Water-soluble Phosphorus Research Articles

Redistribution of phosphorus fraction driven by organic carbon and microbial community during composting

Available information on the coupling relationship between phosphorus fraction and organic carbon during composting remains limited. Thus, this research investigated the changes of phosphorus fraction, dissolved organic carbon fluorescent components and microbial community in swine manure composting with different carbon sources including the maize straw (MS), garden waste (GW) and distillers’ grains (DG), in order to investigate whether the distribution and availability of phosphorus are influenced by different carbon sources used in the composting of swine manure. The result showed that different carbon sources changed phosphorus availability variously mainly by altering the succession of fungal communities and phosphorus functional genes. The dissolved organic material including tyrosine and tryptophan facilitate the mineralization of organic phosphorus (Org-P) into water-soluble phosphorus, thereby improving phosphorus availability. However, humic acid-like carbon components promote the conversion of inorganic-phosphorus to Org-P, which is the direct cause of the reduced phosphorus availability during composting. The results of this study provide support for the development of phosphorus-rich, stable, and clean compost products.

Effect of Eighteen Years of Continuous Crop Residue Application on Crop Yields, Soil P Fractions, and Crop P Uptake in Conservation Tillage Under Semi-Arid Tropical Rainfed Conditions

The continuous use of crop residue in soil can enhance the crop yield and potential availability and mobility of P fractions to crops in conservation tillage. A field experiment was conducted to assess the long-term effects of surface crop residue applications on soil P fractions and their relationship with P uptake and crop yields. Field experiment was conducted at ICAR-Central Research Institute for Dryland Agriculture, Hyderabad, India during 2005 to 2022. The experimental treatments applied were: T1 - no crop residue application, T2 - application of crop residue @ 2 t ha-1, T3 - application of crop residue @ 4 t ha-1, and T4 - application of crop residue @ 6 t ha-1 in conservation tillage. The test crops viz. sorghum (Sorghum vulgare) and cowpea (Vigna unguiculata) were grown in a yearly rotation every year in the kharif season in conservation tillage. The results of the long-term study revealed that the per cent increase in sorghum (Sorghum vulgare) grain yield with the application of crop residue at the rate of 2, 4 and 6 t crop residue ha-1was to the tune of 7.9, 16.1 and 26.0%, respectively over no crop residue application. Similarly, the per cent increase in the cowpea (Vigna unguiculata) seed yield was to the extent of 25.2, 43.0 and 64.1% in 2, 4 and 6 t ha-1, respectively over no crop residue application. The sorghum and cowpea stover yield also significantly (p=0.05%) increased with the added levels of the crop residue. Significantly higher P uptake by sorghum and cowpea was recorded in 6 t crop residue ha-1 as compared to the other crop residue treatments. Results of the current study also showed the significant positive response of long-term crop residue application on the P fractions viz., water-soluble phosphorus (WS-P), aluminum bound P (Al-P), iron bound P (Fe-P), calcium bound P (Ca-P) and reductant soluble P (RS-P), and on available P and total P in soil as compared to no crop residue application. The average percent contribution of P fractions toward the sum-total of extracted P was in the order: Fe-P (30.8%)>RS-P (30.7%)>Al-P (24.2%)>Ca-P (9.4%)>WS-P (4.8%). The WS-P and Al-P were found to be the P fractions indicating their specificity by cowpea crop, and WS-P and Ca-P were found to be P fractions indicating their specificity by sorghum crop. The results of the present study will be highly useful in understanding the effect of crop residue application in conservation tillage on the P fractions and their contribution toward P uptake and crop yields.

Apparent digestibility and calcium and phosphorus in urine after feeding different combinations of calcium and phosphorus sources to adult dogs.

