Effect of pyroligneous acid on soil urease, amidase, and nitrogen use efficiency by Chinese cabbage (Brassica campestris var. Pekinensis)

Wood Distillate Interactions with Urea in Soil: A First Step to Developing a Slow-Release Next-Generation Fertilizer

We tested the ability of wood distillate (WD) to interact with urea in agricultural soil. WD is a sustainable material that has been addressed as a promising alternative to synthetic soil corroborants. However, there is little information about the effect of WD on the nitrogen cycle. In this study, soils with different amounts of WD and with/without urea were tested for ammonium, urease, nitrate/nitrite, and potential nitrification activity at different points in a 30 day time frame. High concentrations of WD (1-2%) inhibited the hydrolysis of urea and the oxidation of ammonium to nitrate. Thermal desorption coupled to GC-MS and high-performance liquid chromatography-tandem mass spectrometry characterization allowed us to reveal that WD-urea interactions mainly involve lignin-derived compounds in the distillate, such as catechol, resorcinol, and syringol. This study provides the first evidence of a strong interaction between WD and urea in soil that could be used to develop slow-release fertilizers.

The migration and transformation mechanism of vanadium in a soil-pore water-maize system

The migration mechanism of vanadium (V) in the soil-pore water-maize system has not been revealed. This study conducted pot experiments under artificial control conditions to reveal V's distribution and transport mechanism under different growth stages and V content gradient stress. The V content in the soil pore water gradually increased by an order of magnitude. The V content of pore water in the no-plant group was higher than that in the plant group, indicating that the maize roots absorbed V. The V exists in the form of pentavalent oxygen anions, in which H2VO4- occupies the most significant proportion. With increasing V content, the root area, root number, root length, and tip number decreased significantly. The malondialdehyde content in maize leaves showed an increasing trend, indicating the degree of lipid peroxidation was gradually enhanced. The V content was in the order of root > leaf > stem > fruit and maturity stage > flowering stage > jointing stage, respectively. The transfer coefficient reached a maximum under natural conditions, and increased gradually with the growth. The results of synchrotron radiation X-ray absorption near edge structure (XANES) analysis showed that Fe in maize roots mainly comprised of Fe2O3 and Fe3O4. The Fe in the soil is primarily existed in lepidocrocite and Fe2O3. The μ-XRF analysis showed that V and Fe enriched in the roots with a positive relationship, indicating the synergistic absorption of V and Fe by roots. Part of the Fe2+ reduced V5+ to V4+ or V3+ in the forms of VO2+, V(OH)2+, or V(OH)3 (s), and fixed V at the root. Soil weak acid-soluble fraction V and soil total V were vital factors to maize extraction. This study provides new insights into V biogeochemical behavior and a scientific basis for correctly evaluating its ecological and human health risks.

Co-application of concentrated biogas slurry and pyroligneous liquor mitigates ammonia emission and sustainably releases ammonium from paddy soil

Biogas production causes vast amounts of biogas slurry (BS). Application of BS to croplands can substitute chemical fertilizers while result in higher ammonia emissions. Tremendous variation of ammonium concentration in different BSs induces imprecise substitution, while concentrated BS holds higher and more stable ammonium. Pyroligneous liquor, an acidic aqueous liquid from biochar production, can be used with concentrated BS to reduce ammonia emission. However, the effects of combining concentrated BS with pyroligneous liquor on ammonia emission and soil (nitrogen) N transformation have been poorly reported. In this study, a field experiment applying concentrated BS only, or combining with 5 %, 10 %, and 20 % pyroligneous liquor (v/v) for substituting 60 % N of single rice cultivation was conducted by contrast with chemical fertilization. The results showed that substituting chemical N fertilizers with concentrated BS increased 24.6 % ammonia emission. In comparison, applying 5 %, 10 %, and 20 % pyroligneous liquor with concentrated BS reduced 4.9 %, 20.3 %, and 24.4 % ammonia emissions, respectively. Applying concentrated BS with more pyroligneous liquor preserved higher ammonium and dissolved organic carbon in floodwater, and induced higher nitrate concentration after fertilization. Whereas soil ammonium and nitrate contents were decreased along with more pyroligneous liquor application before and after the topdressing and exhibited sustainable release until rice harvest. In comparison, the soil N mineralization and nitrification rates were occasionally elevated, while the activities of soil urease, protease, nitrate reductase, and nitrite reductase had multiple responses. Applying concentrated BS only, or combining with 5 %, 10, and 20 % pyroligneous liquor, have little effect on soil basic properties but inorganic N. In summary, applying concentrated BS with >10 % pyroligneous liquor could preserve more N with sustainable release and potentially lower N loss to the atmosphere, and we proposed that applying 13.5 % pyroligneous liquor in concentrated BS could achieve maximum soil fertility and minimum ammonia emission.

