Plant and Soil最新文献

Background and aims

Nitrogen (N) and phosphorus (P) fertilisers are widely used in agro-ecosystems but can endanger the diversity of beneficial soil-borne biota. This study aimed to determine the impact of long-term N and P fertilisation on arbuscular mycorrhizal fungi (AMF), a group of symbiotic soil fungi, by distinguishing between the effects of individual and combined nutrient applications.

Methods

We examined the impacts of long-term (i.e. 19 years) N and P fertilisation at two developmental crop stages: V6 (six fully expanded leaves) and R1 (initiation of flowering, after N addition). We measured mycorrhizal colonisation to test the plant-AMF relationship and used Illumina MiSeq sequencing of 18S rRNA gene from rhizospheric soil to evaluate AMF diversity.

Results

N and P fertilisation resulted primarily in additive effects rather than interactive effects. N fertilisation greatly increased alpha diversity (e.g. + 38% Chao2 at R1 sampling time) and changed AMF community composition (presence-absence data at R1). P fertilisation reduced mycorrhizal colonisation (~—8% at V6,—21% at R1), changed community composition (relative abundance data at V6 and R1) and negatively affected the abundance and richness of the predominant family Glomeraceae.

Conclusions

Long-term additions of N and P change AMF communities in distinct ways. While N mainly contributes to increases in alpha diversity, P influences the assembly of AMF by altering the dominance of major taxa within the community. Future studies are needed to disentangle the implications of these changes for crop yields and nutrient use efficiency to ensure the sustainability of agro-ecosystems.

Aims

Straw, biochar, dimethylpyrazole phosphate (DMPP), and polyaspartic acid (PASP) are promising materials to improve soil productivity and alleviate agricultural pollution. However, the comparison of these four materials in rice cultivation, in terms of fertilizer use efficiency and crop yield enhancement, remains limited. A pot experiment was therefore conducted to elucidate the comparative impacts of these materials on gaseous nitrogen loss, rice growth, nutrient uptake, soil properties, and soil nitrifying bacteria during different growth stages with the aim of identifying the optimal material facilitating rice production.

Methods

Six treatments were designed as follows: no nitrogen fertilizer (PK), conventional fertilization (NPK), partial substitution of nitrogen in NPK with straw (NPKS), partial substitution of nitrogen in NPK with biochar (NPKC), NPK plus DMPP application (NPKD), and NPK plus PASP application (NPKP).

Results

For the whole growth period, the inhibition of NH₃ volatilization only occurred in NPKP (17.22%) in comparison with NPK, while DMPP and PASP effectively reduced N₂O emissions by 40.54% and 25.29%, respectively. Moreover, all materials contributed to nitrogen fixation in soil while significantly decreasing the population of AOB bacteria, with PASP and straw demonstrating a significant inhibitory effect on AOA bacteria. Furthermore, straw was more favorable to nutrient uptake and utilization by rice, inducing additional accumulation of nitrogen (71.96%), phosphorus (21.03%), and potassium (14.97%). Lastly, straw, DMPP, and PASP increased the rice yield (> 6%), whereas the impact of biochar was less pronounced.

Conclusion

When considering factors such as environment, soil properties and crop yield, the application of biodegradable PASP demonstrates comprehensive advantages in rice cultivation.

Aims

To improve our understanding of N cycle development during primary succession after glacial retreat, we (i) assessed the role of biological N₂ fixation, (ii) determined gross ammonification rates to identify the onset of mineralization, (iii) quantified the retention of ¹⁵NH₄⁺ and ¹⁵NO₃⁻ in various ecosystem compartments to evaluate the accumulation of deposited N and (iv) followed the ¹⁵NH₄⁺ label into the soil NO₃⁻ pool to explore the development of nitrification along the subtropical alpine Hailuogou glacial retreat chronosequence, SW China.