The present study aimed to investigate the effect of the combination of a water-soluble calcium (Ca) source (CaCl2) with a water-soluble phosphorus (P) source (NaH2PO4*2H2O, diet soluble, SOL) in comparison to a water-insoluble P source (CaHPO4*2H2O, diet insoluble, INS) on apparent digestibility and renal excretion of Ca and P in dogs. The Ca intake was 226 mg/kg bodyweight (bw), the Ca/P ratio 1.9/1 in SOL and 2.0/1 in INS. The percentage of Ca from CaCl2 was 60% in SOL and 33% in INS. Eight adult Foxhound-crossbred dogs FBI, (3-5 years, bw 24-32 kg) were available. Standard digestion trials were carried out (10 days adaptation, 5 days total faecal collection). Spontaneously excreted urine was collected pre- and postprandially. In vitro water solubility of P in the mineral premixes was determined. The Ca digestibility was negative in both trials without significant differences between the groups. Apparent P digestibility was increased in group SOL (26% vs. 20% in INS). In both groups, P content in urine was higher pre- compared to postprandial, with higher concentrations in group SOL. The same was true for the P/Crea ratio. The water solubility of P in the mineral premixes used in the trials showed considerable differences: The P in premix INS was insoluble in water after 1 and after 90 min. By contrast, the P in the premix SOL was highly soluble (98%) after 1 minute. After 90 min, however, the P solubility decreased to 43%, suggesting the formation of insoluble CaP salts, presumably from CaCl2 and NaH2PO4*2H2O. In conclusion, in the present study, apparent Ca digestibility in dogs was not affected by the solubility of Ca and P, while P digestibility and renal P excretion increased.

The Nutrient Content of Litter and Manure from Different Poultry Systems—Updating and Establishing the Nutrient Profile

Representative samples of litter and/or manure from 12 of the most common poultry systems were collected and analysed to provide an accurate nutrient profile from each system. For many systems (turkeys, broilers under indirect heating systems, and pullets), there were no previous values with which to compare composition, but for other systems (broiler breeders and layers), nitrogen and phosphate content were lower as a result of changes in diet and advancements in genetics and management. Nitrogen and phosphate output per 1000 birds was calculated for each system using analysed values for nitrogen and phosphate and measured litter/manure output. Due to a lack of data, it was not possible to compare the nutrient profile of all systems with published values, but where this was possible, some important differences were apparent. For example, the nitrogen and phosphate contents of BB (0–18 weeks) litter were 31% lower and 73% higher than current standard values. Similar differences were also observed for BB (18–60 weeks) (26% lower in nitrogen and 51% higher in phosphate). Turkey litter was found to contain 14% less nitrogen and 37% less phosphate than standard values. Litter from pullet systems contained higher levels of DM (72%), nitrogen, and phosphate than standard values. Litter from free range laying systems also contained higher DM (46%), nitrogen, and phosphate than standard values. This information will be useful in updating environmental legislation and ensuring that poultry producers are able to calculate accurate nutrient management plans for their enterprises. This study also established relations between litter/manure dry matter (DM) and nutrient profile, meaning that this simple measured parameter can be used to predict nutrient profile. The strongest relations were observed between DM and N (R2 = 0.65), DM and phosphate (R2 = 0.53), and DM and MgO (R2 = 0.69). The weakest relation was observed between DM and WSP content (R2 = 0.21), although still significant (p = 0.046). It was concluded that it is necessary to consider the relation within individual systems when using DM as a predictor of nutrient profile rather than using a combined system approach. The water-soluble phosphorus (WSP) content of litter/manure was determined and a baseline was established for each production system. It was also shown that DM is positively related (p < 0.05) to WSP content. This will be important for future legislative compliance based on the WSP content of litter/manure.

Effects of Application of Different Organic Materials on Phosphorus Accumulation and Transformation in Vegetable Fields