Reducing nitrogen leaching using wood vinegar treated in urea-fertilized soil

Wood vinegar (WV) is known to retard the release of ammonium (NH4+) from urea by inhibiting urea hydrolysis. However, the effect of WV on nitrogen leaching in soil is not known, and there are few studies on the effect of WV on microbial activity although WV exhibits antibacterial properties against pathogens in agriculture. Therefore, the purpose of this study was to investigate the effect of WV on controlling nitrogen leaching and soil microbial activity. Soils were treated with urea and WV, and the available inorganic nitrogen concentrations in the soil were compared with those from soils treated with N-(n-butyl)thiophosphoric triamide (NBPT), a commonly used urease inhibitor. The nitrate concentration in the soil was significantly decreased in the WV treatment, although the ammonium concentration was not affected by the WV treatment. Basal soil respiration was significantly increased in the WV and NBPT treatments although the microbial biomass was increased in the urea only treatment. The ammonium nitrogen concentration in the leachate was not significantly different in the WV and urea-treated soil compared to the urea-only treatment. However, the nitrate leaching increased in the soil treated only with urea at 16 days after the treatment although there was no statistically significant difference in the total leached nitrate. Therefore, WV can be used to reduce nitrogen leaching and enhance soil microbial activity.

Waste seaweed compost and rhizosphere bacteria Pseudomonas koreensis promote tomato seedlings growth by benefiting properties, enzyme activities and rhizosphere bacterial community in coastal saline soil of Yellow River Delta, China

This study investigated the effects of waste seaweed compost and rhizosphere bacteria Pseudomonas koreensis HCH2-3 on the tomato seedlings growth in coastal saline soils and chemical properties, enzyme activities, microbial communities of rhizosphere soil. Microcosmic experiment showed that the seaweed compost and rhizosphere bacteria (SC + HCH2-3) significantly alleviated the negative effects of salinity on the growth of tomato seedlings. SC + HCH2-3 amendment significantly increased the plant height and root fresh biomass of tomato seedling by 105.59% and 55.60% in the coastal saline soils, respectively. The soil properties and enzyme activities were also dramatically increased, indicating that the nutrient status of coastal saline soil was improved by SC + HCH2-3 amendment. In addition, Proteobacteria, Actinobacteriota and Firmicutes were the dominant phyla in the rhizosphere soil after adding seaweed compost and rhizosphere bacteria P. koreensis HCH2-3. The relative abundances of Massilia, Azospira, Pseudomonas and Bacillus increased in treatment SC + HCH2-3. Especially, the beneficial bacteria genera, such as Pseudomonas, Bacillus and Azospira, were significantly correlated with the increases of contents of total nitrogen, nitrate nitrogen and ammonium nitrogen in tomato rhizosphere soil samples. Consequently, adding waste seaweed compost and rhizosphere bacteria P. koreensis HCH2-3 into coastal saline soil was suggested as an effective method to relieve salt stress of tomato plants.

