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Background and aims Alkaline dispersive subsoils are characterised by multiple physicochemical constraints that limit plant water and nutrient acquisition. Subsoil amelioration through organic amendments (OAs) requires significant financial investment. Whereas large yield responses can result following amelioration, sometimes small or even negative yield responses can occur, resulting in a significant net financial loss for the farmer. For farmers to feel confident in investing in subsoil amelioration better prediction of the likely yield improvement is required and to achieve this an understanding of the underlying mechanisms such as nutritional and non-nutritional drivers, and the longevity of benefits are required. Our study aimed to ascertain the drivers of yield improvements from subsoil amelioration with OAs. Methods In a controlled environment, wheat (Triticum aestivum L. cv. Scepter) plants were grown until maturity in a Solonetz amended with (i) poultry litter (PL; 20 t ha−1), and (ii) NPKS nutrients and (iii) model organic carbon (MOC) with equivalent amounts of nutrients and total carbon contained in the PL, and (iv) NPKS + MOC. Control (no amendments) and gypsum (5 t ha−1) were included as district practices. Before planting, amendments were applied as a vertical band at 20 – 40 cm depth and pre-incubated. Plant biomass, grain yield, root biomass, and physicochemical properties of the soil associated with the amendment band were quantified at harvest. Results Compared to the control, wheat grain yield was increased by 30% for PL, 43% for NPKS + MOC, and 61% for NPKS, but no differences in yield were detected for MOC or gypsum. The lower yield increase by PL than NPKS with or without MOC was likely due to the readily available form of plant nutrients in the inorganic fertilisers vs slower mineralisation of nutrients from the OAs. Improvement in soil physicochemical properties following amelioration of alkaline dispersive subsoil resulted in better root proliferation and subsoil water use. Grain yield showed a positive correlation with root biomass in the subsoil layers. Conclusions In the short-term (one crop cycle), organic amendments improved soil’s non-nutritional physical and chemical properties but had no additional nutritional effect on wheat grain yield compared to inorganic fertiliser application. Longer-term studies are needed to determine the legacy effect of the nutritional contribution in conjunction with the improvement of soil structure from the OAs in alkaline dispersive subsoils.

Aims Phosphorus (P)-binding colloids (1–450 nm) have been identified as highly mobile and bioavailable P in terrestrial ecosystems. However, the bioavailability of varied colloidal P (Pcoll) sizes remains unclear, especially in situ soils. The purpose of this study was to evaluate the differential contribution of various-sized colloids to plant available P in the rhizosphere and the phosphatase response patterns. Methods In the 45-day rice rhizotron experiment, we applied different size fractioned biogas slurry (BS) colloids with the same total P concentration, including nano-sized colloids (1–20 nm), fine-sized colloids (20–220 nm), and medium-sized colloids (220–450 nm). Colloidal P organic and inorganic fractions, colloidal minerals were investigated in corresponding treatments. Soil zymography was performed during the cultivation period, to examine the processes of enzymic hydrolysis in temporal and spatial dynamics. The biomass and P content of roots and shoots were also recorded. Results The relative bioavailability of colloidal P (RBAcoll) was the highest (64%) for nano-sized BS colloids addition. The phosphatase activities and hotspot areas were found to be significantly 1) correlated with RBAcoll, 2) increased by the colloid-free (truly dissolved P) and nano-sized BS fractions, and 3) affected by the plant growth stage. Conclusion We found that the addition of nano-sized BS colloids increased P uptake by plants and improved the Pcoll bioavailability in the rhizosphere, in which the phosphatase-catalyzed hydrolysis of organic Pcoll played an important role. Nano-sized BS-derived colloids may be an effective substitute for the use of liquid phosphorus fertilizer.

