Nitrogen addition turns a temperate peatland from a near-zero source into a strong sink of nitrous oxide

Peatlands, as important global nitrogen (N) pools, are potential sources of nitrous oxide (N₂O) emissions. We measured N₂O flux dynamics in Hani peatland in a growing season with simulating warming and N addition for 12 years in the Changbai Mountains, Northeastern China, by using static chamber-gas chromatography. We hypothesised that warming and N addition would accelerate N₂O emissions from the peatland. In a growing season, the peatland under natural conditions showed near-zero N₂O fluxes and warming increased N₂O emissions but N addition greatly increased N₂O absorption compared with control. There was no interaction between warming and N addition on N₂O fluxes. Pearson correlation analysis showed that water table depth was one of the main environmental factors affecting N₂O fluxes and a positive relationship between them was observed. Our study suggests that the N₂O source function in natural temperate peatlands maybe not be so significant as we expected before; warming can increase N₂O emissions, but a high dose of N input may turn temperate peatlands to be strong sinks of N₂O, and global change including warming and nitrogen deposition can alter N₂O fluxes via its indirect effect on hydrology and vegetation in peatlands.

Competitiveness of Bradyrhizobium japonicum inoculation strain for soybean nodule occupancy

The competitiveness of Bradyrhizobium japonicum inoculation strain against indigenous rhizobia was examined in a soil pot experiment. The effect of inoculation strain was evaluated under different soil conditions: with or without previously grown soybean and applied commercial inoculant. Molecular identification of inoculation strain and investigated rhizobial isolates, obtained from nodules representing inoculated treatments, was performed based on 16S rDNA and enterobacterial repetitive intergenic consensus (ERIC) sequencing. Inoculation strain showed a significant effect on the investigated parameters in both soils. Higher nodule occupancy (45% vs. 18%), nodule number (111% vs. 5%), nodule dry weight (49% vs. 9%), shoot length (15% vs. 7%), root length (31% vs. 13%), shoot dry weight (34% vs. 11%), shoot nitrogen content (27% vs. 2%), and nodule nitrogen content (9% vs. 5%) was detected in soil without previously grown soybean and applied commercial inoculant. Soil had a significant effect on the shoot, root and nodule nitrogen content, while interaction of experimental factors significantly altered dry weight and nitrogen content of shoots, roots and nodules, as well as number of nodules. Nodulation parameters were significantly related with shoot dry weight, shoot and nodule nitrogen content. Symbiotic performance of inoculation strains in the field could be improved through co-selection for their competitiveness and effectiveness.

Regulation of nitrogen balance and yield on greenhouse eggplant under biochar addition in Mollisol

Maintaining nitrogen (N) balance and inhibiting N leaching loss in the soil-crop system is crucial to maintaining yield and reducing the environmental pollution. This study investigated the effects of soil NO₃⁻-N content and accumulation, eggplant yield, N leaching and balance response to biochar addition, including regular fertilisation and irrigation (W + F), biochar addition with regular fertilisation and irrigation (W + F + B), and biochar addition with 20% fertilisation and irrigation reduction (0.8W + 0.8F + B) treatments. Compared with W + F, W + F + B and 0.8W + 0.8F + B increased soil NO₃⁻-N content in 0–40 cm and soil NO₃⁻-N accumulation in 0–20 cm, and raised harvest index, N surplus and balance. Simultaneously, 0.8W + 0.8F + B compared to W + F enhanced N use efficiency and N partial factor productivity, conversely, it decreased N dry matter production efficiency, N surplus and balance. Stepwise regression analysis demonstrated that the effect of NO₃⁻-N leaching lasted in 60 cm under biochar addition in the first year, and lasted in 20 cm without biochar application in the next year. Altogether, biochar addition with 20% fertilisation and irrigation reduction is the most suitable management strategy to decrease N surplus and leaching, and maintain eggplant N uptake in a two-year cycle system on greenhouse vegetables in Mollisols.

