Background Drought critically compromises agricultural productivity and threatens sustainable wheat production. Streptomyces pactum Act12 confers benefits to plant growth under drought stress, but its possible effects on root-associated microbiomes remain understudied. Here, shotgun metagenome sequencing and culture-dependent approaches were integrated to investigate the responses of rhizosphere and rhizoplane microbiomes in dryland winter wheat to exogenous S. pactum Act12 and their potential linkage to plant drought resistance. Results Seed biopriming with S. pactum Act12 increased plant aboveground dry weight at flowering (by 63.2%) and maturation (by 41.9%) stages, leading to improved grain yield (by 8.7%). Microbial inoculation reduced malondialdehyde contents in wheat leaves and roots at the flowering stage alongside compartment-specific alterations in soil microbiomes. Metagenomic analysis revealed inoculation-induced enrichment of distinct taxa in rhizosphere soils (flowering: Fibrobacterota, Altererythrobacter; maturation: Mucoromycota, Rhodospirillum) and rhizoplane soils (flowering: Pseudomonadota, Serratia; maturation: Candidatus_Pacebacteria, Variovorax). Functional profiling showed up-regulation of key pathways related to oxidative phosphorylation in inoculated rhizosphere soils at the flowering stage. In rhizoplane soils, ABC transporters and pyrimidine metabolism were up-regulated across stages upon inoculation. Two key strains isolated from rhizoplane soils, designated Glycomyces lechevalierae A4 and Microbacterium algeriense B3, demonstrated the ability to enhance drought resistance in wheat seedlings. Conclusions Inoculation of S. pactum Act12 heightens drought resistance in dryland winter wheat through compartment-specific phylogenetic restructuring and functional reprogramming of root-associated microbiomes.

Deep plowing and subsoiling are the primary methods for soil water retention in dryland farming areas of the Loess Plateau during the summer fallow period of winter wheat. Soil nematodes serve as biological indicators of the soil ecological health. However, we have limited understanding of the relationship between soil biological communities in the soil micro-food web of dryland tillage. This study investigated soil nematode and microbial communities, as well as the soil properties under deep plowing tillage (DT), subsoiling (SS), and no tillage (NT) in dryland wheat fields on the Loess Plateau, based on a 5-year experiment. The results indicated that nematodes were mainly distributed in the 0-20 cm soil layer. Plant parasitic nematodes (Pp) were dominant during the wheat growth period, while bacterivore nematodes (Ba) prevailed during the non-wheat growth period. With the lowest plant parasite index (PPI), highest maturity index (MI) and structure index (SI) of the nematode community, DT enhanced soil microecological stability. Additionally, DT demonstrated the highest overall soil quality, characterized by significantly higher soil moisture, available potassium contents, NH4+-N, and NO3--N levels, microbial abundance, and soil enzymatic activities. The highest soil organic carbon content and the most intricate interactions between nematodes and microbial communities were noted under SS, along with the highest level of cooperation among various soil biota. Furthermore, bacteria, fungi, and soil properties positively affected soil nematodes, with the soil properties exerting the most significant impact (P < 0.001), particularly through soil aggregate stability, moisture, and microbial biomass having significant effects. Soil moisture was positively correlated with the most dominant nematode and bacterial genera. In summary, DT significantly enhanced the structures of soil nematodes and microbial communities and stabilized the soil micro-food web by improving soil moisture and quality. It serves as an effective tillage practice for wheat fields in the dry-farming areas of the Loess Plateau.

To explore the impact of tillage and fertilization practices on enhancing the soil micro-ecological environment in the dry farmlands of the Loess Plateau, this study used nematodes as indicator organisms. We investigated the effects of three tillage methods (deep tillage, subsoiling, and no-tillage) and four fertilization methods (no fertilization, full chemical fertilizer, 50 % organic fertilizer substituting chemical fertilizer, and full organic fertilizer) on the soil nematode community and its functions. Our findings indicate that the interaction between tillage and fertilization significantly influenced the soil's total abundance of nematodes and trophic groups. Specifically, the total abundance of nematodes and the relative abundance of bacterial-feeding nematodes were higher under subsoiling in maize and no-tillage in wheat season. Moreover, the energy flux within the food web was more pronounced. Applying chemical fertilizers resulted in greater soil bulk density and a higher proportion of plant parasitic nematodes than other treatments, harming the diversity of soil nematode communities. The nematode community's abundance was positively correlated with alkali-hydrolyzable nitrogen content. In summary, reducing tillage in the wheat-maize annual rotation system, implementing subsoiling in the maize season and no-tillage in the wheat season, combined with organic fertilizer application, can improve soil quality, improve nematode community structure and maintain the stability of the soil food web. This approach positively contributes to improving soil health and ecological stability in the dry farming regions of the Loess Plateau.

