Application Of Phosphate Fertilizers Research Articles

Rock Phosphate and Biochar Effects on Greenhouse Gas Emissions and Soil Fertility in Southern Alberta Potato Field

The application of biochar soil amendment and rock phosphate fertilizer to the soil could lead to achieving net zero emissions and food security; however, the effectiveness of using biochar and rock phosphate in southern Alberta brown chernozemic soil is not yet assessed. In the first trial of this study, varying levels of urea (N), with varying levels of biochar (B) were applied. The same level of rock phosphate (RP) and triple super phosphate (TSP) were applied to compare efficiency of the two fertilizers. The second trial involved applying the same nutrients, but with higher levels than the first trial. The results indicated that the fertilizer application rates did not affect the growth and yield of potatoes because of the application rates of the fertilizer and fertility status of the soil, whereas in the second trial, TSP and RP treatments had the same growth and yield. Furthermore, the high application rate of nitrogen fertilizer and RP with or without biochar in the potato plot emitted high nitrous oxide gas emissions while the low application rate of nitrogen fertilizer and RP kept the carbon dioxide in the soil. Nevertheless, in the second experiment, the application of biochar and rock phosphate reduced nitrous oxide and carbon dioxide emissions. We observed high residual nitrogen and manganese nutrients after harvest in the plot treated to rock phosphate and biochar. Therefore, rock phosphate and biochar have the potential to increase food production and mitigate climate change.

Reduction of chemical phosphate fertilizer application in a rice–rapeseed cropping system through continuous straw return

Context or problemStraw return has the potential to significantly contribute to nutrient recycling and utilization, thus reducing the reliance on chemical fertilizers. Extensive research has focused on nitrogen and potassium fertilizer management and the associated potential for reduction through straw return. However, the potential effect of straw return on reducing phosphorus (P) fertilizer application has been relatively overlooked due to the inherently low P content in straw.Objective or research questionThis study aimed to determine the potential benefits and underlying mechanism of reducing chemical P fertilizer application through straw return in a rice–rapeseed cropping system. MethodsWe conducted a five-year field experiment in a rice–rapeseed cropping system to investigate the effects of chemical P fertilizer reduction through straw return. Six fertilization treatments were investigated: no chemical P fertilization, 30, 60, 90, 120, and 60 kg P2O5 ha−1 with 6000 kg ha−1 straw return. ResultsThe result showed that continuous straw return increased yield, P uptake and P utilization during rice and rapeseed seasons. According to the P uptake level, the benefits from straw return were tantamount to applying 69.8–88.0 kg ha−1 of P fertilizer, which exceeded the actual amount of P input (64.5–70.3 kg ha−1) from fertilizer and straw. Straw C input mainly increased the content of soil microbial biomass C and P (MBC and MBP), which enhanced the supply capacity of available P, thereby increasing crop P uptake and reducing P fertilizer. The rapeseed season showed a higher chemical P fertilizer reduction rate (31.8%) than the rice season (14.0%). Moreover, rapeseed P uptake was more sensitive to soil Olsen-P, MBP and MBC than rice. The substitution efficiency of P fertilizer through the priming effect of straw C was higher in the rapeseed season (7.5 kg P2O5/1000 kg C) than in the rice season (2.1 kg P2O5/1000 kg C). ConclusionsOverall, under the rice–rapeseed cropping system, straw return increased soil MBC and MBP, thereby enhancing the supply capacity of available P. The C priming effect induced by straw return can partially reduce P fertilizer application. Compared with the rice season, straw return significantly substituted P fertilizer in the rapeseed season. IMplications or significanceThis study articulately delineates the role of straw return in enhancing soil P availability and crop P uptake and further highlights the potential of straw return as a strategy to reduce dependence on chemical P fertilizers in the rice–rapeseed cropping system.

