitation owing to the breakdown of macroaggregates. Despite the decrease in biodiversity and SOC stocks, the belowground metabolic capacity was enhanced as indicated by increased enzyme activity and decreased enzymatic stoichiometric imbalance. This could, in turn, expedite carbon loss through respiration, particularly in the slow‐cycling pool. The enhanced belowground metabolic capacity was dominantly driven by greater multitrophic network complexity and particularly negative (competitive and predator–prey) associations, which fostered the stability of the belowground metacommunity. Interestingly, soil abiotic conditions including pH, aeration, and nutrient stocks, exhibited a less significant role. Overall, this study reveals a greater need for soil C resources across multitrophic levels to maintain metabolic functionality as declining SOC results in biodiversity loss. Our researchers highlight the importance of integrating belowground biological processes into models of SOC turnover, to improve agroecosystem functioning and carbon management in face of intensifying anthropogenic land‐use and climate change. [ABSTRACT FROM AUTHOR]

Understanding the spatial distribution of soil organic carbon (SOC) and soil nutrients is crucial for optimizing land management in watersheds. This study explored the spatial distribution of SOC, total nitrogen (TN) and total phosphorus (TP) in topsoil (0-20 cm) at a hilly small watershed site in Northeast China, and identified the controlling factors. The Gaussian mixture model optimally described SOC and TN with the ratio of nugget to sill variance (C0/[C + C0]) indicating moderate spatial dependence for SOC (63.7%) and TN (59.3%). TP was best modelled by the spherical model and demonstrated weak spatial autocorrelation and strong human influence, with a nugget to sill variance of 0.841. Land use significantly affected SOC, TN and TP contents, with the highest values recorded in woodland, followed by farmland and shrubland. Soil properties including bulk density (BD), gravel content (GC), moisture content (MC), soil porosity (SP) and the mean weight diameter (MWD) of water-stable aggregates significantly correlated with SOC and TN content, but not with TP. Redundancy analysis revealed that soil properties (BD, GC and SP), topography (slope and aspect) and gully erosion contributed 55.7%, 24.7% and 4.3% of the spatial variation in SOC, TN and TP, respectively. Hence, these are the dominant factors shaping the spatial variation of SOC and soil nutrients at the site. These results can aid the further development of optimized land management strategies. [ABSTRACT FROM AUTHOR]

Cambodia has faced drastic agrarian changes over the last twenty years with a rapid and massive transformation of the uplands from forest into arable land. Soil quality depletion is one of the main drivers of the resulting decline in crop productivity and increasing production costs in the uplands of Battambang province. The objective of the study was to assess the early effects of conventional plough-based (20 cm) management (CT) and two conservation agriculture-based (CA) cropping systems (the use of a single--CAS vs. multiple cover crop species--CAM) on a maize monocropping system using three soil organic carbon (SOC) fractions on Mollisols in Battambang province. SOC content, permanganate oxidizable carbon (POXC) and soil CO2 basal respiration through SituResp® were recorded at a depth of 0-10 cm. Twelve sampling periods were used over the growth period of the cover crops and during the maize cycle. POXC and SituResp® were highly sensitive to management practices with, across the 12 sampling periods, higher values (p < .05) under CA than CT, with an average increase of 6% and from 20% to 23%, respectively. No difference was observed in SOC content between the practices in our sampling periods. Seasonal variations were observed in both POXC and SituResp®. POXC underwent larger fluctuations following critical weather events than SituResp®. This study showed that POXC and SituResp® were rapidly sensitive to changes in agricultural management practices. POXC and SituResp® are largely influenced by seasonality and could help clarify the impact of weather patterns on soil C dynamics. [ABSTRACT FROM AUTHOR]

