Plant and Soil最新文献

Background and aims

The inoculation of Bradyrhizobium spp. in soybean is a widespread technology in Brazil and one of the most successful cases of plant-bacteria interaction once all the nitrogen required by the plant is provided through biological nitrogen fixation. Co-inoculation of Bradyrhizobium spp. with Azospirillum brasilense AbV5/AbV6 was recommended in Brazil in 2013, but its adoption by farmers has been limited due to variable yield gains. In the present work, we hypothesized that additional traits of A. brasilense, such as resistance to oxidative stress and ammonium excretion, further enhance its growth-promoting effects in soybean when co-inoculated.

Methods

Therefore, an oxidative resistant strain (IH1), two constitutive nitrogen fixing strains (HM053 and HM210) and the commercial strains (AbV5/AbV6) of A. brasilense were co-inoculated with Bradyrhizobium spp. in soybean. The experiments were carried out in four distinct soil and edaphoclimatic regions of Brazil to evaluate soybean nodulation, growth, and yield.

Results

The novel strains of A. brasilense enhanced soybean nodulation and grain yield. The co-inoculation with the HM053 strain resulted in the highest increase in soybean grain yield, ranging from 4.3% to 25.4%, or 151.7 to 878.1 kg/ha, compared to single inoculation.

Conclusion

This promising technology generates environmental and economic gains, since it promotes plant growth, increases yield and contributes for a sustainable agriculture.

Background and aims

Soil microorganisms and dissolved organic matter (DOM) play a prominent role in soil carbon and nutrient cycles. However, the relationship between rhizosphere DOM components and bacterial communities in different cover crops remains unclear. This study accordingly details the relationships between soil DOM and microorganisms in cover crops within apple orchards on the Loess Plateau.

Methods

We selected three cover crops, Gramineae orchardgrass (OG), legume crown vetch (CV), and white clover (WC), to study the bacterial community composition, DOM content and components, and their associations in both rhizosphere and bulk soils.

Results

The available nutrients content in rhizosphere soil was higher than that in bulk soil. The rhizosphere DOM was primarily composed of protein-like substances. The humic-like component predominated in Gramineae treatment, whereas the protein-like component dominated in legume treatment. The rhizosphere bacterial α-diversity decreased compared with that in bulk soil. Network analysis indicated that the relationship between DOM components and bacterial communities in rhizosphere soil was more complex than that in bulk soil, with negative associations being predominant. Moreover, Gramineae cover crops reinforced the association between bacterial community composition and DOM components compared to legume.

Conclusions

Cover crop species significantly affect the relationship between the rhizosphere soil DOM components and bacterial communities, exhibiting a closer relationship under Gramineae cover crop. This study enhances our understanding of the ecological processes through which cover crops regulate bacterial communities and strengthen the interactions with DOM, providing new insights for assessing soil quality in apple orchards.

Aims

Trichoderma species are recognized for their plant growth-promoting and biocontrol properties. This study aimed to isolate effective Trichoderma strains from the rhizosphere of pear (Pyrus betulifolia Bunge) trees and evaluate their growth-promoting effects on various plant species.

Methods

Ten Trichoderma strains were isolated using a gradient dilution plating method, and Trichoderma brevicompactum TB2 was selected through laboratory and greenhouse experiments. The growth-promoting properties of TB2 were assessed in pot experiments with cucumber (Cucumis sativus L.) and apple rootstock (Malus hupehensis Rehd) seedlings. Whole-genome sequencing was performed to annotate TB2 genes across various databases and predict secondary metabolite biosynthetic gene clusters. Production of indole-3-acetic acid (IAA), siderophores, and iron-solubilizing capabilities were measured.