Presently, the improvement of soil organic matter is the basis to ensure food security, but the accumulation and transformation characteristics of soil phosphorus (P) as affected by organic matter remain unclear. The accumulation, transformation, and migration characteristics of soil P in different soil layers of vegetable fields were researched under the application of organic materials. Six treatments were set up in the experiment:control (no fertilization), traditional fertilizer application by farmers, biochar, chicken manure, food waste, and straw application. Available phosphorus (Olsen-P), water-soluble phosphorus (CaCl2-P) content, soil phosphorus forms, soil organic matter (SOM), and pH were determined during the pepper harvest period. In the 0-5 cm and 5-10 cm soil layers, the available phosphorus content of traditional fertilization of farmers was higher, and the available phosphorus content of the four organic materials was in the order of straw > biochar > chicken manure > food waste. Compared to that with food waste, the straw and biochar treatments increased soil available phosphorus by 59.6%-67.3% and 29.1%-36.9%, respectively. The straw treatment could easily enhance the soil labile P pool, and soil labile P in the 0-5 cm soil layer increased by 47.3% and 35.1% compared with that under the chicken manure and food waste treatments, respectively. With the increase in soil depth, the proportion of available phosphorus in the chicken manure treatment decreased the least, and available phosphorus of the 20-30 cm soil layer accounted for 55.9% of the topsoil layer but only accounted for 16.0%-34.0% under treatment with the other three materials. Compared with that under the traditional fertilization of farmers, the pH significantly increased by 0.18-0.36 units after the application of organic fertilizer, and the pH of the chicken manure and food waste treatments was significantly higher than that of biochar and straw (P < 0.05). SOM content under the biochar treatment significantly increased by 7.7%-17.6% compared to that under the other three organic materials. Among the four organic materials, the straw treatment boosted the labile P pool the most, which was conducive to the rapid increase in plant-available P. Phosphorus was most likely to migrate downward under the chicken manure treatment. In the field management based on soil fertility enhancement, the application of biochar could not only improve soil pH and SOM but also avoid excessive accumulation of phosphorus in the surface layer, which decreases environmental risks.

PROCESSING OF A WASHED DRY CONCENTRATE CONTAINING 26% P2O5 INTO AMMOPHOSPHATE, SULPHO- AND NITROAMMOPHOSPHATE FERTILIZERS

The process of obtaining ammophosphate by means of phosphoric acid decomposition of washed dried concentrate (WDC) with 26 % Р2О5 and 10 % СО) - raw material for the production of thermally fired concentrate, has been studied. The extraction phosphoric acid contains (mass. %): 16.46 P2O5, 0.06 CaO, 1.11 MgO, 0.27 Fe2O3, 0.41 Al2O3, 2.98 SO3 and 0.99 F. The mass ratio of WPPA: WDC ranged from 100: 10 to 100: 30. Then acidic phosphate pulps (at 65°C) after 45 minutes were ammoniated to pH = 3.8, granulated and dried at 85 - 90°C. It has been shown that the nitrogen content in the finished product ranges from 4.92 - 7.11 %, total phosphorus (P2O 5t.) 41.48 - 46.44 %, phosphorus assimilated by plants (P2O5acceptable) 34.79 - 45.11 %, water-soluble phosphorus (P2O 5w.s.) 23.49 - 37.73 %. The addition of 5 - 7.5 % H2SO4 or HNO3 in the form of a monohydrate makes it possible to intensify the process of phosphoric acid decomposition of phosphate raw materials and to obtain sulfo- and nitroammophosphate with significantly highcontents of P2O5 acceptable and P2O5 w.s.. So, with a weight fraction of WDC equals to 30 and weight fractions of H2SO4 - 5 and 7.5, there have been 37.6 and 34.47 % P2O5 total in sulfoammophosphate; 24.11 and 22.06 % CaO t. , 88.75 and 96.4 % P2O5 acceptable: P2O5t., 77.39 and 79.54 % P2O5 w.s. : P2O5t., 6.03 and 7.08 % nitrogen, respectively. In the case of using HNO3, nitroammophosphate contains the largest amount of nitrogen due to additionally introduced nitric acid, but the phosphate raw material has a relatively low decomposition coefficient. The strength of granules of all brands of fertilizers averages 3.50 MPa and are quite suitable for bulk storage and transportation. Material balances for the production of ammophosphate, sulfoammophosphate and nitroammophosphate have been calculated.

