Phosphorus Availability Research Articles

Effect of Different Types of Biochar Applications and Phosphate Fertilizer on the Quality and Yield of Edamame Soybeans on Andisols

Edamame soybean (<em>Glycine max </em>(L.) Merr.) cultivation in phosphorus-limited Andisols presents a formidable challenge due to restricted phosphorus availability despite high phosphorus retention. Unlocking the full potential of this crop demands innovative solutions. This study delves into the transformative effects of biochar and phosphorus fertilizer, individually and synergistically, on edamame soybean growth in Andisols. Employing a randomized complete block design, researchers investigate three types of biochar (B0: control, B1: biochar pellets, B2: biochar powder) and four phosphorus fertilizer rates (P0: control, P1: 27 kg ha<sup>-1</sup> P<sub>2</sub>O<sub>5</sub>, P2: 54 kg ha<sup>-1</sup> P<sub>2</sub>O<sub>5</sub>, P3: 81 kg ha<sup>-1</sup> P<sub>2</sub>O<sub>5</sub>). The bamboo-derived biochar was produced using the Kon-tiki method at ±500 °C. The study reveals no significant interaction between biochar and phosphorus fertilizer. Individually, treatments with B1, B2, and phosphorus fertilizers significantly enhance ammonium, nitrate, and phosphorus availability compared to B0 and P0. Biochar-induced modifications improve phosphorus and nitrogen absorption by roots, resulting in increased shoot dry weight and the root/shoot ratio. However, the number of leaves is solely influenced by phosphorus fertilizer treatment. Additionally, both biochar and phosphorus fertilizers contribute to nitrate reductase activity, root volume, an increased number of pods per plant and higher protein content in edamame soybeans. B2 outperforms B1 and high P3 intensifies this effect, improving nutrient uptake and yield. In summary, biochar and phosphorus fertilizers demonstrate significant potential to revolutionize edamame soybean cultivation in phosphorus-limited Andisols, optimizing pod number per plant and enhancing quality with elevated protein content.

Microbial community interactions determine the mineralization of soil organic phosphorus in subtropical forest ecosystems.

In subtropical forest ecosystems with few phosphorus (P) inputs, P availability and forest productivity depend on soil organic P (Po) mineralization. However, the mechanisms by which the microbial community determines the status and fate of soil Po mineralization remain unclear. In the present study, soils were collected from three typical forest types: secondary natural forest (SNF), mixed planting, and monoculture forest of Chinese fir. The P fractions, Po-mineralization ability, and microbial community in the soils of different forest types were characterized. In addition, we defined Po-mineralizing taxa with the potential to interact with the soil microbial community to regulate Po mineralization. We found that a higher labile P content persisted in SNF and was positively associated with the Po-mineralization capacity of the soil microbial community. In vitro cultures of soil suspensions revealed that soil Po mineralization of three forest types was distinguished by differences in the composition of fungal communities. We further identified broad phylogenetic lineages of Po-mineralizing fungi with a high intensity of positive interactions with the soil microbial community, implying that the facilitation of Po-mineralizing taxa is crucial for soil P availability. Our dilution experiments to weaken microbial interactions revealed that in SNF soil, which had the highest interaction intensity of Po-mineralizing taxa with the community, Po-mineralization capacity was irreversibly lost after dilution, highlighting the importance of microbial diversity protection in forest soils. In summary, this study demonstrates that the interactions of Po-mineralizing microorganisms with the soil microbial community are critical for P availability in subtropical forests.IMPORTANCEIn subtropical forest ecosystems with few phosphorus inputs, phosphorus availability and forest productivity depend on soil organic phosphorus mineralization. However, the mechanisms by which the microbial community interactions determine the mineralization of soil organic phosphorus remain unclear. In the present study, soils were collected from three typical forest types: secondary natural forest, mixed planting, and monoculture forest of Chinese fir. We found that a higher soil labile phosphorus content was positively associated with the organic phosphorus mineralization capacity of the soil microbial community. Soil organic phosphorus mineralization of three forest types was distinguished by the differences in the composition of fungal communities. The positive interactions between organic phosphorus-mineralizing fungi and the rest of the soil microbial community facilitated organic phosphorus mineralization. This study highlights the importance of microbial diversity protection in forest soils and reveals the microbial mechanism of phosphorus availability maintenance in subtropical forest ecosystems.