Results

TB2 showed high production of IAA, siderophores, and iron-solubilizing abilities. The draft genome, spanning 18 scaffolds totaling 38.70 Mb with 10,436 protein-coding genes, revealed 431 genes encoding carbohydrate-active enzymes involved in metabolic pathways. Application of TB2 spore suspension (1.0 × 10⁶ CFU/g soil) significantly increased fresh and dry weights across all tested plants and enhanced root development metrics in C. sativus and P. betulifolia seedlings. TB2 inoculation also boosted major and minor nutrient levels in the leaves of M. hupehensis seedlings.

Conclusions

TB2 exhibits strong growth-promoting effects across different plant species, improving physiological indicators such as plant height, stem diameter, and biomass, while enhancing nutrient absorption without host specificity. TB2 can thus be utilized as an excellent agricultural microbial resource strain.

Aims

Large portions of the western United States have witnessed extended dry intervals between rainfall events due to an intensified hydrological cycle triggered by global warming. Semiarid ecosystems in these regions are particularly susceptible to temporal repackaging of rainfall, but how such rainfall repackaging alters plant phenology remains unknown.

Methods

We examined the effects of rainfall temporal repackaging during the growing season (July–September, from frequent/small events to infrequent/large events, with constant total seasonal rainfall) on plant phenology through a manipulative experiment in a semiarid grassland ecosystem. Using automated high-frequency digital photography, we monitored canopy and plant greenness at both the plot and plant functional type levels, and derived phenological metrics including the start, end and length of the growing season.

Results

We found that canopy onset was delayed by 17 to 24 days under infrequent/large events compared to normal historical pattern, with no significant differences among these treatments in canopy descent or growing season length. The phenology metrics of plant functional types showed opposite responses to rainfall repackaging. Perennial grasses had a longer growing season, while annuals had a shorter season under infrequent/large events compared to frequent/small events. Furthermore, growing season length of perennial grasses responded more strongly to deep than shallow soil water conditions.

Conclusions

Our analysis demonstrates the potential of high-frequency plant monitoring to enhance our fundamental understanding of community composition and ecological processes that shape semiarid ecosystem responses to rainfall temporal repackaging and its implications for global biogeochemical cycling.

Aims and methods

Conservation agriculture practices have been developed for rice-based cropping systems in eastern India to mitigate the negative effects of continuous monocropping. However, the effects of individual and combined conservation agriculture components on carbon (C) and nitrogen (N) mineralization, soil enzyme activities, and C and N fractions are unknown. This study aimed to evaluate the effects of key components of conservation agriculture such as, reduced tillage, crop residue retention and crop diversification both individually and in combinations with the control making 8 treatments, on soil carbon and nitrogen dynamics under direct seeded rice-green gram system.

Results

Reduced tillage alone and in combination with diversification resulted in 10% and 6% lower CO₂-C release than the plots with residue retained. Carbon mineralization in terms of mean cumulative CO₂-C (mg CO₂-C kg⁻¹) fits well with first-order kinetics (R² = 0.97–0.99), suggesting that degradation is concentration-dependent. Potentially mineralizable N content ranged from 192.2–222.4 kg ha⁻¹ day⁻¹ with mineralization half-time of 28.1–32.3 days. Diversification alone showed the highest dehydrogenase (43–127% higher than control at all stages), fluorescein di-acetate (22–62% higher than control at maximum tillering and panicle initiation stages) and β-glucosidase (27–40% higher than control in all stages) activities, while residue retention in the rice-green gram system showed the highest nitrate reductase activity (53–83% higher than control at maximum tillering and panicle initiation stages). At all growth stages, diversification had the highest values for microbial biomass C, ammonium N and nitrate N which were 59–95%, 22–53% and 2.2–10 times higher than the control, respectively.

Conclusion

The effect of conservation agriculture component, such as crop diversification and residue retention in direct seeded rice-green gram system, is more effective for better C and N cycling. While reduced tillage may take longer to show effects, enzymatic activities have significantly increased under diversification and residue retention. By diversifying crops and retaining crop residues, the soil is able to maintain higher levels of C and N. Additionally, the increase in soil enzyme activities improves microbial activity, which can further enhance nutrient availability for plants. The synergistic effect of residue retention and crop diversification is beneficial for improving soil health in this system.