Drought is a major obstacle to the development of naked oat industry. This work investigated mechanisms by which exogenous Streptomyces albidoflavus T4 and Streptomyces rochei D74 improved drought tolerance in naked oat (Avena nuda) seedlings. Results showed that in the seed germination experiment, germination rate, radicle and hypocotyl length of naked oat seeds treated with the fermentation filtrate of T4 or D74 under PEG induced drought stress increased significantly. In the hydroponic experiment, the shoot and root dry weights of oat seedlings increased significantly when treated with the T4 or D74 fermentation filtrate under the 15% PEG induced drought stress (S15). Simultaneously, the T4 treatment also significantly increased the surface area, volume, the number of tips and the root activity of oat seedlings. Both T4 and D74 treatments elicited significant increases in proline and soluble sugar contents, as well as the catalase and peroxidase activities in oat seedlings. The results of comprehensive drought resistance capacity (CDRC) calculation of oat plants showed that the drought resistance of oat seedlings under the T4 treatment was better than that under the D74 treatment, and the effect was better under higher drought stress (S15). Findings of this study may provide a novel and effective approach for enhancing plant defenses against drought stress.

The present study endeavored to tackle the challenges posed by limited diversity in oat varieties and suboptimal nitrogen fertilizer utilization in the arid landscapes of the Loess Plateau. We selected three oat varieties, including early-maturing oats (E), medium-maturing oats (M), and late-maturing oats (L). In 2022, four nitrogen applications were set up as CK (0 kg N ha−1), N1 (60 kg N ha−1), N2 (90 kg N ha−1), and N3 (120 kg N ha−1). We introduced two additional nitrogen applications, N4 (180 kg N ha−1) and N5 (240 kg N ha−1), in 2023. The two-year study results demonstrated a significant increase in oat yield due to nitrogen application (p < 0.05). The highest grain yield was observed for E oats at 2216.63 kg·ha−1 under the N3 treatment, while M and L oats had the highest grain yields at 2505.43 kg·ha−1 and 2946.30 kg·ha−1 under N4, respectively. The protein content of L oats reached a peak of 14.15% under N4, and the order of protein contents in oat protein components was globulin > gliadin> glutenin > albumin. The β-glucan content of L oats reached a peak of 4.92% under N3. The nitrogen fertilizer utilization efficiency (NFUE) of the three oats was highest under N2. L oats exhibited enhanced NFUE owing to an elevated pre-flowering nitrogen translocation amount (PrNTA), with a 42.94% and 29.51% increase relative to E and M oats, respectively. The pre-flowering nitrogen translocation contribution (PrNTC) in oats surpassed the post-flowering nitrogen accumulation contribution (PoNAC). Therefore, nitrogen application positively impacted oat growth, yet excessive application had an inhibitory effect. There is a significant positive correlation among oat yield, quality, nitrogen accumulation, and utilization efficiency. In summary, oat crops exhibited optimal performance in terms of yield, quality, and nitrogen use efficiency when nitrogen application rates ranged between 90 and 180 kg·ha−1. Late-maturing oats coincide with the rainy and hot season in the northern dryland regions, making them more suitable for planting in the dryland areas of the Loess Plateau.