Pengaruh Pemberian Berbagai Macam Bahan Organik terhadap Ketersediaan Hara Nitrogen, Fosfor dan Kalium serta Serapan Nitrogen oleh Jagung (Zea mays L.) pada Tanah Ultisols

Ultisols distributes spreadly in Indonesia, but this soil has low fertility. Therefore, the application of organic matter (OM) is a common management to increase this soil fertility. The purpose of this study was to determine the role of different types of OM (originated from animals and plants) on the availability of nitrogen, phosphorus, and potassium as well as nitrogen uptake in maize in Ultisols. Soil with a mass of 5 kg without organic matter (control), with the application of chicken manure, cow manure, swallow manure, kirinyuh, babadotan, and kalopo manure were incubated in experimental pots for two weeks at 60% field capacity. After the completion of the incubation period, soil sub-sampling was carried out for the determination of available N, available P and exchangeable K. Furthermore, in each experimental pot, corn seeds were planted, and the observations of dried-weight of corn and nitrogen uptake in corn were observed in a vegetative phase. The results showed that the application of different types of organic matter increased soil pH, nitrate content, exchangeable K, plant dried-weight and plant nitrogen uptake. The content of ammonium and available P was not affected by OM addition. The results also showed that OM derived from animals resulted in higher increases in pH and exchangeable K than those derived from plants. However, OM derived from plants resulted in higher increases in nitrate, plant dry weight and better plant N uptake than OM from animal waste. The results of this study show that the application of OM results in increases in some soil chemical properties, in which the degree of increases in soil chemical characteristics is controlled by the OM origin.

The Effect of Nitrogen Reduction and Applying Bio-Organic Fertilisers on Soil Nutrients and Apple Fruit Quality and Yield

In this study, we investigated the effect of partially substituting inorganic nitrogen with bio-organic fertiliser on the ‘Tianhong2’ Fuji apple planting in Xinjiang. Bio-organic fertiliser was applied, and nitrogen was reduced by 20% (T2), 40% (T3), and 60% (T4) during the blooming and fruit expansion periods with conventionally fertilised fields used as control (T1); soil nutrient, soil enzyme activity, leaf nutrients, fruit quality, and yield were measured. The total nitrogen (TN), total phosphorus (TP), total potassium (TK), total calcium (TCa), available phosphorus (AP), available potassium (AK), and soil organic matter (SOM) contents, as well as the soil catalase (S-CAT), soil uretrase (S-UE), soil saccharase (S-SC), and soil nitrate reductase (S-NR) activities, significantly increased in the experimental soils compared with those in T1. In addition, TP, TCa, and total magnesium (TMg) content in apples significantly increased. Compared to T1, the T2 and T3 treatments significantly improved the fruit yield and quality, increasing the sugar–acid ratio, soluble protein, soluble sugar, peel carotenoid, and anthocyanin content and reducing peel chlorophyll content. The brightness (L*), red–green axis (a*), yellow–blue axis (b*), colour intensity (C), and tone (h°) values changed. The yield per hectare and nitrogen fertiliser partial productivity values were significantly increased. Overall, the T2 treatment resulted in the best outcome for the Yili area. In conclusion, partially substituting inorganic nitrogen with bio-organic fertiliser can effectively increase soil and leaf nutrient content and improve fruit yield and quality.

Boosting the Soil Phosphorus Availability to Plants by Using Silicon-Rich Crop Residues and Reducing Fertilizer Requirements

Boosting the Soil Phosphorus Availability to Plants by Using Silicon-Rich Crop Residues and Reducing Fertilizer Requirements

Soil fungal community is more sensitive than bacterial community to modified materials application in saline-alkali land of Hetao Plain.

Soil salinization has become a major challenge that severely threatens crop growth and influences the productivity of agriculture. It is urgent to develop effective management measures to improve saline-alkali soil. Thus, in this study, soil properties, microbial communities, and function under desulfurization gypsum (DE), soil amendment (SA), farm manure (FA), and co-application of desulfurization gypsum, soil amendment, and farm manure (TA) in a field experiment were examined by high-throughput sequencing. The results showed that the application of modified materials is an effective approach in improving saline-alkali soil, especially TA treatment significantly increased the content of available phosphorus (AP), available potassium (AK), soil organic matter (SOM), and alkaline hydrolysis nitrogen (AHN) and decreased pH, bulk density (BD), and electrical conductivity (EC). The application of modified materials resulted in notable enhancement in fungal diversity and altered the composition and structure of the fungal community. Conversely, the effect on the bacterial community was comparatively minor, with changes limited to the structure of the community. Regarding the fungal community composition, Ascomycota, Mortierellomycota, and Basidiomycota emerged as the dominant phyla across all treatments. At each taxonomic level, the community composition exhibited significant variations in response to different modified materials, resulting in divergent soil quality. The TA treatment led to a decrease in Mortierellomycota and an increase in Ascomycota, potentially enhancing the ability to decompose organic matter and facilitate soil nutrient cycling. Additionally, the sensitivity of fungal biomarkers to modified materials surpassed that of the bacterial community. The impact of modified materials on soil microbial communities primarily stemmed from alterations in soil EC, AP, AK, and SOM. FUNGuild analysis indicated that the saprotroph trophic mode group was the dominant component, and the application of modified materials notably increased the symbiotroph group. PICRUSt analysis revealed that metabolism was the most prevalent functional module observed at pathway level 1. Overall, the application of modified materials led to a decrease in soil EC and an increase in nutrient levels, resulting in more significant alterations in the soil fungal community, but it did not dramatically change the soil bacterial community. Our study provides new insights into the application of modified materials in increasing soil nutrients and altering soil microbial communities and functions and provides a better approach for improving saline-alkali soil of Hetao Plain.

