Effects of Microbial Fertilizers on Soil Improvement and Wheat Growth Characteristics in Saline-alkali Land

[Objectives]This study was conducted to further enrich the research on saline-alkali land improvement,and explore the effects of biological bacterial fertilizers containing Bacillus subtilis and Bacillus velezensis HM-3 in saline-alkali land improvement and crop growth promotion.[Methods]Wheat was planted in saline-alkali land in Huanghua City,Hebei Province,and a mixed application experiment was carried out using biological agents from Hemiao Biotechnology Co.,Ltd.[Results]Compared with the field of control check(CK),water-soluble salts and pH value in the experimental fields decreased,and living bacteria count in the soil increased.Meanwhile,the economic characters of wheat in the experimental fields showed excellent performance,with yields increasing by 39.09%and 27.49%compared with the CK.It could be seen that the application of biological bacterial fertilizers achieved obvious effects of improving saline-alkali soil and increasing wheat yield.[Conclusions]In this study,the effects of biological bacterial fertilizers on saline-alkali land and wheat growth characters were clarified,providing some technical support and theoretical guidance for wheat planting in Huanghua saline-alkali land.

Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China

Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0–200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops.

Effects of Biochar and Wood Vinegar on Labile Phosphorus Pool in Soda Saline-Alkaline Soil

A pot experiment was conducted to research the effect of biochar and wood vinegar on labile phosphorus fractions in saline-alkali soil.There were eight treatments,including CK(0 kg•hm-2 biochar+0 kg•hm-2 wood vinegar),C1(0.6 t•hm-2 biochar),C2(0.6 t•hm-2 wood vinegar),C3(1.2 t•hm-2 wood vinegar),C4(1.8 t•hm-2 wood vinegar),C5(0.6 t•hm-2 biochar+0.6 t•hm-2 wood vinegar),C6(0.6 t•hm-2 biochar+1.2 t•hm-2 wood vinegar),and C7(0.6 t•hm-2 biochar+1.8 t•hm-2 wood vinegar).The results showed that biochar without wood vinegar and the co-application of biochar and wood vinegar significantly increased soil total phosphorus content.Meanwhile,compared with CK,all of treatments increased resin phosphorus and sodium bicarbonate-extracted inorganic phosphorus(NaHCO3-Pi)contents in saline-alkali soil.Especially,the contents of resin phosphorus and NaHCO3-Pi under C5,C6,and C7 treatments were higher than those of C2,C3,and C4 treatments,respectively,indicating that the increases of labile phosphorus contents under the co-application of biochar and wood vinegar were better than those of the alone application of biochar and wood vinegar.Each treatment increased the proportion of labile phosphorus pool in saline-alkali soil and the proportion of labile phosphorus pool increased with the increase of the amount of wood vinegar.In addition,the application of biochar and wood vinegar increased the 100-grain weight of rice,and C6 treatment had the best effect,increasing the 100-grain weight by 134.35%.Therefore,the application of biochar and wood vinegar in saline-alkali soil could improve the soil phosphorus availability,increase the weight of rice grains,thereby realizing the resource utilization of agricultural waste and the sustainable development of agriculture.

Design and test of a dual-axis layered rotary tillage stubble exterminator in saline-alkali land based on discrete elements

Considering the problems of poor straw mulching performance,low soil crushing rate and poor straw mulching performance of the traditional rotary tiller on saline-alkali soils,a two-axis layered rotary stubble cutter for saline-alkali soils with front-axis positive rotation of the front axle and rear-axis counter-rotation of the rear axle was developed,focusing on the kinetic properties of the straw and soil under positive and counter-rotation.In addition,the most important structural parameters and the arrangement of the front-axis stubble cutting knife and the rear-axis return knife were analyzed and determined.Hertz-Mindlin with bonding was used to create a discrete element model of the agglomerate of implement,straw and soil.The forward speed,horizontal distance and vertical distance were used as test factors,and the straw return rate and soil fragmentation rate were used as test indexes to analyze the straw-soil transport law under different operating parameters from a microscopic point of view,and then Design-Expert was used to conduct the test 1.07 km/h,horizontal distance of 569.55 mm,vertical distance of 176.59 mm.To validate the performance of the two-axis,layered rotary tiller,a field trial was conducted and the results show that the straw return ratio was(91.59±0.41)%,soil fragmentation ratio was(91.90±0.29)%and tillage depth stability was(91.52±0.46)%,which met the requirements for peanut seedbed preparation on saline-alkali land.