Predicting river phytoplankton blooms and community succession using ecological niche modeling

AbstractExcessive phytoplankton concentrations in rivers can result in the loss of plant and invertebrate communities, and threaten drinking water supplies. Whilst the physicochemical controls on algal blooms have been identified previously, how these factors combine to control the initiation, size, and cessation of blooms in rivers is not well understood. We applied flow cytometry to quantify diatom, chlorophyte, and cyanobacterial group abundances in the River Thames (UK) at weekly intervals from 2011 to 2022, alongside physicochemical data. A niche modeling approach was used to identify thresholds in water temperature, flow, solar radiation, and soluble reactive phosphorus (SRP) concentrations required to produce periods of phytoplankton growth, with blooms only occurring when all thresholds were met. The thresholds derived from the 2011 to 2018 dataset were applied to a test data set (2019–2022), which predicted the timing and duration of blooms at accuracies of > 80%. Diatoms and nano‐chlorophyte blooms were initiated by flow and water temperature, and usually terminated due to temperature and flow going out of the threshold range, or SRP and Si becoming limiting. Cyanobacterial bloom dynamics were primarily controlled by water temperature and solar radiation. This simple methodology provides a key understanding of phytoplankton community succession and inter‐annual variation and can be applied to any river with similar water quality and phytoplankton data. It provides early warnings of algal and cyanobacterial bloom timings, which support future catchment management decisions to safeguard water resources, and provides a basis for modeling changing phytoplankton bloom risk due to future climate change.

Comparative Analysis of Soil Phosphorus Determination Methods and Their Correlation with Plant Phosphorus in Standing Wheat Crops

This study compared the accuracy of various soil phosphorus assessment methods to measure the soil's ability to supply plants with phosphorus over a brief period in the field. Twenty individual soil samples were collected from a standing wheat (Triticum aestivum L) crop at depths ranging from zero to twenty centimeters. An equivalent plant spike sample was also procured from the soil sampling fields. In comparison to the wet acid digestion method used to detect phosphorus in plants, several methods were utilized to assess phosphorus in the soil, including resin extractable phosphorus, AB-DTPA extractable phosphorus, NaHCO3 extractable phosphorus, water-soluble phosphorus in suspension, and paste. The levels of variation and deficiency of phosphorus, which were found by different methods followed different patterns as shown by the fact that, AB-DTPA method finds phosphorus deficiency in 20% of samples while on the other hand, Olsen method finds phosphorus deficiency in 80% of samples. Even with such a small sampling area, none of the procedures showed a significant correlation with any other method that might account for uneven variation among the samples when determined by distinct procedures. However, corrections were observed to a certain degree between ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) extractable and resin, as well as between other procedures and the plant P scale. Both resin and ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) had a strong relationship with plant phosphorus, with the former showing a significant correlation of 0.48 and 0.21, respectively. Hence Resin and AB-DTPA methods are recommended for the determination of phosphorus under certain soil and plant conditions.

PH-Dependent molecular switch based on Pv porphyrin

Water-soluble phosphorus(v) porphyrin with p-amino- phenoxy groups as axial ligands was obtained, and its photophysical and photochemical properties were investigated and rationalized using quantum chemical calculations. It was demonstrated that at pH ≥ 6.1 this porphyrin did not emit or generate singlet oxygen, whereas at pH ≤ 2.0 it completely converted into the N-protonated form, which exhibited fluorescence and the ability to generate singlet oxygen.

Adsorption and immobilization of phosphorus from water and sediments using a lanthanum-modified natural zeolite: Performance, mechanism and effect

The challenge of effectively controlling endogenous pollution and achieving phosphate recovery remains a hotspot worldwide. The development of a passivator with high adsorption capacity and superior passivating effect is crucial for effective implementation in controlling endogenous pollution. In this study, a lanthanum-modified natural zeolite (LZ) and a lanthanum-modified magnetic zeolite (LMZ) were synthesized using precipitation and hydrothermal methods. Additionally, characterization and incubation experiments were conducted to assess the adsorption and passivation effects of the material. The results showed that the LZ and LMZ had excellent phosphorus (P) adsorption and passivation capabilities. LZ and LMZ exhibited remarkable adsorption capacities of 122.7 and 109.17 mg/g, respectively, surpassing those of most lanthanum-modified materials. The characterization showed that inner sphere complexation and electrostatic attraction served as the primary mechanisms facilitating phosphate adsorption. Moreover, LZ and LMZ were also used as sediment passivators to immobilize P within sediments. The addition of LZ and LMZ could not only control the release of P in overlying water but also transform unstable iron-bound phosphorus (BD-P) and organoclastic phosphorus (Org-P) into stable aluminum-bound phosphorus (OH-P) and calcium-bound phosphorus (H-P). The application of both LZ and LMZ could effectively reduce various forms of Bio-P in the sediment, including algal-available phosphorus (Al-P), sodium bicarbonate extractable phosphorus (Olsen-P), water-soluble phosphorus (WA-P), and iron oxide extractable phosphorus (Fe-P). The amount of LZ and LMZ needed for fixed Fe-P in sediments could be quantitatively calculated within a certain range. Since LMZ could be recovered from water under the action of an applied magnetic field and had better effects on the potential active phosphorus (Mob-P) and Bio-P in the sediments, LMZ could have high potential for use as a passivator for internal pollution control.