Significance of phosphorus deficiency for the mitigation of mercury toxicity in the Robinia pseudoacacia L.– rhizobia symbiotic association

Nitrogen (N2)-fixing legumes can be used for phytoremediation of toxic heavy metal Mercury (Hg) contaminated soil, but N2-fixation highly relies on phosphorus (P) availability for nodule formation and functioning. Here, we characterized the significance of P deficiency for Hg accumulation and toxicity in woody legume plants. Consequences for foliar and root traits of rhizobia inoculation, Hg exposure (+Hg) and low P (-P) supply, individually and in combination were characterized at both the metabolite and transcriptome levels in seedlings of two Robinia pseudoacacia L. provenances originating from contrasting climate and soil backgrounds, i.e., GS in northwest and the DB in northeast China. Our results reveal that depleted P mitigates the toxicity of Hg at the transcriptional level. In leaves of Robinia depleted P reduced oxidative stress and improved the utilization strategy of C, N and P nutrition; in roots depleted P regulated the expression of genes scavenging oxidative stress and promoting cell membrane synthesis. Rhizobia inoculation significantly improved the performance of both Robinia provenances under individual and combined +Hg and -P by promoting photosynthesis, increasing foliar N and P content and reducing H2O2 and MDA accumulation despite enhanced Hg uptake. DB plants developed more nodules, had higher biomass and accumulated higher Hg amounts than GS plants and thus are suggested as the high potential Robinia provenance for future phytoremediation of Hg contaminated soils with P deficiency.

Exploration capacity versus specific enzymatic activity of ectomycorrhizas in response to primary productivity and soil phosphorus availability in Bornean tropical rainforests.

Ectomycorrhizal (ECM) fungi are functionally important in biogeochemical cycles in tropical ecosystems. Extracellular enzymatic activity of ECM on a ground-area basis is the product of two attributes; exploration capacity (ECM surface-area) and specific enzymatic activity. Here, we elucidated which attribute better explained the ECM enzymatic activity in response to different levels of soil phosphorus (P) and Nitrogen (N) availability in five Bornean tropical rainforests. We determined the surface area of ECM root tips as well as the enzymatic activities per ECM surface area for carbon (C), N and P degrading enzymes in each site. We evaluated the relationship of ECM enzyme activities with the resource availabilities of C (Above-ground net primary production; ANPP), N, and P of ECM by a generalized linear mixed model. The ECM enzymatic activities on a ground-area basis were more significantly determined by specific enzymatic activity than by the exploration capacity. Specific enzymatic activities were generally negatively affected by C (ANPP) and soil P availability. ECM fungi enhance the specific enzyme activity rather than the exploration capacity to maintain the capacity of nutrient acquisition. The less dependence of ECM fungi on the exploration capacity in these forests may be related to the limitation of C supply from host trees. We highlighted the adaptive mechanisms of ECM fungi on nutrient acquisition in tropical ecosystems through the response of enzymatic activity to nutrient availability across the elements.

Distribution patterns and influential factors of pathogenic bacteria in freshwater aquaculture sediments.