Effects of Forest Types on Soil Available Nutrients and Carbon Contents in Coastal Areas,China

Clarifying the soil nutrient dynamics caused by forest type variations in the coastal region helps scientifically to apply fertilizer to forest plantations and enhance the carbon(C)sink capacity.Pure forests of Ligustrum and Metasequoia,as well as their mixed forests,in a coastal region of China were investigated by collecting 0-20 and 20-40 cm soil samples and analyzing their differences in bulk density,water content,pH,soil organic matter(SOM),ammonium(NH_(4)^(+)-N),nitrate(NO_(3)^(-)-N)and total nitrogen(TN),available phosphorus(AP)and potassium(AK),microbial biomass C(MBC)and N(MBN),and enzyme activity.The results demonstrated that different forest types had no significant(p≥0.05)effect on 0-20 cm soil bulk density,water content,pH,NH_(4)^(+)-N,and SOM.However,the surface soil NO_(3)^(-)-N,TN,AP,and AK contents as well as enzyme activity changed significantly(p<0.05),in which the soil AK content of the ligustrum×metasequoia mixed forest was 47.5%and 65.5%higher than that of the ligustrum and metasequoia pure forest,respectively.The mixed forest soil had the highest MBN content,which was significantly(p<0.05)25.1%higher than that in the pure metasequoia forest.Meanwhile,soil phosphatase activities in ligustrum and metasequoia pure forests were significantly(p<0.05)lower than those in the mixed forests by 17.4%and 43.1%,respectively.However,soil NO_(3)^(-)-N and AP contents in the metasequoia pure forest were significantly(p<0.05)higher than those in the ligustrum pure forest and mixed forests.Soil MBC content and reductase NO_(3)^(-)-N activity were significantly(p<0.05)higher in ligustrum pure forest than in metasequoia pure forest and mixed forests.In addition,the results of two-way ANOVA showed that there were no significant(p≥0.05)differences in nutrient contents(e.g.,NH_(4)^(+)-N,AP,AK,and SOM)in different soil layers(0-20 and 20-40 cm)within the same forest type,except for NO_(3)^(-)-N.However,forest types had a significant(p<0.05)impact on NO_(3)^(-)-N and AP contents in 20-40 cm soil layer.Combining the two factors of forest stand and soil layer,there was a significant(p<0.05)interaction effect for their soil NH_(4)^(+)-N,NO_(3)^(-)-N,AP,and AK contents.In conclusion,significant(p<0.05)differences were observed in nutrient contents in 0-20 cm soil layer from different forest types,with soil fertility indices inmixed forests generally higher than in pure forests.Therefore,establishing mixed forests in coastal saline region is recommended to retain soil fertility and to enhance the C sink capacity of forestry.

Effect of Mirabilis jalapa (Linn.) Growth on Microbial Community in Bioremediation of Petroleum-contaminated Saline-alkali Soil

Microbial biomass and species in the rhizosphere soil of Mirabilis jalapa（Linn.）（the saline-alkali soil contaminated by total petroleum hydrocarbon（TPH））were studied with the technology of phospholipid fatty acids（PLFAs） analysis,to explore the effects of Mirabilis jalapa（Linn.） growth on the structure characteristics of microbial communities and degradation of TPH in the petroleum-contaminated salinealkali soil.The result showed that compared with the CK soil without Mirabilis jalapa（Linn.）,the kind change rates of PLFAs were 71.4%,69.2% and 33.3% in spring,summer and autumn,respectively,and the degradation of TPH increased by 47.6%,28.3%,and 18.9% in the rhizosphere soil in spring,summer and autumn,respectively.Correlation analysis was used to determine the correlation between the degradation of TPH and the soil microbial communities：77.8% of the microbial PLFAs showed positive correlation（the correlation coefficient r﹥0） with the degradation of TPH,and 55.6% of the PLFAs had high positive correlation with the degradation of TPH with a correlation coefficient r ≥0.8.In addition,the relative contents of SAT and MONO had high correlation with the degradation of TPH in the CK soil,and the correlation coefficients were 0.92 and 0.60,respectively;but in the rhizosphere soil,42.1% of the PLFAs had positive correlation with it,and only21.1% had high positive correlation with the degradation of TPH,the relative contents of TBSAT,MONO and CYCLO had moderate or low positive correlation with the degradation of TPH,and the correlation coefficients were 0.56,0.50 and 0.07 respectively.It was shown that the growth of mirabilis jalapa（Linn.） highly affected the microbial community structure and TPH degradation speed in the rhizosphere soil,providing a theoretical basis for the research on phytoremediation of petroleumcontaminated saline-alkali soil.

