Phosphorus Losses Research Articles

Optimizing irrigation and planting strategies to prevent non-point source pollution in the Hetao Irrigation District using SWAT-MODFLOW-RT3D model

Non-point source (NPS) pollution is a significant issue in the Hetao Irrigation District (HID), affecting local water environment and ecological safety. To explore solutions for managing NPS pollution in the HID, this study establishes the SWAT-MODFLOW-RT3D (SMFR) model based on data from recent years. The results show that the determination coefficient (R2) of monthly drainage simulation for both the calibration and validation periods are >0.6, the Nash-Sutcliffe efficiency (NSE) values are >0.7, and the percent bias (PBIAS) values are <10 %. For pollutant transport simulation (total nitrogen and total phosphorus), the R2 values for both calibration and validation periods exceed 0.6, the NSEs are >0.75, and the PBIAS values are below 20 %. The model demonstrates good performance in simulating hydrology and pollutant transport in the study area, indicating strong applicability. Building on this, the spatial and temporal distribution characteristics of nitrogen and phosphorus losses in the HID were analyzed, and the impacts of different agricultural management practices, such as irrigation and fertilization regimes, drip irrigation under film (DIUF), and crop structure adjustments, on NPS pollution were assessed. Extensive scenario testing indicates that deficit irrigation and DIUF reduce total nitrogen (TN) in agricultural NPS pollution by 7.74 % and 9.34 %, respectively, and total phosphorus (TP) by 35.12 % and 40.99 %, respectively. In contrast, crop structure adjustments have a relatively moderate reduction effect on TN and TP, ranging from 2.66 % to 6.80 %. Additionally, the study examines the NPS pollution control effects of various combined scenarios. Through economic benefit evaluation, it was found that the scenario combining deficit irrigation with crop structure adjustments has a lower cost-effectiveness (CE) ratio and a higher cost-benefit (CB) ratio, making it a more favorable measure for controlling NPS pollution in the HID.

Phosphorus dynamics and sustainable agriculture: The role of microbial solubilization and innovations in nutrient management

Phosphorus (P) is an essential element for plant growth, playing a crucial role in various metabolic processes. Despite its importance, phosphorus availability in soils is often restricted due to its tendency to form insoluble complexes, limiting plant uptake. The increasing demand for phosphorus in agriculture, combined with limited global reserves of phosphate rock, has created challenges for sustainable plant production. Additionally, the overuse of chemical phosphorus fertilizers has resulted in environmental degradation, such as eutrophication of water bodies. Increasing agronomic phosphorus (P) efficiency is crucial because of population growth and increased food demand. Hence, microorganisms involved in the P cycle are a promising biotechnological strategy that has gained global interest in recent decades. Microorganisms' solubilization of phosphate rock (PR) is an environmentally sustainable alternative to chemical processing for producing phosphate fertilizers. Phosphorus-solubilizing microorganisms (PSMs), including bacteria and fungi, and their enzymatic processes offer an eco-friendly and sustainable alternative to chemical inputs by converting insoluble phosphorus into forms readily available for plant uptake. Integrating PSMs into agricultural systems presents a promising strategy to reduce dependence on chemical fertilizers, enhance soil health, and contribute to the transition toward more sustainable and resilient agricultural practices. It can be an alternative that reduces the loss of phosphorus in the environment, especially the eutrophication of aquatic systems. This paper explores the challenges of phosphorus availability in agriculture and the potential of microbial phosphorus solubilization as a sustainable alternative to conventional practices.