Excessive use of inorganic fertilizers disrupts soil nutrient balance and leads to soil degradation and a decrease in biodiversity. In contrast, bio-fertilizers enhance soil structure and fertility and promote plant growth and sustainable agriculture development. Therefore, this study focused on a rotation system of winter wheat and summer maize and aimed to explore the effects of applying chemical fertilizer (NPK) and bio-fertilizer (BF) in the winter wheat season on the sustainable soil development of current wheat and subsequent maize. Before sowing winter wheat four fertilization treatments were, respectively CK (100% NPK at 750 kg ha−1), A (60% NPK at 450 + 20% BF at 150 kg ha−1), B (60% NPK at 450 + 40% BF at 300 kg ha−1), and C (60% NPK at 450 + 60% BF at 450 kg ha−1), conducted. The results showed that treatment A (60% NPK + 20% BF) replacing the NPK at 300 kg ha−1 with BF at 150 kg ha−1 significantly soil nutrient contents, enzyme activity, and microbial metabolic activity. The study also found a positive correlation between soil parameters (total nitrogen, alkaline nitrogen, available phosphorus, organic matter, urease, and alkaline phosphatase in the winter wheat and maize cropping season). Furthermore, the soil microbial composition showed significant enrichment of Proteobacteria, Acidobacteria, Actinobacteria, and Firmicutes, and variations among treatments. Moreover, the application of biofertilizer enhanced the diversity of soil fungi species, particularly during the winter wheat season. This study highlights the importance of integrating biofertilizers with NPK fertilizer for agricultural system conversion and promoting agricultural production and sustainability.

探索黑糯玉米硒吸收利用和营养品质对叶面喷施有机硒肥的响应，对生产中合理施用硒肥，进而支撑山西“特”“优”农业高质量发展具有重要意义。本研究以品种晋鲜糯8号为试验材料，于2020—2021年连续2年在山西晋中黑糯玉米典型种植区开展田间试验，设置一次喷施不同用量有机硒0、6和12 g Se hm -2 ，以及喷施量12 g Se hm -2 条件下分2次喷施，共4个处理，研究叶喷有机硒对黑糯玉米产量、硒吸收利用、籽粒花青素和铁锰铜锌含量的影响。结果表明，喷硒量和喷硒次数对黑糯玉米鲜食期产量和成熟期地上部生物量无影响。相比不喷硒，喷硒可提高鲜食期籽粒和成熟期地上部各器官硒含量、硒积累。喷硒12 g Se hm -2 时，籽粒硒含量达到满足人体硒营养需求的最低目标值100 μg kg -1 ，增幅最大，介于110～181 μg kg -1 。成熟期，植株各器官硒积累从高到低依次为叶片、籽粒、茎秆、苞叶、穗轴。喷硒12 g Se hm -2 ，分2次喷施的平均籽粒硒强化指数和籽粒硒回收率分别为6.95 (μg kg -1 ) (g hm -2 ) -1和2.4%，优于1次喷施。同时，鲜食期籽粒花青素和铁锰锌含量也最高，2年平均值分别为209、27.9、15.9和22.8 mg kg -1 ，但各处理间籽粒铜含量无差异。因此，兼顾硒吸收利用和籽粒营养品质同步提升，该区黑糯玉米生产中叶喷有机硒肥用量至少应不低于12 g Se hm -2 ，且分2次喷施效果较优。

Rhizosphere bacterial community plays a crucial role in diverse biochemical processes, soil type modulates the composition of rhizosphere bacterial community, affects crop yields. In this study, four soil types including Grey clayey soil (GCS), Yellow clayey soil (YCS), Granitic sandy soil (GSS), and Purple clayey soil (PCS) in four rice growth stages were investigated for their impact on bacterial community related to rice rhizosphere and grain yield. The results showed that rice rhizosphere bacterial communities changed with both soil type and growth stage. Diversity index and OTUs number of bacterial community were more heavily influenced by soil type. The results of high-throughput sequencing showed that the Gemmatimonadetes and Acidobacteria were commonly inhabited in the rhizosphere of rice. Among them, Acidobacteria showed the greatest effect on grain yield (lambda=0.71, R2=0.51). Based on unweighted pair-group method with arithmetic means (UPGMA) clustering and principal component analysis, the influence of soil type on bacterial community structure was higher than rice growth stage. The physical and chemical properties and bacterial community of soil under YCS treatment were the best. Soil properties had a significant positive effect on rice yield. Bacterial community had a certain effect on rice yield, but the effect did not reach the significant level.