Spatio-Temporal Changes of Soil Salinity in Arid Areas of South Xinjiang Using Electromagnetic Induction

The aim of this paper was to research the spatio-temporal changes in total soluble salt content （TS） in a typical arid region of South Xinjiang, China, where the climate is arid and soil salinization happens easily. The total soluble salt content was interpreted by measurements made in the horizontal mode with EM38 and EM31. The electromagnetic induction （EM） surveys were made three times with the apparent soil electrical conductivity （ECa） measurements taken at 3 873 locations in Nov. 2008, 4 807 locations in Apr. 2009 and 6 324 locations in Nov. 2009, respectively. For interpreting the ECa measurements into total soluble salt content, calibtion sites were needed for EM survey of each time, e.g., 66 sites were selected in Nov. 2008 to measure ECa, and soils-core samples were taken by different depth layers of 0-10, 10-20 and 20-40 cm at the same time. On every time duplicate samples were taken at five sites to allevaite the local-scale variability, and soil temperatures in different layers through the profiles were also measured. Factors including TS, pH, water content, bulk density were analyzed by lab experiments. ECa calibration equations were obtained by linear regression analysis, which indicated that soil salinity was one primary concern to ECa with a determination coefficient of 0.792 in 0-10 cm layer, 0.711 in 10-20 cm layer and 0.544 in 20-40 cm layer, respectively. The maps of spatial distribution were predicted by Kriging interpolation, which showed that the high soil salinity was located near the drainage canal, which validated the trend effect caused by the irrigation canal and the drainage canal. And by comparing the soil salinity in different layers, the soluble salt accumulated to the top soil surface only in the area where the soil salinization was serious, and in the other areas, the soil salinity trended to increase from the top soil surface to 40 cm depth. Temporal changes showed that the soil salinity in November was higher than that in April, and the soil salinization trended to aggravate, especially in the top soil layer of 0-10 cm.

Present situation and tendency of saline-alkali soil in west Jilin Province

Taking west Jilin Province as an example, this paper put forward the assessment index of salinization, and based on it, the authors present the distribution characteristics of saline-alkali soil in the 1980s and the 1990s in west Jilin and analyze its physical and chemical properties in detail. The developing tendency of salinization was also inferred by comparing the saline-alkali soil of the 1980s with that of the 1990s. Finally, the natural and human factors leading to salinization are analyzed.

SUSTAINABLE AGRICULTURE DEVELOPMENT IN SALINE-ALKALI SOIL AREA OF SONGNEN PLAIN,NORTHEAST CHINA

There is great potential for agriculture in saline-alkali soil area in Songnen Plain, Northeast China. But the sustainable crop production in this area has been restricted by a few of main factors, such as less precipitation, h igher evaporation and frequent drought, high salinity and alkalinity, high excha ngeable sodium content and poor infiltration of the soil, and insufficiency and low availability in nutrition. It is also considered that there are a few of fav orable conditions for agricultural development in this region, such as sufficien t light and heat resources, rich ground water resources, plenty of manure produc ed by livestock, and so on. At the same time, scientific management and measurem ents have been employed; rational irrigation and drainage system has been establ ished; reclamation, amendment and fertilization of soil, and suitable strategies of cropping practices have been made for the sustainable development of agricul ture. Great progress has been made during 1996-2000.

Microbial diversity in the saline-alkali soil of a coastal Tamarix chinensis woodland at Bohai Bay, China

Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of y-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.

