Phosphorus (P) recycling or reuse by pyrolyzing crop residue has recently elicited increased research interest. However, the effects of feedstock and pyrolysis conditions on P species have not been ...fully understood. Such knowledge is important in identifying the agronomic and environmental uses of biochar. Residues of three main Chinese agricultural crops and the biochars (produced at 300°C-600°C) derived from these crops were used to determine P transformations during pyrolysis. Hedley sequential fractionation and (31)P NMR analyses were used in the investigation. Our results showed that P transformation in biochar was significantly affected by pyrolysis temperature regardless of feedstock (Wheat straw, maize straw and peanut husk). Pyrolysis treatment transformed water soluble P into a labile (NaHCO3-Pi) or semi-labile pool (NaOH-Pi) and into a stable pool (Dil. HCl P and residual-P). At the same time, organic P was transformed into inorganic P fractions which was identified by the rapid decomposition of organic P detected with solution (31)P NMR. The P transformation during pyrolysis process suggested more stable P was formed at a higher pyrolysis temperature. This result was also evidenced by the presence of less soluble or stable P species, such as such as poly-P, crandallite (CaAl3(OH)5(PO4)2) and Wavellite (Al3(OH)3(PO4)2·5H2O), as detected by solid-state (31)P NMR in biochars formed at a higher pyrolysis temperature. Furthermore, a significant proportion of less soluble pyrophosphate was identified by solution (2%-35%) and solid-state (8%-53%) (31)P NMR, which was also responsible for the stable P forms at higher pyrolysis temperature although their solubility or stability requires further investigation. Results suggested that a relatively lower pyrolysis temperature retains P availability regardless of feedstock during pyrolysis process.
Sewage sludge is by-product in the process of centralized wastewater treatment. Land application of sewage sludge is one of the important disposal alternatives. Mudflats in the interaction zone ...between land and sea can be important alternative sources for arable lands if amended by large amount of organic fertilizers. Rich in organic matter and other nutrients, sewage sludge has been considered as the economic choice for an initial fertility driver. However, sewage sludge amendment has been greatly hampered due to availability of potential toxic metals. Using sewage sludge in compliance with the national standards for agricultural usage could avoid the accumulation of heavy metals. Nevertheless, it is not clear whether massive input of sewage sludge would increase heavy metals concentration in crops. The objective of this study was to investigate impact of sewage sludge amendment (SSA) as an initial fertility driver by one-time input, with the rates of 0, 30, 75, 150, and 300tha−1, on biomass of green manures, soil chemical properties, and growth and heavy metals uptake of maize (Zea mays L.) grown in mudflat soil. Results showed that one-time sewage sludge amendment promoted an initial fertility for infertile mudflat soil, supported growth of ryegrass as the first season green manure. By tilled ryegrass, it modified the chemical properties of mudflat soil by increasing soil organic carbon, total and available N and P, and decreasing soil salinity and pH, which promoted subsequent growth of two green manures for sesbania and ryegrass. The sewage sludge as an initial fertility driver combined with planting and tilling green manures, increased dry matter of the aerial part and grain yield of maize grown in mudflat soil. Cd and Ni concentrations in grain of maize were positively correlated with sewage sludge amendment rates. Importantly, heavy metal concentrations in grain of maize at all SSA rates did not exceed the safety standard for food in China (GB 2762-2012). The study suggests that sewage sludge can be applied as an initial fertility driver for mudflat soil amendment, which provides an innovative solution for arable land resources and solid waste disposal.
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•Sewage sludge amendment is an innovative solution for new arable land resources and solid waste disposal.•Sewage sludge as an initial fertility driver combined with planted and tilled green manures decreased salinity and pH, and increased OC, N and P concentrations in mudflat soil.•The initial fertility driver increased grain yield of maize•Heavy metals concentrations in grain of maize did not exceed the safety standard for food.