Body size: A hidden trait of the organisms that influences the distribution of antibiotic resistance genes in soil

Body size is a key life-history trait of organisms, which has important ecological functions. However, the relationship between soil antibiotic resistance gene (ARG) distribution and organisms' body size has not been systematically reported so far. Herein, the impact of organic fertilizer on the soil ARGs and organisms (bacteria, fungi, and nematode) at the aggregate level was analyzed. The results showed that the smaller the soil aggregate size, the greater the abundance of ARGs, and the larger the body size of bacteria and nematodes. Further analysis revealed significant positive correlations of ARG abundance with the body sizes of bacteria, fungi, and nematodes, respectively. Additionally, the structural equation model demonstrated that changes in soil fertility mainly regulate the ARG abundance by affecting bacterial body size. The random forest model revealed that total phosphorus was the primary soil fertility factor influencing the body size of organisms. Therefore, these findings proposed that excessive application of phosphate fertilizers could increase the risk of soil ARG transmission by increasing the body size of soil organisms. This study highlights the significance of organisms' body size in determining the distribution of soil ARGs and proposes a new disadvantage of excessive fertilization from the perspective of ARGs.

Glyphosate residues in soil and phosphate fertilizer affect foliar endophytic microbial community composition and phytohormone levels in potato

Glyphosate, the active ingredient of glyphosate-based herbicide (GBH) controls the growth of weeds by inhibiting shikimate pathway, thereby interrupting amino acid biosynthesis in plants. However, several microbes have shikimate pathway and the action of glyphosate on these non-target organisms are ignored. Along with other agrochemicals such as phosphate fertilizers, the action of GBH is further complicated, often varying their mode of action depending on soil type or plant species. To address the impact of GBH and phosphate fertilizer, we simulated agricultural application of GBH and phosphate fertilizer in a field study, investigating the composition of endophytic microbial communities and correlation of phytohormone concentrations with the microbial diversity of potato (Solanum tuberosum). In leaves, glyphosate residues in soil from GBH treatment alone and in combination with phosphate significantly shifted bacterial community whereas phosphate alone and in combination with glyphosate significantly altered the composition of fungal community. There were no significant changes in microbial communities in roots and tubers. Plants treated with GBH showed higher ratios of potentially glyphosate-resistant bacteria, with Xanthomonadaceae and Moraxallaceae being more abundant. Additionally, phytohormone concentrations showed various correlations with bacterial and fungal diversity in different treatments. The study highlights the impact of GBH residues in soil, particularly in combination with phosphate fertilizers on the composition of plant-associated microbial communities. Together with changes in phytohormone concentrations, plant health may be affected. Moreover, future studies could provide insights to whether these agrochemicals influence plant microbiome, leading to changes in phytohormones or vice-versa.

Effect of various phosphorus levels on the extraction of Cd, the transformation of P, and phosphorus-related gene during the phytoremediation of Cd contaminated soil

Phytoremediation has emerged as a common technique for remediating Cd pollution in farmland soil. Moreover, phosphorus, an essential element for plants, can alter the pectin content of plant cell walls and facilitate the accumulation of Cd in plant tissues, thereby enhancing phytoremediation efficiency. Therefore, pot experiments were conducted in order to investigate the effect of phosphorus levels on Cd extraction, phosphorus transformation and phosphorus-related genes during phytoremediation. The results revealed that an optimal application of suitable phosphate fertilizers elevated the soil's pH and electrical conductivity (EC), facilitated the conversion of soil from insoluble phosphorus into available forms, augmented the release of pertinent enzyme activity, and induced the expression of phosphorus cycling-related genes. These enhancements in soil conditions significantly promoted the growth of ryegrass. When applying phosphorus at a rate of 600 mg/kg, ryegrass exhibited plant height, dry weight, and chlorophyll relative content that were 1.27, 1.26, and 1.18 times higher than those in the control group (P0), while the Cd content was 1.12 times greater than that of P0. The potentially toxic elements decline ratio and bioconcentration factor were 42.86% and 1.17 times higher than those of P0, respectively. Consequently, ryegrass demonstrated the highest Cd removal efficiency under these conditions. Results from redundancy analysis (RDA) revealed a significant correlation among pH, total phosphorus, heavy metal content, phosphorus forms, soil enzyme activity, and phosphorus-related genes. In conclusion, this study suggests applying an optimal amount of suitable phosphate fertilizers can enhance restoration efficiency, leading to a reduction in soil Cd content and ultimately improving the safety of crop production in farmlands.