The soil microbial community diversity of wheat rhizosphere was affected by the amount of nitrogen fertilizer. In addition to bacterial community, ammonia-oxidizing archaea, nitrogen-fixing bacteria and denitrifying bacteria also play important roles in nitrogen cycle. At present, the microecological mechanism of its response to nitrogen application is still unclear. In this study, the rhizosphere soil microorganisms of winter wheat were used as the research object. The changes of soil bacteria, ammonia-oxidizing archaea, nitrogen-fixing bacteria and denitrifying bacteria communities under five nitrogen rates of 0—N(0), 90—N(6), 180—N(12), 240—N(16), 300—N(20) kg N ha–2 were studied by high-throughput sequencing technology. Under N(12) treatment, the Alpha diversity index of bacteria, AOA and nifH nitrogen-fixing bacteria and the Shannon and Simpson indices of nirK denitrifying bacteria were significantly increased. N(12) treatment significantly increased the relative abundance of Proteobacteria, but no significant difference was found at the nifH and nirK bacterial phyla levels. Under the high nitrogen treatment of N(16) and N(20), the dominant bacteria of nirK-type denitrifying bacteria increased significantly compared with N(12) treatment, there was no significant difference in microbial community distribution between N(20) and the control group. Therefore, the nitrogen addition under N(12) treatment was most conducive to the absorption and utilization of nitrogen fertilizer by soil microorganisms. The effect of nitrogen addition on microbial community was weaker than that of soil properties and wheat yield, and nitrogen addition was significantly correlated with yield, reaching the highest yield at 300 kg ha–2.

保护性耕作与有机肥施用是黄土高原旱作农业区缓解生态脆弱问题的有效解决手段之一,合理的耕作与施肥措施对山西中部旱区实现麦玉一年两熟具有重要意义.以黄土高原旱作农田为研究对象,采用裂区试验设计,主区为3种耕作方式(深翻(DT)、深松(SS)、免耕(NT)),副区为4种施肥水平(不施肥对照(CK)、全量化肥(CF)、50％化肥+50％有机肥(OF)、全量有机肥(OM)),探究不同耕作与施肥方式下土壤容重、速效养分及麦玉周年产量的变化特征.结果表明,有机肥施用后SS、NT处理0～20 cm土壤容重较DT处理有所下降,其中小麦季SS+OF处理下耕层土壤容重为1.13 g/cm3,显著低于DT+OF处理.整个周年复种连作体系中,以NT+OM处理土壤质量含水量最高,较其他施肥处理平均升高7.88百分点;SS+OM处理下土壤的三相比更为理想,三相比偏离值偏低.3种耕作方式下,碱解氮与有效磷含量大小总体呈现OM>OF>CF>CK的趋势,速效钾含量与施肥方式存在极显著关系,其中CF处理下含量最高;玉米季增施有机肥较单施化肥显著提高了糯玉米鲜穗产量,但有机肥施用比例间的差异并不显著,SS+OM处理下麦玉周年产量最高,达19145 kg/hm2.综上,该试验条件下,SS、NT耕作方式与有机肥施用结合可明显改善土壤的物理性状,碱解氮与有效磷含量也有一定程度的提升,其中,SS+OM处理更有利于黄土高原地区麦玉周年复种连作田产量的提升.

