Phosphorus quantification in soil using LIBS assisted by laser-induced fluorescence.

Quantification and monitoring of phosphorus in soil plays a critical role in environmentally friendly agriculture, especially in mitigation of phosphorus leakages to water systems and subsequent risk for eutrophication. On the other hand, deficiency in phosphorus would lead to problems in development and growth of cultivated crops. Therefore, monitoring and quantification of phosphorus status in soil is essential. In this work, laser-induced breakdown spectroscopy assisted by laser-induced fluorescence (LIBS-LIF) is introduced for quantification of readily soluble phosphorus in soil and compared to the analytical performance of the conventional LIBS method. Mineral soils with variable phosphorus status were used for the analysis. The calibration curves are plotted to evaluate the detection limit of the soluble phosphorus. Compared results demonstrate improvement in detection limit from 3.74 mg/kg to 0.12 mg/kg for clay soil and from 10.94 mg/kg to 0.27 mg/kg for silt loam/loam soil in LIBS and LIBS-LIF measurements, respectively. For the LIBS-LIF measurement, detection limits are comparable with established chemical soil analyses. The proposed method would substantially reduce required sample preparation and laboratory work compared with conventional phosphorus quantification. In addition, as the calibration curves demonstrate that the calibration for soluble phosphorus holds within a soil type, LIBS-LIF has the potential to be used for high throughput soil analysis.

Efficient protection of the Baltic Sea needs a revision of phosphorus metric.

Eutrophication of the Baltic Sea is driven by phosphorus and nitrogen. While the anthropogenic point source loads of both nutrients have decreased markedly, further reductions are needed. This is true particularly for phosphorus, as highlighted by its stringent abatement targets in HELCOM's Baltic Sea Action Plan. To meet the targets, more results need to be achieved in non-point source abatement, specifically from agricultural sources. The growing pressure for phosphorus abatement from agriculture may lead to environmentally and economically inefficient outcomes unless we account for the variability in how different forms of phosphorus respond to abatement measures, and how these forms contribute to eutrophication. The precautionary and efficiency improving way to advance policies is to either replace or supplement the Total Phosphorus metric with a metric more accurate in reflecting the biologically available phosphorus. This policy fix becomes more important as the relative share of agricultural emissions of total pollution increases.

Pulp and paper mill sludges decrease soil erodibility.

Declining carbon (C) content in agricultural soils threatens soil fertility and makes soil prone to erosion, which could be rectified with organic soil amendments. In a 4-yr field trial, we made a single application of three different organic sludges from the pulp and paper industry and studied their effects on cereal yield, soil C content, and fungal and bacterial composition. In laboratory rainfall simulations, we also studied the effects of the soil amendments on susceptibility to erosion and nutrient mobilization of a clay-textured soil by measuring the quality of percolation water passing through 40-cm intact soil monoliths during 2-d rainfall simulations over four consecutive years after application. A nutrient-poor fiber sludge reduced wheat yield in the first growing season, but there were no other significant effects on cereal yield or grain quality. An input of ∼8 Mg ha-1 C with the soil amendments had only minor effects on soil C content after 4 yr, likely because of fast microbe-mediated turnover. The amendments clearly changed the fungal and bacterial community composition. All amendments significantly reduced suspended solids (SS) and total phosphorus (TP) concentrations in percolation water. The effect declined with time, but the reduction in SS and TP was still >25% 4 yr after application. We attributed the lower tendency for particle detachment in rain simulations to direct interactions of soil minerals with the added particulate organic matter and microbe-derived compounds that stabilize soil aggregates. In soils with low organic matter content, pulp and paper industry by-products can be a viable measure for erosion mitigation.

Are there environmental or agricultural benefits in using forest residue biochar in boreal agricultural clay soil?

Short-term agronomic and environmental benefits are fundamental factors in encouraging farmers to use biochar on a broad scale. The short-term impacts of forest residue biochar (BC) on the productivity and carbon (C) storage of arable boreal clay soil were studied in a field experiment. In addition, rain simulations and aggregate stability tests were carried out to investigate the potential of BC to reduce nutrient export to surface waters. A BC addition of 30 t ha-1 increased soil test phosphorus and decreased bulk density in the surface soil but did not significantly change pH or water retention properties, and most importantly, did not increase the yield. There were no changes in the bacterial or fungal communities, or biomasses. Soil basal respiration was higher in BC-amended plots in the spring, but no differences in respiration rates were detected in the fall two years after the application. Rain simulation experiments did not support the use of BC in reducing erosion or the export of nutrients from the field. Of the C added, on average 80% was discovered in the 0-45 cm soil layer one year after the application. Amendment of boreal clay soil with a high rate of BC characterized by a moderately alkaline pH, low surface functionalities, and a recalcitrant nature, did not induce such positive impacts that would unambiguously motivate farmers to invest in BC. BC use seems unviable from the farmer's perspective but could play a role in climate change mitigation, as it will likely serve as long-term C storage.