Pathogenic bacteria, the major causative agents of aquaculture diseases, are a serious impediment to the aquaculture industry. However, the bioinformatics of pathogenic bacteria and virulence factors (VFs) in sediments, an important component of freshwater aquaculture ecosystems, are not well characterized. In this study, 20 sediment samples were collected from fish pond sediments (FPS), shrimp field sediments (SFS), fish pond sediment control (FPSC), and shrimp field sediment control (SFSC). Molecular biological information was obtained on a total of 173 pathogenic bacteria, 1093 virulence factors (VFs), and 8475 mobile genetic elements (MGEs) from these samples. The results indicated that (1) aquaculture patterns and sediment characteristics can affect the distribution of pathogenic bacteria. According to the results of the Kruskal-Wallis H test, except for Mycobacterium gilvum, there were significant differences (P < 0.05) among the four sediment types in the average abundance of major pathogenic bacteria (top 30 in abundance), and the average abundance of major pathogenic bacteria in the four sediment types followed the following pattern: FPS > SFS > FPSC > SFSC. (2) Pathogenic bacteria are able to implement a variety of complex pathogenic mechanisms such as adhesion, invasion, immune evasion, and metabolic regulation in the host because they carry a variety of VFs such as type IV pili, HSI-I, Alginate, Colibactin, and Capsule. According to the primary classification of the Virulence Factor Database (VFDB), the abundance of VFs in all four types of sediments showed the following pattern: offensive VFs > non-specific VFs > defensive VFs > regulation of virulence-related genes. (3) Total organic carbon (TOC), total phosphorus (TP), available phosphorus (AP), nitrite, and nitrate were mostly only weakly positively correlated with the major pathogenic bacteria and could promote the growth of pathogenic bacteria to some extent, whereas ammonia was significantly positively correlated with most of the major pathogenic bacteria and could play an important role in promoting the growth and reproduction of pathogenic bacteria. (4) Meanwhile, there was also a significant positive correlation between CAZyme genes and major pathogenic bacteria (0.62 ≤ R ≤ 0.89, P < 0.05). This suggests that these pathogenic bacteria could be the main carriers of CAZyme genes and, to some extent, gained a higher level of metabolic activity by degrading organic matter in the sediments to maintain their competitive advantage. (5) Worryingly, the results of correlation analyses indicated that MGEs in aquaculture sediments could play an important role in the spread of VFs (R = 0.82, P < 0.01), and in particular, plasmids (R = 0.75, P < 0.01) and integrative and conjugative elements (ICEs, R = 0.65, P < 0.05) could be these major vectors of VFs. The results of this study contribute to a comprehensive understanding of the health of freshwater aquaculture sediments and provide a scientific basis for aquaculture management and conservation.

Quantifying the characteristics of magnetic oil–water contacts in mature hydrocarbon reservoirs and their capacity for understanding hydrocarbon remigration

SUMMARY Increasing magnetization within mature hydrocarbon reservoirs provides a new technique in identifying oil–water contacts (OWCs) in cored wells with the potential to assess yield thereby reducing the need for further exploration. Authigenic precipitation of magnetic minerals at OWCs may also help locate palaeocontacts (PCs), where structural changes to the petroleum system have caused hydrocarbon remigration. This study determines the magnetic characteristics of magnetic enhancements at OWCs and possibly PCs in silliclastic and carbonate reservoirs at the Wytch Farm oil field, Wessex Basin, UK. Increases in saturation magnetization and susceptibility are observed at the OWC in 11 of the 12 analysed cored reservoirs owing to the increased presence of magnetite and vivianite. Geochemical analysis and shallow reservoirs suggest biogenic and inorganic mineral precipitation is extensive at the OWC depending on iron, sulphur and phosphorus availability. Similar magnetic characteristics have been observed in magnetic enhancements above the OWC in numerous wells which may represent OWCs before a basin-wide easterly tilt caused hydrocarbon remigration in the Cenozoic. Multiple magnetic enhancements above the OWC in westerly onshore wells, suggest this remigration may have occurred as numerous phases.

Residual phosphorus availability after soil application of different organic waste in varying soil P status soils

Transformations of applied phosphorus (P) fertilizer to inaccessible residual soil P is the main cause of inadequate P availability to plants in the majority of the cultivated soils. This study investigated the effect of organic wastes (rice-residue biochar, farmyard manure (FYM), poultry manure (PM), green manure (GM), and wheat straw (WS) on residual-P mobilization and its bioavailability in maize crops under different P status soils. Surface soil samples of ‘medium-P’ (12.5–22.5 kg P ha−1) and ‘high-P’ (22.5–50.0 kg P ha−1) status soils were collected from a long-term differential P fertilization experiment on maize-wheat rotation and were subjected to examine P adsorption/desorption, phosphatase activity and microbial biomass P (MBP) after incubation with organic amendments of varying elemental composition. The incorporation of organic manures decreases P sorption with maximum decrease in FYM-treated soils, indicating increased P concentration in soil solution. In contrast, WS due to its wider C/P ratio increased P sorption and did not produce any significant impact on the bioavailability of P. High-P status soils witnessed lower P sorption than medium-P soils. The MBP increased in the order of PM > FYM > GM > WS > biochar irrespective of soil P status. The availability and mobility of residual-P with FYM and PM was significantly higher than that of residual-P from biochar, GM and WS. Organics with wider C/P ratio immobilize bioavailable P in the short term regardless of soil P status.

Effects of forest regeneration types on phosphorus fractions of soil aggregates in subtropical forest.