Intercropping is an important planting method for the sustainable use of land resources, and soil nematodes are an indicator of soil health, which can reveal the function of food webs in underground ecosystems. To explore the effects of different intercrop-ping patterns of oats on yield and soil nematode communities, five treatments were set up: oat monoculture, and intercropping systems of oat||soybean, oat||rice bean, oat||potato, and oat||sweet potato. The effects of different intercropping patterns of oats on crop yield and the number, diversity, and community structure of soil nematodes were analyzed to determine the best intercropping pattern.The results showed that, compared with monoculture, intercropping had certain advantages in terms of land utilization rate and total crop yield. The intercropping of oats and potatoes had the highest land equivalent ratio（1.36）, Followed by the intercropping of oats and soybeans, the land equivalent ratio is 1.29. A total of 39 genera were identified, including 12 bacterivorous nematodes, 4 fungivorous nematodes, 13 plant-parasitic nematodes, and 10 omnivorous predatory nematodes. The four oat intercropping patterns significantly reduced the relative abundance of plant-parasitic nematodes, increased the relative abundance of beneficial nematodes（bacterivorous and fungivorous）, and optimized the soil nematode community structure. Among them, the best intercropping pattern was oat and soybean, with the highest proportion of microbial-feeding nematodes（88.42%） and the lowest proportion of plant-parasite nematodes（6.31%）. Additionally, the intercropping pattern of oat and soybean was significantly higher than that of oat monoculture（P＜0.05） in multiple ecological indexes（Wasilewska index, nematode channel ratio, Shannon-Wiener index, and enrichment index）,and was also the best among the four intercropping patterns. The enrichment index of oat and rice bean intercropping was the highest,and the plant parasite index was the lowest, indicating that the soil nematode community was the least disturbed. The enrichment index and structure index of each cropping pattern were lower than 50, and the soil nematode food web was in quadrant D, indicating that the soil environment was in a stressed state, the food web was degraded, and the soil nematode community was unstable at the experiment location. Pearson correlation analysis showed that soil nematode community ecological indices were correlated with soil physical and chemical properties. Organic matter was significantly negatively correlated with the evenness index（r=-0.635, P＜0.05）,significantly negatively correlated with the Shannon-Wiener index（r=-0.641, P＜0.01）, and significantly positively correlated with the plant parasitic index（r=0.633, P＜0.05）. There was a significant positive correlation between available K content and the nematode channel ratio（r=0.722, P＜0.01）, increasing available K content could change the decomposition pathway of soil organic matter and contribute more to the decomposition of soil organic matter. In conclusion, intercropping can optimize the soil nematode community structure, improve the soil ecological environment, and increase crop yield. Among the four intercropping patterns, oat and soybean intercropping were the best method, not only having the highest crop yield but also the most beneficial nematode community structure for soil health, which showed the strong production and ecological advantages of traditional Gramineae and Leguminosae intercropping.

作物轮作种植在中国应用历史悠久,而针对不同地区不同栽培目的的轮作模式研究一直处于探索中.笔者以轮作在土壤生态学方面对土壤的改良作用着手,分析国内外学者关于多种轮作模式下土壤线虫与微生物群落的相关研究,讨论轮作模式下土壤理化性状对两者的影响以及在团聚体中微生物和线虫群落的关系.从宏观及微观空间尺度下分析两者在土壤生态系统食物网中的相互作用,根据其互作效应探究微生物、线虫对土壤环境的指示作用,以此来达到合理轮作、培肥土壤、作物可持续稳产高产的目的,使得农田土壤状况向着更有利于作物生长发育的方向发展.

通过对黄土高原地区冬小麦在不同施氮水平下土壤细菌群落多样性和理化性质的研究,揭示不同施氮量下土壤细菌群落结构的变化规律,为科学施肥以及土壤生态系统的可持续提供依据.本试验处理为 5 个不同施氮(N)量0(N0)、90(N6)、180(N12)、240(N16)、300(N20)kg/hm2,N0 处理为对照,采用高通量测序技术,研究不同施氮量对小麦耕层土壤细菌群落结构及理化性质的影响.结果表明:增施氮肥显著增加了土壤水稳性团聚体平均重量直径(MWD)(P＜0.05).随着施氮量的增加,土壤酶活性先升高后下降,在N12处理下土壤酶活性均最高.施氮量对土壤细菌多样性指数有显著影响.不同施氮量处理中土壤细菌16SrRNA基因拷贝数为6.47×1010～15.18×1010,在N12处理达到最大值.在门水平上,15个样品获得的类群中变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)、绿弯菌门(Chloroflexi)和芽单胞菌门(Gemmatimonadetes)为优势类群,其中N12处理显著提高变形菌门、硝化螺旋菌门的相对丰度,且N12处理的酸杆菌门相对丰度最低.主成分分析结果表明N12处理与其他处理距离较远.冗余分析表明,土壤理化性质及土壤酶与细菌群落密切相关.因此,施氮量显著影响土壤细菌群落结构及理化性质,施氮量(N)为180 kg/hm2时有利于提高细菌群落多样性及改善土壤结构.