Geospatial analysis of groundwater arsenic and fluoride in Quaternary aquifers of southern Ontario, Canada

The geological setting of an area plays a critical role in the transfer and ultimate distribution of hydrochemical constituents present in groundwater. In southern Ontario, Canada, the present physiography was significantly influenced by glacial processes during the Quaternary period. The heterogeneous nature and complex pattern of shallow subsurface glacial overburden sediments, likely affect the fate of different groundwater constituents. In this study, arsenic (As) and fluoride (F−) concentrations from 515 water wells, that are constructed within overburden sediment, were analyzed with the physiographic map of southern Ontario along with other related variables. Geospatial mapping and several spatial statistical analyses were performed to examine the possible geological influence on As and F− distribution and water-well susceptibility at a regional scale. Key findings suggest four physiographic settings were significant variables influencing the distribution of As and F− in differently constructed bored/dug and drilled wells. Bored/dug wells in Bevelled Till Plains and bored/dug wells in Undrumlinized and Bevelled Till Plains were found to be relatively susceptible to As and F− contamination respectively. In contrast, bored/dug and drilled wells in Drumlinized Till Plains and Drumlins and drilled wells in Sand Plains seemed to be relatively safe from F− and As respectively. The statistical regression analyses suggested that other variables, such as the application of phosphate fertilizer and the textures of till, influenced the spatial distribution of As and F− as well as which types of wells (bored/dug or drilled) were impacted. The geospatial mapping and statistical cluster analysis indicated that the possible sources of elevated As and F− in drilled wells are the clasts of underlying bedrock. The relationship between physiographic settings and impacted overburden wells in southern Ontario provides planners with an approach to water-well susceptibility assessments at the regional scale, which in turn can guide further local analysis for water resource management.

Pengaruh Pupuk Hayati Jamur Mikoriza Dan Pupuk Rock Phosphate Terhadap Serapan P, Pertumbuhan serta Hasil Tanaman Cabai Rawit (Capsicum frutescens L.)

Application of mycorrhizal fungi biological fertilizers and rock phosphate fertilizers can increase plant P uptake, growth and yield of cayenne pepper (Capsicum frutescens L.). The purpose of this study was to determine the effect of the interaction between mycorrhizal fungi biofertilizer and rock phosphate fertilizer on P uptake, growth and yield of cayenne pepper. The experimental design used was a completely randomized design (CRD) factorial with 2 factors and 3 replications. The first factor was the application of 0 gr (M0), 10 g (M1) and 20 g (M2) mycorrhizal fungal biofertilizers and the second factor was the application of 0 kg rock phosphate fertilizer or the equivalent of 0 g (R0), 150 kg or 1 g (R1) and 300 kg or 2.6 g (M2). The variables observed were plant height, number of fruit planted, fruit fresh weight, plant fresh weight, root volume, root infection, plant dry weight, root shoot ratio and P uptake. The observed data were tested using analysis of variance (ANOVA) and tested further. using Duncan multiple range test (DMRT) at 95% confidence level. The results showed that there was no interaction between the application of mycorrhizal fungi biofertilizers and rock phosphate fertilizers. Application of mycorrhizal fungal biofertilizer (M1) can increase the degree of root infection by 72.22%, the number of fruit planted, fruit fresh weight, plant fresh weight, plant dry weight, root volume, root infection, P uptake and root shoot ratio. Application of rock phosphate fertilizer can also increase the number of fruit plants, plant fresh weight, plant dry weight, root volume and P uptake.

Improved chlorophyll fluorescence, photosynthetic rate, and plant growth of Brassica napus L. after co‐application of biochar and phosphorus fertilizer in acidic soil

AbstractAimsBiochar has been used as an amendment to improve soil fertility and increase crop yield. A pot trial and incubation experiment were conducted to evaluate the effects of combined biochar and phosphate fertilizer applications on changes in soil physiochemical properties, photosynthetic parameters, and plant growth of Brassica napus L. in acidic soil.MethodsBiochar (B) was applied at rates (B0: 0%, B1: 2%, and B2: 4% w/w) to the soil, while phosphorus (P) as KH2PO4 was added at P0: 0 mg kg–1 soil, P1: 100 mg kg–1 soil, and P2: 150 mg kg–1 soil. Non‐amended soil served as the control (Ck).ResultsThe study found that the maximum photochemical quantum yield of photosystem II (Fv/Fm) and non‐photochemical quenching were affected by biochar and P fertilizer treatments. The Fv/Fm was significantly lower in the Ck while the highest in B2P1. Compared to the Ck treatment, the electron transport rate and photosynthetic rate were significantly increased under the application of biochar with P fertilizer. Additionally, malondialdehyde content declined by 68.9% when biochar was added with P fertilizer treatments. Furthermore, the plant P content and plant growth parameters were significantly increased. Biochar with and without P fertilizer treatments increased soil pH significantly, compared to the application of P fertilizer alone. Water‐soluble P decreased with incubation time, while Al‐P decreased significantly by 69.9% and 76.4% under B1 and B2 treatments, respectively, compared to CK.ConclusionThe findings revealed a positive effect of the combined application of biochar with phosphate fertilizer on the growth of oilseed rape in acidic soil.