Salinity is one of the main environmental constraints in soil restricting plant growth and agricultural productivity; however, the utilization of salt-affected land brings substantial benefits. This ...study investigated an in situ remediation method that involved planting Jerusalem artichokes in naturally occurring saline-alkali soils with different salinities (g salt kg−1 soil), specifically, high salinity (H, >4.0), moderate salinity (M, 2.0–4.0) and low salinity (L, 1.0–2.0), in the coastal saline zone of southeast China. We compared these conditions with corresponding soil controls that were not planted. Soil pH and salinity were increased in bulk and unplanted control soils compared to rhizosphere soils. Neutral phosphatase and invertase showed a significant negative correlation with soil salinity, and there was a significant positive correlation between these two enzymes. While catalase activity decreased in the reverse order. The lowest calcite, muscovite and quartz contents as well as the highest chlorite and albite contents were found in the control soils. Planting Jerusalem artichoke also enhanced bacterial microbiota in saline-alkali soils. Bulk soil Operational Taxonomic Units (OTUs) numbers at high (H), moderate (M) and low (L) salinity were 4177, 5325 and 3672, respectively, and they were 1.27, 1.02 and 1.25 times lower than those in rhizosphere soil. This finding demonstrated that the Jerusalem artichoke played a significant role in enhancing soil microbial richness. In conclusion, Jerusalem artichoke could improve the physical and chemical properties of the soil by released root exudates into soil, increased the diversity and richness of soil microbial communities, and so on, so as to achieved the effect of improved the saline-alkali soil in coastal areas of Dafeng, Jiangsu Province, which provided scientific basis for elaborated the salt-tolerant characteristics of Jerusalem artichoke and improved the mechanism of coastal saline soil function.
•The utilization of salt-affected land brings substantial benefits;•Planting JA decreased Soil pH and salinity and optimized soil structure;•Planting JA enhanced phosphatase and invertase activities;•Planting JA enhanced bacterial microbiota•Planting JA could improve saline-alkali soil quality
Coastal mudflat areas are regarded as the important reserve land resource in China. Rational exploitation and development of the mudflat areas can relieve the stress of inadequate land resources. ...Probing into the developing models of resource exploitation of coastal tidal mudflats is one of the important components of achieving the sustainable development in the coastal areas. Therefore, the development history of coastal mudflats after 1950s in China is briefly introduced in this paper. Then, the status in quo of the modes of development and utilization of coastal mudflat in China the paper is reviewed with a special attention payed to the agricultural use of coastal resource, especially halophytes and improved salt-tolerant varieties planting, agricultural dyke pond and coastal saline-alkali soil remediation. Based on related research frontier, sustainable developmental prospects of these coastal areas are presented as well.
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•Coastal mudflat areas are as the important reserve land resource in China•Exploitation of mudflat can relieve the stress of inadequate land resources•Aquaculture and agriculture are the primary modes of utilization of mudflats•In the exploitation of mudflats, environmental problems have arisen•We offer some suggestions for the sustainable development of mudflat areas
Coastal saline-alkali soil can be transformed to agricultural soil with sewage sludge amendment. However, sewage sludge contains a large number of microplastics (MPs), and the fate of MPs in ...sludge-treated saline-alkali soil needs to be studied. Therefore, we investigated the accumulation and migration of MPs, and their influencing factors in saline-alkali soil after one-time sewage sludge application (0, 25, 50, 100 and 200 t ha−1 SSA). The results indicated that sewage sludge input contributed to MP accumulation in soil, and the MP abundance in 20–40 cm soil was significantly lower than that in 0–20 cm soil. Fragments and fibers were the most abundant MPs in soil, and the proportions of fragments and 50–200 µm MPs in 20–40 cm soil were lower than those in 0–20 cm soil, while the < 50 µm MP proportion was higher than that in 0–20 cm soil. Correlation analysis showed that MP accumulation rate (0–40 cm) and migration rate (20–40 cm) were negatively correlated with soil organic matter (SOM) content and SSA, but positively correlated with soil pH. Stepwise regression analysis further showed that SOM and SSA were the main factors affecting MP accumulation rate, which explained 47.7% and 46% of its variation, respectively, while pH was the crucial factor affecting the migration rate of MPs, followed by EC and SSA. In conclusion, SSA caused MP accumulation in saline-alkali soil, and SSA primarily affected the MP abundance, while soil OM, pH and EC directly affected MP migration in soil.
