Abstract:【Objective】Biochar has been shown to improve soil physicochemical properties and enhance crop yields. The results of previous studies on soil temperature were inconsistent, the changes of crop emergence rate under the change of biochar application rate were not analyzed in detail, and the relationship between crop emergence rate and soil physicochemical properties such as soil bulk density, temperature and organic carbon was neglected. Thus, it is important to estimate the most appropriate application rate of biochar for improving soil physicochemical properties and crop yield to provide a basis for field management. 【Method】In this paper, a salinization soil in south Xinjiang was researched and field cotton and sugarbeet growth experiments were carried out in plots under different biochar treatments (0, 10, 50, and 100 t·hm-2) and combined with drip irrigation mode under plastic mulching. The improvement extent and influences of biochar application on soil physicochemical properties and crop germination rates were detailed investigated at the biochar application rates. The relationship between germination rates and soil physicochemical properties was further investigated and compared. 【Result】The results showed that the fluctuations of daily air temperature and solar radiation directly affected the fluctuations of soil temperatures in various depths with biochar applications. The increase of biochar application amounts significantly reduced the soil bulk density at the 0-30 cm depths, in which cotton and sugar beet decreased by 0-0.32 and 0.04-0.25 g·cm-3, respectively. The application of biochar at 100 t·hm-2 significantly increased the soil temperature at the 5 cm depth at different growth stages of cotton and sugar beet, but the application of biochar at 10 and 50 t·hm-2 only significantly increased the soil temperatures of the 5 cm depth at seedling and bolling stages of cotton. During the two experimental years of 2018 and 2019, biochar application have significantly increased the soil organic carbon content of cotton and sugar beet at the seedling and harvesting stages by 0.98-13.2 and 0.66-12.1 g·kg-1 if the differences of planting year and growth periods were not considered, respectively. Also, the increase rate was 1.20-7.43 at the cotton seedling stage and 0.66 to 13.2 g·kg-1 at the harvest stage if the differences of planting year and crops were not considered, respectively, and was proportional to the application rates at the seedling stage. The emergence rate of cotton and sugar beet both increased with the increased soil bulk density, and increased first and then decreased with the increased soil temperature. The optimum temperature range for cotton and sugar beet germination was 22 to 26 ℃. The germination rate increased first and then decreased with the increased soil organic carbon contents, indicating that the excess increase of soil organic carbon content caused by high biochar application rates inhibited crop germination. When the application amount of biochar was 10 t·hm-2, the seedling emergence rates of cotton and sugar beet were greater than 0.7, which was higher than that of the other three biochar application rates. However, when the biochar application rate was greater than 10 t·hm-2, the emergence rates of cotton and sugar beet were lower than that of the treatment without biochar application. 【Conclusion】Therefore, a biochar application amount of 10 t·hm-2 is recommended as the optimal amount for cotton and sugar beet field management considering its comprehensive effects on improving soil properties and crop germination rate.

Abstract:【Objective】After receiving precipitation, exposed rock surface in a rocky desertification area exposed to bedrock is easy to form rock surface flow, which carries organic and inorganic substances on the rock surface to the surrounding soil. This has a significant impact on the change of soil nutrients at the rock-soil interface. 【Method】 This study was designed to investigate the effect of rock surface flow on the leaching and input of nitrogen and phosphorus in the soil at the rock-soil interface. Three plots: fallow land (one-year rock surface flow), abandoned irrigated grassland (five-year rock surface flow), and sloping farmland (no/little rock surface flow) with obvious bedrock exposure, were chosen. We chose three special shapes of the rock surface, namely convex, straight, and concave, at different horizontal distances from the rock surface and soil layer to study the variation characteristics of total nitrogen and total phosphorus in the soil at rock-soil interfaces and non-rock-soil interfaces. 【Result】 The results indicated that rock surface flow contributed either to the input or leaching of nitrogen and phosphorus in the 0-10 cm surface of the rock-soil interface soil. However, it had a minimal effect on nitrogen and phosphorus in the 10-20 cm deep rock-soil interface soil. The intensity of the leaching and input of nitrogen and phosphorus in the surface soil of the rock-soil interface formed by different rock surface shapes followed concave > straight > convex. In the 1-year fallow land, under the action of rock surface flow, the influence of rock surface flow formed by concave rock surface on soil nitrogen at the rock-soil interface was mainly manifested as leaching, while flat and convex rock surfaces exhibited input effects. Also, the effects of rock surface flow with different shapes on soil phosphorus at the rock-soil interface showed leaching. For the 5-year rock surface flow, the result depicted mainly an input phenomenon. 【Conclusion】These results can provide a scientific basis for further understanding the influence of exposed rock on soil characteristics of the karst ecosystem.