Methods

We measured N stocks and δ¹⁵N values in the dominant tree species, organic layer and 0–10 cm of the mineral soil and quantified N turnover rates and accumulation via ¹⁵N tracer experiments.

Results

N accumulated in the ecosystem at a fast mean rate of 4.5 ± 1.0 g m⁻² yr⁻¹ favored by an initially near-neutral soil pH value. The δ¹⁵N values of the vegetation started near 0‰ and decreased to a range of -2.7 to -4.4‰ in 127 years. Gross ammonification rates were initially low but increased with ecosystem age from 0.025 to 50.6 mg kg⁻¹ d⁻¹ N, matching those of mature (sub)tropical forests. The maximum accumulation of deposited N shifted from the bryophyte via the shrub layer to the soil organic layer. The ¹⁵NH₄⁺ label hardly appeared in the NO₃⁻ pool reflecting little nitrification.

Conclusions

Strong initial biological N₂ fixation and retention of deposited N was succeeded by a tight N cycling between soil and vegetation at the older sites within approximately 120 yr.

Aims

Many studies used physical barriers to separate the roots of different species to dissect the contributions of above- and below-ground interspecies interactions to yield and phosphorus (P) uptake. However, the extent to which the presence of barriers itself alters these contributions remains unknown.

Methods

The field study, conducted in 2010 and 2011, used root barriers in both sole cropped and intercropped maize at two P levels. We examined the contributions of interspecies interactions to yield, biomass and P content in all treatments. The field experiment followed a split plot design with two P levels (P0: 0 kg ha⁻¹, and P35: 35 kg P ha⁻¹), three cropping systems (sole maize, sole faba bean and maize/faba bean intercropping), and two types of root separation (solid barrier -SB- and no barrier -NB-).

Results

The presence of a solid barrier negatively impacted the yield of sole maize, reducing it by 26% in 2010 and by 56% in 2011 compared with conditions without a barrier, indicating that the barrier itself adversely affected the growth of sole maize. Notwithstanding the barrier's influence, the belowground interspecies interactions were the primary contributors to the increased grain yield and P content observed in maize/faba bean intercropping under the P0 treatment. In contrast, aboveground interactions were more significant in enhancing the performance of the intercropping system at the P35 treatment.

Conclusions

Phosphorus fertilization diminished the effects of belowground interspecies interactions while amplifying the impact of aboveground interspecies interaction on the advantages of intercropping, regarding grain yield and P uptake.

Background and aims

Root water uptake (RWU) depends on root development, influenced by water and salt stress (WAS). Modeling RWU requires calibration of soil and root parameters using lysimeter data, which is challenging. The study introduces a global sensitivity index-based estimability method for parameter assessment and selection, optimizing them using observations from lysimeter experiments.

Methods

A variance-based global sensitivity and estimability analyses was performed on the HYDRUS-1D model. The analyses evaluate the impact of soil hydraulic and stress parameters on pressure head, soil moisture, bottom flux, and electrical conductivity. Interactions among parameters across the root zone were analyzed for model parameter selection. The selected parameters were calibrated from soil-column lysimeter experiments on berseem (Trifolium alexandrinum) under saline and non-saline conditions.

Results

The analyses identify water stress and residual soil moisture as less estimable, while major soil and salt stress parameters as more estimable, especially from bottom flux and soil moisture data. Excluding saturated soil moisture, which strongly influenced parameter estimability, improved optimization results. For the maximum scenarios, the simulated salt-water dynamics showed fair agreement with the observed data (r² > 0.7). For moderate salinity, reduced RWU was compensated by an increase of 0.01 d⁻¹, while high salinity significantly reduced this compensation to 0.002 d⁻¹ with uniform RWU of 0.004 d⁻¹.

Conclusion

The study demonstrates how different data sets contribute to accurate parameter estimation. Under high salinity, the compensation mechanism for reduced RWU was diminished, and the prolonged uniform RWU pattern suggested potential permanent root morphological changes.