Optimization of phosphate fertilizer application strategies to improve phosphorus availability and utilization in maize

AbstractThe optimization of phosphate (P) fertilizer application strategies to improve the utilization of P fertilizer in farmlands is urgently required. The objective of this study is to evaluate the effect of P fertilizer application rate and position on maize (Zea mays L.) P utilization. A 2‐year field experiment was conducted with P fertilizer application rate (0, 40, 80, and 120 kg ha−1) and position (5 and 10 cm). Compared with the 5‐cm P position, the 10‐cm P position significantly increased the available phosphorus (AP) content in rhizosphere soil. Surprisingly, the rhizosphere AP content increased or remained the same when the amount of P fertilizer was reduced to 80 kg ha−1 at a distance of 5 cm, compared with that when the amount of P fertilizer was 120 kg ha−1 at a distance of 10 cm. Additionally, there was also an improvement in the root weight, root number, biomass, and maize yield in the 5‐cm position compared to the 10‐cm position. The P fertilizer use efficiency was significantly increased at the 5‐cm position compared to the 10‐cm P position, with increases of 8.93% and 4.11% (P40), 6.38% and 5.10% (P80), and 4.72% and 2.36% (P120) in 2021 and 2022, respectively. Our results showed that a closer position increased the available P content in rhizosphere soil, promoted maize growth, and improved P fertilizer utilization and maize yield, suggesting that the agronomy method with proper location of P increases the soil P availability in rhizosphere soil and P utilization in maize.

Response of Transplanted Rice to Seedling Root-dip in Phosphorus and Biofertilizer Slurry in Acid Soils of North East India- A Participatory Assessment in Farmers’ Field

Background: Rice production is mainly constrained by low P-use efficiency (PUE) and P-recovery efficiency (PRE) in acid soils of the North East hill region of India. Efficient P fertilizer management strategies for rice production is very essential to achieve higher yield per unit of P fertilizer applied. Rhizosphere-based P management in wetland rice is considered as an efficient strategy to minimize the quantity of applied P to obtain a profitable yield. Methods: Seedling root dipping in P slurry technique in farmers’ field condition was studied in comparison to the conventional methods of application of recommended dose of fertilizer (RDF) and the integrated nutrient management (INM) practices to identify a suitable cost effective method of application of phosphatic fertilizer for the acid soils of this hill region of North East India. Result: The highest plant height, maximum number of effective tillers and root biomass were recorded in SSP root dip+Phosphate Solubilizing Bacteria (PSB) followed by INM practices. P root dip had greater root biomass (4.36 g plant-1) which was significantly higher than RDF (3.82 g plant-1). Root dip application showed higher yields (5.80 t ha-1), compared with INM (5.53 t ha-1) and RDF (5.46 t ha-1) and control (4.25 t ha-1). The result of the present study demonstrated that P-dipping can achieve high applied P use efficiency (1193.42) in transplanted rice compared to conventional incorporation of P (625.43). Thus, P-dipping is a potential strategy to overcome low applied P use efficiency in high P-fixing soils and hence reduces the need for excess P application.