Spatiotemporal variations of cropland phosphorus runoff loss in China

Quantitative assessment of cropland phosphorus (P) loss via surface runoff is essential for developing effective pollution mitigation strategies. In this study, we compiled 812 datasets from 114 peer-reviewed papers for cropland P loss across China. We then developed machine learning (ML) approaches to estimate temporal and spatial variations in P runoff loss across China from 1990 to 2020. Four prevalent ML models were considered, namely, multiple linear regression (MLR), random forest (RF), classification and regression trees (CART), and boosted regression trees (BRT). Among these four models, RF exhibited the highest predictive accuracy for both uplands (calibration: R2 = 0.86, n = 293; validation: R2 = 0.61, n = 96) and paddy fields (calibration: R2 = 0.88, n = 137; validation: R2 = 0.60, n = 44). According to RF, China’s croplands are estimated to have lost an average of 148 ± 27 Gg P yr−1 from 1990 to 2020, with uplands and paddy fields contributing 114 ± 26 Gg P yr−1 and 34 ± 4 Gg P yr−1, respectively. There was a significant increase in upland TP runoff loss over the study period (p < 0.001), whereas paddy field TP loss remained relatively constant. Regions in southern, eastern, and southwestern China, notably in Hainan, Guangxi, and Fujian provinces, were identified as hotspots of cropland TP runoff loss. Improved cropland management scenarios were predicted to reduce TP runoff loss by 1.4–11.8 %, with the best results obtained by minimizing runoff depth. To effectively mitigate TP runoff loss, an integrated management approach involving water, soil, and fertilizer is recommended. This study enhances quantitative understanding of cropland TP runoff loss in China, providing crucial insights for efficient cropland P management, which is key to managing nonpoint source pollution on a national level.

Increasing phosphorus loss despite widespread concentration decline in US rivers

The loss of phosphorous (P) from the land to aquatic systems has polluted waters and threatened food production worldwide. Systematic trend analysis of P, a nonrenewable resource, has been challenging, primarily due to sparse and inconsistent historical data. Here, we leveraged intensive hydrometeorological data and the recent renaissance of deep learning approaches to fill data gaps and reconstruct temporal trends. We trained a multitask long short-term memory model for total P (TP) using data from 430 rivers across the contiguous United States (CONUS). Trend analysis of reconstructed daily records (1980-2019) shows widespread decline in concentrations, with declining, increasing, and insignificantly changing trends in 60%, 28%, and 12% of the rivers, respectively. Concentrations in urban rivers have declined the most despite rising urban population in the past decades; concentrations in agricultural rivers however have mostly increased, suggesting not-as-effective controls of nonpoint sources in agriculture lands compared to point sources in cities. TP loss, calculated as fluxes by multiplying concentration and discharge, however exhibited an overall increasing rate of 6.5% per decade at the CONUS scale over the past 40 y, largely due to increasing river discharge. Results highlight the challenge of reducing TP loss that is complicated by changing river discharge in a warming climate.

CLINICAL CASE OF FAMILIAL HYPOPHOSPHATEMIC RICKETS IN A CHILD

X-linked hypophosphatemic rickets is an inherited disorder caused by mutations in the PHEX gene (phosphate- regulating proteinwith homology to endopeptidases on the X chromosome). Chronic hypophosphatemia leads to impaired bone mineralization, resulting ingrowth retardation, rickets, and damage to other organs and systems, including maxillofacial abnormalities. Clinically, these manifestationsbecome signifi cant when the child begins to walk.The purpose of the study is to describe a clinical case of congenital hypophosphatemic rickets in a child.Material and methods of the study. clinical, biochemical, genetic and imaging examination of the child Results of the study. The article presents a clinical case of a 9-year-old boy, who was adopted after being removed from an unfavorable psychosocial environment and admitted to the Odesa Regional Children’s Clinical Hospital to clarify the diagnosis and treatment tactics.On admission, the mother reported complaints of delayed psychophysical development, memory impairment, psychosocial dysfunction, deformities of the bones of the upper and lower extremities, chest and skull. The examination revealed a decrease in the level of phosphorus in the blood, increased levels of parathyroid hormone and alkaline phosphatase, and signs of osteomalacia in the x-ray. The diff erential diagnosis included vitamin D-dependent rickets, mucopolysaccharidosis, nanism, hyperparathyroidism, and metaphyseal chondrodystrophy. Based on the data obtained, the fi nal diagnosis was made and appropriate treatment was prescribed.Conclusions. The expanded diff erential diagnosis of rickets with rickets-like diseases contributed to the correct clinical diagnosis. Timely pathogenetic treatment reduces renal tubular phosphorus loss, improves mineral metabolism and quality of life. Prescription of growth hormone will reduce the manifestations of nanism.