Changing in the production of anticancer drugs (vinblastine and vincristine) in Catharanthus roseus (L.) G. Don by potassium and ascorbic acid treatments

Catharanthus roseus seedling was treated with different concentrations (1.5, 3.16, 15, and 30 mmol) and forms (K₂SO₄ and KNO₃) of potassium (K⁺) via Hoagland’s nutrient solution. Ascorbic acid (AsA) was sprayed twice (plant days 68 and 78) with different concentrations (750 and 1 500 mg/L) on the leaves. Vinblastine, vincristine, tryptophan contents, D4H and DAT genes expression, peroxidase activity, and H₂O₂ content of leaves were measured. Potassium in KNO₃ form increased vinblastine (60%) and vincristine (50%), compared to 30% and 20% using K₂SO₄. Vinblastine and vincristine inhibit microtubule assembly and ultimately metaphase-arrested caused by the polymerisation. The genes expression was higher 3 times in KNO₃ and 2.5 times in K₂SO₄ in excess of K⁺. Foliar application of 750 mg/L AsA led to an increase in vinblastine (20%) and vincristine (16%). Both concentrations of AsA had the same additional effect on the expression of D4H and DAT about 30% and 60%, respectively, compared to the control plant. Tryptophan decreased 2.5 times in excess of K⁺ and 35% due to the exterior of AsA. H₂O₂ decreased while peroxidase activity increased along with AsA treatment. A positive interaction existed between the K⁺ and AsA on the amount of vinblastine, vincristine, tryptophan, and gene expression.

Decomposition of rice straw residues and the emission of CO2, CH4 under paddy rice and crop rotation in the Vietnamese Mekong Delta region – A microcosm study

This study investigated the influence of soil undergoing different crop rotations on the CH₄, CO₂ emissions, and decomposition of rice straw. The studied soil undergoing crop rotation systems were rice-rice-rice (SR) and baby corn-rice-mungbean (SB). Two main microcosm set-ups: anaerobic (SR-AN, SB-AN) and aerobic (SR-AE, SB-AE) conditions. Litter bags containing rice stems were inserted into the soil and recollected at different time points for chemical analysing and the gas sampling was collected to measure the CO₂ and CH₄ emissions. The results indicated that the total carbon (TC) decreased around 30%, and the TC removal in anaerobic was significantly higher than in aerobic conditions. The residue cellulose content varied in a range from 68.2% to 78.6%, while the hemicellulose content varied from 57.4% to 69.3% at day 50 after incorporation. There were no significant differences in the total nitrogen removal, cellulose, hemicellulose, and lignin contents among the microcosm set-ups. CO₂ emission increased in all the microcosm set-ups with the treatments without rice straw (CTSR, CTSB) in both aerobic and anaerobic conditions. CH₄ release in the SR-AN treatments did not differ significantly compared with the SB-AN treatments. This study confirmed that the decomposition of rice straw residues is faster in the anaerobic paddy soil condition compared to the aerobic crop rotation condition.

Micro plastics in soil ecosystem – A review of sources, fate, and ecological impact

In recent years, environmental experts and stakeholders have paid increased attention to the pollution of micro plastics in the soil. As persistent pollutants, micro plastics have a significant impact on the soil ecology, agricultural production, and the overall health of the ecological environment. Micro plastics can influence soil bio-physicochemical properties and the mobility of other contaminants in soil, with potentially significant implications on soil ecosystem functionality. Thus, functions including litter decomposition, soil aggregation or those related to nutrient cycling can be altered. Furthermore, micro plastics can influence soil biota at different trophic levels, and even threaten human health through food chains. Despite this potential negative interaction, there is limited research on micro plastics in the soil environment. The primary goals of this review are to summarise the sources, distribution characteristics, migration and degradation laws of micro plastics in the soil ecosystem, to summarise the combined effects of micro plastics and other pollutants in the soil ecosystem, to analyse the effects of micro plastics on soil physical and chemical properties, animals, plants, and microorganisms, and to reveal the effects of micro plastics on soil ecosystem and to according to the distribution characteristics of soil micro plastics, degradation, migration and ecological effects, propose pollution control measures. This current review will provide a comprehensive understanding of soil pollution by micro plastic and offer a scientific basis for the formulation of novel management practices that will protect and improve soils, and contribute to the sustainable development of the ecological environment and highlight important areas for future research.