A Global Perspective on Integrated Strategies to Manage Soil Phosphorus Status for Eutrophication Control without Limiting Land Productivity.

Unnecessary accumulation of phosphorus (P) in agricultural soils continues to degrade water quality and linked ecosystem services. Managing both soil loss and soil P fertility status is therefore crucial for eutrophication control, but the relative environmental benefits of these two mitigation measures, and the timescales over which they occur, remain unclear. To support policies toward reduced P loadings from agricultural soils, we examined the impact of soil conservation and lowering of soil test P (STP) in different regions with intensive farming (Europe, the United States, and Australia). Relationships between STP and soluble reactive P concentrations in land runoff suggested that eutrophication control targets would be more achievable if STP concentrations were kept at or below the current recommended threshold values for fertilizer response. Simulations using the Annual P Loss Estimator (APLE) model in three contrasting catchments predicted total P losses ranging from 0.52 to 0.88 kg ha depending on soil P buffering and erosion vulnerability. Drawing down STP in all catchment soils to the threshold optimum for productivity reduced catchment P loss by between 18 and 40%, but this would take between 30 and 40+ years. In one catchment, STP drawdown was more effective in reducing P loss than erosion control, but combining both strategies was always the most effective and more rapid than erosion control alone. By accounting for both soil P buffering interactions and erosion vulnerability, the APLE model quickly provided reliable information on the magnitude and time frame of P loss reduction that can be realistically expected from soil and STP management. Greater precision in the sampling, analysis, and interpretation of STP, and more technical innovation to lower agronomic optimum STP concentrations on farms, is needed to foster long-term sustainable management of soil P fertility in the future.

Surface and Subsurface Phosphorus Discharge from a Clay Soil in a Nine-Year Study Comparing No-Till and Plowing.

No-till as a water protection measure is highly efficient in controlling erosion and particulate P (PP) loss but tends to increase dissolved reactive P (DRP) concentrations in runoff water. In a 9-yr field study on a clay soil in Southwest Finland, the effects of no-till and autumn plowing on surface runoff and subsurface drainage water quality were compared. The site had a 2% slope and was under spring cereal cropping, with approximately replacement fertilizer P rates. Vertical stratification of soil-test P that had developed during a preceding 6-yr grass ley was undone by plowing but continued to develop under no-till. During the 9-yr study period, no-till soil had 27% lower cumulative total P losses than plowed soil (10.0 vs. 13.7 kg total P ha). Concentrations and losses of PP were clearly lower under no-till than under plowing (5.6 vs. 12.3 kg PP ha), but DRP loss showed the opposite trend (4.3 vs. 1.4 kg DRP ha). There was an increasing trend in subsurface drainflow DRP concentration under no-till, possibly because of development of a conductive pore structure from soil surface to drain depth. The potential benefit of no-till in water protection depends on how much of the PP transported to water is transformed into a bioavailable form and used by aquatic organisms. The beneficial effect of no-till in controlling P-induced eutrophication at the study site would only be realized if the bioavailable share of PP exceeds 43%. Otherwise, no-till would not be an efficient eutrophication control measure at this site.

Spatial modeling of sediment transfer and identification of sediment sources during snowmelt in an agricultural watershed in boreal climate.

Sediment transfer patterns during snowmelt were studied in a small Finnish agricultural watershed. Erosion rates were high as a consequence of high runoff volumes over saturated soil that partly lacked vegetation cover. Automatic high-frequency monitoring data of sediment and phosphorus concentrations in stream showed a clock-wise hysteresis loop as a dominant pattern. GIS-based modeling of runoff and soil erosion, using LiDAR DTM data, suggested that runoff and erosion mostly came from cropland that had the highest sediment contribution index. Also sediment fingerprinting with Cesium-137 suggested cropland and stream bank were the most important sources of suspended sediments in streams. Because a major part of annual sediment transfer takes place during snowmelt, it is a critical period for annual losses of pollutants. Management practices that minimize springtime sediment and pollutant losses from cropland would be needed to make a marked impact on annual pollution transfer to stream waters.