Potential Release of Phosphorus by Runoff Loss and Stabilization of Arsenic and Cadmium in Mining-Contaminated Soils with Exogenous Phosphate Fertilizers

Phosphate has been proven to be effective in remediating soils contaminated with potentially toxic elements (PTEs); however, the potential release of phosphorus (P) through runoff and the impact on PTEs’ transport in this process have never been assessed. A rainfall simulation study was conducted to investigate P runoff loss and its impact on the stability of arsenic (As) and cadmium (Cd) after applying potassium dihydrogen phosphate (PDP), superphosphate (SSP), and ground phosphate rock (GPR) in soil trays packed with As–Cd-contaminated soil. The phosphorus loss through runoff and sedimentary phases followed the order of SSP &gt; PDP &gt; GPR &gt; control. Phosphate fertilizers’ application reduced the mobility of As and Cd. In the first rainfall, the enrichment ratios (ERs) of As and Cd in the sedimentary phase after PDP, SSP, and GPR treatment were 0.12, 0.04, and 0.08 and 0.24, 0.16, and 0.07 units lower than the control, respectively. The &lt;53 μm fraction in the sedimentary phase accounted for 53.06–75.95%, and phosphate fertilizers significantly enhanced the As and Cd stability in this fraction. The XPS analysis showed that the conversion of As(III) to As(V) and the generation of Cd–phosphate compounds were important reasons for enhancing As and Cd stability. This study demonstrated that PDP might be capable of the remediation of As–Cd contamination with the least release of P to watersheds.

Simulating Agricultural Water Recycling Using the APEX Model

Irrigation plays a vital role in many agricultural crop production regions. Drainage water recycling (DWR) is a popular irrigation water management system that collects excess water drained from cropland fields and stores it in on-site reservoirs for reuse. The efficacy of these systems varies by location, climate, irrigation frequency, and crop demands. Simulating this system would be beneficial for assessing the impact of water and land management practices on agriculture and natural resources. This study presents the development of computational algorithms for DWR simulation with the Agricultural Policy Environmental eXtender (APEX) model, along with the results for 39 testing sites where both reservoir and drainage systems are adopted. Simulating a DWR system with the revised reservoir module, the APEX model simulates irrigation water reuse ranging between 29% and 93%; sediment reduction of around 66%; nitrogen loss reduction of 23% and 73% for the mineral and organic forms, respectively; and phosphorus loss reduction of 22% and 79% for the soluble and sediment-transported forms, respectively. In conclusion, the results provided by the APEX model for sediment loss reduction align with field data, but discrepancies for nitrogen and phosphorus losses emerged from this test.

Optimum Thermal Treatment for Removing Antibiotic Resistance Genes and Retaining Nutrients in Poultry Broiler Manure

Poultry broiler manure is a reservoir of antibiotic resistance genes (ARGs), antibiotics, organic carbon, and plant nutrients. However, its direct application leads to spread of ARGs in agricultural fields, causing public concerns. It is thus crucial to identify optimum heating conditions that remove ARGs while retaining nutrients. This study examined the effects of heating temperatures (100-500oC) and durations (30, 120 and 240min) on the removals of ARGs and antibiotics from poultry broiler manure and nutrient retention. The results showed that the poultry broiler manure contained a total of 211 ARG subtypes, which were susceptible to temperature. The contents of ARGs and antibiotics decreased with increasing temperature. The temperature had a significant effect on the loss of available phosphorus (r = -0.893, P <0.01), while other nutrients had no significant loss. The results show that the heat treatment at 110°C for 240min maximized the removals of ARGs while the loss of nutrients was minimized. Under these optimum conditions, all ARGs and antibiotics (e.g., oxytetracycline, tetracycline, doxycycline, tilmicosin, tylosin, sulfamethazine, and sulfadiazine) were removed while 91.98% of total carbon, 99.89% of total nitrogen, 92.38% of total phosphorus, 50.10% of available phosphorus, 99.96% of total potassium, and 95.02% available potassium were preserved. These findings suggest that heat treatment at 110oC for 240min could be an effective and affordable approach to safe use of poultry broiler manure.

