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 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.

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.

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.

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.

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.

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.

Saline-alkali land reclamation boosts topsoil carbon storage by preferentially accumulating plant-derived carbon

Saline–alkali land is an important cultivated land reserve resource for tackling global climate change and ensuring food security, partly because it can store large amounts of carbon(C). However, it is unclear how saline–alkali land reclamation(converting saline–alkali land into cultivated land) affects soil C storage.We collected 189 adjacent pairs of salt-affected and cultivated soil samples(0–30 cm deep) from the Songnen Plain, eastern coastal area, Hetao Plain, and northwestern arid area in China. Various soil properties, the soil inorganic C(SIC), organic C(SOC), particulate organic C(POC), and mineral-associated organic C(MAOC) densities, and plant-and microbial-derived C accumulation were determined.Saline–alkali land reclamation inconsistently affected the SIC density but significantly(P < 0.001)increased the SOC density. The SOC, POC, and MAOC densities were predicted well by the integrative soil amelioration index. Saline–alkali land reclamation significantly increased plant-derived C accumulation and the plant-derived C to microbial-derived C ratios in all saline–alkali areas, and less microbial transformation of plant-derived C(i.e., less lignin degradation or oxidation) occurred in cultivated soils than salt-affected soils. The results indicated that saline–alkali land reclamation leads to plant-derived C becoming the dominant contributor of SOC storage. POC storage and MAOC storage were strongly linked to plant-and microbial-derived C accumulation, respectively, caused by saline–alkali land reclamation.Our findings suggest that saline–alkali land reclamation increases C storage in topsoil by preferentially promoting plant-derived C accumulation.

Saline-alkali soil reclamation and utilization in China:progress and prospects

Soil salinity is a global threat to the productivity of arable land. With the impact of population growth and development of social economy in China, the area of arable land has been shrinking in recent decades and is approaching a critical threshold of 120 Mha, the minimum area for maintaining the national food security. Saline-alkaline land, as important backup reserve, has been receiving increased attention as an opportunity to expand land resources. This review first summarizes the general principles and technologies of saline soil reclamation to support plant growth, including leaching salts or blocking the rise of salts, and soil fertility enhancement to improve the buffering capacity.Then the progress in this area in China is described including the customization of technologies and practices used in different saline-alkali regions. Following the soil management strategies, the concept of selecting crops for saline soil is proposed. This encompasses halophyte planting, salt-tolerant crop breeding and the application of saline-adapted functional microorganisms to improve the adaptation of crops. Finally, the current problems and challenges are evaluate, and future research directions and prospects proposed for managing this major soil constraint.

Effects of flue gas desulfurization gypsum and clover planting on qualities of soil and winter jujube in coastal saline-alkali orchard of north China

Flue gas desulfurization gypsum and clover planting alleviated the soil salinization stress.Soil pH and total phosphorus affected the bacterial communi-ties.Total phosphorus affected the fungal communities.Flue gas desulfurization gypsum and clover planting improved jujube quality.The coastal area of Shandong Province,characterized by coastal saline tidal soil,is one of the main production areas of winter jujube in China.However,the low soil fertility and poor soil structure in jujube orchard restricted the development of the jujube industry.The objectives of this study were to 1)evaluate the effect of application of flue gas desulfurization(FGD)gypsum and clover planting on soil quality improvement and soil microbial community structure of jujube orchard;2)investigate the effects of two measures on the nutrition and quality of winter jujube.The results showed that FGD gypsum reduced the soil total salt content by 65.6%,and clover planting increased the soil organic matter content by 30.7%,which effectively alleviated the soil salinization stress and improved the soil structure.Soil pH and total phosphorus(TP)were the main determinants influencing bacterial community composition,and TP was the dominant factor of the fungal community composition in the saline-alkali soils.Meanwhile,FGD gypsum addition and clover planting significantly increased the sugar degree and Vc content of winter jujube,thus improved jujube quality,and further contributed to the ecological sustainable development of winter jujube industry.