•The MP abundance was increased with sewage sludge application rates.•Compared with 0–20 cm soil, there were less MPs but more small size (<50 µm) MPs in 20–40 cm soil.•Soil OM, pH, EC can directly affect MP migration in soil.•MPs tended to migrated to deeper soil (>40 cm) rather than 20–40 cm soil.
The changes in content of endogenous hormones in stolons and tubers of Jerusalem artichoke (Helianthus tuberosus L.) regulate tuber growth, but the specific knowledge about the importance of balance ...among the endogenous hormones is lacking. Two varieties of Jerusalem artichoke (NY-1 and QY-2) were tested for the endogenous zeatin (ZT), auxins (IAA), gibberellins (GA3) and abscisic acid (ABA) in regulating sugar and dry matter accumulation in tubers. The dry matter content and sugar accumulation in tubers were correlated positively with endogenous ZT and negatively with GA3 content and GA3/ABA and IAA/ABA content ratios. Throughout the tuber formation, ZT content was higher in NY-1 than QY-2 tubers, whereas ABA content was higher in QY-2 than NY-1 tubers. The content ratios GA3/ABA and IAA/ABA were greater in NY-1 than QY-2 before tuber initiation, but QY-2 surpassed NY-1 during the tuber growth stage. The GA3/ABA and IAA/ABA content ratios declined during tuber growth. The results suggested that a dynamic balance of endogenous hormones played an important role in tuber development.
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•Jerusalem artichoke is tolerant to various environmental stresses.•Jerusalem artichoke is an alternative as feedstock for biorefinery.•The GA3/ABA and IAA/ABA were greater in NY-1 than QY-2 before tuber initiation.•The GA3/ABA and IAA/ABA in QY-2 surpassed NY-1 during the tuber growth stage.•A dynamic balance of endogenous hormones was important for tuber development.
Robinia pseudoacacia is the main arbor species in the coastal saline–alkali area of the Yellow River Delta. Because most studies focus on the aboveground parts, detailed information regarding root ...functioning under salinity is scare. Root traits of seedlings of R. pseudoacacia including morphological, physiological and growth properties under four salinity levels (CK, 1‰, 3‰ and 5‰ NaCl) were studied by the pot experiments to better understand their functions and relationships with the shoots. The results showed that seedling biomass decreased by the reduction of root, stem and leaf biomass with the increase of salinity levels. With increasing salinity levels, total root length (TRL) and total root surface area (TRSA) decreased, whereas specific root length (SRL) and specific root area (SRA) increased. Salt stress decreased root activity (RA) and the maximum net photosynthetic rate (Amax) and increased the water saturation deficit (WSD) significantly in the body. Correlation analyses showed significantly correlations between root morphological and physiological parameters and seedling biomass and shoot physiological indexes. R. pseudoacacia seedlings could adapt to 1‰ salinity by regulating the root morphology and physiology, but failed in 5‰ salinity. How to adjust the water status in the body with decreasing water uptake by roots was an important way for R. pseudoacacia seedlings to adapt to the salt stress.
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•Salt stress is the key limited factor of plantation construction in the Yellow River Delta.•The growth of Robinia pseudoacacia seedlings was significantly inhibited by saline–alkali degrees.•Eco-physiological adaptability of R. pseudoacacia was determined by aboveground parts and root.•To control water uptake of R. pseudoacacia seedling by rhizosphere was an important way under salt stress.