An integrated tool for cost-effectively applying nutrient management practices for corn, soybeans, and wheat

Harmful algal blooms (HABs) problem in Lake Erie has become critical recently—primarily triggered by phosphorus losses from cropland in the Maumee River watershed (major crops of corn/soybeans/wheat). Implementing agricultural best management practices (BMPs) is crucial to reduce excess nutrient loadings. Nutrient management is the management of nutrient applications for crop production that maximizes nutrient use efficiencies and minimizes nutrient losses. However, an integrated watershed-scale tool is needed for cost-effectively applying nutrient management practices for corn/soybeans/wheat considering the 4Rs (Right nutrient source, Right rate, Right time, and Right place of nutrient applications). In this study, by combining an improved Soil and Water Assessment Tool (SWAT) for nutrient management (SWAT-NM) and an improved BMP Cost Evaluation Tool (BMP-COST) for economic evaluations of nutrient management (BMP-COST-NM) considering the 4Rs for corn/soybeans/wheat, an integrated tool SWAT-COST-NM was created. SWAT-COST-NM was demonstrated in the AXL watershed (a typical agricultural area in the Maumee River watershed). The impacts of single nutrient management practices (single-NM, which separately changed the rate, place, time, or nutrient source of fertilizer applications) and combined-NM practices (multiple single-NM practices combined as one nutrient management practice) for corn/soybeans/wheat were evaluated. Tradeoffs in yearly net costs, crop yields, and March–July/yearly nutrient losses (Total Phosphorus-TP, Dissolved Reactive Phosphorus-DRP, and Total Nitrogen-TN) existed. Nutrient management did not necessarily lead to sufficient increases in crop yields to generate extra revenues that match or exceed the additional costs of the activities (compared to existing practices). One of the combined-NM practices could simultaneously reduce March–July TP, DRP, and TN losses by 5.89%, 8.19%, and 8.23%, respectively, while increasing crop yields with additional income (0.50 $/ha/yr of cropped area). SWAT-COST-NM, which can quantify various factors and tradeoffs when evaluating the impacts of nutrient management practices for corn/soybeans/wheat, can assist decision-makers in cost-effectively applying nutrient management practices considering the 4Rs.

Assessment of nitrogen and phosphorus losses due to erosion in compost-treated and non-treated vineyard soils: effect of rainfall intensity

Vineyards in Mediterranean areas suffer from significant soil degradation through erosion, due to rainfall and soil characteristics, as well as soil management practices. Previous studies pointed out the nutrient losses produced by erosion and the benefits that some management practices could have on reducing erosion. This research tried to evaluate the effect of events of different intensities and to assess whether the beneficial effect of compost amendment may pose a potential risk of nutrient loss and environmental pollution in particular under high-intensity events. The study compared soil and nutrient losses in compost-treated and non-treated vineyard soils after rainfall events of different intensities analyzed over 2 years in two vineyards. Runoff samples were collected by triplicate in treated and non-treated soils. Sediment and nitrogen and phosphorous concentrations in the runoff samples were analyzed. The results reveal a reduction in runoff rates and an increase in soil water content in compost-treated soils, which represents a benefit for rainfed vineyards. Both nitrogen and phosphorus losses depended on rainfall characteristics. Although for low intensities there were no significant differences in the amount of nutrient lost by runoff in both treated and non-treated soils, nitrogen and phosphorus losses were higher after high-intensity rainfall events in compost-treated soils. With the expected increase in high-intensity rainfall events associated with climate change in the Mediterranean region, organic amendments should be applied in several splits or incorporated into the soil to avoid increased nutrient loss to water bodies.