Abstract:【Objective】 As a by-product of fruit tree shaping and pruning, pear branches are important biomass resources. The use of crushed branches for soil mulch under trees is one of the effective ways to utilize waste resources, which is conducive to increasing soil organic matter and improving soil fertility in pear orchards. 【Method】 In order to assess the effects of short-term pear branch mulching on soil properties and structure of microbial community, soil samples were collected from five pear orchards in different latitudes (Bijie City of Guizhou Province, Changli City of Hebei Province, Harbin City of Heilongjiang Province, Zhijiang City of Hubei Province and Xuchang City of Henan Province) after 1-2 years of mulching. Soil basic physiochemical characteristics of the soil and the bacterial, fungal and protist communities were detected. 【Result】 Results showed that the soil organic matter and available phosphorus content were significantly increased in pear branches mulching treatment in general, and the soil bacterial, fungal and protists community structure also changed significantly. Specifically, the mulching of pear branches significantly enriched the relative abundance of taxa such as Proteobacteria and Acidobacteria in bacteria, Basidiomycota in fungi, and Rhizaria and Alveolata in protists. The model prediction accuracy was as high as 94.44%, and the key species were mainly bacteria, including Acidibacter, Xanthobacteraceae, Nitrosomonadacee and other microorganisms related to the degradation of organic residues. Soil-available phosphorus content was found to be the main driver of variations in soil microbial community structure. 【Conclusion】 The study preliminarily assessed the effect of pear tree branch mulching on soil nutrients and microbiome and excavated potential key microorganisms. The findings can serve as a reference for managing the health and fertility of orchard soils.

Abstract:【Objective】 Overuse of Nitrogen (N) fertilizer results in a low N use efficiency and intensive soil nitrate accumulation in arid farmland critical zone of China, which threatens eco-environmental safety. Elucidating characteristics of soil nitrate accumulation and its influencing factors can provide scientific reference for integrated management of water and fertilizers. 【Method】 The Aksu region, a typical arid region, was selected as the study area. Regolith core samples were collected from three drilling sites including XJ1 (40°36′48.7″N, 80°48′14.2″E), XJ2 (41°16′16.2″N, 80°19′9.1″E), and XJ3 (41°20′37.6″N, 80°17′11.0″E) along a topographic sequence from south to north, with depths of 7.75 m, 10.52 m, and 9.91 m, respectively. The drilling sites were located in a 60-year-old cotton field, a 32-year-old apple orchard, and a 15-year-old apple orchard, respectively. Key soil properties were measured and their relationship to soil nitrate concentration accumulation was analyzed using linear and nonlinear correlations. 【Result】 Significant accumulation of soil nitrate concentration was found under cotton fields with a low altitude and apple orchards with different planting years and a high altitude. Soil nitrate concentrations at depth can reach 44 mg·kg-1 and soil nitrate accumulation occurs deeper than 10 m. Key soil properties including soil water content and soil particle (gravel, sand, silt and clay fractions) sizes could explain about 50% variations of soil nitrate concentrations with depth. Among key soil properties, soil water content and soil particle sizes were found to be the main factors determining soil nitrate accumulation at depth. Soil nitrate concentration was generally accumulated under conditions with a high soil water content and a fine soil particle. Notable denitrification below the groundwater table at a depth of 4 m occurred under cotton fields and led to a low nitrate concentration below 1 mg·kg-1. Notable denitrification was not observed below 10 m under apple orchards with a deep groundwater table and soil nitrate concentration was intensively accumulated beyond the root zone deeper than 5 m. 【Conclusion】 Soil water content was found to be the below-ground direct factor determining soil nitrate accumulation at depth. Soil particle sizes were found to be the fundamental factor determining soil nitrate accumulation via controlling soil water content variations.