Black soils store a high amount of soil organic carbon (SOC) and play a crucial role in climate change, food security, and land degradation neutrality. However, data and information regarding black soils in tropical regions, including Indonesia, are limited. This study aimed to characterize and identify the utilization of black soils in Indonesia based on legacy soil survey data. We collated 142 soil pedon samples of Mollisols from articles, technical reports, and existing datasets. The site information (site position, elevation, land use type, parent material) and selected physicochemical properties were stored in a spreadsheet, from which exploratory data analysis was conducted. The result showed that the median SOC content was 1.53%, ranging from 0.6 to 8.2 %; cation exchange capacity was 30 cmol kg-1, ranging from 9 to 95 cmol kg-1; base saturation was 87%, ranging from 11 to 100 %; and bulk density was 1.21 g cm-3, ranging from 1.13 to 1.36 g cm-3. Other soil characteristics (particle size distribution, exchangeable bases, pH, pore, and water retention) varied with horizon type and land use/land cover. The black soils have been used for paddy fields, dryland farming, and gardens with low management intensity. Main cultivated crops include rice (Oryza sativa), corn (Zea mays), cassava (Manihot esculenta), sweet potato (Ipomoea batatas), and nutmeg (Myristica fragrans), clove (Syzygium aromaticum), coconut (Cocos nucifera), and cocoa (Theobroma cocoa). Threats to black soil functions include soil erosion, carbon loss, and nutrient imbalance. Soil and water conservation measures, integrated soil nutrient management, and agroforestry are among the best land management practices for black soils.

[Objective] The effects of climate change on the stability of organic carbon were revealed from the perspective of the molecular structure of organic carbon in order to provide a theoretical basis for clarifying the impact of future climate change on organic carbon stability and soil fertility in mollisols. [Methods] A long-term field experiment dealing with the simulation of climate change through the use of open-top chambers (OTCs) at the Hailun Agroecological Experiment Station of the Chinese Academy of Sciences provided data for this study. We analyzed the organic carbon content and infrared spectral characteristics of various aggregates and density fractions in the 0—20 cm topsoil of black soil under three treatments: ① ambient temperature and CO2 concentration (aTaCO2); ② temperature elevated by 2 ℃ and ambient CO2 concentration (eTaCO2); ③ temperature elevated by 2 ℃ and CO2 enrichment to (700±25) μmol/mol (eTeCO2). [Results] Neither eTaCO2 nor eTeCO2 significantly affected organic carbon content of the bulk soil compared with aTaCO2 (p>0.05). However, eTaCO2 increased soil organic carbon (SOC) contents by 13.45% and 52.89% in the 0.25 mm size aggregate, but increased the -CH/C=C ratio of organic carbon in the 0.25—0.053 mm size aggregates (p

The study area located at Erbil province, Kurdistan, Iraq, seven pedons were elected. Twenty-one soil samples were collected in the study area. Different physiochemical and fertility indices have been used to determine the soils development, despite of generating interpolated maps for them. The results indicated that the low values of clay were found in the less pedon developed and argillic horizon existed in development pedons. Study soils were non-saline, slightly to moderately alkaline, and had relatively high bulk density values. Organic matter is concentrated at the soil surface. Considerable total carbonates are found in studied soils and have irregular distribution manner, as well as have high CEC values. Low C/N ratio due to highly decomposed organic matter. The active CaCO3/total CaCO3 increases with depth in all pedons, while, slightly fluctuated in one pedon. The ratio of total clay in BH /AH was found just in some pedons and more than (1) therefore these soils are considered development, and are more developed depending on the ratio of fine clay/total clay. Soils are classified into three groups the first was the least developed soils, the second group has the most development. Third group are intermediate in their development. Pedogenic processes included leaching, illuviation, eluviation, alkalization, humification, lessivage, desalinization, calcification, decomposition, and littering. Studied soils classified as Inceptisols and Mollisols. [ABSTRACT FROM AUTHOR]