Temporal variations of N and P losses via surface runoff from Chinese farmland after fertilisation

The loss of nitrogen (N) and phosphorus (P) via surface runoff induced by fertilisation leads to water pollution and aggravates water scarcity. Studies estimating N and P losses from farmland have focused on the efficacy of agricultural management actions at reducing the amount of N and P lost. However, a gap remains in understanding the dynamics of N and P losses from farmland, especially differences among types of farmland, crop and fertiliser. Thus, the temporal variations of N and P losses via surface runoff from farmland induced by fertilisation were estimated using 5530 groups of paired observations collected in China. The results showed that N and P losses via surface runoff from paddy fields associated with fertilisation were greater than losses from upland fields. However, after > 90 days post-fertilisation, the effects of fertilisation on N and P loss from paddy fields were non-significant, while the effects of fertilisation on N and P losses from upland fields remained significant. Organic fertilisation decreased N losses from upland and paddy fields, but at more than 60 days post-fertilisation, N and P losses from upland fields were greater with organic than chemical or combined fertilisation. Increasing the fertilisation rate led to higher N and P losses from upland and paddy fields and extended the occurrence time of N and P loss from paddy fields. Overall, this study demonstrates the dynamic processes associated with fertilisation underlying N and P losses from farmland via surface runoff.

Biofilm modulation and demineralization reduction after treatment with a new toothpaste formulation containing fluoride, casein phosphopeptide-amorphous calcium phosphate, and sodium trimetaphosphate: In situ study

ObjectiveThis in situ study aimed to evaluate a new toothpaste formulation containing fluoride (F), casein phosphopeptide amorphous calcium phosphate (CPP-ACP) and sodium trimetaphosphate (TMP) on the process of dental demineralization and biofilm composition. MethodsThis crossover double-blind study consisted of five phases, in which 10 volunteers wore intraoral appliances containing four bovine enamel specimens. The cariogenic challenge was performed using 30 % sucrose solution. Blocks were treated 3 ×/day with the following toothpastes: 1) Placebo (No F-TMP-CPP-ACP), 2) 1100 ppm F (1100F), 3) 1100F + 3 %TMP (1100F-TMP), 4) 1100F + 10 %CPP-ACP (1100F-CPP-ACP) and 5) 1100F-CPP-ACP-TMP. After 7 days, the percentage loss of surface hardness (%SH), integrated loss of subsurface hardness (ΔKHN), F, calcium (Ca) and phosphorus (P) concentration in the enamel was determined. The concentration of F, Ca, P and insoluble extracellular polysaccharide (EPS) in the biofilm were analyzed. ResultsThe addition of CPP-ACP-TMP to 1100F reduced %SH by 42 % and 39 % when compared to the 1100F and 1100F-CPP-ACP (p < 0.001); in addition, to a reduction in lesion body (ΔKHN) by 36 % for the same treatments. The treatment with 1100F-CPP-ACP-TMP led to a significant increase in the concentration of F, P and Ca in the enamel and biofilm, and reduced the concentration of EPS (p < 0.001). SignificanceToothpaste formulation containing 1100F-CPP-ACP-TMP prevented the reduction of enamel hardness and significantly influenced the ionic biochemical composition and insoluble extracellular polysaccharide (EPS) in biofilm formed in situ. These results are promising and provide valuable insights for the design of further clinical trials.

Predicting Accumulation and Potential Edge-of-Field Loss of Phosphorus to Surface Water from Diverse Ecosystems

Phosphorus (P) is an important nutrient essential for agricultural production, but it is highly reactive, leading to its soil accumulation and making it susceptible to environmental impact footprints. The goal of our study was to determine the critical threshold values of both soluble reactive P (SRP) and oxalate-extracted P (Ox-P) to predict soil P accumulation and its susceptibility to edge-of-field loss. Composite soils were collected from geo-referenced ecosystems within the Lake Erie drainage basin under agriculture in northwestern Ohio, USA. Soils were analyzed for SRP, Ox-P, Fe, and Al concentrations to calculate P sorption capacity, P saturation ratio, degree of P saturation (DPS), and P storage capacity (SPSC). A threshold P saturation ratio of 0.12 (~ 24% DPS), corresponding to 2.4 mg SRP/kg (equivalent Ox-P), was determined to calculate SPSC for predicting the risk of SRP accumulation. A significant relationship between the SPSC and SRP suggested that soils under all the agroecosystems had accumulated SRP compared to the forest. Surface soils (0–10 cm depth) under tilled, chemically fertilized, and organically managed corn (Zea mays)-soybean (Glycine max (L) Merr.) rotations, including those treated with chicken and dairy manure, exhibited excessive SRP accumulation, making them susceptible to edge-of-field losses. While the soils at 10–20 cm depth were acting as transitional, the deeper soils (20–30 cm depth) still acted as a net sink. When accounting for bulk density to calculate SPSC stocks, it showed that surface soils across the agroecosystems were saturated with 148 to 240 kg SRP/ha and were susceptible to edge-of-field loss to the water systems. In conclusion, we suggest that SPSC could be used as an early indicator to predict the risk of SRP accumulation and its potential edge-of-field loss to Lake Erie from agroecosystems.