Influence of the pyrolysis temperature on fresh and pelletised chicken litter with focus on sustainable production and utilisation of biochar

AbstractThis study focused on determining the influence of temperature (500–700 °C) during pyrolysis of pelletised chicken litter (PCL) and fresh chicken litter (FCL). The composition of all pyrolysis products was analysed, and their potential applications were discussed. An analysis of phosphorus speciation in FCL and PCL along with their derived biochars revealed that the share of water-soluble phosphorus was greatly reduced in the biochar, implying lower risk of eutrophication in agricultural applications of biochar when used as a soil improver. Indeed, water-soluble phosphorus decreased from 60% for PCL to as low as 3% for the biochars. In addition, the concentration of other nutrients and heavy metals in biochar, and its potential for agriculture application was discussed. Heavy metals content was below the upper limits set out in the European Fertilising Products Regulation only for biochars produced at 500 °C, but biochars produced at higher temperatures did not meet the limits for Zn and Ni content. The energy balance analysis showed that pelletisation of chicken litter is not necessary, as the properties of both PCL and FCL allow for energetically sustainable pyrolysis when hot pyrolysis gas is combusted, and biochar recovered for nutrient recycling.

Addressing Phosphorus Waste in Open Flow Freshwater Fish Farms: Challenges and Solutions

Legislation and interest exists to protect and restore freshwater and marine ecosystems from the environmental impact of aquaculture. However, aquaculture-induced eutrophication remains a major environmental concern. Water soluble phosphorus, uneaten feed, feces, and metabolic waste from farmed fish increase phosphorus concentrations in adjacent waters. In open freshwater fish farms, in particular, the effects can be more immediate, as excess phosphorus is introduced directly into ecosystems. Several intestinal enzymes, transporters, and regulating factors have been implicated in farmed fish dietary phosphorus retention. For example, alkaline phosphatase and other transporters aid in the absorption of phosphorus in the anterior intestine, while pH, calcium, and vitamin D influence these enzymes and transporters. This process may also be influenced by intestinal morphology and the gut microbiome. To reduce phosphorus pollution from open flow fish farms, a thorough understanding of the processes that affect nutrient retention and absorption, as well as the impact of dietary factors, anti-nutritional substances, and intestinal morphology, is required. Aquaculture can be made more sustainable by reducing phosphorus release. This can be achieved by optimizing feed composition, adding functional feed ingredients, managing gut health, and treating effluent aquaculture waters with bioremediation and absorbing materials. Anti-nutritional factors can be mitigated through processing and through the use of functional feed additives. Addressing these issues will reduce aquaculture’s environmental impact, ensuring aquatic ecosystem health and global food security. In addition, treating effluent aquaculture waters with bioremediation and absorbing materials can remove phosphorus from the water, preventing it from entering the environment. This can further reduce the environmental impact of aquaculture and help to ensure the sustainability of this sector.

Comparative study of sediment phosphorus immobilization via the addition of lanthanum-modified and thermal-modified drinking water treatment sludge.