Agronomic selenium (Se) biofortification of grain crops is considered the best method for increasing human Se intake, which may help people alleviate Se-deficiency. To investigate the efficiency of agronomic Se biofortification of oat, four Se fertilizer application treatments were tested: topsoil (T), foliar (S), the combination of T and S (TS), and control without Se application (CK). Compared with CK, TS significantly increased the 1000-grain weight, grain yield, Se contents in all parts of oats, contents of soil available N, K, and organic matter by 18%, 8.70%, 19.7–60.2%, 6.00%, 8.02%, and 17.95%, respectively. Leaves, roots, and ears had the highest conversion rate of exogenous Se in S (644.63%), T (416.00%), and TS (273.20%), respectively. TS also increased the activities of soil urease, alkaline phosphatase, and sucrose and the diversity of soil bacterial communities. TS and T increased the relative abundance of bacteria involved in the decomposition of organic matter, such as Actinobacteria, Gemmatimonadetes, Chloroflexi, and Bacteroidetes positively correlated with soil nutrients and enzyme activities, and reduced Proteobacteria and Firmicutes negatively correlated with them, Granulicella, Bacillus, Raoultella, Lactococcus, Klebsiella, and Pseudomonas. Furthermore, TS significantly increased the relative abundance of Planctomycetes, Chlorobi, Nitrospinae, Nitrospirae, Aciditeromonas, Gemmatimonas, Geobacter, and Thiobacter. T significantly increased the abundance of Lysobacter, Holophaga, Candidatus-Koribacter, Povalibacter, and Pyrinomonas. S did not significantly change the bacterial communities. Thus, a combined foliar and soil Se fertilizer proved conducive for achieving higher yield, grain Se content, and improving Se transport, the diversity of rhizosphere bacterial community, and bacterial functions in oats.

Reasonable application of selenium (Se) fertilizer is beneficial for improving Se contents in grains and can affect soil ecology. No study has compared Se fertilizer application methods on biofortification, yield, and soil bacterial community. This study investigated the effects of topsoil (T), foliar (S), and soil+foliar (TS) application of Se fertilizer on oats. TS treatment significantly increased oat yield compared with the control and S. The Se content in grains was increased in the order of TS > S > T. T and TS increased the nutrients, soil organic matter, activities of urease, alkaline phosphatase, and sucrose, as well as the diversity and abundance of soil bacterial communities. According to PCA analysis, TS and T increased the relative abundance of bacteria involved in the decomposition of organic matter, such as Proteobacteria, Chloroflexi, and Bacteroidetes, while reduced Granulicella, Bacillus, Raoultella, Lactococcus, Klebsiella, and Pseudomonas. Furthermore, TS significantly increased the relative abundance of Aciditeromonas, Gemmatimonas, Geobacter, and Thiobacter. While, T significantly increased the abundance of Lysobacter, Holophaga, Candidatus-Koribacter, Povalibacter, and Pyrinomonas. S did not significantly change the bacterial communities. The redundancy analysis revealed that soil nutrients and enzyme activities were positively correlated with the abundance of Actinobacteria, Acidobacteria, Gemmatimonadetes, Bacteroidetes, Planctomycetes, and Chloroflexi, but negatively correlated with the abundance of Proteobacteria and Firmicutes. Thus, a combined application of foliar and soil Se proved most conducive for achieving higher yield, grain Se content, and improving bacterial community structure and functional gene expression in rhizosphere soil.

[目的]探索燕麦与豆科作物间作模式中的土壤酶与土壤微生物的作用机制,明确燕麦与豆科作物的间作优势,为燕麦间作模式生产提供科学依据.[方法]设置燕麦单作(TO)、大豆单作(TB)、豌豆单作(TP)、燕麦/大豆间作(TOB)和燕麦/豌豆间作(TOP)5种种植方式,以裸地为对照(CK),测定燕麦3个生育时期的土壤脲酶、蔗糖酶、碱性磷酸酶和过氧化氢酶4种酶活性,土壤细菌和真菌数量,及燕麦、大豆和豌豆的产量,并分析其相关关系.[结果]燕麦与豆科作物间作条件下,土壤脲酶、过氧化氢酶和蔗糖酶显著高于相应的单作方式和裸地对照.TOP的脲酶活性成熟期比CK提高了151.37％;TOP与TOB的过氧化氢酶活性显著高于单作TP、TO、TB;TOP的蔗糖酶活性显著高于CK,提高12.48％;碱性磷酸酶在间作模式下显著低于燕麦单作和对照,且随生育期呈现下降趋势,尤其TOP成熟期比苗期降低65.96％,比CK降低56.58％.土壤酶相对活性综合指数(REACI)随生育期的推进,均呈先增后降的变化,顺序为TOP>TP>TOB>TB>TO.间作模式下的土壤细菌数量显著高于单作,而真菌相反,且细菌的数量与土壤酶活相关性更高.与单作相比,燕麦/大豆间作、燕麦/豌豆间作优势明显,土地当量比(LER)分别为1.43和1.51.[结论]燕麦与豆科作物间作在不施肥条件下,可提高土壤酶活性,使土壤向健康的"细菌型"转变,改善土壤微生态环境,且有明显间作优势.