The application of organic materials contributes to the sustainable development of agriculture. Increased manure inputs have a fundamental effect on the composition and dynamics of soil organic carbon (SOC). In this study, we conducted a 10-year field experiment in Changchun, Jilin, Northeast China, to investigate the effects of manure addition on soil organic carbon components and soil microorganisms. Specifically, we established four treatments: (i) chemical fertilizer or no addition of manure (CK), (ii) pig manure with chemical fertilizer (ZF), (iii) cow manure with chemical fertilizer (NF), and (iv) chicken manure with chemical fertilizer (JF). The results showed that the JF treatment significantly increased the soil organic carbon (SOC), dissolved organic carbon (DOC), and readily oxidized organic carbon (ROC) content by 20.36%, 105.9%, and 61.32%, respectively, relative to CK. The microbial biomass carbon (MBC) content in JF, ZF, and NF treatments were significantly higher than that of CK, which increased by 107.24%, 116.45%, and 96.71%, respectively. The particulate organic carbon (POC) content in NF and JF treatments differed significantly, increasing by 25.61% and 19.01%, respectively, relative to CK. Redundancy analysis showed that continuous manure application had a positive effect on soil microbial community diversity and abundance, which was favorable for the accumulation of soil carbon. We also found that soil fungi were more sensitive than bacteria to changes in soil carbon composition following manure application. In conclusion, adding different organic materials can better support biodiversity conservation and realize ecosystem services of surface carbon storage and soil conservation. Our results reveal the importance of microbial fixation in soil carbon dynamics according to the different distribution of active organic carbon pools, which will help enhance our understanding of the carbon cycle. [ABSTRACT FROM AUTHOR]

Soil degradation in the Mollisol region of Northeast China is ubiquitous partly due to poor soil hydraulic characteristics. Improving soil hydraulic characteristics thus delivers benefits to soil sustainability. In this study, the effects of organic amendments on soil hydraulic characteristics were explored at the laboratory scale. Soil samples were subjected to three low‐cost and eco‐friendly organic amendments, including corn straw juice (CSJ), fulvic acid (FA), and humic acid (HA). The soil infiltration capacity, soil water characteristic curve (SWCC) and soil water retention capacity were determined by using a steel‐ring method and a centrifuge method. The parameters of the SWCC were fitted by a van Genuchten (VG) model, and the specific water capacity [C(h)] was calculated. In addition, bulk density (BD), macroporosity, and soil organic matter (SOM) were measured, and the relationships between the variables and processes were evaluated. The results indicated that the soil infiltration capacity (i.e., initial infiltration rate, cumulative infiltration, and steady infiltration rate) was significantly increased in the CSJ and FA treatments (p < 0.05) but decreased in the HA treatment compared to the control (CK) treatment. All the selected organic amendments improved the soil water release and supply capacity, and the CSJ2 treatment showed the best effect. The incorporation of CSJ, FA, and HA significantly improved the soil water retention capacity by increasing the saturated soil water content, field capacity, and plant available water capacity (p < 0.05). Such changes were significantly associated with macroporosity and SOM (p < 0.05). In this sense, our results showed that the CSJ treatment with 4 L m−2 and 50% volumetric concentration could be an effective soil amendment to improve the soil hydraulic characteristics in Mollisols and deserves further research. [ABSTRACT FROM AUTHOR]

Purpose: More information is needed on the comparative evaluation of C sequestration and soil fertility conservation between straw and biochar application. Particularly, the effect of the co-application of straw and biochar on the quantity and quality of soil organic matter (SOM) remains unknown. Methods: A 3-year field experiment was conducted in a Mollisol, and included the following treatments: no application (CK), straw (CS) and biochar application (BC), and mixing straw with biochar (BS). C groups were identified by solid-state 13C NMR. Results: Applying straw and biochar significantly increased the contents of SOM (10.02–20.99%), labile and humic C, and corn yield (11.01–22.78%), compared to CK. BC had a more significant potential to increase SOM, C pool index, and corn yield than CS, while CS had the highest C lability index and C management index. BC improved the hydrophobicity and aromaticity, whereas CS increased the aliphatic and hydrophilic properties in SOM chemical composition. BS greatly reduced the ratios of alkyl C/O-alkyl C and aliphatic C/aromatic C. Conclusions: BC is more conducive to the stability and accumulation of SOM, while CS is beneficial to exerting soil fertility attributed to the improvement in the bioavailability and reactivity of SOM. BS could synergistically improve the biological activity and stability of SOM to some degree. Considering biochar production cost, we recommend introducing a small amount of biochar into straw returning practice as a booster to promote the stability and activity of SOM and consequent crop production, synergistically realizing a low C strategy and fertility conservation. [ABSTRACT FROM AUTHOR]