Phosphorus fertiliser application mitigates the negative effects of microplastic on soil microbes and rice growth

Soil microplastics (MPs) have attracted widespread attention recently. Most studies have explored how soil MPs affect the soil's physicochemical parameters, matter circulation, and soil microbial community assembly. Similarly, a key concern in agricultural development has been the use of phosphorus (P) fertiliser, which is essential for plant health and development. However, the relationship between MPs and phosphate fertilisers and their effects on the soil environment and plant growth remains elusive. This study assessed the influence of adding low-density polyethylene MPs (1%) with different phosphate fertiliser application rates on microbial communities and rice biomass. Our results showed that MPs changed the structure of soil bacterial and phoD-harbouring microbial communities in the treatment with P fertiliser at the same level and suppressed the interactions of phoD-harbouring microorganisms. In addition, we found that MPs contamination inhibited rice growth; however, the inclusion of P fertiliser in MP-contaminated soils reduced the inhibitory action of MPs on rice growth, probably because the presence with P fertiliser promoted the uptake of NO3--N by rice in MP-contaminated soils. Our results provide further insights into guiding agricultural production, improving agricultural management, and rationally applying phosphate fertilisers in the context of widespread MPs pollution and global P resource constraints.

Temporal Changes in Cd Sorption and Plant Bioavailability in Compost-Amended Soils

The application of Cd-contaminated phosphate fertiliser has enriched concentrations of this non-essential element in many agricultural soils. Consequently, concentrations of the metal in some agricultural products exceed the Maximum Limit in foods. Composts can reduce the transfer of Cd from soil to plants; however, it is unclear how long this beneficial effect endures. We aimed to determine temporal changes of phytoavailable Cd in two market garden soils (an Allophanic Orthic Granular Soil and a Recent Silt Loam). Soils were amended with either municipal green waste compost or sawdust and animal waste compost at a rate of 2.5% w/w under three incubation regimes: at 19 °C, at 30 °C, and at 30 °C with additional N added as urea at 0.6 g urea/kg soil added over 1 year. Each replicate was sampled after 1, 5, 9, 13, 21, 31, and 49 weeks, and phytoavailable Cd was estimated through 0.05 M Ca(NO3)2 extraction. Seed potato (Solanum tuberosum), ‘Nadine’ variety, was grown in the Pukekohe Allophanic Orthic Granular Soil, freshly amended with municipal compost and the same soil aged for one year. The concentration of Cd in all samples was analysed using an ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer). The C concentration in the soil—compost mixtures decreased over the year, with the greatest decreases occurring in the soils incubated at 30 °C with added N. Unexpectedly, the concentration of Ca(NO3)2-extractable Cd in the compost-amended soils did not increase over time and in some cases even decreased. This was confirmed through a pot experiment, which showed the Cd concentration in potato was reduced by 50% in both the freshly amended soil and the amended soil aged for one year. Cadmium immobilisation in soils might be due to both the sorption of Cd by organic matter and the occlusion of sorbed Cd by oxy-hydroxides of iron and aluminium. Over 49 weeks, soluble Cd does not increase as organic matter oxidises. The application of municipal compost to soil will reduce both plant Cd solubility and plant Cd uptake for at least one year in the soils tested.

Effects of Phosphate Fertilization Rates on Physicochemical Properties of Potato Starch

AbstractThe objective of this study is to seek correlations between phosphate fertilization rates in potato cultivation and the chemical composition and physicochemical properties of the potato starch. Potato starches are prepared from the potato tubers cultivated in two different districts in Hokkaido, Japan, with different soil characteristics using varied phosphate fertilization rates. The chemical composition of the potato starches such as the amylose, phosphorus, and potassium contents and their physicochemical properties such as the swelling power, solubility, and pasting and thermal properties are evaluated. The results show that the phosphate fertilization rate has a moderate and positive correlation with the amylose content, while no correlations are found with any other chemical composition and physicochemical properties, including the phosphorus content. One plausible explanation for the lack of the correlation between the phosphate fertilization rate and the phosphorus content in the starch is that a sufficient amount of phosphorus has already been accumulated in the soils to phosphorylate the starch to the highest possible degree without further application of phosphate fertilizers. The present results imply that reducing the phosphate fertilization rate in potato cultivation in the studied fields has no negative impact on the chemical composition and physicochemical properties of potato starch.