Lanthanum-modified drinking water treatment sludge (DTSLa) and thermal-modified drinking water treatment sludge (TDTS) were prepared from drinking water treatment sludge(DTS). The adsorption properties of DTSLa and TDTS on phosphate in water and the effects on the controlled release and morphology of phosphorus in sediment at different dosages (0%, 2.5%, 5%) were discussed. Combining with SEM, BET, XRD, FTIR, and XPS characterization methods, the immobilization mechanism of DTSLa and TDTS on phosphorus in sediment was explored. The addition of TDTS can transform NH4Cl-P (loosely sorbed P), BD-P (bicarbonate-dithionite extractable P), and Org-P (organic P) into stable NaOH-rP (metal oxide-bound P) in sediment, and the conversion amount will increase with the increase of TDTS supplemental amount. DTSLa converted NH4Cl-P, BD-P, Org-P, and NaOH-rP to more stable HCl-P (calcium-bound P). At the same time, the content of WSP (water-soluble phosphorus) and olsen-P (NaHCO3 extractable P) in sediment can be reduced by the addition of DTSLa and TDTS, reducing the risk of the release of phosphorus from the sediment to the overlying water. In addition, phosphorus can be directly removed from the interstitial water by DTSLa and TDTS, so as to reduce the phosphorus concentration gradient between the overlying water and the interstitial water, thus inhibiting the release of phosphorus from interstitial water to overlying water. The results showed that DTSLa is better than TDTS in terms of its adsorption capacity and adsorption effect on endogenous phosphorus in water, so DTSLa is more suitable to be used as a sediment conditioner to control the phosphorus content in water and sediment.

Antimicrobial activity of photosensitizers: arrangement in bacterial membrane matters.

Porphyrins are well-known photosensitizers (PSs) for antibacterial photodynamic therapy (aPDT), which is still an underestimated antibiotic-free method to kill bacteria, viruses, and fungi. In the present work, we developed a comprehensive tool for predicting the structure and assessment of the photodynamic efficacy of PS molecules for their application in aPDT. We checked it on a series of water-soluble phosphorus(V) porphyrin molecules with OH or ethoxy axial ligands and phenyl/pyridyl peripheral substituents. First, we used biophysical approaches to show the effect of PSs on membrane structure and their photodynamic activity in the lipid environment. Second, we developed a force field for studying phosphorus(V) porphyrins and performed all-atom molecular dynamics simulations of their interactions with bacterial lipid membranes. Finally, we obtained the structure-activity relationship for the antimicrobial activity of PSs and tested our predictions on two models of Gram-negative bacteria, Escherichia coli and Acinetobacter baumannii. Our approach allowed us to propose a new PS molecule, whose MIC50 values after an extremely low light dose of 5J/cm2 (5.0 ± 0.4μg/mL for E. coli and 4.9 ± 0.8μg/mL for A. baumannii) exceeded those for common antibiotics, making it a prospective antimicrobial agent.

Investigating the novel process for thorough removal of eutectic phosphate impurities from phosphogypsum

Phosphogypsum is the major component in solid waste of phosphoric acid manufacturing. After purification, phosphogypsum can be used as an alternative material to natural gypsum. Phosphate impurities, especially eutectic phosphorus, are challenging to be removed thoroughly from phosphogypsum. In this work, we reported a novel phosphogypsum purification process, in which the phase transition activation by calcination was combined with sulfuric acid dissolution during hydration. The two critical parameters, activation temperature and H2SO4 concentration were optimized for this process. Moreover, powder X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) were used to determine the purification efficiency for removing eutectic phosphate impurity from phosphogypsum. The comprehensive characterization results suggested that this novel process can remove eutectic phosphate impurities through the mutual transformation of different crystalline forms of calcium sulfate combined with sulfuric acid dissolution. Under the optimal purification condition (165 °C activation and 1.0 wt% H2SO4), the removal rate of eutectic phosphorus reached up to 98.3%, corresponding to overall eutectic phosphorus content decreasing from 0.58% to 0.01%. Meanwhile, the water-soluble phosphorus and insoluble phosphorus were also completely removed. Thus, 99.4% of phosphate impurity (as P2O5) was removed from phosphogypsum after the two-step treatment. The findings of this paper indicated that this novel process could separate phosphate impurity in an efficient and thorough manner, enabling sustainable utilization of phosphogypsum.