Bacteria play essential roles in soil ecosystems. This study aims to investigate rice rhizosphere bacterial communities, soil nutrition, and grain yield affected by long-term (30 years) fertilization practices. Four fertilizations were applied to experimental red paddy soils: no fertilizer (NF), chemical fertilizer (CF), harvested residue returned to soil (HRR), and 60% organic manure plus chemical fertilizer (OCF). Bacterial communities were then assessed by means of denaturing gradient gel electrophoresis (DGGE) targeting 16S rRNA genes. Results showed that the bacterial community structure of OCF was similar to HRR, which was the most diverse and stable compared to the other treatments. Moreover, CF's effects were similar to NF, which was markedly less diverse. Eight bacterial phyla were identified by sequence analysis of the DGGE bands from rhizosphere inhabitants in the red paddy soils. In addition, soil microbial biomass C and N were significantly higher in HRR and OCF than in CF and NF. Furthermore, double rice grain yield and dry matter in OCF plots were significantly highest (P < 0.05). Long-term treatment of organic matter containing fertilizers promoted rhizospheric bacterial diversity and soil quality. The combination of inorganic and organic fertilizers (OCF) improved grain yields more than solely inorganic (CF) or organic (HRR) fertilizers.

甘薯茎线虫(Ditylenchus destructor)是国际检疫植物寄生线虫,甘薯茎线虫病是危害我国甘薯生产的严重病害之一.本文通过不同种植方式下甘薯根际土壤线虫群落结构的变化,探索轮作对甘薯茎线虫病防治的作用,明确变性梯度凝胶电泳(DGGE)在土壤线虫群落研究上应用的可行性.试验在河北省卢龙县多年连作的甘薯地上进行,种植方式分别为:A1,休闲→甘薯;A2,玉米-冬闲→甘薯;A3,玉米-黑麦→甘薯;A4,大豆-冬闲→甘薯;A5,大豆-黑麦→甘薯;CK,甘薯连作.提取3个时期甘薯根际土壤线虫,扩增线虫ITS区序列,采用DGGE技术分析土壤线虫群落.结果表明,与连作相比,轮作方式显著提高甘薯根际土壤线虫群落多样性,降低根际土壤甘薯茎线虫数量(P＜0.05),冬季轮作黑麦(A3,A5)使甘薯根际土壤线虫群落结构更加稳定,随时间变化幅度小.甘薯根际土壤中检测到的线虫优势属有:茎线虫属、矛线虫属、滑刃线虫属、头叶线虫属、短体线虫属、小环线虫属、刺线虫属、真滑刃线虫属、双胃线虫属.轮作方式提高甘薯产量42.08％～55.83％,降低病情指数22.72％～30.79％,不同轮作方式之间对甘薯产量和病情的影响差异不显著,收获期的甘薯茎线虫数量与甘薯产量和病情指数显著相关(P＜0.05).因此,轮作方式能够显著提高甘薯根际土壤线虫群落多样性和甘薯产量,DGGE可有效检测土壤线虫群落;大豆-黑麦→甘薯是经济效益和生态效益较好的轮作措施.

通过田间取样和实验室测定分析,研究免耕(NT)、深翻(DT)和深松(SS)3种夏闲期耕作措施对土壤细菌、真菌、放线菌和氨化细菌数量的影响.结果表明,在小麦整个生育期,土壤细菌、放线菌和真菌数量呈现先下降后上升再下降的趋势,而氨化细菌呈现先下降后上升的趋势.在播种前,细菌、放线菌和真菌数量在SS,DT处理下显著高于NT处理;在越冬期,SS处理的氨化细菌数量显著高于DT处理;收获期NT处理的微生物总量最高,SS处理的微生物总量最低,NT处理的细菌与真菌的数量比值高于SS处理.NT处理微生物菌群较稳定,而SS处理及DT处理的微生物在播种前数量较高,在后期微生物数量降低.