Soil aggregates are important for the storage and availability of phosphorus in the soil. However, how forest regeneration types affect phosphorus fractions of soil aggregates remains unclear. In this study, we examined the composition of aggregate particle size, phosphorus fractions, phosphorus sorption capacity index (PSOR), legacy phosphorus index (PLGC) and degree of phosphorus saturation by Mehlich 3 (DPSM3) in bulk soils and soil aggregates of Castanopsis carlesii secondary forest (slight disturbance), C. carlesii human-assisted regeneration forest (moderate disturbance), and Cunninghamia lanceolata plantation (severe disturbance), aiming to explore the impact of forest regeneration types on phosphorus availability and supply potential of bulk soils and soil aggregates. The results showed that forest regeneration types significantly influenced the composition of soil aggregates. The proportion of coarse macroaggregates (>2 mm) in the soil of C. carlesii secondary forest and human-assisted regeneration forest was significantly higher than that in the C. lanceolata plantation, while the proportion of silt and clay fraction (<0.053 mm) showed an opposite trend. The composition of soil aggregates significantly affected the contents of different phosphorus fractions. The contents of soil labile phosphorus fractions (PSOL and PM3) decreased as aggregate particle size decreased. The contents of soil total phosphorus (TP), total organic phosphorus (Po), mode-rately labile phosphorus fractions (PiOH and PoOH), and occluded phosphorus (POCL), as well as PSOR and PLGC, exhibited a trend of decreasing at the beginning and then increasing as particle size decreased. The contents of TP, Po, and PiOH in coarse and silt macroaggregates was significantly higher than that in fine macroaggregates (0.25-2 mm) and microaggregates (0.053-0.25 mm). Forest regeneration types significantly influenced the contents of phosphorus fractions of bulk soils and soil aggregates. The contents of TP, Po, PSOL, and PM3 in the soil of C. carlesii secondary forests was significantly higher than that in C. carlesii human-assisted regeneration forest and C. lanceolata plantation. The contents of PSOL and PM3 in different-sized aggregates of C. carlesii secondary forests were significantly higher than that in the C. lanceolata plantation. Forest regeneration types significantly influenced the composition and supply potential of phosphorus fractions in soil aggregates. The proportions of PSOL, and PM3 to TP in different-sized soil aggregates were significantly lower in C. carlesii human-assisted regeneration forest compared with C. carlesii secondary forest. PSOR and DPSM3 in different-sized soil aggregates were significantly lower in C. lanceolata plantation than that in C. carlesii secondary forest. Overall, our results indicated that natural regeneration is more favorable for maintaining soil phosphorus availability, and that forest regeneration affects soil phosphorus availa-bility and its supply potential by altering the composition of soil aggregates.

Beneath the Surface: Investigating soil microbial and metazoa communities at various depths in a natural desert ecosystem inhabited by Karelinia caspia

Soil organisms play a pivotal role in terrestrial ecosystems, sparking growing curiosity about the comprehensive diversity of subterranean biota across large ecological levels. Soil inhabitants’ exhibit varied responses to soil physicochemical properties (SPPs) across desert ecosystem. Yet, the knowledge of their population dynamics across different soil depths (SDs) in the indigenous natural dominant zone of Karelinia caspia, a primary desert shrub in China, remains limited. This study employed advanced illumina sequencing to assess soil bacteria, fungi, archaea, protist, and metazoa populations across six distinct SDs (0 to 100 cm) within the K. caspia desert landscape. Our findings indicate a descending alpha diversity pattern in bacteria, archaea, and protists as soil depth increases, contrary to fungi and metazoa, which exhibit the opposite trend. SDs significantly shape soil biota beta diversity, notably impacting bacteria, protists, and fungi, as revealed by Non-Metric Dimensional Scaling. Prominent classes include Actinobacteria, Sordariomycetes, Nitrososphaeria, Spirotrichea, and Nematoda for soil bacteria, fungi, archaea, protists, and metazoa, respectively. Correlation analysis between predominant biotic communities' vertical distribution and SPPs variations revealed total potassium (TK) and pH's pronounced influence on bacteria, while fungi were affected by total nitrogen (TN) and soil water content (SWC). Archaea exhibit sensitivity to SWC, available potassium (AK), and available phosphorus (AP); protists respond to C/N-Ratio, nitrate (NO3), and total phosphorus (TP); metazoa correlate with SWC, pH, and NO3. Overall, these findings offer valuable insights regarding population fluctuations of soil biota within naturally established K. caspia across vertical soil strata within China's desert ecosystem.

Straw Soil Conditioner Modulates Key Soil Microbes and Nutrient Dynamics across Different Maize Developmental Stages.