To study the forms and vertical distributions of soil phosphorus (P) in a newly formed coastal wetland in the Yellow River Delta estuary, China, two transects from the Yellow River bank to the bare ...beach that encompassed a variety of vegetation covers were selected for soil sampling and field monitoring. A modified sequential fractionation method was used to partition the soil P, and the related properties were measured. The soils in this newly formed estuarine coastal wetland, only covered by salt‐tolerant plant communities, are strongly alkaline (pH 8.4–9.2) with high soil salinity (mean, 6.23‰). The content of total P (Pt) ranged from 548.3 to 728.5 mg kg−1 in these soils. Dil.HCl‐Pi (extracted with 1 M HCl) was the highest P fraction (mean, 58.1–72.8%), whereas NaHCO3‐Pi was the lowest fraction (mean, 0.4–1.7%) of all the P forms. Vertical distributions showed a surface accumulation of Resin‐P. Resin‐P, NaHCO3‐Pi, NaOH‐Pi, and Conc.HCl‐Pi (extracted with 11.3 M HCl) were positively or negatively correlated with some properties. Attributed to the spatial deposition and hydrology, Dil.HCl‐Pi presented a poor correlation with Ca. The results also showed some clear differences in the P forms and P availability among vegetation covers. The vegetation cover could modify the soil quality, and Suaeda heteroptera, as the pioneer plant community species, significantly enhanced the freely exchangeable Pi and increased P availability, providing important ideas for salt‐soil sustainable use.
Land degradation resulting from soil salinization is becoming a growing menace in almost all over the world. The degraded soil shows poor performance in water conductance and soil aeration, which ...threatens plant growth and development. Therefore, to discover the resistance genes and breed plant with stress tolerance are necessary. The modern molecular biotechnology makes the plant with enhanced adaption possible. To do this, KvHSP70 with 1950 bp open reading frame (ORF) from Kosteletzkya virginica was isolated, studied, and transformed into tobacco for functional study. Our research showed that it encodes a typical HSP70 protein with 649 amino acids and it could be induced by salt, high temperature, drought, and abscisic acid (ABA). The transgenic tobacco with it overexpression had higher chlorophyll content, less electrolyte leakage, lower water potential and increased proline content under salt stress. Meanwhile, the transgenic acquired superior antioxidant enzyme activities and decreased MDA content. All results highlight the significance of the new found gene in breeding salt resistant plants with molecular manipulation. Hence, K. virginica provides us with helpful information and gene resources to culture new variety adapted to salt‐affected soil and available for land rehabilitation perhaps in the future.
Applying sewage sludge to mudflat salt‐soils can rapidly improve soil physicochemical properties and enhance pollution potential. Nevertheless, the heavy metal distribution in leachate and mudflat ...salt‐soils with sludge amendment remains unclear. The present work was aimed primarily at investigating the fates of Cd, Cu, Pb, and Zn in mudflat salt‐soils amended by sludge. A leaching column experiment in a greenhouse was conducted to analyze the leaching losses of the metals in the sludge‐amended soils and to evaluate the uptake of these metals by maize (Zea mays L.) seedlings, using a mudflat salt‐soil amended with 0, 30, 75, 150, and 300 g sludge per kg soil. The results indicated that metal concentrations were significantly correlated negatively with pH and positively with dissolved organic carbon concentration in leachate of sludge‐amended soils. The sewage sludge application enhanced metal uptake without inhibiting the growth of maize. The sludge treatments enhanced metal concentrations in top layer (0–20 cm) of soil in the leaching column but did not change metal concentrations in soil layer of 20–40 cm (p > .05). Immobile fraction of Pb and mobile fraction of Cd, Cu, and Zn increased with increasing rates of sludge addition. Long‐term field studies are required for further evaluation of the impacts of recycling sludge on heavy metal behaviors including leaching, accumulation, and dynamic change of metal fractions in mudflat salt‐soils.
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