Graphical abstract

Background and aim

Sediments serve as the primary reservoir for nitrogen and phosphorus nutrients in lakes, and the release of these nutrients plays a crucial role in contributing to lake eutrophication. The restoration of submerged vegetation has emerged as a promising area of lake ecosystem research and is recognized as an effective method for managing eutrophic lakes. However, the validity of previous findings may be compromised by artificial experimental conditions and the brief duration of the studies, potentially underestimating the long-term effectiveness of submerged plants in restoring eutrophic lakes.

Methods

We restored a eutrophic lake through the reconstruction of submerged vegetation. Continuous sampling and monitoring of lake water and sediments were conducted throughout the project. By analyzing the spatiotemporal variations and factors driving nitrogen and phosphorus concentrations in the overlying water and sediments, we explored the effects of the restoration of submerged vegetation on nitrogen and phosphorus loading in the sediment‒water system.

Results

The restoration of submerged vegetation significantly improved the environmental conditions in overlying water in the lake by increasing transparency and dissolved oxygen levels while reducing nitrogen and phosphorus concentrations. Moreover, throughout their growth period, submerged plants could significantly reduce nitrogen and phosphorus loads in surface sediments (0–5 cm), particularly the concentrations of organic nitrogen (ON), ammonium nitrogen (NH₄⁺-N), Ca-bound P (Ca-P), and P bound to Fe, Al and Mn oxides and hydroxides (Fe–P).

Conclusion

Our findings suggest that the restoration of submerged vegetation effectively controlled the nutrient loads of nitrogen and phosphorus in the overlying water and sediments of the lake. To further stabilize and extend the function of submerged plants in controlling internal nutrients and purifying water quality, it is necessary to strengthen the construction of a multi-seasonal and age-structured submerged plant community to promote the benign cycle of the lake ecosystem.

Graphical abstract

Aim

Litchi (Litchi chinensis) is a commercially valuable subtropical fruit, and understanding its phenology is crucial for optimizing orchard management and improving fruit production. This study investigates the phenological development of litchi cv. Dehradun under the subtropical climate of Himachal Pradesh, using the extended BBCH (Biologische Bundesanstalt, Bundessortenamt, and Chemische Industrie) scale.

Methods

Studies conducted from 2021 to 2023, focuses on key growth stages such as bud break, leaf and shoot development, inflorescence emergence, flowering, fruit development, and maturity. Heat unit accumulation, measured through growing degree days (GDD), was tracked at each stage to provide a detailed phenological profile.

Results

The study identifies 74 distinct secondary growth stages, offering precise descriptions of each phenophase. Results show that temperature plays a critical role in determining the success of flowering and fruit set, with deviations impacting flowering intensity and fruit quality. The phenological data derived from the BBCH scale has been suggested as a guide to the litchi growers in optimizing irrigation schedules, pest control, and the use of plant growth regulators (PGRs) to enhance fruit quality and yield.

Conclusions

This study provides a framework for sustainable litchi cultivation by aligning agricultural practices with the crop’s developmental needs according to the growing degree days, minimizing input costs and environmental impact.

Purpose

Climate warming has increased interests in establishing plantations to enhance carbon (C) sequestration. As a fundamental factor, planting density can profoundly influence tree growth and mortality. Although the effect of stand density on tree biomass C stocks is well known, how it affects soil organic C (SOC) stocks and stability remains largely uncertain. Here, we explored mechanisms behind stand density effects on SOC stocks and fractions.

Methods

We leveraged 25 of 40-year-old Mongolian pine (Pinus sylvestris var. mongolica) stands with stand densities ranging from 350 to 1500 trees per hectare, and measured tree biomass C stocks, litter quantity and quality, soil nitrogen (N) and phosphorous (P) concentrations, microbial biomass, C-degrading enzymes, and SOC stocks and fractions.