Study on the mechanism of vacuum carbothermal reduction of Ca3(PO4)2 enhanced by SiO2

Vacuum carbothermal reduction mechanism of Ca3(PO4)2 with addition SiO2 was studied by combining FactSage 8.1 thermodynamic theoretical calculations with experiments. The theoretical calculations showed that adding SiO2 effectively reduced the initial reaction temperature. The experimental results showed that the addition of SiO2 significantly improved weight loss and volatilization rates of phosphorus. Ca2SiO4 and CaSiO3 were generated during the reaction. When the SiO2/CaO ratio was 1.25 at 1300 °C, the reduction effect of Ca3(PO4)2 and the volatilization rate of phosphorus was optimal, with a volatilization rate of 91.98 %. Excessive SiO2 led to insufficient contact between the reactants and reducing agent C, thereby hindering the reaction. Simultaneously, a large amount of liquid phase was produced, which deteriorated the kinetic conditions of gas diffusion and affected the reaction. In the reduction process, Ca3(PO4)2 reacted with reducing agent C to generate CaO, then reacted with external SiO2 to generate low melting point CaSiO3, which wrapped the unreacted core. With an increase in the low melting point CaSiO3, the mass transfer in the reaction changed from diffusion mass transfer to flow mass transfer, which promoted the inward diffusion of reducing agent C to contact the unreacted core until the reduction reaction was completed.

Tillage and cover cropping influence phosphorus dynamics in soil and water pools

AbstractWinter cover crops (CCs) have the potential to reduce phosphorus (P) loss by temporarily fixing P into CC biomass. A field experiment with no‐tillage (NT) and conventional tillage (CT) was used to study the ability of different CC species planted after corn (Zea mays L.) and soybean (Glycine max L.) harvests to reduce the P availability in soil solution. The effect of three crop rotations (corn–no CC–soybean–no CC [C–S], corn–cereal rye (Secale cereale)–soybean–hairy vetch (Vicia villosa) [C–R–S–HV], corn–cereal rye–soybean–oats (Avena sativa)+ radish (Raphanus sativus L.) [C–R–S–OR]) and two tillage (NT and CT) treatments was determined on soil available P and soil solution P content through pan (A horizon) and tension (100‐cm depth) cup lysimeters. The experiment was set up as a randomized complete block design with tillage as a split factor with three replicates. Over the study period, incorporating hairy vetch in C–R–S–HV rotation reduced the Mehlich‐3 P content in soil by 26%–29% compared to the C–S and C–R–S–OR rotation. Both CC rotations (C–R–S–HV and C–R–S–OR) were effective in reducing dissolved reactive P (DRP) concentration in pan and tension cup lysimeters compared to the C–S in both CT and NT systems. However, these results varied with CC species grown and seasonal variability in precipitation. A significantly lower DRP load with crop rotation and tillage treatments was observed mainly during the CC growing season. During the study period, crop rotations with reduced labile soil P content and DRP loss were ranked in an order of C–R–S–HV &gt; C–R–S–OR &gt; C–S. Overall, this study showed that CCs have the potential in both CT and NT systems to significantly reduce P in soil and soil solution, and these effects are resilient to a wide range of precipitation conditions.