Summary Application of biochar to rice has shown to elicit positive environmental and agricultural impacts due to its physicochemical properties. However, the relationship between greenhouse gas (GHG) emissions, rice yield, and soil nutrient status under biochar amendment remains unclear. In this study, rice yield and methane (CH4) and nitrous oxide (N2O) emissions were quantified in response to biochar application rate (0, 10, 20, and 40 t ha−1) to early and late subtropical rice cropping systems. We found that application of 10 t of biochar ha−1 to early rice reduced average CH4 emission fluxes, while all biochar application rates diminished average emissions in late rice paddy. Total global warming potential (GWP) and GHG intensity (GHGI) were inherently greater in late rice than early rice cropping. In early rice, GWP and GHGI were found to be similar between soil control, 10 and 20 t of biochar ha−1 treatments, although the largest occurred in the 40 t of biochar ha−1 treatment, whereas in late rice cropping, they were not affected by biochar application rates. Compared to the nil-biochar application, biochar application at varied rates did not affect rice yield. However, compared to 10 t biochar ha−1, increasing biochar application rate to 40 t ha−1 significantly decreased total rice yield (sum of early and late cropping). Generally, application of biochar increased soil salinity and total Fe and Fe2+ content while reducing soil bulk density. Temporal effects of biochar application were noted on CH4 emission flux, soil temperature, and soil Fe2+ and Fe3+ in early rice; and soil temperature, salinity, NH4+-N, NO3−-N, and soil Fe2+ and Fe3+ in late rice. This study confirms that the application of biochar at the lower rate of 10 t ha−1 is optimal for maintaining rice yield while reducing GHG emissions. Moreover, the study demonstrates the potential benefit of biochar in sustainable subtropical rice production.

A 120-day field experiment was conducted to investigate the responses of soil N2O emissions, plant biomass N content, and N cycling-related functional genes to yak (Bos grunniens) dung pat size, including full-size dung pat (FDP), 1/4FDP, 1/8FDP, and 1/16FDP (i.e., FDP split into four, eight, and sixteen equal-sized dung pat fragments) in an alpine steppe on the Qinghai-Tibetan Plateau. The yield-scaled and cumulative N2O emissions were lower in the 1/16FDP and 1/8FDP than in the FDP and 1/4FDP treatments. In addition, the 1/16FDP treatment had the smallest N2O emission factor (0.002%), possibly due to lower denitrification as shown by the lower nisS, nirK, and nosZ gene copy numbers in the first (day 30) and second (day 72) samplings, and increased aboveground plant N concentration and content, which was 23–32% and 21–36%, respectively, greater than in the other treatments. In conclusion, splitting the yak dung pat into 1/16 fragments would be an effective strategy for managing yak dung to reduce N2O emissions and improve aboveground plant biomass N content which enhances the sustainability of alpine steppe ecosystems on the Qinghai-Tibetan Plateau. The implication from this study is that long-term field experiments should be conducted to further investigate the potential antagonistic or synergistic effects of yak dung pat fragmentation combined with other amendments (e.g., nitrogen inhibitors, lime, or biochar) on reducing N2O emissions.

Passion fruit is a tropical fruit crop with significant agricultural, economic and ornamental values. The growth and development of passion fruit are greatly affected by climatic conditions. In plants, the basic helix-loop-helix (bHLH) gene family plays essential roles in the floral organ and fruit development, as well as stress response. However, the characteristics and functions of the bHLH genes of passion fruit remain unclear. Here, 138 passion fruit bHLH members were identified and classified into 20 subfamilies. The structural analysis illustrated that PebHLH proteins of the specific subfamily are relatively conserved. Collinearity analysis indicated that the expansion of the PebHLH gene family mainly took place by segmental duplication, and the structural diversity of duplicated genes might contribute to their functional diversity. PebHLHs, which potentially regulate different floral organ and fruit development, were further screened out, and many of these genes were differentially expressed under various stress treatments. The co-presence of different cis-regulatory elements involved in developmental regulation, hormone and stress responses in the promoter regions of PebHLHs might be closely related to their diverse regulatory roles. Overall, this study will be helpful for further functional investigation of PebHLHs and provides clues for improvement of the passion fruit breeding.