A model for buried site potential has been developed and presented here following extensive geoarchaeological investigations conducted along the White River valley in Indiana. Backhoe-trenching efforts identified 35 buried archaeological sites dating from the Late Archaic through postcontact periods. Buried archaeological sites were found primarily in soils classified as inceptisols, with fewer found in soils classified as mollisols and entisols. Geochronological dating and artifact analysis suggest that after 3000 BP the White River valley transitioned from lateral to vertical accretion, providing landforms suitable for precontact occupation. [ABSTRACT FROM AUTHOR]

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Mollisols (from Latin mollis, "soft") are the types of highly fertile soil with a thick layer of humus, high organic matter content, and strong nutrient capacity. The natural granary has played an indispensable role in the crucial agricultural and livestock production activities in many countries. A perfect tradeoff can be required for high crop yields with less nutrient loss in the soil under intensified farming practices. Among them, the organic matter greatly contributes to the high fertility, particularly at the medium to high latitudes in the cold and cool regions. Excessive depletion of organic matter can directly impact grain production in the sustainable development. An important approach to restoring organic carbon can be returning the organic materials to the soil via organic matter incorporation. Two common approaches are employed in conventional cultivation: straw incorporation and organic fertilizer application. However, there is an ongoing debate regarding which one is more beneficial for sequestering organic carbon. It is of significant importance to investigate the conditions under which straw incorporation or organic fertilizer application is more advantageous for carbon sequestration. Additionally, the organic matter incorporation is also dependent on various factors, such as fertilization duration and carbon input. The organic materials vary significantly in the decomposition with the increasing fertilization duration, leading to different effects on the soil organic carbon retention. Carbon input is one of the most important limiting factors in soil organic carbon sequestration and the carbonto-nitrogen ratio. Previous studies have focused mostly on controlled experiments to investigate the effects of different organic matter incorporation on soil organic carbon sequestration. Less attention was paid to the different fertilization durations and carbon inputs under organic matter incorporation. In this study, a meta-analysis approach was utilized to examine the impact of straw incorporation and organic fertilizer application on soil carbon sequestration under various fertilization durations and carbon inputs in Mollisols. A systematic search of peer-reviewed articles was conducted to apply the following criteria for reliability: 1) The experiments included both laboratory and field trials, consisting of control groups without fertilizer application, and experimental groups with either straw incorporation or organic fertilizer application; 2) The trials were performed on Mollisols to record the latitude, longitude, and climatic conditions of the experimental sites; 3) Relevant indicators of soil property with their means, standard deviations, and the number of replicates was directly extracted from the articles' text, tables, or figures. A total of 41 articles with 2012 observations were obtained after the screening process. The results indicated that the organic manure return was more effective in increasing the soil organic carbon content, compared with the straw return. There was a significant increase of 42.99% in soil organic carbon, 39.97% in total soil nitrogen, and 74.01% in total soil phosphorus in Mollisols. By contrast, the straw return resulted in a significant increase of 14.96% in soil organic carbon, 15.03% in total soil nitrogen, and 20.03% in total soil phosphorus. Moreover, the organic manure return was more effective than the straw return with the increase of treatment years, in terms of the soil organic carbon content. There were different effects of organic manure return to the field on the soil carbon sequestration under different carbon input conditions. The organic carbon sequestration of organic manure returning to the field can be significantly higher than that of straw under medium carbon input conditions. Some suggestions were proposed that the organic manure return under long-term medium carbon input was more beneficial to the increase of organic carbon sequestration. Overall, the findings can provide valuable insights for the scientific selection of organic materials in the field return in Mollisols. [ABSTRACT FROM AUTHOR]