Results

Ecosystem C stocks logarithmically increased with increasing stand densities, and this C accretion was ascribed to tree biomass C sequestration. Mineral-associated organic C (MAOC) stocks in the 0–10 cm soil layer decreased with increasing stand densities, which was related to the decline of soil cellobiohydrolase activity and total P concentration. The decrease of litter C:N ratio was associated with the increase of particulate organic C (POC) stocks in the 10–20 cm soil layer with increasing stand densities. Moreover, stand density had positive effects on POC and MAOC stocks in the 20–40 cm but not in the 40–100 cm soil layers.

Conclusions

These findings highlight that stand density alters the vertical distribution of SOC stocks and suggest that soil biochemical properties and litter quality mediate the dynamics of SOC stocks and fractions along the stand density.

Background and aims

Seasonal precipitation regimes can affect soil nitrogen (N) transformation rates, yet the underlying driving factors remain poorly studied.

Methods

To address this knowledge gap, we conducted a precipitation manipulation experiment in a subtropical forest in China from 2020 to 2022. We utilized the in situ resin-core method to assess soil physicochemical properties, microbial biomass, net nitrification rate (N_nit) and net N mineralization rate (N_min) under three treatments: control (CK), decreased precipitation by 50% during the dry season with extremely increased precipitation (≥ 50 mm) during the wet season (IE) and decreased precipitation by 50% during the dry season with proportionally increased precipitation (≤ 20 mm) during the wet season (IP).

Results

IE and IP significantly decreased N_nit (57.9% and 72.5%, respectively) and N_min (82.5% and 89.6%, respectively) during the dry season. However, the results were reversed during the wet season (increased by 64.3% and 79.5% and by 64.2% and 81.1%, respectively), and the effects of IP were significantly stronger than those of IE. Structural equation modeling indicated that seasonal precipitation regimes significantly affected N_nit and N_min by changing soil water content, NH₄⁺-N, microbial biomass N and soil C:N ratio. Moreover, N_nit and N_min were mainly influenced by soil physicochemical properties during the dry season, whereas microbial biomass played a more important role during the wet season.

Conclusions

Seasonal precipitation regimes can significantly affect N_nit and N_min in forest ecosystems, with the magnitude of these effects varying depending on the specific form of the seasonal precipitation regime. 

Background and aims

The effects of elevated tropospheric ozone (O₃) concentrations on terrestrial ecosystems have been extensively researched by numerous O₃ fumigation experiments and syntheses. While the detrimental impacts of O₃ stress on aboveground plant physiological traits are well-documented, there remains a gap in our understanding of how elevated O₃ influences soil microbes and plant–microbe interactions.

Methods

Here, we synthesized data from 71 O₃ fumigation experiments conducted globally to evaluate the effects of elevated O₃ on soil microbial characteristics, including biomass, community composition, and extracellular enzyme activities (EEAs).

Results

Elevated O₃ led to an average reduction of 14.2% in microbial biomass carbon (MBC). It was largely attributable to decreased plant carbon input, as the effect size of MBC was closely correlated with declines in both aboveground and root biomass. Fungal communities appeared more vulnerable to O₃ stress than bacterial communities, as evidenced by a 10.7% decrease in fungal phospholipid fatty acids (PLFAs), while total and bacterial PLFAs were only marginally affected. Furthermore, the negative impacts on microbes intensified with increasing O₃ concentrations but tended to diminish over time. In addition, elevated O₃ significantly reduced hydrolytic EEAs, which target simple compounds, by 12.9%, while increasing oxidative EEAs, which degrade recalcitrant compounds, by 12.0%. It suggests that O₃ stress would affect the decomposition of soil organic matter by shifting EEAs.

Conclusion

Elevated O₃ impairs soil microbial growth and changes microbial C utilization strategies, which could profoundly impact C cycling in terrestrial ecosystems.