China is not only a main source area of Asian dust but also a significantly affected area of dust deposition in the world. However, the influence range of Asian dust deposition and its influence on soil provenance remains unclear, particularly in subtropical regions. This study identified the substantial effect of Asian dust on soils and quantified its contribution to subtropical soils of China. Three soil profiles derived from basalt in subtropical area (Shaoxing, Zhejiang, China) were selected and sampled. The pH, bulk density, and cation exchange capacity (CEC) of soils were determined. The Neodymium (Nd) and Thorium (Th) concentrations and Nd isotope of soils were determined. We used the Nd elemental and isotopic geochemistry to assess the deposition of Asian dust in soil profiles (up to 1 m depth). The upper soil layers have negative $${\varepsilon }_{Nd}(0)$$ values, which were close to those of Asian dust $${\varepsilon }_{Nd}\left(0\right)=-3.30)$$ , indicating the input of Asian dust to soils. Further, the high dust-derived Nd proportion in the soils $${(f}_{dust}^{Nd}=43\%)$$ also suggested a great contribution of Asian dust on soils. A comparison of Nd in the soils from subtropics (Zhejiang province, Southeast China) and tropics (Hainan province, China’s southernmost point) indicated that both regions were influenced by Asian dust but at different degrees. Asian dust has been identified as a vital source of Nd in subtropical soils of China. The high mass fraction of dust-derived Nd in the soil profiles indicated the important role of dust input in soil genesis. The results also suggest that Nd isotopes are powerful fingerprints in tracing the origin of soil materials.

Crassulacean acid metabolism photosynthesis pathway highlights the possible of sustainable production on margin agricultural land and crop improvement with higher water use efficiency by engineering CAM into C3 crops. A comprehensive view of the regulatory network of CAM photosynthesis is prerequisite for utilization CAM pathway. Diverse factors were involved in the regulation but many of them remain unexplained. Alternative splicing (AS) is a common and crucial posttranscriptional mechanism which get deep involved in responding to biotic and abiotic stresses. Using all the available RNA-seq data of pineapple, which is the most economic valuable CAM crops with abundant omics resource, we re-assembled a reference transcriptome and used to perform alternative splicing analysis associated with crassulacean acid metabolism. The results shown that AS events were prevalent in pineapple. CAM core genes, circadian clock genes, stomatal movement and starch metabolism related genes were found to be significantly differentially alternative spliced between photosynthesis and non-photosynthesis tissues across time course. Isoform switch events were found in many DAS genes, which indicated the sensitivity of AS across the CAM processes in pineapple. The dataset described here also contributed to identify promising candidate genes such as nAco00160 involved in CAM photosynthesis. Our results suggested that AS play an important regulatory role in CAM photosynthesis in pineapple and would help to gain a more systematic understanding about the regulatory networks of CAM photosynthesis.

Conversion of forestland to intensively managed agricultural land occurs worldwide and can increase soil nitrous oxide (N

Agronomic management practices present an opportunity to improve the sustainability of crop production, including reductions of greenhouse gas emissions through impacts on soil organic carbon (SOC) dynamics. We investigated the impacts of contrasting application rates of nitrogen (N)-enriched biochar (4 and 8 t ha

Wetland soil denitrification removes excess inorganic nitrogen (N) and prevents eutrophication in aquatic ecosystems. Wetland plants have been considered the key factors determining the capacity of wetland soil denitrification to remove N pollutants in aquatic ecosystems. However, the influences of various plant communities on wetland soil denitrification remain unknown. In the present study, we measured variations in soil denitrification under different herbaceous plant communities including single Phragmites karka (PK), single Paspalum thunbergia (PT), single Zizania latifolia (ZL), a mixture of Paspalum thunbergia plus Phragmites karka (PTPK), a mixture of Paspalum thunbergia plus Zizania latifolia (PTZL), and bare soil (CK) in the Estuary of Nantiaoxi River, the largest tributary of Qingshan Lake in Hangzhou, China. The soil denitrification rate was significantly higher in the surface (0-10 cm) than the subsurface (10-20 cm) layer. Wetland plant growth increased the soil denitrification rate by significantly increasing the soil water content, nitrate concentration, and ln(nirS) + ln(nirK). A structural equation model (SEM) showed that wetland plants indirectly regulated soil denitrification by altering the aboveground and belowground plant biomass, nitrate concentration, abundances of denitrifying functional genes, and denitrification potential. There was no significant difference in soil denitrification rates among PT, PK and ZL. The soil denitrification rate was significantly lower in PTZL than PTPK. Two-plant communities did not necessarily enhance the denitrification rate compared to single planting, the former had a greater competitiveness on N uptake and consequently reduced the amount of nitrate available for denitrification. As PTPK had the highest denitrification rate, co-planting P. thunbergia and P. karka could effectively improve N removal efficiency and help mitigate eutrophication in adjacent aquatic ecosystems. The results of this investigation provide useful information guiding the selection of appropriate wetland herbaceous plant species for wetland construction and the removal of N pollutants in aquatic ecosystems.