Impact of phosphorus omission fertilizer on growth, nutritional status, biochemical and physiological parameters in a Pinus taeda L. plantation

Low availability of phosphorus (P) in the soil is one of the factors limiting the productivity of Pinus taeda plantations. Phosphate fertilizer application in Pinus shows divergence in growth responses. Thus, understanding the response of plant photosynthetic efficiency and growth in relation to phosphate fertilizer application can serve as a basis to guide management practices in Pinus taeda plantations. The study aimed to evaluate the impact of P omission fertilizer on growth parameters, nutritional, biochemical, and physiological status of a Pinus taeda L. plantation. The experiment was conducted on a Pinus taeda plantation subjected to P fertilization: Control - without addition of N, P and K; P–fertilized - with addition of N, P and K; and P–omission - addition of N and K, and P omission fertilizer. The parameters height, stem and canopy diameter and productivity factor, P concentration in needles, soil available P, electron transport rate (ETRm), maximum quantum yield of PSII (Fv/Fm), initial (Fo) and maximum (Fm) fluorescence, chlorophyll a, b and total, carotenoids, superoxide dismutase (SOD) and peroxidase (POD), hydrogen peroxide (H2O2), lipid peroxidation (TBARS), and acid phosphatase activity, were evaluated. P fertilized application increased soil available P, providing largest P uptake by roots and P concentration in needles. The increase in available soil P contributed to elevate photosynthetic parameters, such as ETRm, Fv/Fm, chlorophyll a, b and total, and carotenoids. These factors contributed to increase C assimilation, height, stem and canopy diameter and productivity factor parameters. On the other hand, the P–omission and control conditioned the growth of Pinus taeda under stress, elevating the values of Fo, Fm, SOD and POD, which reduced plant development.

Evidence for the accumulation of toxic metal(loid)s in agricultural soils impacted from long-term application of phosphate fertilizer

Phosphate fertilizers may contain elevated concentrations of toxic metals and metalloids and therefore, their excessive application can result in the accumulation of both phosphorus (P) and metal(loid)s in agricultural soils. This study aims to investigate the occurrence, distribution, and potential plant-availability of metal(loid)s originating from phosphate fertilizer in a long-term experimental field at the Tidewater Research Station in North Carolina, where topsoil (10–20 cm deep) and subsoil (up to 150 cm deep) samples were collected from five plots with consistent and individually different application rates of P-fertilizer since 1966. We conducted systematic analyses of P and metal(loid)s in bulk soils, in the plant available fraction, and in four sequentially extracted soil fractions (exchangeable, reducible, oxidizable, and residual). The results show that P content in topsoils were directly associated with the rate of P-fertilizer application (ρ = 1, p < 0.05). Furthermore, P concentrations were highly correlated with concentrations of Cd, U, Cr, V, and As in the bulk topsoil (ρ > 0.58, p < 0.05), as well as the potential plant-available fraction (ρ > 0.67, p < 0.01), indicating the accumulation of the fertilizer-derived toxic metal(loid)s in the topsoil. Significant correlations (p < 0.001) of metal(loid)s concentrations between the bulk soil and the potential plant-available fraction raises the possibility that P-fertilizer application could increase the accumulation of toxic metal(loid)s in plants, which could increase human exposure. Results from sequential leaching experiments revealed that large portions of the trace elements, in particular Cd, occur in the soluble (exchangeable and reducing) fractions of topsoil with higher P-fertilizer input, whereas the levels of redox-sensitive elements (As, V, U, Cr) were higher in the reducible and oxidizable fractions of the soils. Overall, the data presented in this study demonstrate the effect of long-term P-fertilizer application on the occurrence and accumulation of a wide range of toxic metal(loid)s in agricultural topsoil.

Effects of Phosphate Application Rate on Grain Yield and Nutrition Use of Summer Maize under the Coastal Saline-Alkali Land

Saline-alkali soil is a major threat to global food security. Phosphorus (P) fertilizer is essential for crop growth and yield production. Nevertheless, the optimal phosphate fertilizer application rates for summer maize under coastal saline–alkali soil are still unclear. A field experiment with five phosphate application rates (0, 45, 90, 135, and 180 kg ha−1, referred to as T1, T2, T3, T4, and T5, respectively) was conducted during the 2018–2020 summer maize seasons study the effects of phosphate rates on the grain yield, biomass, and nitrogen (N), P and potassium (K) accumulation, and N, P, and K physiological efficiency (denoted as NPE, PPE and KPE, respectively). Results showed that P application notably improved maize grain and biomass yield, the total uptake of N, P, K, and NPE and KPE across three seasons. As the P addition increased to 135 kg ha−1, the grain yield achieved a maximum of 7168.4 kg ha−1, with an average NPE of 2.15 kg kg−1, PPE of 0.19 kg kg−1, and KPE of 1.49 kg kg−1. However, PPE continuously decreased with the input of phosphate. P application rates exceeding 135 kg ha−1 were not considered effective due to a decline in grain yield, nutrient uptake, and NPE. Furthermore, the effect of the planting season was significant on the total uptake of N and K, and the use efficiency of N, P, and K. TOPSIS revealed that a phosphate application rate of 90–135 kg ka−1 was the optimal pattern for maize production. These results may give a theoretical basis for the phosphate management of maize production in saline–alkali soil.