Understanding the multifunctionality of pyroligneous acid from waste biomass and the potential applications in agriculture

Efforts have been directed to the development of environmentally friendly processes and manufacturing of green products, use of renewable energy and more sustainable agricultural practices. Pyroligneous acid (PA) is a byproduct of biomass pyrolysis that consists of a complex mixture of bioactive substances. The complexity and richness of PA composition have opened a window for PA application in agriculture and mitigation of environmental pollution. This review brings a brief historical on the use of PA and regulatory policies adopted in Brazil, China, Japan and Thailand for PA application in agriculture. The composition and stability of PAs of several origins are presented, together with a discussion of the use of PA to boost plant growth and crop productivity, remove toxic metals from soil, inhibit soil ureases, mitigate the emission of greenhouse gases, control phytopathogen proliferation and weed dissemination. A great variety of biomass types are reported as feedstock to produce PA with distinct chemically diverse and active substances at wide-ranging concentrations. PA has been shown to successfully improve farming practices in a more sustainable fashion. The disclosure of the mechanisms of action that drive the PA's effects, together with the pursue of safety and efficacy data in a case-by-case way to address toxicity and shelf stability, will be valuable to expand the use of PA worldwide for food production.

Combinations of waste seaweed liquid fertilizer and biochar on tomato (Solanum lycopersicum L.) seedling growth in an acid-affected soil of Jiaodong Peninsula, China

Biochar application is an effective strategy for improving soil degradation and productivity. However, the effects of the combination of biochar and other fertilizers to improve seedling growth in abiotic stress-affected soils remains unknown. We investigate the effect of biochar derived from reed straw (RBC) and waste seaweed liquid fertilizer (SLF) on tomato (Solanum lycopersicum L.) seedling growth in an acid-affected soil of Jiaodong Peninsula, China. The results revealed RBC, SLF, and the combination of RBC with SLF (RBC+SLF) significantly elevated the dry weight of tomatoes by 23.33 %, 29.93 %, and 63.66 %, respectively. The malondialdehyde content in the tomato seedling roots, stems, and leaves was significantly lower in the RBC+SLF treatment, which might be related to the enhanced contents of proline, soluble sugar, and soluble protein. The synthesis and accumulation of zeatin riboside, indole-3-acetic acid, and gibberellic acid 3 in tomato under RBC+SLF amendment may be attributed to the enhanced plant growth. Moreover, RBC, SLF, and RBC+SLF improved the soil status (including ammonium nitrogen, nitrate nitrogen, laccase, and urease) in the acid-affected soil. Biochar and waste seaweed liquid fertilizer significantly increased the relative abundance of Pseudomonas and Azospira (beneficial bacteria) in tomato rhizosphere. The microbial amino acid metabolism was associated with changes in soil properties and enzyme activities. Consequently, biochar and waste seaweed liquid fertilizer are viable soil conditioners for acid-affected soil.

Potential impact of polyethylene microplastics on the growth of water spinach (Ipomoea aquatica F.): Endophyte and rhizosphere effects

Microplastic contamination has received much attention, especially in agroecosystems. However, since edible crops with different genetic backgrounds may present different responses to microplastics, more research should be conducted and focused on more edible crops. In the current study, pot experiments were conducted to investigate the potential impact of polyethylene microplastic (PE) (particle sizes: 0.5 μm and 1.0 μm, addition levels: 0 (control), 0.5% and 1.0% (w/w)) addition on the physiological and biochemical variations of I. aquatica F.. The results indicated that PE addition caused an increase in the soil pH and NH₄⁺-N and soil organic matter contents, which increased by 10.1%, 29.9% and 50.1% when PE addition at A10P0.5 level (10 g (PE) kg^-1 soil, particle size: 0.5 μm). While, PE exposure resulted in a decrease in soil available phosphorus and total phosphorus contents, which decreased by 53.9% and 10.5% when PE addition at A10P0.5 level. In addition, PE addition altered the soil enzyme activities. Two-way ANOVA indicated that particle size had a greater impact on the variations in soil properties and enzyme activities than the addition level. PE addition had a strong impact on the rhizosphere microbial and root endophyte community diversity and structure of I. aquatica F.. Two-way ANOVA results indicated that the particle size and addition level significantly altered the α-diversity indices of both rhizosphere microbial and root endophyte (P < 0.05, P < 0.01 or P < 0.001). Moreover, PE was adsorbed by I. aquatica F., which was clearly observed in the transverse roots and significantly increased the H₂O₂, ·O₂^-, malondialdehyde and ascorbic acid contents in both the roots and aerial parts of I. aquatica F., leading to a decrease in I. aquatica F. biomass. Overall, the current study enriches the understanding of the effect of microplastics on edible crops.