Aims

Mixed planting enhances forest productivity and soil nutrient content, crucial for maintaining forest ecosystem stability and promoting sustainable forest management. While phylogeny is directly related to plants, it remains to be verified whether it will have an effect on soil nutrient content.

Methods

Here, we attempted to explain the relationship between soil nutrient content in Pinus massoniana mixed forests and the evolutionary history of tree species from the perspective of phylogenetic constraints. We complied a dataset consisting of 572 field measurements, including soil organic carbon, total nitrogen, available nitrogen, total phosphorus, and available phosphorus, from Pinus massoniana mixed forests with different species, covering 15 families, 26 genera, and 34 species. This dataset aims to explore the trends in soil nutrient content changes and their phylogenetic signals, while also quantifying the relative importance of environmental factors and divergence time in modifying soil nutrient content.

Results

Our results indicated that the contents of soil organic carbon, total nitrogen, and total phosphorus in Pinus massoniana mixed forests exhibited positive phylogenetic signals. Tree species positioned further apart on the phylogenetic tree showed more pronounced increase in soil nutrient contents. Relative analysis indicates that divergence time, like environmental factors, significantly contributes to the enhancement of soil nutrients in Pinus massoniana mixed forests.

Conclusion

This study provided valuable insights for the efficient establishment and application of mixed forests and serves as a theoretical basis for the selection of tree species in mixed planting.

Background, aims and methods

Investigating and quantifying the transfer of heavy metals from soil to rice plants under different environmental conditions is crucial. This study explores the characteristics of heavy metals transfer within soil-rice system and the environmental implications of translocation coefficients (TCs) through analysis of data from major rice-growing regions in Asia.

Results

The translocation patterns of different heavy metals demonstrate variability, varying across geographical areas. For instance, As and Cd show high transfer propensity from soil to roots (average TCs: 3.71 for As and 3.63 for Cd), but their subsequent retranslocation to straw is substantially constrained, with average TC_straw/root and TC_grain/straw values dramatically decreasing (0.18 for As and ≤ 0.45 for Cd). Rice plants effectively regulate the transport Cu and Zn from roots to aerial tissues: TC of Cu decreases from 0.87 (TC_root/soil) to 0.27 (TC_straw/root), then increased to 0.78 (TC_grain/straw); for Zn, TC_root/soil, TC_straw/root and TC_grain/straw are 0.74, 0.65 and 0.63, respectively. Cluster analysis reveals distinct translocation patterns, with elements like Pb in the Yangtze River Delta showing a “parabola” transfer pattern, characterized by anomalously high TC_straw/root, along with Cr, Ni and Hg.

Conclusion

The sketched pattern generated by TCs exhibits available implication for environment condition. The abnormal translocation patterns observed for Pb, Cr, Ni and Hg suggest that these elements in rice aerial tissues may originate from atmospheric sources, influenced possibly by historical Pb-containing petrol use or non-ferrous mining activities.

Background and aims

Climate change and associated weather extremes pose major challenges to agricultural food production, necessitating the development of more resilient agricultural systems. Adapting cropping systems to cope with extreme environmental conditions is a critical challenge. This study investigates the influence of contrasting root system architectures on microbial communities and functions in top- and subsoil.

Methods

A column experiment was performed to investigate the effects of different root architectures, specifically deep (DRS) and shallow (SRS) root systems of wheat (Triticum aestivum L.) on microbial biomass, major microbial groups, and extracellular enzyme activities in soil. We focused on β-glucosidase (BG) activity, which is an indicator for microbial activity, during different plant growth stages, using destructive and non-destructive approaches.

Results

We found that the DRS promoted microbial biomass and enzyme activity in subsoil, while the SRS increased the microbial biomass and enzyme activity in topsoil. In-situ soil zymography provided fine-scale spatial insights, highlighting distinct patterns of BG activity near root centers and formation of enzyme activity hotspots, which were defined as regions where enzyme activity exceeds the mean activity level by 50%. Temporal changes in BG activity further underscored the dynamic nature of root-microbe interactions. Extracellular enzyme activities indicated varying carbon, nitrogen and phosphorus acquisition strategies of rhizosphere microorganisms between top- and subsoil.