In-Vessel Aerobic Composting of Organic Waste Using Synthetic and Natural Bulking Agents

The escalating growth in municipal solid waste production underscores the imperative need for efficient waste management, especially given that a substantial portion of MSW comprises biodegradable materials suitable for composting. This study investigates the impacts of using a synthetic bulking agent (perforated plastic balls) in conjunction with biochar, a natural bulking agent, on the aerobic composting of kitchen waste. The study aim to evaluate the effectiveness of this combined approach in optimizing the composting process. Four trials, each spanning 30 days, were conducted to assess the effects of different combinations of synthetic and natural bulking agents. The study uses a uniform-size perforated synthetic bulking agent in combination with biochar to enhance the composting process. Results indicate that incorporating the perforated plastic balls (8% by weight) alongside biochar significantly influenced key composting parameters. This approach accelerated the initial rise in temperature to 55°C, enhanced the reduction of total organic carbon, improved total Kjeldahl nitrogen retention, and facilitated the achievement of optimal carbon-nitrogen (C/N) ratios ranging from 19 to 20. Furthermore, the analysis of phosphorus (P) and potassium (K) loss during composting revealed that potassium is more susceptible to leaching than phosphorus due to its higher mobility. The study concludes that the addition of a uniform-size perforated synthetic bulking agent, constituting 8% (by weight), in conjunction with a natural bulking agent, effectively enhances the composting process.

Evaluation of Minnesota Phosphorus Loss Index performance.

Supported by the National Phosphorus (P) Research Project led by Dr. Andrew Sharpley, Minnesota developed its statewide P-Index, the Minnesota P Loss Index (MNPI), to manage critical source areas of agricultural P. The MNPI has remained unchanged since its last revision in 2006. The overall goal of this study was to critically evaluate the MNPI to determine, in the parlance of Sharpley, if the MNPI remains "directionally and magnitudinally correct." Observed P loss from 67 site-years of annual edge-of-field data was compared with MNPI-predicted P loss. Our assessment indicates that MNPI performance is directionally correct: it correctly ranks fields that are more at risk than others. The MNPI performed better in years with high-intensity rainfall events. Averaging MNPI assessment across multiple years of data input, along with minor adjustments to the calculation algorithm, improved the robustness of MNPI estimates. Continued re-evaluation of the MNPI will ensure that this important tool for nutrient management is properly evaluating P loss potential. This study reflects Dr. Sharpley's decades-long effort to improve and revise P indices so that they reflect advances in the science and management of agricultural P.

Co-application of fly ash and zeolite increases N uptake but decreases P uptake and biomass of rice fertilized with fermented liquid manure

ABSTRACT Fermented liquid pig manure (LPM) can be used as a nutrient source to replace synthetic fertilizers (SF). However, concerns remain regarding nitrogen (N) and phosphorus (P) losses from rice (Oryza sativa L.) paddies fertilized with LPM. Fly ash (FA) has a high calcium content (Ca) and zeolite (Z) has a high negative-charge; thus, they can immobilize P and N through the fixation of P with Ca and NH4 + onto negatively charged sites, respectively. This study investigated the effects of the co-application of FA and Z (FAZ) on the nutrient availability and growth of rice fertilized with LPM. Four treatments were evaluated: no input (control), synthetic fertilizer (SF), and LPM at two levels, with or without FAZ application, for 104 days. The pH (pHwater), electrical conductivity (ECwater), N (Nwater), and P (Pwater) concentrations in the ponding water of rice fields were analyzed 18 times during rice growth. The rice biomass and uptake of N and P were measured, and the concentrations of mineral N and available P in soil were determined after harvest. LPM application increased (p < 0.001) N and P availability in the absence of FAZ, leading to rice biomass comparable to that of SF. However, FAZ diminished the fertilization effects of LPM on rice growth. The Nwater decreased by 50% and the rice uptake of N increased by 6% after FAZ application, probably because of the retention of N by Z and its subsequent release. By contrast, FAZ increased (p < 0.001) soluble Pwater (85% for LPMS) and decreased (p = 0.004) P uptake (8%–40%), reducing the rice biomass by 20%–25%. The decreased P uptake is probably due to the strong immobilization of P by FA. Therefore, it is cautioned that P-limitation through immobilization of P by FA under alkaline conditions may hinder rice growth in FAZ-amended paddy fertilized with LPM. An appropriate application rate of FA for improved P nutrition needs to be explored.