Activated ZnCl2 biochar and humic acid as additives in monoammonium phosphate fertilizer: Physicochemical characterization and agronomic effectiveness

Activated zinc biochar (ZnBC) and humic acid (HA) were used as coating agents in a soluble monoammonium phosphate (MAP) to modify phosphorus (P) use efficiency by altering adsorption/desorption kinetics between the granule region and the soil. The coated treatments MAPZnBC and MAPHA were compared with MAP through P diffusivity, kinetics, and agronomic evaluation. Eucalyptus sawdust was used as biomass for biochar synthesis, and a pre-pyrolysis treatment with zinc chloride (ZnCl2) was applied. The P diffusivity was evaluated in the fertosphere zone. Adsorption and desorption potential of the ZnBC compared with control biochar (BC) was evaluated separately. Desorption kinetics of P from soil was assessed after incubation with MAPZnBC and MAPHA. The shoot dry matter yield (SDM), P uptake, and P use efficiency (PUE) were evaluated with a pot experiment in a clay Oxisol sown with maize and soybeans as successive plant trials, under glasshouse conditions. Surface area values of 940 and 305 m2 g−1 combined with adsorption capacities of 106 and 53 mg P g−1 for ZnBC and BC, respectively, confirm the increased capacity of activated biochar to adsorb P. Both MAPZnBC and MAPHA decreased P diffusivity compared to MAP after 20 days of incubation. Moreover, MAPZnBC and MAPHA presented 20% and 34% more water-soluble phosphorus recovery. MAPZnBC expressed an increase in SDM while MAPHA highlighted P uptake and PUE compared with MAP. Both kinetic studies and agronomic evaluations showed that ZnBC and HA are suitable as coatings for phosphate fertilizers in terms of increasing P efficiency in the fertosphere on high P-fixing soils.

Digestion and utilization of plant-based diets by transgenic pigs secreting β-glucanase, xylanase, and phytase in their salivary glands.

Novel transgenic (TG) pigs co-expressing three microbial enzymes, β-glucanase, xylanase, and phytase, in their salivary glands were previously generated, which exhibited reduced phosphorus and nitrogen emissions and improved growth performances. In the present study, we attempted to explore the age-related change of the TG enzymic activity, the residual activity of the enzymes in the simulated gastrointestinal tract, and the effect of the transgenes on the digestion of nitrogen and phosphorus content in the fiber-rich, plant-based diets. Results showed that all the three enzymes were stably expressed over the growing and finishing periods in the F2 generation TG pigs. In simulated gastric juice, all the three enzymes exhibited excellent gastrointestinal environment adaptability. The apparent total tract digestibility of phosphorus was increased by 69.05% and 499.64%, while fecal phosphate outputs were decreased by 56.66% and 37.32%, in the TG pigs compared with the wild-type littermates fed with low non-starch polysaccharides diets and high fiber diets, respectively. Over half of available phosphorus and water-soluble phosphorus in fecal phosphorus were reduced. We also found the performance of phosphorus, calcium, and nitrogen retention rates were significantly improved, resulting in faster growth performance in TG pigs. The results indicate that TG pigs can effectively digest the high-fiber diets and exhibit good growth performance compared with wild type pigs.

Prediction of phosphorus concentrations in shallow groundwater in intensive agricultural regions based on machine learning

Excessive accumulation of phosphorus in soil profiles has become the main source of phosphorus in groundwater due to the application of phosphorus fertilizers in intensive agricultural regions (IARs). Elevated phosphorus concentrations in groundwater have become a global phenomenon, which places enormous pressure on the safe use of water resources and the safety of the aquatic environment. Currently, the prediction of pollutant concentrations in groundwater mainly focuses on nitrate nitrogen, while research on phosphorus prediction is limited. Taking the IARs approximately 8 plateau lakes in the Yunnan-Guizhou Plateau as an example, 570 shallow groundwater samples and 28 predictor variables were collected and measured, and a machine learning approach was used to predict phosphorus concentrations in groundwater. The performance of three machine learning algorithms and different sets of variables for predicting phosphorus concentrations in shallow groundwater was evaluated. The results showed that after all variables were introduced into the model, the R2, RMSE and MAE of support vector machine (SVM), random forest (RF) and neural network (NN) were 0.52–0.60, 0.101–0.108 and 0.074–0.081, respectively. Among them, the SVM model had the best prediction effect. The clay content and water-soluble phosphorus in soil and soluble organic carbon in groundwater had a high contribution to the prediction accuracy of the model. The prediction accuracy of the model with reduced number of variables showed that when the number of variables was equal to 6, the RF model had R2, RMSE and MAE values of 0.53, 0.108 and 0.074, respectively, and the number of variables increased again; there were small changes in R2, RMSE and MAE. Compared with the SVM and NN models, the RF model can achieve higher accuracy by inputting fewer variables.