INVESTIGATION OF THE PHENOMENON OF MIGRATION OF MOBILE FLUORINE COMPOUNDS IN THE SOILS OF THE COASTAL ZONE IN THE GUSKA RIVER

Today, there is significant contamination of soils with various chemical substances due to the action of the anthropogenic factor. Fluorine compounds are one of the dangerous pollutants contaminating the soil. The main source of their entry into the soil is the application of phosphate fertilizers, which contain fluorides in the form of impurities. In Ukraine, the problem of soil contamination with fluorides is particularly relevant due to the significant volumes of agro-industrial production.&#x0D; Fluorine compounds pose a particular danger due to the ability of their mobile (soluble) forms to spread (migrate) over considerable distances in the soil solution. This leads to the possibility of contamination of territories that were not directly fertilized.&#x0D; The article describes the importance of fluorine compounds for living organisms, as well as the consequences of their lack and excess in plant and animal organisms.&#x0D; Forms of the existence of Fluorine compounds in soils have been established: mobile form (soluble fluorides: NaF, KF) and immobile form (insoluble fluorides: CaF2, AlF3, FeF3), which are in constant dynamic equilibrium. The main factors affecting the relationship between the specified forms in the soil are described.&#x0D; In the course of the research, the content of mobile compounds of Fluorine in the soils of the coastal zone of the Huska River was measured. During the analysis of soil samples in 2021, a significant level of contamination was revealed. Exceeding the MPC was found in 9 samples out of 18 (MPC of mobile fluorides in soils – 2.8 mg/kg). On average, the samples exceeding the MPC had a fluoride content of 4.95 mg/kg. In 2022, none of the 20 samples exceeded the MPC of mobile fluorides.&#x0D; During the analysis of the obtained results, the phenomenon of migration of mobile compounds of Fluorine was investigated. To detect the phenomenon of migration of mobile compounds of Fluoride in the soils of the coastal zone of the Huska River, a sampling scheme was drawn up in order to monitor the content of fluorides along the potential direction of their migration. That is why the soil samples were taken in pairs: "field" - "shore", where "field" is the territory where phosphate fertilizers were applied, and "shore" is the coastal area that is close to the point of sampling from the field. Therefore, according to the results of research in 2021, a significant level of migration of mobile compounds of Fluorine was revealed. In particular, in 3 out of 9 pairs of samples, the MPC was exceeded both on the territory of the "field" and on the "shore" site. This indicates a certain contribution of the phenomenon of migration to the pollution of the environment by mobile compounds of Fluorine. Thus, according to the results of the study, the presence of the phenomenon of migration of mobile fluorides in these territories was revealed. This is evidenced by the exceedance of the MPC of fluorides in areas where fertilizers were not applied. A likely factor contributing to migration is the topography of the studied area.

Lead isotopes and rare earth elements geochemistry of global phosphate rocks: Insights into depositional conditions and environmental tracing