Returning straw to the field, coupled with fertilizer application, is an effective means to improve the fertility of black soil in Northeast China. Previous studies have mainly focused on the physical and chemical properties of soil structure and fertility. However, few efforts have been made to study the impact of straw returning on the microbial community of black soil in Northeast China. Here, we studied the typical northeast black soil in Heilongjiang Province to characterize the effects of long-term chemical fertilizer application and straw returning on its bacterial community structure. High-throughput sequencing was conducted to characterize the bacterial community of northeast black soil under different agricultural fertilization treatments, and the main factors affecting the bacterial community of northeast black soil were revealed through bioinformatic analyses. The results of high-throughput sequencing analyses demonstrated that the main bacterial phyla in the black soil in Northeast China were Actinomycetes, Proteobacteria, Acidobacteria, Chloroflexus, and Bacteroidetes. Long-term application of chemical fertilizers significantly increased the fertility and crop yield of black soil in Northeast China but led to significant changes in bacterial community structure and a significant decrease in diversity. Although straw returning improved soil fertility, it did not alleviate the adverse effects of the long-term application of chemical fertilizers on soil bacterial communities. Furthermore, our results demonstrated that changes in soil pH were the main factor leading to variations in soil bacterial communities. Returning straw to the field based on fertilizer application can improve black soil fertility in Northeast China but fails to alleviate the adverse effects of fertilizer-induced soil acidification on the composition and diversity of soil bacterial communities. This suggests that returning straw to the field may not have a significant beneficial impact on the microbial ecology of the black soil of Northeast China. Therefore, further research is needed to establish new straw return strategies to maximize agricultural yields while minimizing ecological impacts. [ABSTRACT FROM AUTHOR]

Soil surface roughness is an important factor affecting hydrology and soil erosion processes, and its development is influenced by precipitation, topography, and tillage practices. In this study, the typical mollisol area in northeast China was taken as the research object. Then, the variation in soil surface roughness with time was analyzed under different terrains, as well as different tillage methods, and the effect of the precipitation condition on roughness was also discussed in detail. Through the design of field experiments, the height information of the soil surface was measured using a probe-type roughness plate. Two parameters, the root-mean-square height (RMSH) and the correlation length (CL), were selected to quantitatively characterize the soil surface roughness. In addition, the dynamic change patterns of surface roughness resulting from five tillage methods, including rotary tillage, combined tillage, no tillage, conventional tillage, and reduced tillage, under both sloping and flat land, were compared and analyzed throughout the soybean growing season, under the influence of rainfall. The results show that with the increase in rainfall, the RMSH of the soil surface, under different tillage methods, showed a trend of first decreasing, and then increasing. The results also showed that the RMSHs under rotary tillage, combined tillage, conventional tillage, and reduced tillage in flat land were greater than those in sloping land, and that the CLs of the soil surface under different tillage methods in flat land were smaller than those in sloping land. In addition, the degree of variation in the soil surface roughness was greater in flat land than that in sloping land under all tillage practices, indicating that this study is of great practical importance in the rational selection of tillage methods, and in the scientific quantification of soil erosion, which also show obvious significance for soil and water conservation. [ABSTRACT FROM AUTHOR]

Biochar application affects the soil organic carbon (SOC) content and distribution, which is relevant to facility agriculture and soil aggregates. However, how the fertilization management of facility agriculture affects the SOC content and aggregate stability at different soil depths in Mollisols is unclear. Intended to provide a basis for developing a reasonable fertilizer amount when adding biochar, the facility vegetable eggplant in Northeast China was used to explore the effects of biochar addition on the distribution and SOC content of whole soils and the organic carbon (OC) content of aggregates of each size in the profile (0–100 cm) of Mollisols. Three treatments were set up: WF (conventional application amounts of water and fertilizer), WFB (conventional application amounts of water and fertilizer and added biochar), and 80%W80%FB (20% water reduction and 20% fertilizer reduction and added biochar). The results demonstrated that the 80%W80%FB treatment significantly increased the SOC content by 56.1% and 34.0% in whole soils at a 0–20 cm soil depth compared to WF and WFB treatments, respectively. Simultaneously, compared with WF and WFB treatments, the significant increase in the OC content of 1–0.25 mm sized aggregates of 81.4–130.2% and 4.3–10.1% and the enhanced proportion of >2 mm sized aggregates of 0.22–16.15- and 0.33–0.83-fold both improved aggregate stability in the 0–20 cm soil layer under the 80%W80%FB treatment, which was proven to result in 32.6% and 30.6% increments in the weight diameter (MWD) value. Therefore, biochar addition with water and fertilizer reductions increases surface soil aggregate stability for greenhouse eggplants in Mollisols. [ABSTRACT FROM AUTHOR]