Comparative study on plant growth-promoting bacterial inoculation by irrigation and spraying for promoting Bidens pilosa L. phytoremediation of cadmium-contaminated soil

A field study was conducted to compare FM-1 inoculation by irrigation and spraying for promoting Bidens pilosa L. phytoremediation of cadmium (Cd)-contaminated soil. Cascading relationships between bacterial inoculation by irrigation and spraying and soil properties, plant growth-promoting traits, plant biomass and Cd concentrations in Bidens pilosa L. were explored based on the partial least squares path model (PLS-PM). The results indicated that inoculation with FM-1 not only improved the rhizosphere soil environment of B. pilosa L. but also increased the Cd extracted from the soil. Moreover, Fe and P in leaves play vital roles in promoting plant growth when FM-1 is inoculated by irrigation, while Fe in leaves and stems plays a vital role in promoting plant growth when FM-1 is inoculated by spraying. In addition, FM-1 inoculation decreased the soil pH by affecting soil dehydrogenase and oxalic acid in cases with irrigation and Fe in roots in cases with spraying. Thus, the soil bioavailable Cd content increased and promoted Cd uptake by Bidens pilosa L. To address Cd-induced oxidative stress, Fe in leaves helped to convert GSH into PCs, which played a vital role in ROS scavenging when FM-1 was inoculated by irrigation. The soil urease content effectively increased the POD and APX activities in the leaves of Bidens pilosa L., which helped alleviate Cd-induced oxidative stress when FM-1 was inoculated by spraying. This study compares and illustrates the potential mechanism by which FM-1 inoculation can improve the phytoremediation of Cd-contaminated soil by Bidens pilosa L., suggesting that FM-1 inoculation by irrigation and spraying is useful in the phytoremediation of Cd-contaminated sites.

Potassium fulvic acid alleviates salt stress of citrus by regulating rhizosphere microbial community, osmotic substances and enzyme activities

Salt stress damage to plants has been becoming a global concern for agriculture. The application of potassium fulvic acid (PFA) is a promising strategy to alleviate the damage to plants and improve soil quality. However, the study of PFA on plant growth and rhizosphere microbial community remains limited. In this study, microcosmic experiments were conducted to verify the effect of PFA on citrus. Trifoliate orange (Poncirus trifoliata), the most important citrus rootstock, was used to evaluate the effect of PFA on salt damage. The results showed that PFA significantly increased the contents of chlorophyll a, chlorophyll b and carotenoid by 30.09%, 17.55% and 27.43%, and effectively avoided the yellowing and scorching of leaves under salt stress. Based on the results of two-way ANOVA, the mitigation of salt stress on trifoliate seedlings primarily attributed to the enhancement of protective enzyme activities, K⁺/Na⁺ ratio and the contents of soluble sugar, soluble protein and proline. Moreover, PFA enhanced neutral protease (S-NPT), sucrase (S-SC) and urease (S-UE) of rhizosphere soil and improved soil nutrition status. The abundance of Bacillus, a kind of rhizosphere beneficial bacteria, was improved by PFA under salt stress, which was mainly associated with the increased activities of S-NPT, S-SC and S-UE. Overall, the application of PFA showed great potential for the alleviation of salt damage on citrus.