The lateral organ boundary domain (

Crabs may elicit effects on wetland carbon (C), nitrogen (N), and phosphorus (P) concentrations and associated ecological stoichiometry. In this study, we assessed effects of crabs on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions; soil C, N, and P concentrations; and stoichiometry in upper and mid-tidal flats of an estuarine wetland in China. The results showed that averaged CO2, CH4, and N2O fluxes were greater in the upper and mid-tidal flats in the presence of crabs, being 46.4, 66.7, and 69.7% and 53.6, 143, and 73.1% greater than control, respectively. Mixed model analyses showed overall positive relationships between wetland soil CO2 CH4 and N2O emissions (F = 4.65, P = 0.033; F = 42.42, P = 0.042 and F = 10.2, P = 0.0018, respectively) in the presence of crabs, taking into account season, flooding intensity, and plot effects. This may be related to the direct effects of respiration and the indirect effects of feeding, excretion, and disturbance of soil on microorganisms and/or plant roots. There were no effects of crabs on total C or N concentrations, whereas decreased soil total P concentrations, especially in the upper-tidal flats (P = 0.04). Crab presence was positively associated with soil C/P and N/P ratios (P

Colloidal phosphorus (P

Incorporating amendments of industrial waste such as biochar and steel slag in cropland has been used to enhance the storage of soil organic carbon (SOC) while sustaining crop production. Short-term laboratory and field studies have identified important influences of biochar on active SOC fractions associated with soil microbial activity in paddy soils, but the long-term effects remain poorly understood. To address these knowledge gaps, we examined the effects of slag, biochar, and slag+biochar treatments on total SOC concentration, active SOC fractions and soil microbial communities in a paddy field two years after incorporation. Across both two seasons, the addition of slag, biochar, slag+biochar increased soil salinity by 26-80%, 1.3-37% and 42-79%, and also increased soil pH by 0.8-5.7%, 2.1-2.4% and 4.0-6.3%, respectively, relative to the control. SOC concentration was higher in the slag, biochar, and slag+biochar treatments across both rice seasons by 4.3-5%, 0.5-17% and 4.3-7%, respectively. Soil C-pool activity and C-pool management indices in the late paddy season were significantly lower in the slag+biochar treatment than the control by 26.3 and 21.3%, respectively, indicating that the amendments contributed to the stability of SOC. The C concentrations of the biochar and slag amendments affected bacterial abundance more than fungal abundance and affected C cycling. Our study suggests that combined slag and biochar amendments may increase bacterial abundance that may maintain SOC storage and reduce the abundances of potential SOC decomposers in key functional genera, indicating strong coupling relationships with changes of soil properties such as salinity, pH, and SOC concentration. These outcomes due to the amendments (e.g. slag+biochar) may increase microbial C-use efficiency and support the stability of active SOC fractions, with opportunities for long-term C sequestration.

SBT (Subtilisin-like serine protease), a clan of serine proteolytic enzymes, plays a versatile role in plant growth and defense. Although SBT family genes have been obtained from studies of dicots such as Arabidopsis, little is known about the potential functions of SBT in the monocots. In this study, 54 pineapple SBT genes (AcoSBTs) were divided into six subfamilies and then identified to be experienced strong purifying selective pressure and distributed on 25 chromosomes unevenly. Cis-acting element analysis indicated that almost all AcoSBTs promoters contain light-responsive elements. Further, the expression pattern via RNA-seq data showed that different AcoSBTs were preferentially expressed in different above-ground tissues. Transient expression in tobacco showed that AcoSBT1.12 was located in the plasma membrane. Moreover, Transgenic Arabidopsis ectopically overexpressing AcoSBT1.12 exhibited delayed flowering time. In addition, under the guidance of bioinformatic prediction, we found that AcoSBT1.12 could interact with AcoCWF19L, AcoPUF2, AcoCwfJL, Aco012905, and AcoSZF1 by yeast-two hybrid (Y2H). In summary, this study provided valuable information on pineapple SBT genes and illuminated the biological function of AcoSBT1.12 in floral transition.