Soil amendments may enhance crop yield and quality by increasing soil nutrient levels and improving nutrient absorption efficiency, potentially through beneficial microbial interactions. In this work, the effects of amending soil with straw-based carbon substrate (SCS), a novel biochar material, on soil nutrients, soil microbial communities, and maize yield were compared with those of soil amendment with conventional straw. The diversity and abundance of soil bacterial and fungal communities were significantly influenced by both the maize growth period and the treatment used. Regression analysis of microbial community variation indicated that Rhizobiales, Saccharimonadales, and Eurotiales were the bacterial and fungal taxa that exhibited a positive response to SCS amendment during the growth stages of maize. Members of these taxa break down organic matter to release nutrients that promote plant growth and yield. In the seedling and vegetative stages of maize growth, the abundance of Rhizobiales is positively correlated with the total nitrogen (TN) content in the soil. During the tasseling and physiological maturity stages of corn, the abundance of Saccharimonadales and Eurotiales is positively correlated with the content of total carbon (TC), total phosphorus (TP), and available phosphorus (AP) in the soil. The results suggest that specific beneficial microorganisms are recruited at different stages of maize growth to supply the nutrients required at each stage. This targeted recruitment strategy optimizes the availability of nutrients to plants and ultimately leads to higher yields. The identification of these key beneficial microorganisms may provide a theoretical basis for the targeted improvement of crop yield and soil quality. This study demonstrates that SCS amendment enhances soil nutrient content and crop yield compared with conventional straw incorporation and sheds light on the response of soil microorganisms to SCS amendment, providing valuable insights for the future implementation of this material.

Analysis of soil fertility and toxic metal characteristics in open-pit mining areas in northern Shaanxi

The study specifically focused on the Hongliulin mining area, where a total of 40 soil samples were meticulously collected and analyzed from within a 1000 m radius extending from the tailings dam. The findings revealed that soil pH within the 0–1000 m range generally leaned towards the alkaline side. In terms of soil nutrient content, encompassing factors such as soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali nitrogen (AK), available phosphorus (AP), and quick-acting potassium (AK), the variations fell within the following ranges: 2.23–13.58 g/kg, 0.12–0.73 g/kg, 0.18–1.15 g/kg, 9.54–35.82 g/kg, 2.89–6.76 mg/kg, 3.45–11.25 mg/kg, and 5.86–130.9 mg/kg. Collectively, these values indicate relatively low levels of soil nutrients. Within the 0–500 m range of soil samples, the average concentrations of Cd, Hg, Pb, and As were 0.778, 0.198, 24.87, and 17.92 mg/kg, respectively. These concentrations exceeded the established soil background values of Shaanxi Province and emerged as the primary pollutants in the study area. Within this same range, the mean values of eight toxic metals (Pi) were ranked in the following descending order: 1.726 (Hg), 1.400 (As), 1.129 (Cr), 1.109 (Pb), 0.623 (Zn), 0.536 (Cd), 0.309 (Cu), and 0.289 (Ni). With the exception of Hg, As, Cr, and Pb, which exhibited slight pollution, the other toxic metals were found to be within acceptable pollution limits for this sampling range, in line with the results obtained using the geo-accumulation index method. The average potential ecological risk index for the eight toxic metals in the study area stood at 185.0, indicating a moderate overall pollution level. When assessing individual elements, the proportions of ecological risk attributed to Hg, As, Pb, and Cd were 34.57%, 27.44%, 25.11%, and 23.11%, respectively. This suggests that the primary potential ecological risk elements in the study area are Hg and As, followed by Cd and Pb. Notably, toxic metals Hg and Pb, as well as As and Pb, exhibited significant positive correlations within the sampling area, suggesting a common source. An analysis of the relationship between soil physicochemical properties and toxic metals indicated that soil pH, SOM, TN, and TP were closely linked to toxic metal concentrations. The toxic metal elements in the research area's soil exhibit moderate variability (0.16 < CV < 0.36) to high variability (CV > 0.36). Within the range of 0–200 m, the CV values for Cd and Hg exceed 1, indicating a high level of variability. The coefficient of variation for SOM, TP, AP, AK and TK is relatively high with the of 2.93, 2.36, 2.36, 21.01, 7.54. The soil in the sampling area has undergone significant disturbances due to human activities, resulting in toxic metal pollution and nutrient deficiencies.