Transport Characteristics of Soil Salinity in Saline- alkali Land under Water Storage and Drainage Conditions

To test the variation and transport of soil salinity in saline- alkali land under water storage and drainage treatments,an experimental model was established in Fuping,Shaanxi Province,2009. The variation of soil salinity during 0- 160 cm soil depth under the two treatments was determined and analyzed. Results showed that the average soil water content under water storage treatment was 4. 47% higher than that under drainage treatment,which means that the water storage treatment could help to improve soil moisture to satisfy the crop's growth needs. The profile distribution of soil soluble solids( TDS),anion( Cl-,HCO3-,SO2-4) and cation( Ca2 +,Na+,K+) content and the variation of soil p H were also measured and analyzed. PCA( Principal Component Analysis) was used to explore the relationship between the soil salinity and its ions,which showed that the water storage treatment could significantly decrease the surface salinity of soil and accelerate the desalination of topsoils,and finally,the soil quality was improved significantly,demonstrating that the water storage treatment has a remarkable effect on soil salinity management.

Straw interlayer improves sunflower root growth:Evidence from moisture and salt migration and the microbial community in saline-alkali soil

A straw interlayer added to soil can effectively reduce soil salinity effects on plant growth,however,the effects of soil moisture,salt and microbial community composition on plant growth under a straw interlayer are unclear.A rhizobox study was conducted to investigate the role of straw interlayer thickness on soil moisture,salt migration,microbial community composition,as well as root growth in sunflower.The study included four treatments:Control(no straw interlayer);S3(straw interlayer of 3.0 cm);S5(straw interlayer of 5.0 cm);S7(straw interlayer of 7.0 cm).Straw interlayer treatments increased soil moisture by 8.2–11.0%after irrigation and decreased soil salt content after the bud stage in 0–40 cm soil.Total root length,total root surface area,average root diameter,total root volume and the number of root tips of sunflower plants were higher under straw interlayer treatments than in the control,and were the highest under the S5 treatment.This stimulated root growth was ascribed to the higher abundance of Chloroflexi and Verrucomicrobia bacteria in soil with a straw interlayer,which was increased by 55.7 and 54.7%,respectively,in the S5 treatment.Addition of a straw interlayer of 5 cm thickness is a practical and environmentally feasible approach for improving sunflower root growth in saline-alkali soil.

Influences of Soda Soil on the Ultrastructure and Storage Inclusions of Chloroplasts of <i>Syringa oblata</i>Lindl.

With a high pH value, soda soil restricts the growth of plants. It had previously been assumed that the inhibition of plant growth by neutral salt stress was partly due to the changes of the ultrastructure and storage inclusions of chloroplasts. The aim of this paper is to investigate the effects of alkali-salt mixed stress of soda soil on chloroplasts of higher plant Syringa oblata Lindl. Testing S. oblata plants had grown for more than five years in soda soil, and transmission electron microscope was used for determining the ultrastructure and storage inclusions of chloroplasts. The results showed that some chloroplasts were destroyed, the normal chloroplasts became smaller, and the envelopes of the functional chloroplasts were slightly expanded generally in soda-stressed plants. The most noteworthy fact was that much more starchgrains accumulated in the chloroplasts of S. oblata growing in soda soil than in neutral soil. The total contents of plastoglobules in chloroplasts did not change considerably, and plastoglobules with different electron densities appeared in chloroplasts in the plants growing in soda soil. We presume that the reduction of the volume and number of functional chloroplasts and the occupation of carbon resources by starch grains accumulated in chloroplasts were the possible reasons for the inhibition of S. oblata growth by soda soil. The accumulation of starch grains was one of the adaptive traits of S. oblata, which promoted the survival of plants in soda soil for that the starch grains could serve as a steady source of soluble sugars, which were known as protectors of plant cells under stressed conditions. Soda soil did not significantly change the total content of plastoglobules in chloroplasts, but changed their compositions.