Abstract:【Objective】Microbial biomass carbon(C)metabolism is vital in the formation and stabilization of organic C in soil, constituting a critical parameter in the models of terrestrial ecosystems. Yet, the variances in the microbial C metabolism indices in soils developed from different lithological origins remain undefined. 【Method】To address the scientific gap in the characteristics and driving factors of microbial biomass C metabolism in soils developed from different rocks, we sampled forest soils developed from limestone and clastic rocks as research objects. Using 18O-H2O labeling, we measured the microbial growth rate, respiration rate, carbon use efficiency (CUE), and turnover time. Combined with soil physicochemical properties, soil organic matter mineral protection characteristics, soil enzyme activity, and microbial biomass and community composition, we clarified the influencing mechanism of lithology on forest soil microbial biomass C metabolism. 【Result】The findings indicate that the pH and the 0.002～0.05 mm particle content in limestone-derived soils surpass those in clastic rock-derived soils, whereas soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon(DOC), C: P and N: P ratios were lower in limestone-derived soils (P<0.05). The limestone-developed soils had a higher content of exchangeable calcium and magnesium (Ca/Mg) and free iron and aluminum ((Fe+Al)d) than the clastic rock-developed soils, but the content of amorphous iron and aluminum((Fe+Al)o)was lower than that in the clastic rock-developed soils. Furthermore, the enzyme activity related to C, N, and P cycling in limestone-developed soils was significantly lower than that in clastic rock-developed soils (P< 0.05). In addition, the microbial biomass phosphorus (MBP) in limestone-developed soils was higher than that in clastic rock-developed soils, but microbial biomass carbon(MBC), fungi: bacteria ratio (F: B), and Gram-positive to Gram-negative bacteria ratio (G+: G-)were significantly lower than those in clastic rock-developed soils (P<0.05). The microbial growth rate and turnover rate in limestone-derived soils were significantly higher than in clastic rock-derived soils (P<0.05), but there was no significant difference in the microbial respiration rate and CUE between the two types of soils. Correlation analysis revealed that the soil microbial growth rate and turnover rate were significantly positively correlated with soil pH, (Ca+Mg): (Fe+Al)o, (Ca+Mg): SOC, (Fe+Al)d: SOC, and Gram-negative bacteria(P<0.05), and significantly negatively related to DOC, organic C bound to iron and aluminum, enzyme activity, MBC: MBN, F: B, and G+: G- ratio(P<0.05). The soil CUE was significantly negatively correlated with MBC and MBC: MBN (P<0.05) while microbial respiration rate was only significantly negatively correlated with phenol oxidase activity (P<0.05). In summary, the higher pH, weaker amorphous iron-aluminum mineral protection, lower microbial resource limitation, and larger bacterial biomass (especially Gram-negative bacteria) in limestone-derived soils may lead to greater microbial motility in these soils and stronger substrate availability, resulting in larger microbial growth and turnover rates. However, there was no difference in the soil microbial biomass CUE between the two rock types, which may be due to the similar soil C: N ratio. 【Conclusion】The microbial biomass C metabolism of forest soils developed from two types of rocks is controlled by biological and non-biological factors. These research results provide a new mechanism for explaining the differences in organic carbon pools in forest soils developed from different rocks.

Abstract:The evaluation and quantification of aquifer structure in the Earth Critical Zones (CZ) are of great significance to the hydrological cycle and water resources management. 【Objective】 However, the characterization of complex CZ structures at spatial scales remains a huge challenge. In this paper, research was conducted on a small karst dolomite watershed (1.20 km2) in northwest Guangxi province, China, to quantify the distribution characteristics of aquifer media in CZ and analyze its influencing factors. 【Method】 a total of 21 electrical resistivity tomography survey lines with a total length of 12, 605 meters was set up and combined with hydrological drilling at the watershed scale. 【Result】 The results show that tectonic movement and dynamic metamorphism resulted in the development of multiple fault zones in the small watershed. This provided the material and dynamic basis for the spatial distribution of karst water-bearing media (including soil, surface karst zone, and surface karst spring). The fault zone was concentrated in the depression, which has a good hydrodynamic and dissolution environment. As a result, the soil and epikarst thickness in the depression was higher than that in hillslope, and there was a significant (P < 0.05) negative linear relationship with elevation. Besides, the spatial coupling degree of soil and epikarst thickness was high, showing a significant positive linear relationship (R2 = 0.63, P < 0.01) between soil and epikarst thickness. It was related to slope erosion and confluence, and special water-CO2-rock interaction in the soil-epikarst zone system. Karst aquifer flows out of the depression or down hillslope, and its hydrological characteristics were related to the distribution and water storage features of the soil-epikarst system. 【Conclusion】 This study provides data and technical support for the characterization of the karst aquifer at the catchment scale and construction of the land surface model in future studies.