Effects of an efficient straw decomposition system mediated by Stropharia rugosoannulata on soil properties and microbial communities in forestland

Cultivation of Stropharia rugosoannulata with straw in forestland is effective for straw biodegradation and can prevent the waste of straw resources and environmental pollution and generate economic benefits. However, there is a lack of systematic evaluation of spent mushroom substrate (SMS) input into forestland, such as soil properties and microbial succession. In this experiment, 0 (CK), 10 (SA), 20 (SB), 30 (SC), 40 (SD), and 50 (SE) kg/m2 straw were used to cultivate S. rugosoannulata, and two soil layers (0–10 cm, 10–20 cm) of the cultivated forestland were analyzed. The results indicated that SMS significantly promoted nutrient accumulation in forestland. The bacterial alpha diversity in the SC treatment group was greater than that in the control and gradually decreased to the control level with interannual changes, while the trend of fungal alpha diversity was opposite to that of bacterial alpha diversity. Furthermore, the SC treatment group positively affected soil nitrogen metabolism-related microorganisms for two consecutive years and significantly promoted tree growth. Habitat niche breadth and null model analysis revealed that bacterial communities were more sensitive than fungal communities after SMS input. Linear mixed model (LMM) analysis revealed that SMS supplementation significantly positively affected bacteria (Gammaproteobacteria and Bacteroidota) and significantly negatively affected fungi (Coniochaetales). The constructed fungal-bacterial co-occurrence networks exhibited modularity, and the five types of bacteria were significantly correlated with soil organic matter (SOM), soil organic carbon (SOC), available potassium (AK), available phosphorus (AAP) and available nitrogen (AN) levels. The structural equation model (SEM) showed that bacterial diversity responded more to changes in soil nutrients than did fungal diversity. Overall, 30 kg/m2 of straw decomposition and 2 years of continuous cultivation were beneficial to soil health. This study provides new insights into the rational decomposition of straw and maintenance of forestland ecological balance by S. rugosoannulata.

Intraspecific variation in seagrass anti-herbivore defenses along a natural gradient in phosphorus availability impacts herbivore feeding decisions

Plant nutritional properties, physical defenses, and chemical defenses impact herbivore feeding decisions. While herbivores often prefer plants enriched with nitrogen, less is known about how phosphorus impacts plant-herbivore interactions. In this study, we investigated how seagrass-herbivore interactions vary along a natural gradient in phosphorus availability, using turtle grass Thalassia testudinum collected from 3 sites in Florida (USA) along the gradient (Weeki Wachee: low phosphorus and nitrogen; Homosassa: high phosphorus and nitrogen; Crystal River: high phosphorus and low nitrogen) and 2 common herbivores, variegated sea urchin Lytechinus variegatus and emerald parrotfish Nicholsina usta. T. testudinum plants from the phosphorus-poor site (Weeki Wachee) exhibited increased physical and chemical anti-herbivore defenses. Plants in Weeki Wachee had higher leaf fiber content, lower specific leaf area, and up to 2 times higher concentrations of phenolic acids and condensed tannins. Both L. variegatus and N. usta avoided consuming the plants from Weeki Wachee, preferring plants from sites with higher nutrient availability. However, feeding preferences varied between the 2 herbivore species, with L. variegatus often consuming similar amounts of the plants from the 2 phosphorus-rich sites (Homosassa and Crystal River) and N. usta preferring the plants from Homosassa, which had the highest concentrations of both phosphorus and nitrogen. These findings suggest that plants at the phosphorus-poor site invest more resources in anti-herbivore defenses, and this higher investment in defenses, along with lower leaf tissue phosphorus concentrations, deterred multiple herbivore species.

Enhancing the Production Performance and Nutrient Utilization of Laying Hens by Augmenting Energy, Phosphorous and Calcium Deficient Diets with Fungal Phytase (Trichoderma reesei) Supplementation

A ten-week trial was conducted to evaluate the enhancement of production performance and nutrient utilization of laying hens through augmenting energy, phosphorous, and calcium deficient diets with fungal phytase (Trichoderma reesei) supplementation. 720 Hy-line Brown hens aged 28 weeks were randomly divided into 5 groups; each group had 8 replicates of 18 hens. Five experimental diets were prepared and fed to corresponding groups. A positive control (PC) diet contained 3.50% of calcium (Ca), 0.32% of non-phytate phosphorus (NPP), and apparent metabolic energy (AME) of 11.29MJ/kg, while a negative control (NC) diet contained 3.30% of Ca, 0.12% of NPP, and lower AME of 300 kJ/kg. The other three diets were supplemented with 250 FTU/kg phytase (PHY-250), 1000 FTU/kg phytase (PHY-1000), and 2000 FTU/kg phytase (PHY-2000) in addition to a regular NC diet. Results indicated that the positive control (PC) diet group had higher body weight gain, egg weight, and average daily feed intake. However, laying rate, egg mass, and FCR were most improved in the PHY-2000 group, followed by the PHY-1000 and PHY-250 groups (p &lt; 0.05). Improved yolk color was most notable in laying hens fed the diet with PHY-1000 as opposed to the PC and NC groups (p &lt; 0.05), but no overall difference was found among all of the phytase treated groups. The apparent availability of dry matter, energy, phosphorus, and phytate P was significantly higher in the PHY-2000 group than in the PC and NC groups (p &lt; 0.05). Compared to the PC group, nitrogen retention was significantly higher in the PHY-1000 group, while calcium availability was higher in the PHY-250 group. The results suggested that the addition of phytase to diets with low P, Ca, and AME improved laying performance and apparent availability of dietary nutrients. Thus, it was concluded that the laying hen diet could be supplemented with 1000–2000 FTU/kg phytase for improving laying production and nutrient availability and mitigating the negative impact of reduced nutrient density in laying hen diets.