Phosphate rock bears both geologically and environmentally significant information. Rare earth elements and yttrium (i.e., REY) characteristics have been commonly used for reconstructing the redox conditions of depositional environments and the effects of post-depositional diagenetic alteration on phosphate rock. In addition, phosphate rock is typically enriched in a range of trace elements such as uranium (U) and cadium (Cd) that can be dispersed as contaminants into the environment with phosphate mining and phosphate fertilizer application. Here we report the lead (Pb) isotope compositions combined with Pb and REY concentrations of both global sedimentary and igneous phosphate rocks, aiming to evalute the geological origin of phosphate rocks over time and the potential of using them for environmental tracing. Phopshate rock samples analyzed in this study were sourced from major economic phosphate deposits in the world, including China, Southern Tethys (e.g., Morocco, Tunisia, Israel), the U.S., India, South Africa and Russia. Our results show a wide range of 208Pb/204Pb (35.70 to 60.58), 207Pb/204Pb (15.20 to 18.25), and 206Pb/204Pb (16.369 to 71.806) ratios in the phosphate rocks, with sedimentary phosphate rocks being significantly more radiogenic than igneous rocks. The majority of sedimentray phosphate rocks show a notable isotopic overprinting by non-radiogenic terrestrial Pb, except for those from Israel and Morocco that have the most radiogenic Pb isotope compositions. Correspondingly, phosphate rocks with more radiogenic Pb isotope ratios show relatively pristine seawater REY features, likely suggesting their preservation of the original oxic seawater conditions and/or minimal diagenetic alteration. In contrast, phosphate rocks with less radiogenic Pb isotope compositions show REY indications for more anoxic seawater redox conditions and/or greater diagenetic alteration. We further evaluate the potential utility of Pb isotopes for tracing the associated contamination with phosphate rock mining and fertilizer application in the environment. In most cases, the radiogenic Pb isotope composition of phosphate rocks and corresponding P-fertilizers is distinctive from both natural crustal Pb and major anthropogenic Pb sources (e.g., Pb ore deposits and pesticides), which provides a great advantage for applying Pb isotopes as an environmental tracer for metal(loid) contamination from phosphate sources. The combination of Pb isotope ratios and REY proxies could further constrain the Pb source discrimination. Overall, this study provides new Pb isotopic and REY geochemical data on global phosphate rocks and fertilizers, which lays the groundwork for future regional and local studies on both their geological and environmental implications.

Phosphorus Balance in Sandy Soil Subjected to 12 Years of Successive Applications of Animal Manure and Mineral Phosphate Fertilizer in Subtropical Climate

Assessing the phosphorus (P) balance in agricultural soils is crucial for optimizing its use and reducing contamination risks. The objective of this study was to evaluate the impact of different animal wastes on the distribution of P in soil profiles subjected to 12 years of successive applications of animal wastes and mineral phosphate fertilizer, within a crop rotation system under no-till system. The study was conducted from 2004 to 2016 in the southern region of Brazil. The treatments were the applications of pig slurry (PS), cattle slurry (CS), pig deep-litter (PD), mineral fertilizer (MF), and a control treatment without application. The highest accumulation of P and its movement was observed in the 0–40 cm layer, in the soil submitted to applications of all P sources. The inputs of P via MF, CS, PS, and PD promoted the accumulation of 18, 42, 48, and 100 kg P ha−1 year−1. The P mass balance showed that between 77 and 98% of the P added by animal manure and MF was accounted for in grain exports (17–34%), soil storage (41–72%), and post-harvest residues (&lt;1%), with the remaining 2–33%, unaccounted for, which was attributed, especially, to P transfer at the soil surface.

Fluoride contents in commonly used commercial phosphate fertilizers and their potential risks in China.

The application of phosphate fertilizer is an important source of anthropogenic fluoride in agricultural soil. However, relatively few studies have examined the fluoride content of phosphate fertilizers, and that has limited our understanding of the phosphate fertilizer contribution to soil fluoride accumulation and distribution. To examine this problem, we first quantified the total fluoride (TF) and water-soluble fluoride (WF) contents of six of the most commonly used commercial phosphate fertilizers in China (potassium dihydrogen phosphate (MKP), calcium superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), ternary compound fertilizer (NPK), and water-soluble macroelement fertilizer (WSF)). After calculating the [P2O5]/TF ratio for each of those fertilizers, we used those ratios and the average P2O5 application per crop of five typical crops grown in China (apples, greenhouse vegetables, wheat, corn, and rice) to estimate the annual fluoride accumulations in their soils after application of each type of phosphate fertilizer. Among the six fertilizer types, SSP, DAP, and NPK had much higher total fluoride and water-soluble fluoride contents than MKP, MAP, and WSF had. During crop production, the risk of fluoride accumulation was lower with MKP, MAP, and WSF (high [P2O5]/TF ratios) and higher with SSP, DAP, and NPK (low [P2O5]/TF ratios), especially in cash crops (fruit and greenhouse vegetables), which traditionally have unreasonably high P2O5 applications. Based on our findings, we proposed steps that should be taken to help effectively mitigate fluoride accumulation in China's agricultural soils.