Abstract:To explore the effect of different carrier materials on microbial degradation of phenanthrene, the biodegradation of phenanthrene was investigated in the liquid phase by gram-negative bacteria Sphingobium sp. PHE3 immobilized on montmorillonite, goethite and maize straw-derived biochar. The results of scanning electron microscopy showed that there was the largest number of bacteria adhered to the surface of the biochar with the best morphology. The addition of montmorillonite and biochar significantly (P<0.05) improved the degradation rate of phenanthrene by microorganisms, as well as the increase of polysaccharide and protein production in bacterial extracellular polymeric substance (EPS). Nevertheless, there was no obvious effect on phenanthrene biodegradation and EPS production with the addition of goethite. Furthermore, quorum sensing might play a role in biofilm formation. The signal molecules C8-HSL and C12-HSL secreted by PHE3 might mediate the production of EPS and phenanthrene biodegradation to some extent.

Abstract:【Objective】Maintaining moderate soil phosphorus (P) supply intensity and determining the P application rate based on the P requirement of the crop target yield, and combining with acid, slow-release water-soluble P fertilizers and applied in the early stages of crop growth is a novel P management approach in cotton. Here we test the feasibility and effectiveness of this method and provide a basis for reducing the P fertilizer application amount and increasing its use efficiency. 【Method】A two-year field experiment was employed using cotton (Gossypium hirsutum) in the moderate Olsen-P soil (23.6 mg·kg-1) in Shihezi, Xinjiang. Based on the P requirement of the target lint yield of 2.7 t·hm-2, 52.4 kg·hm-2was selected as the P application rate. Four treatments were set-up with three types P fertilizers: (1) no P fertilizer (CK); (2) monoammonium phosphate (MAP); (3) urea phosphate (UP); and (4) ammonium polyphosphate (APP). It was analyzed that the lint yield, P uptake and above-ground biomass of cotton in different treatments. The partial productivity of P fertilizer (PFP), agronomic efficiency (AEP), P utilization efficiency (PUE) and P recovery index (the ratio of shoot P uptake to the amount of P fertilizer application, PRI) were calculated. Through stratified sampling, soil Olsen-P and P fractions in different soil layers were tested. Those allowed us to clarify the relationships between the P spatial availability and cotton growth requirements with different P fertilizers. 【Result】The significant results were: (1) The average lint yield of P applied treatments in two years was 2.73 t·hm-2, which was classified as the high yield level in northern Xinjiang. Compared with the CK treatment, the lint yield of MAP, UP, and APP treatments were increased by 21%, 25%, and 11%, respectively. (2) The P surplus was 2.2-4.8 kg·hm-2 and the P use efficiency was 24% across P applied treatments. The P recovery index of MAP, UP, and APP treatments was 91.7%, 95.6%, and 94.8%, respectively. (3) P fertilizer applied by drip irrigation in the cotton bud and boll stages can move to the 10-20 cm soil layer, which may maintain the soil P supply intensity during the cotton-growing period. Compared with the CK treatment, the mean Olsen-P in P applied treatments were increased by 94%～302%, 104%～144%, and 42%～67% in the 0～5 cm, 5～10 cm, and 10～20 cm soil layers, respectively. 【Conclusion】In summary, our results indicate that maintaining soil available P near the agronomic thresholds and determining the P application rate according to the P requirement of the target yield, and combining with acid, slow-release P fertilizer and applied in the cotton bud and boll stages can improve lint yield and P use efficacy under balanced P input-output conditions. Furthermore, the P recovery index based on the balanced P input-output can better reflect the real P use efficiency.

Abstract:[Objective] Periphyton is ubiquitously distributed in paddy fields, directly affecting nutrient cycles and their bio-availabilities. However, no study regarding effects of periphyton on rice growth has been reported.[Method] In this study, model paddy ecosystems with three types of soils were simulated under controlled conditions to investigate the effects of periphyton on rice seed germination and seedling growth.[Result] Results show that periphyton of three types of soils was mainly composed of Proteobacteria, Cyanobacteria and Bacteroidetes, while the diversity of periphyton of the three soils was significantly different, and that grown in soil from Yanbian (YBP) had the highest OTU number and Chao1 index. Furthermore, there were significant differences in carbon metabolic activity among the three periphyton (P<0.05). The Pearson correlations indicated that periphyton composition and diversity was positively correlated with soil pH, TP, TOC and Mn contents (P<0.05). The carbon metabolism activity of YBP was the highest during the whole growth period, while that of soil from Yingtan (YTP) was the lowest. The presence of periphyton greatly increased the germination index of rice seed (by maximally 18%), and α-amylase activity in the presence of periphyton was increased significantly (P<0.05). Besides, the periphyton covering on paddy soil surface from Yanbian (YBP) significantly promote shoot length and its biomass (P<0.05). The Pearson correlations indicated that seed germination and survival rate was positively correlated with periphyton chemical properties.[Conclusion] To summarize, this study indicates that the presence of periohyton biofilm during seed germination period was propitious for rice growth. Results of this study provided an insight into understanding the periphyton-plant relationships with different soil-types and also new approaches to controlling plant phenology by regulating the growth of periphyton.