Soil Carbon, Nitrogen and Phosphorus Concentrations and Stoichiometries Across a Chronosequence of Restored Inland Soda Saline-Alkali Wetlands, Western Songnen Plain, Northeast China

Soil carbon(C), nitrogen(N) and phosphorus(P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon(SOC), total nitrogen(TN), and total phosphorus(TP) pools, for a chronosequence of three restored wetlands(7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C∶N(RC N), C∶P(R CP), and N∶P(R NP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr(P > 0.05). Soil nutrients changes occurred mainly in the upper layers(≤ 30 cm), and no significant differences were found in deeper soils(> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RC N, R CP, and RN P in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC(r =-0.704, P < 0.01), TN(r =-0.722, P < 0.01), and TP(r =-0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

Crop yields and soil organic carbon dynamics in a long-term fertilization experiment in an extremely arid region of northern Xinjiang, China

A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon （SOC） from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control （CK） and six different combinations of phosphorus （P）, potassium （K）, nitrogen （N）, straw （S） and animal manure （M）. The balanced fertilization treatments had significantly （P〈0.05） higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate （NPK） and 1/3 N from farmyard manure （NPKM） had a higher average yield than the other treatments. The average yields （over the 23 years） in the treatments of NPK, and urea, calcium superphosphate （NP） did not differ significantly （P〉0.05） but were higher than that in the treatment with urea and potassium sulfate （NK; P〈0.05）. The results also show that the highest increases in SOC （P〈0.05） occurred in NPKM with a potential increase of 1.2 t C/（hm2.a）. The increase in SOC was only 0.31, 0.30 and 0.12 t C/（hm2.a） for NPKS （9/10 N from NPK and 1/10 N from straw）, NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.

Significant changes in arbuscular mycorrhizal community and soil physicochemical properties during the saline-alkali grassland vegetation succession

Arbuscular mycorrhizal(AM)fungi are widely distributed in various habitats,and the community composition varies in response to the changing environmental conditions.To explore the response of community composition to the succession of saline-alkali land,soil samples were collected from three succession stages of Songnen saline-alkali grassland.Subsequently,the soil characteristics were determined and the AM fungi in soil samples were analyzed by high-throughput sequencing.Then,the response relationship between community composition and soil characteristics was studied by Canonical correlation and Pearson analyses.The soil properties improved with the succession of saline-alkali grassland.There was no significant difference in alpha diversity between the first and second succession stage(Suaeda glauca and Puccinellia tenuiflora,respectively),and the microbial community had a dense association network at the third stage(Leymus chinensis);in addition,each succession stage had significantly enriched amplicon sequence variants(ASVs)and functional pathways.All the soil properties except cellulase activity had significant effects on community composition.Furthermore,the pH,organic carbon,organic matter,and sucrase activity significantly correlated with alpha diversity indices.These results provide a theoretical basis for realizing the significant changes in AM fungal community and soil properties during the saline-alkali grassland vegetation succession.

Characteristics of land use conversion in soda saline-alkali soil region of central Northeast China

Since the 1970s,the soda saline-alkali soil region,which is located in the semiarid-arid region of the central Northeast China,has experienced drastic climate variability.Meanwhile,human activities and socio-economic development have led to an increase in water consumption.These factors have brought out considerable land use change and a lot of soil salinize-alkalization.The land use types were obtained from remote sensing images interpretation based on Landsat MSS in 1970s,TM,ETM in 1990s and 2010s.The characteristics of land use conversion and its response to climate change and influence of human activities were explored in the study area during 1970-2010.The results include:(1)The land use types had changed significantly,especially farmland and grassland,with annual growth rates of 0.31% and 0.35%,respectively.In terms of the saline-alkali land,the area increased greatly during 1970-1990,and its increase was mainly from grassland.There was a decrease from 1990 to 2010,and the loss of saline-alkali was replaced by farmland and grassland.(2)Climate change in the study area is obvious,showing a trend of decreasing precipitation and increasing temperature.The change of saline-alkali land area is closely related to the precipitation,with R2=0.78,passed a passing the 0.01 significance test.(3)The correlation of land use degree index and human activity index with saline-alkali land was not obvious,and the changes in these indices only reflected the land use patterns.Under sufficient rainfall,the saline-alkali land was developed into farmland by humans,which caused the decrease of the saline-alkali land.Therefore,climate change is the main driving force of land salinization in the study area.