Mitigation measures designed to reduce soil compaction decrease the surface runoff, soil erosion and phosphorus losses from tramlines in agricultural fields

AbstractThe use of tramlines or wheelings to carry out agricultural operations, such as spraying and fertilizer applications, is common across the world. They are often orientated up and down the slope and the soil that is driven on becomes compacted because of machinery weight transferring stress through the soil profile. This compaction leads to tramlines becoming conduits for water moving over the soil surface. Like water, sediment and phosphorus are also detached and transported. Reducing surface runoff and diffuse pollution losses from surface runoff associated with wheelings has received some research attention, but results are often difficult to interpret. This is because of the low number of replicates that are possible in agricultural landscapes, if the research is to be conducted at meaningful scales and to remain feasible. To address this, we utilize effect sizes and confidence intervals to analyse surface runoff and diffuse pollution data from a series of studies at five arable field sites, in the UK where surface runoff, sediment and phosphorus was collected from hillslope scale tramline plots utilizing the same methodology. In addition, we tested the impact of very flexible tyres, rotary harrows and a surface profiler roller on surface runoff and diffuse pollution loses. Although the monitoring period did not encompass widespread flood inducing storms, we demonstrate that the magnitude of the sediment and total phosphorus (TP) losses from the tramline plots across the study sites are significant in the UK context. Annual sediment losses from the study plots are in the order of 0.5–4.5 Mg ha−1 yr.−1 and consistent with the magnitudes of soil erosion in the UK. TP fluxes observed at the study plots, ranged between 0.8 and 3.9 kg ha−1 yr.−1, are consistent with the TP losses reported for surface runoff from arable plots in the UK. By utilizing effect size analysis, we demonstrate the significant impact of tramline mitigation on surface runoff and diffuse pollution losses. The rotary harrow performed best overall, and the combination of the rotary harrow and the very flexible tyre was superior to all other methods. This was the case for all treatments apart from some, where the surface profiler performed well in reducing sediment fluxes. Our work supports the need for incorporating tramline management measures into soil management strategies for arable landscapes and provides evidence for policymakers developing measures for agri‐environmental schemes.

How to effectively reduce sloping farmland nutrient loss and soil erosions in the Three Gorges Reservoir area

Fertilization and soil conservation measures play crucial roles in influencing nutrient loss and soil erosion on sloping farmlands. However, the long-term effects of these measures and the characterization of nutrient loss and sediment yield under different rainfall types and crop growth stages were not well studied. Therefore, we designed six treatments for sloping farmlands in the Three Gorges Reservoir Area with a field experiment. A field experiment included downslope cultivation with chemical fertilizer (DF), downslope cultivation with chemical fertilizer plus manure (DFM), cross-slope cultivation with chemical fertilizer plus manure (CFM), no-till straw cover with chemical fertilizer plus manure (NSFM), ridge plant hedges with chemical fertilizer plus manure (RFM), and biochar interception ditches with chemical fertilizer plus manure (BFM). The results indicated that soil and water conservation measures in association with manure substitution significantly reduced runoff depth (14.3–22.5 %), sediment yield (10.3–46.5 %), and total nitrogen (TN) loss (13.5–36.5 %) compared to DF. NSFM significantly reduced total phosphorus (TP) loss by 17.4 % and the TP loss from the other treatments did not show significant differences compared to DF. Rainfall intensity and runoff depth were identified as critical factors influencing nutrient loss and soil erosion. NSFM showed maximal nutrient reduction performance under different rainfall intensities, while DFM was not significantly effective. NO3--N and particulate P dominated the loss of TN and TP. The first 30 minutes of runoff generation and the seedling stage were identified as risk periods for N and P loss. The study suggests that the NSFM treatment was the appropriate method to prevent soil and water nutrient loss. This provides important insights for the precise control of nutrient loss and soil erosion on sloping farmlands.