Applying industrial waste amendments, such as steel slag and biochar, to soils is an increasingly common practice to improve soil fertility, crop yield, and soil carbon (C) pool storage and stability. However, the effects of separate and combined applications of slag and biochar on total and active soil organic C (SOC) pools and the associated relationships between soil microorganisms and C cycling are unclear. Therefore, this study examined the effects of steel slag, rice straw biochar, and slag+biochar amendments to subtropical early and late rice paddy soils on total and active SOC concentrations and microbial abundance and diversity. The results showed that slag+biochar increased SOC content in early and late rice, with increases in dissolved organic C of 28.7 and 52.6 % in the early and late rice jointing stages, respectively. Soil organic C was positively correlated with soil C: N ratios in the two crop seasons. Applications of slag and biochar alone increased the diversity of soil bacteria in early rice but decreased in late rice. Meanwhile, the combined application of slag and biochar decreased diversity of soil bacterial community diversity and increased the relative abundance of some beneficial bacterial taxa, such as Pseudomonas, Bacillus, Flavisolibacter, and Ferruginibacte which are related to SOC cycling and sequestration. The results highlight that the combined slag and biochar amendments can improve soil specific properties, such as pH and SOC stocks, which elicit alterations in soil bacterial composition, especially of some keystone genera, altogether resulting in enhanced soil C sequestration and C pool stability.

Despite their notable root mutualism with blueberries (Vaccinium spp.), studies related to Ericoid mycorrhizal (ERM) are relatively limited. In this study, we report the isolation of 14 endomycorrhizal fungi and their identification by fungal colony morphology characterization combined with PCR-amplified fungal internal transcribed spacer (ITS) sequence analyses. Six of the isolated strains were confirmed as beneficial mycorrhizal fungi for blueberry plants following inoculation. We observed the formation of typical ERM hyphae coil structures—which promote and nutritionally support growth—in blueberry seedlings and significant nitrogen and phosphorous content increases in diverse tissues. QRT-PCRs confirmed changes in VcPHT1s expression patterns. After the formation of ERM, PHT1-1 transcription in roots was upregulated by 1.4- to threefold, whilst expression of PHT1-3 and PHT1-4 in roots were downregulated 72% and 60%, respectively. Amino acid sequence analysis of all four VcPHT1s genes from the blueberry variety “Sharpblue” revealed an overall structural similarity of 67% and predicted transmembrane domains. Cloning and overexpression of PHT1-1 and PHT1-3 genes in transgenic Arabidopsis thaliana plants significantly enriched total phosphorus and chlorophyll content, confirming that PHT1-1 and PHT1-3 gene functions are associated with the transport and absorption of phosphorus.

Background and aims: Incorporation of biochar into the soil sequesters C for millennia, but the concomitant effects on plant rhizodepositions and nutrient (e.g., nitrogen; N) trade-offs via interactions of heterotrophic microbiota, might offset this sequestration. Methods: Ryegrass (Lolium perenne L.) with and without biochar amendment were pulse labelled in a 13CO2 atmosphere and 15N fertilizer added. Ryegrass and soils were destructively sampled at 16 and 30 days after seedling emergence. Isotope analysis was coupled with MiSeq sequencing of bacterial (16s rRNA) and fungal (ITS) genes to identify the effect of biochar on the associated microbiota involved in 13C allocation into soil aggregates and promotion of 15N uptake by L. perenne. Results: Biochar increased root biomass and 15N uptake but decreased rhizodeposited-13C recovery from large and small macroaggregates (by 12–57% and 57–72%, respectively). These changes in 13C flow and 15N uptake were accompanied by an increase in microbial biomass, and enhanced negative correlations between bacteria and fungi. O2PLS indicated members of seventeen genera that were correlated with soil stabilization of rhizodeposits in soil and plant N-uptake. For instance, Xanthomonadales (Proteobacteria) and RB41 (Acidobacteria), previously reported to be plant growth promoting rhizobacteria, were found to be positively correlated with 15N uptake by L. perenne. Conclusions: Our research explored the genera associated with biochar-modified 15N uptake by Lolium perenne and photosynthate 13C allocation into soil aggregates. Future research with SIP is required to fully assess microbial turnover, the ubiquity of similar rhizosphere microbiota and their fundamental importance for sequestration in the plant-soil-microbe-biochar systems.