Relationship between spatio-temporal evolution of soil pH and geological environment/surface cover in the eastern Nenjiang River Basin of Northeast China during the past 30 years

To illuminate the spatio-temporal variation characteristics and geochemical driving mechanism of soil pH in the Nenjiang River Basin,the National Multi-objective Regional Geochemical Survey data of topsoil,the Second National Soil Survey data and Normalized Difference Vegetation Index(NDVI)were analyzed.The areas of neutral and alkaline soil decreased by 21100 km^(2)and 30500 km^(2),respectively,while that of strongly alkaline,extremely alkaline,and strongly acidic soil increased by 19600 km^(2),18200 km^(2),and 15500 km^(2),respectively,during the past 30 years.NDVI decreased with the increase of soil pH when soil pH>8.0,and it was reversed when soil pH<5.0.There were significant differences in soil pH with various surface cover types,which showed an ascending order:Arbor<reed<maize<rice<high and medium-covered meadow<low-covered meadow<Puccinellia.The weathering products of minerals rich in K_(2)O,Na_(2)O,CaO,and MgO entered into the low plain and were enriched in different parts by water transportation and lake deposition,while Fe and Al remained in the low hilly areas,which was the geochemical driving mechanism.The results of this study will provide scientific basis for making scientific and rational decisions on soil acidification and salinization.

Effects of Different Halophytes on Soil Microflora and Enzyme Acti-vities of Saline-alkali Soil

In the pot experiment,seven varieties of halophytes were grown in saline-alkali soil to investigate the responses of microflora and soil enzymes in the rhizosphere.The results showed that compared to the control,the population of bacterial colony(84.8%-95.6%),actinomycetes colony(12.0%-14.5%)and fungi colony(0.5%-1.1%)increased significantly(P<0.05).The population of ammonia bacteria,aerobic cellulose decomposition bacteria in the soil of Vicia sativa L.(201.99%and 395.49%),Medicago sativa(152.43%and 319.90%)and Sesbania cannabina(Retz.)Pori(193.14%and 396.08%)were higher significantly than that of Panicum virgatum L.(49%and 60%),Sorghum bicolor(L.)Moench(99%and 210%),Amaranthus hypochondriacus L.(75%and 36%)and Aneurotepidimu chinense(75%and 77%)(P<0.05).However,Sorghum bicolor(L.)Moench was evidently higher than Panicum virgatum L.,Amaranthus hypochondriacus L.and Aneurotepidimu chinense(P<0.05)in the soil.The population of ammonia bacteria and aerobic cellulose-decomposing bacteria was significantly correlated with the five enzymes(P<0.05),which could improve the microenvironment in saline-alkali soil to accelerate the element cycling and promote the sustainable development of agriculture through cultivating Medicago sativa,Vicia sativa L.,Sesbania cannabina(Retz.)Pori and Sorghum bicolor(L.)Moench.

Effects of Soil Improver on Wheat in Saline-Alkali Lands in the Yellow River Delta

Field experiment carried out to test the effects of soil improver on wheat yield and soil physical-chemical properties. The results indicated that soil improver could optimize soil aggregates structure, decrease soil bulk density, soil pH and soil salt content, increase soil organic matter and 1 000-grain weight, thereby enhancing wheat yield. With the increase of soil improver application amount, soil physical-chemical properties became better and wheat yield increased. However, there was no significant difference in the treatments with the application amounts of 3%, 4% and 5%. In addition, the treatment of reducing nitrogen showed no superiority in soil physical-chemical properties and wheat yield, indicating that sufficient nitrogen was essential for the growth of wheat.