A Circular Economy Model to Improve Phosphate Rock Fertiliser Using Agro-Food By-Products

Phosphorus (P) is an essential nutrient for the plant life cycle. The agricultural management of phosphorus is complicated by the inefficient use of phosphorus by plants, consequent environmental losses, and the rapid consumption of slowly renewed phosphate rock (PR). These issues represent a huge environmental burden and jeopardise food production. In this study, we proposed the combination of this fertiliser with food-processing by-products such as olive pomace, barley spent grain, and citrus pomace to increase phosphate rock solubility and the efficient use of P. Phosphate rock, by-products, and mixtures of phosphate rock and by-products were placed into litterbags and buried in sand. Periodically, one replicate per treatment was collected for the destructive measurement of total and water-soluble phosphorus. In parallel, pH, organic matter, and ash content were measured to investigate the mechanisms behind changes in P content. The mixtures’ P-release values ranged between 80% and 88%, whereas phosphate rock lost 23% of its P over 30 days. Phosphate rock showed a constant water-soluble P fraction at the four sampling times, whereas the mixtures exhibited a highly water-soluble P fraction that tended to decrease over time. Specifically, citrus pomace led to the significant and rapid release of phosphorus, barley spent grain maintained the highest water-soluble fraction over 30 days, and olive pomace was not the best-performing product but still performed better than pure phosphate rock. Moreover, the increased solubility of phosphate rock in mixtures was significantly (p < 0.001) ascribed to the reduction in pH. The results of this experiment are promising for in vivo trials and suggest the possibility of simple and easily achievable solutions for more sustainable production systems and effective P-fertilisation strategies. Proposing such easily applicable and inexpensive solutions can reduce the distance between research achievements and field applications.

Shallow Groundwater Around Plateau Lakes: Spatiotemporal Distribution of Phosphorus and Its Driving Factors

The extensive application of phosphorus fertilizers to croplands and the aggregation of towns and villages around plateau lakes has resulted in the continuous accumulation of phosphorus in the soil profile and the discharge of phosphorus pollutants, which causes phosphorus pollution in shallow groundwater around the lakes. The phosphorus entering the lake with shallow underground runoff in the region around the lake also affects the water quality safety of plateau lakes. The spatiotemporal differences in phosphorus concentrations in 452 shallow groundwater samples and the driving factors were analyzed by monitoring wells in croplands and residential areas around the eight lakes in Yunnan province during the rainy and dry seasons from 2019 to 2021. The results showed that seasonal changes and land use influenced phosphorus concentrations and their composition in shallow groundwater. The concentration of phosphorus in shallow groundwater in the rainy season was higher than that in the dry season, and it was also greater in cropland than that in residential areas. DTP was the dominant form of TP, accounting for 75%-81%, and DIP was the dominant form of DTP, accounting for 74%-80%. Nearly 30% of the samples around the eight lakes had TP concentrations exceeding the surface water Class Ⅲ standard (GB 3838); the exceeded rates of phosphorus in groundwater around the Erhai Lake (52%), Qiluhu Lake (45%), Xingyun Lake (42%), and Dianchi Lake (29%) were far higher than those of Yangzonghai Lake (16%), Fuxianhu Lake (13%), Chenghai Lake (6%), and Yilonghu Lake (5%). The key driving factors of phosphorus concentrations in shallow groundwater were water-soluble phosphorus (WEP), water content (MWC), soil organic matter (SOM), total nitrogen (TN), pH in the soil profile, and pH and groundwater level in the shallow groundwater (P<0.05). The increases in WEP, SOM, TN, and MWC in the soil and pH in groundwater significantly increased the concentrations of DIP and DTP in shallow groundwater, whereas the decrease in groundwater level significantly reduced the concentrations of DTP and DIP in the groundwater.