Application of organic amendments (OAs) combined with inorganic fertilizers or gypsum in poorly structured soils has recently received much attention as an agricultural management practice aiming to ameliorate physicochemical constraints and improving soil carbon (C) storage. Although microbial C-use efficiency (CUE) is recognized as a critical parameter in ecological models to predict soil C cycling and storage, little is known about the effects of OAs with exogenous nutrient supply (to balance the resource nutrient stoichiometry) or gypsum on microbial biomass and CUE. Here, we examined the role of OAs (C4 vegetation-derived: δ13C – 12 to − 15‰) in altering microbial biomass, C mineralization, and CUE, i.e., microbial growth relative to microbial C uptake (microbial growth + respiration + death) over the long-term, in an alkaline sodic-subsoil (C3 vegetation-derived: δ13C – 24‰). Four different OAs (sorghum stubble, sugarcane bagasse, sugarcane mill mud, and sugarcane mill mud + sugarcane mill ash) were used at 6.2 g C kg−1 soil, with and without the exogenous supply of nutrients and/or gypsum. The nutrients were added with the aim to convert OAs to stable soil organic matter (SOM) with a C/nitrogen (N)/phosphorus (P) stoichiometric ratio of 100:8.3:2. Over 90 days, the cumulative mineralization of OA-C varied across OA types and ranged between 42 and 497 mg CO2-C g−1 OA-C. The OA-derived microbial biomass C (MBC) ranged between 20 and 350 mg C kg−1 soil across the treatments, which was highest with sorghum stubble that contained the highest dissolved (labile) organic C. The mill mud with an inherently balanced C/nutrient stoichiometry had the highest CUE, i.e., 0.3–0.8, compared to the sorghum stubble and sugarcane bagasse (with imbalanced nutrient stoichiometry), i.e., 0.1–0.6. Balancing the nutrient stoichiometry of sorghum stubble and sugarcane bagasse via nutrient inputs increased MBC but not CUE. The input of gypsum to the OA-treated soil had no impact on either MBC or CUE. In conclusion, balanced C/nutrient stoichiometry and labile C content of OAs are critical properties to control their impact on C mineralization, MBC, and CUE, with implications for soil C storage upon amendment into a poorly structured sodic-subsoil.

Understanding the legacy effect of tillage-based farming systems on soil organic carbon (SOC) mineralisation and nutrient [nitrogen (N), phosphorus (P) and sulphur (S)] supply after crop residue input is critical to appropriately manage plant available nutrients at the farm scale. To enhance this understanding, crop residues [canola (Brassica napus: δ13C 124‰) or wheat (Triticum aestivum: δ13C 461‰)] were added to Luvisol and Vertisol from two long-term (16–46 years) field experiments and incubated under a controlled environment for 126 days. The practices in the Luvisol were conventional tillage (CT) and reduced tillage (RT) under mixed crop-pasture rotation, and no-till (NT) under continuous cereal-cover crop rotation. The practices in the Vertisol were CT and NT under wheat-wheat rotation. The residue input significantly stimulated SOC mineralisation via “positive priming”, which was greater (p wheat) after 26–50% of residue-C was mineralised over 126 days, and the Vertisol had greater net available P than Luvisol. Our results suggest that considerable quantities of available P and S may release from the soil reserves via SOC priming, and possibly via dissolution/desorption reactions in the soils, in addition to their direct release from the residues. In conclusion, crop residue input to historical farming systems enhanced the supply of available P and S, which varied with tillage, crop residue and soil type.