Arbuscular Mycorrhizal Fungal Colonization at Different Succession Stages in Songnen Saline-Alkali Grassland

Arbuscular mycorrhizal(AM)fungi can form symbiosis with 90%of the vascular plants and play important roles in ecosystem.To realize the AM fungal colonization at different succession stages in saline-alkali land and screen AM fungi species with great functions,roots and soil samples were collected from the three succession stages of Songnen saline-alkali grassland.The soil properties and AM fungal colonization were measured,and the fungus distributed extensively in three stages was annotated by sequencing for AML1/AML2 target,subsequently,maize was selected as the host to verify its colonization.The results showed that the soil properties improved with the succession of saline-alkali grassland.The plants’communities of the three stages could be colonized by AM fungi,and the colonization rate of Leymus chinensis(the third stage)ranged from 66.67%to 100%,Puccinellia tenuiflora(the second stage)ranged from 50%to 80%,while the Suaeda glauca(the first stage)was only 35%–60%.Glomeraceae sp1 was identified as the dominant AM fungi species which occurred frequently in the succession of saline-alkali land with the isolation frequency,relative abundance,and importance value of 100%,18.1%,and 59.1%,respectively.The colonization rate of Glomeraceae sp1 in maize ranged from 80%to 87%and similar mycorrhizal characteristics were detected in the roots of P.tenuiflora,S.glauca,and L.chinensis,indicating that Glomeraceae sp1 colonized the samples in the field.The correlation matrix indicated that colonization rate,colonization intensity,and vesicle abundance were closely related to soil conditions most,and they were related significantly to all the soil properties except cellulase activity.Besides,redundancy analysis(RDA)showed that soil properties drove the changes of AM fungal colonization and sporulation.These results will provide theoretical support for realizing the relationship between AM fungal colonization and soil conditions,and also for the exploration of AM fungi species with great functions.

作物轮作对多年连作棉田土壤细菌群落结构的影响

新疆棉田连作问题突出,作物轮作是缓解棉田连作障碍的有效措施。通过对长年连作棉田轮作苜蓿、大豆、花生等六种作物后土壤进行细菌群落结构分析,评价六种作物对棉田土壤微生态的影响程度,筛选能够显著改善提升连作棉田土壤微生态的作物。结果表明:大豆、花生、苜蓿三种豆科作物根际的土壤细菌群落结构与棉花相似性较高,对棉田土壤细菌ACE指数、Chao1指数虽有提升但无显著差异。而番茄、玉米、甜菜三种作物对棉田土壤细菌群落结构影响较大,显著降低了棉田土壤细菌Alpha多样性及不同分类水平细菌种群的数量。在物种组成方面,变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和酸杆菌门(Acidobacteria)为土壤中优势细菌门,变形菌门在番茄根际土壤的丰度最高(58.4%),在苜蓿根际最低(40.5%);放线菌门在苜蓿根际丰度最高(15.8%),在番茄根际最低(6.5%);酸杆菌门在大豆根际丰度最高(10.2%),在番茄根际最低(5.5%)。土壤中显著差异细菌种群主要富集在苜蓿、大豆根际,但是不同作物单季轮作未对土壤中主要有益细菌种群的相对丰度产生显著影响。综合看,大豆、花生、苜蓿三种豆科作物单季轮作对棉田土壤细菌群落结构的影响较小;番茄、玉米和甜菜能够显著降低棉田土壤细菌多样性和种群数量,其中甜菜的影响作用最显著。

秸秆还田与沼液配施对盐渍化土壤养分及酶活性的影响

于2023年开展120 d的室内培养试验,设置棉秆全量还田(AS)、低量沼液单施(LB)、高量沼液单施(HB)、棉秆还田配施低量沼液(AS+LB)、棉秆还田配施高量沼液(AS+HB)共5个处理,分别于3、6、10、20、30、40、60、80、100、120 d进行破坏性采样,分析不同处理土壤主要理化指标和关键酶活性的变化,为南疆棉花秸秆在盐渍环境中的高效腐解和沼液合理利用提供参考。结果表明,棉秆还田配施沼液处理的土壤有机质变化呈现快速增加(0~10 d)和慢速积累(>10 d)两个阶段。与棉秆全量还田相比,高量沼液配施处理土壤有机质、全氮、有效磷和速效钾含量分别增加25.15%、35.26%、79.25%和66.90%,土壤过氧化氢酶、碱性磷酸酶和蔗糖酶活性分别增加90.67%、66.54%和44.25%,土壤电导率也有所提升。冗余分析(RDA)揭示了有机质是土壤酶活性变化的主控因子,解释了方差变异的54.30%。因此,秸秆还田与沼液配施能够增加棉田盐渍化土壤有机质和全氮含量,促进酶活性增加,但沼液过量配施会增加土壤盐渍化风险。