Hydrochars as slow-release phosphorus fertilizers for enhancing corn and soybean growth in an agricultural soil

Hydrochars as carbonaceous amendments rich in porous structures and nutrients can be used as promising slow-release fertilizers and soil health amendments. Yet, the performance of hydrochars derived from different feedstocks in improving crop plant growth and soil phosphorus (P) availability is not well understood. Here, a batch of sewage sludge (SS) and chicken manure (CM) derived hydrochars (SSCs and CMCs) were produced at 125 and 225 °C (SS125/225 and CM125/225) to investigate their characteristics and performances in improving the seedling growth of two representative crops, soybean (Glycine max) and corn (Zea mays), as well as the P availability in an acidic agricultural soil in comparison with triple super phosphate (TSP), a conventional P fertilizer. Compared with CMCs, SSCs with more porous and rougher surfaces contained relatively lower contents of carbon (C; 32.3–33.3%), hydrogen (H; 3.9–4.69%), and potassium (K; 29.2–51 mg g−1), but higher contents of P (37.4–85.4%) and nitrogen (N; 2.26–4.9%), as well as more O-containing and N-containing functional groups. The impacts of hydrochars on soybean and corn growth showed distinct variations. The application of SSCs showed little effect on soybean growth (i.e., biomass, chlorophyl contents, and number of leaves), while CMCs significantly increased its total dry biomass by 23.2–66.2%. For corn, both SSCs and CMCs increased the total dry biomass by 32.8–92.4% and 21.8–69.7%, respectively, compared to those in the un-amended soils. In addition, compared with the higher temperature hydrochars (SS225 and CM225), the lower temperature ones (SS125 and CM125) increased the total dry biomass by 24.6% and 34.9% for soybean and 44.8% and 39.3% for corn, respectively. The significant improvement in crop growth by hydrochars was mainly due to the direct nutrient supply (particularly P) by the hydrochars, which was supported by the increased soil and shoot P concentrations. Moreover, hydrochar application led to a rise in soil water soluble P (WSP) levels. However, as time progressed, these levels fell due to the fixation and adsorption of P via precipitation, electrostatic attraction, and ion exchange on the hydrochars. Contrarily, TSP maintained persistently high soil WSP levels, increasing the leaching risk of P through the soil profile. Our results provide direct evidence for hydrochars as slow-release P fertilizers to enhance crop growth and production and give better insights for producing functionalized P-rich chars as an alternative to chemical P fertilizers to maintain sustainable agricultural production.Graphical

Divergent responses between lineages of arbuscular mycorrhizal fungi to soil phosphorus and nitrogen availability

Arbuscular mycorrhizal (AM) associations are multifunctional. Two important functions they perform are facilitating nutrient uptake in host plants and protecting plants from biotic stress, among other functions. AM fungal taxa vary in how capably they perform these functions and can also respond differently to environmental selection. Therefore, there is a need to better understand how particular environmental variables might alter the response of AM fungal communities. Here, we analysed data from a DNA-based survey of fungal communities in soils collected throughout Australia to observe relationships among soil nitrogen and phosphorus availability and the abundance of two AM fungal taxa that reportedly vary in function – the Gigasporaceae (putatively more important for nutrient uptake) and Glomeraceae (putatively more important for biotic stress). Relationships were assessed in three vegetation types – grasslands, forests and woodlands – to assess whether associations with soil nutrition varied depending on carbon availability for AM fungi. Fungi from the Gigasporaceae decreased in frequency as available phosphorus increased, while those from the Glomeraceae increased or were unresponsive as available phosphorus increased. Similar patterns were observed for nitrate availability, although only in woodlands. These patterns are consistent with expectations that AM fungi from the Gigasporaceae, in general, are better suited to alleviate nutrient limitation in hosts as soil chemical fertility decreases. This knowledge may aid in implementing optimal strategies involving AM fungal inoculum best suited to the local conditions of future land management and agricultural projects.