Abstract:[Objective] To have the soils in Xinjiang (short for the Xinjiang Uygur Autonomous Region of China) reasonably, clearly and scientifically classified will lay down a good foundation for development, utilization, mapping and management of the soil resources in the arid regions of China. In the process of the research, contradictions are found in the Chinese Soil Taxonomy (3rd ed.). The definition of the Aridic epipedon in the CST states that from the soil surface, there is no salt or sodic vesicular layer or a mixture layer of soil and salt underlying it, however, this definition does not specify depth of the specific underlay. In addition, according to this definition, the surface or the underlying soil layer without saltilizing is excluded. At the same time, the Sali-Orthic Aridosols is defined as Salic horizon, Hypersalic horizon or Salipan with upper boundary within 100 cm of the mineral soil surface, which is obviously contradictory to the previous one, thus leading to classifying some of the soils containing Salic horizon into Aridisols. Moreover, under Calci-Orthic Aridosols, no Subgroup is set specifically for salt accumulation. Hence, even though some soil profiles do have Aridic epipedon, Calcic horizon and Salic horizon, their characteristics of salt accumulation are not reflected in their names as a type of soil. Therefore, it is necessary to study these contradictions for solution.[Method] In this paper, 17 typical Aridisols and Halosols soil profiles of Xinjiang were selected as objects for the study. Based on analyses of their morphological properties and physicochemical properties, the 17 soil profiles were sorted in attribution in CST. And as to the above contradictions, the following suggestions were put forth. The definition relevant to Aridic epipedon should be modified to:Down from the soil surface, no salt vesicular layer or sodic vesicular layer or underlying soil and salt mixture layer (not in compliance with the salt horizon condition). The definition of Sali-Orthic Aridosols should be modified to:Other Orthic Aridosols that contain a Salic horizon, a Hypersalic horizon or a Salipan with its upper boundary varying in the range of 30 cm to 100 cm in depth. And in addition, a Subgroup named Salic Calci-Orthic Aridosols should be augmented. Then classification of the 17 soil profiles was performed according to the proposed revisions, and Profiles No.1~No.11 were used as references between WRB, ST and CST.[Result] Classification in light of CST shows that of the 17 soil profiles, 15 profiles are of Aridisols and 2 profiles of Halosols. However, nine of the soil profiles (No.1, 4, 5, 9, 12, 14, 15, 16 and 17) are found to have a Salic horizon within 30 cm in depth, and hence they do not comply with the proposed definition of Aridic epipedon in CST, and should be shifted from Aridisols to Halosols in classification. Profile No.2 has an Aridic epipedon and a Calcic horizon, and a Salic horizon, too, down below 30cm in depth, but was named as Salic Calci-Orthic Aridosols. References between WRB, ST and CST show that Profiles No.1~No.11 are all in the order of Aridisols in light of ST and 10 in the order of Solonchaks and one in the order of Solonetz in light of WRB.[Conclusion] The contradictions in CST has expanded the area of Aridisols and reduced that of Halosols, which is not conducive to the amelioration and exploitation of Halosols. In this paper, the suggestions are put forward for revision of certain definitions to settle the contradictions in CST, such definitions of Aridic epipedon and Sali-Orthic Aridosols, and for augmentation of a Subgroup. Salic Calci-Orthic Aridosols. According to the proposed revisions, among the 17 soil profiles, the number of Aridisols reduced from 15 to 6, and the number of Halosols increased from 2 to 11, and one soil profile was renamed as Salic Calci-Orthic Aridosols, a newly augmented suborder as proposed. In this paper, only the typical Aridisols and Halosols in Xinjiang are taken as examples for the preliminary study. The next step is to expand the study area to have Aridisols and Halosols in other arid areas covered, for comparative analysis so as further perfect the Chinese Soil Taxonomy.