Crop sequence effects on energy efficiency and land demand in a long-term fertilisation trial

The effect of crop sequences (CR – continuous winter rye; CropR – three-field crop rotation of winter rye-spring barley-bare fallow) and fertilisation systems (unfertilised control, mineral fertiliser (NPK), farmyard manure (FYM)) on crop yield, energy efficiency indicators and land demand were analysed in a long-term experiment under Pannonian climate conditions. Due to lower fuel consumption in the bare fallow, the total fuel consumption for CropR was 27% lower than in CR. It was for NPK and FYM fertilisation by 29% and 42% higher than in the control. Although the energy output was lower in CropR than CR, the energy use efficiency for grain production increased by 35% and for above-ground biomass production by 20%. Overall crop sequences, the NPK treatment had higher crop yields, energy outputs and net-energy output with a lower energy use efficiency than the unfertilised control. CropR increased the land demand just by 20% in comparison to CR, although one-third of the land was not used for crop production. The land demand could be decreased with fertilisation by 50% (NPK) or 48% (FYM). A bare fallow year in the crop rotation decreased the crop yield, energy input and increased the energy use efficiency and land demand.

Effect of coexisting metal ions on bio-precipitation of Cu2+ phosphate by Rahnella sp. LRP3 and its stability in soil

The phosphate precipitation of heavy metal induced by microorganisms plays an important role in immobilising heavy metal in soil. However, there is little knowledge about the effect of coexisting metal ions on the induction of Cu phosphate mineral and its stability. In this paper, the Cu phosphate precipitations, coexisting with Pb²⁺ or Ca²⁺ induced by strain LRP3, were characterised, and the stabilisation of the induced phosphate precipitates was also studied. The coexistence of Cu with Pb or Ca decreased the removal efficiency of Cu²⁺ by 17.18% and 9.78%, respectively, indicating the competitive adsorption between cations. Strain LRP3 could induce a new phosphate mineral of CuCa₁₀(PO₄)₇ when coexisting with Ca and also generate the phosphate minerals of Pb(H₂PO₄)₂ and Cu₃(PO₄)₂ when coexisting with Pb. The Cu-Ca coprecipitate could enhance the stability of Cu in dilute acid solution and soil with or without a plant, whiles the Cu-Pb one showed the opposite effect. Also, the Cu-induced phosphate precipitates were relatively stable and not easy to be absorbed by Pakchoi (Brassica rapa var. chinensis). The results showed that the influence of coexisting metal ions should be considered when phosphate mineralisation technology is used to immobilise heavy metals in the environment.

Chitosan in modern agriculture production

In the perspective of return to nature, using scientific and technical progress for improved living standards, people began to search for solutions to alleviate environmental pollution. Researchers intend to make clean, affordable products that are gentle yet effective. Chitosan derived from the exoskeleton of crustaceans, cuticles of insects, cell walls of fungi, and some algae are renowned for many decades to exhibit biotic properties, especially anti-microbial characteristics. Here we review each ingredient for sourcing organic chitosan, with clean raw materials that can make pure, rich, and powerful products working naturally. Our study elaborates advances and utilisation of chitosan for industrial control-release fertilisers by physical, chemical, and multifaceted formulations such as water-retaining super absorbent, polyacrylic acid, and resins. Plant growth-promoting properties of chitosan as a growth regulator, pest/disease resistance, signalling regulation, effect on nuclear deformation, and apoptosis. Chitosan can improve the plant defence mechanism by stimulating photochemistry and enzymes related to photosynthesis. Furthermore, electrophysiological modification induced by chitosan can practically enable it to be utilised as a herbicide. Chitosan has an excellent role in improving soil fertility and plant growth as well as plant growth promoters. It is concluded, chitosan can play a key role in modern agriculture production and could be a valuable source promoting agricultural ecosystem sustainability. Future suggestions will be based on current achievements and also notable gaps. In addition, chitosan has a huge contribution to reducing fertilisers pollution, managing agricultural pests and pathogens in modern-day agriculture.

Effects of wheat root exudates on bacterial communities in the rhizosphere of watermelon

In this study, we investigated the effects of wheat root exudates on soil bacterial communities in the watermelon rhizosphere using quantitative PCR and Illumina MiSeq sequencing. The qPCR results showed that wheat root exudates significantly increased the abundance of total bacteria, Pseudomonas, Bacillus and Streptomyces spp. Illumina MiSeq sequencing results showed that wheat root exudates significantly changed the bacterial community structure and composition. These results indicated that plant root exudates play a role in plant-to-plant signalling, strongly affect the microbial community composition.