Conclusion

This study underscores the need to consider root system architecture in agricultural strategies, as it plays a crucial role in influencing microbial communities and enzyme activities, ultimately affecting carbon and nutrient cycling processes in top- and subsoil.

Background and aims

Plant-beneficial microbes may attenuate climate change-induced stresses on plants such as drought. We investigated the potential of beneficial microbial consortia (BMc) on plant growth and rhizosphere bacterial/archaeal community under drought.

Methods

Seeds of Zea mays B73 were inoculated with six plant-beneficial bacterial isolates either alone or combined in two three-member consortia (BMc1, BMc2) before sowing in loamy or sandy substrates in the greenhouse. A known effective consortium (BMc3) was included as positive control. Drought treatment was established with the BMc treatments by omitting watering in the last of the five weeks growth period. The maize growth in single and BMc treatments was determined. Colony-forming units (CFUs) of inoculants were evaluated by selective plating, and effects of BMc treatments on the native rhizosphere bacterial/archaeal community were assessed using 16S rRNA gene amplicon sequencing of basal root and root tip rhizosphere of plants grown in loam.

Results

In both substrates and water conditions, CFUs of single and BMc inoculations were higher at rhizosphere basal roots than root tips. Under well-watered conditions, seed inoculation with a single bacterial isolate had no effect on maize growth in both substrates. BMc treatment resulted in higher shoot (but not root) growth compared to non-inoculated controls in both water conditions in loam. The root zone was the most important driver for bacterial/archaeal beta-diversity, followed by water conditions, while BMc treatments showed no effect.

Conclusion

Our study suggests that BMc seed inoculation has the potential to attenuate drought stress during maize growth.

Background and aims

Numerous studies have demonstrated the enhancement effects of organic amendment additions on soil organic carbon (SOC) accumulation in agroecosystems. However, the effects of different organic amendment types on stable SOC formation through belowground inputs remain poorly understood, especially under stress conditions. This study aims to investigate the effects of three organic amendment types, namely lignin- (LDA), humus- (HDA), and vetch-derived (VDA) organic amendments, on the transformation process of ¹³C-rhizodeposits into SOC in sodic soil.

Methods

Sorghum bicolor L. was used in the experiments, and labelled using ¹³C-CO₂ for seven days after 75 days growing in a closed glass chamber.

Results

Our results showed that the nitrogen (N) compounds in the organic amendments accounted for 0%, 6.21%, and 11.37% of the LDA, HDA, and VDA, respectively. Organic amendments with low C/N ratios (HDA and VDA) enhanced the transformation of ¹³C-rhizodeposits into SOC, particularly into mineral-associated carbon (¹³C-MAOC). In addition, HDA and VDA substantially decreased the exchangeable sodium percentage (ESP) and increased the soil nutrient contents (e.g., total N and total phosphorus) compared with LDA, providing more favorable environmental conditions for both the crop and rhizosphere microbial growth. These effects, consequently, enhanced the deposition of the crop root exudates into ¹³C-MAOC in the sodic soil. Furthermore, compared with LDA, HDA and VDA enriched beneficial bacteria (e.g., Bacillaceae and Vermamoebidae) and inhibited pathogenic bacteria (Burkholderiaceae) through potential cross-trophic interactions, promoting crop growth and enhancing the production of root exudate deposition into ¹³C-MAOC.

Conclusion

Organic amendments with low C/N ratios enhanced the conversion of ¹³C-rhizodeposits into ¹³C-MAOC, by providing more favorable envrionmental conditions and enriching beneficial bacteria for plants. Our study provides a novel approach to selecting organic amendments with suitable and effective chemical structures to promote stable SOC formation through belowground inputs, especially under sodic conditions.