Sediment from Agricultural Constructed Wetland Immobilizes Soil Phosphorus.

Phosphorus (P) losses from agricultural soils impair the quality of receiving surface waters by enhancing eutrophication. This study tested the potential of using sediment from agricultural constructed wetlands (CWs) to immobilize soil P using two soils differing in texture and soil test P (STP). A silty clay soil (SIC) with high STP (24 mg ammonium acetate-extractable P [P] L) and a sandy loam soil (SL) with excessive STP (210 mg P L) were incubated with increasing amounts of clayey CW sediment. The soil-sediment mixtures were studied with the quantity/intensity (Q/I) technique, using chemical extractions, and by exposing the mixtures to simulated rainfall. In both Q/I and simulated rainfall tests, P solubility steadily decreased with increasing sediment proportion in the mixtures. However, in chemical extractions this effect was observed only at high sediment addition rates (10 or 50% [v/v] sediment). At a practically feasible sediment addition rate of 5%, dissolved reactive P (DRP) in percolating water from simulated rainfall decreased by 55% in SIC and by 54% in SL ( < 0.001 in both cases). Particulate P (PP) also showed a decreasing trend with increasing sediment addition rate. Upon prolonged simulated rainfall, the decreasing effect of sediment on DRP and PP declined somewhat. The effects of sediment addition can be attributed partly to increased salt concentrations in the sediment, which have a short-term effect on P mobilization, but mostly to increased concentrations of Al and Fe (hydr)oxides, increasing long-term P sorption capacity. Adding CW sediment at a rate of up to 5% of surface soil volume to soils could provide an alternative to chemical treatment (e.g., with metal salts) for immobilizing P in small, high-risk P leaching areas, such as around drinking troughs in pastures.

A Simple Dynamic Model of Soil Test Phosphorus Responses to Phosphorus Balances.

Soil test P (STP) concentration indicates whether annual P applications can be expected to give yield increases and can also indicate an elevated risk of P mobilization and potential for P transfer to surface waters and groundwater from a particular field. Changes in STP with time thus project agronomic benefits and environmental risks of different P use strategies. To predict STP changes with time, we constructed a simple dynamic model for which the input variables are P balance and initial STP. The model parameters (soil type-specific constants) were fitted using data originating from 44 P fertilizer experiments with different P rates. Model performance was evaluated using independent data sets that either had reasonably accurate input values ( = 103) or were obtained from farmers through interviews ( = 638). The simulations were in agreement with measured STP changes for both evaluation data sets when fittings were performed separately for four main soil types (clays, silts, coarse mineral soils, and organic soils). Statistical analysis confirmed that the model captured the trends in STP (NHOAc test) with acceptable accuracy and precision, with of 0.83 and 0.66 for the data with more accurate input and for farmer interview data, respectively; the corresponding model efficiency statistics were 0.88 and 0.66. The model is not restricted to use with one soil test, as fittings for several different types of soil tests can be generated. In this study, we fitted the model for Olsen P data retrieved from the literature. Agronomic use of the model includes evaluation of P use strategies, e.g., when a certain STP level is targeted or when long-term economy of P use is calculated. In an environmental context, the model can be used to predict STP changes with time under variable P balance regimes, which is essential for realistic assessment of changes in the potential for dissolved P losses.

Future agriculture with minimized phosphorus losses to waters: Research needs and direction.

The series of papers in this issue of AMBIO represent technical presentations made at the 7th International Phosphorus Workshop (IPW7), held in September, 2013 in Uppsala, Sweden. At that meeting, the 150 delegates were involved in round table discussions on major, predetermined themes facing the management of agricultural phosphorus (P) for optimum production goals with minimal water quality impairment. The six themes were (1) P management in a changing world; (2) transport pathways of P from soil to water; (3) monitoring, modeling, and communication; (4) importance of manure and agricultural production systems for P management; (5) identification of appropriate mitigation measures for reduction of P loss; and (6) implementation of mitigation strategies to reduce P loss. This paper details the major challenges and research needs that were identified for each theme and identifies a future roadmap for catchment management that cost-effectively minimizes P loss from agricultural activities.

Labile organic carbon regulates phosphorus release from eroded soil transported into anaerobic coastal systems.

Coastal eutrophication is expected to increase due to expanding and intensifying agriculture which causes a large amount of soil-associated P to be transported into aquatic systems. We performed anaerobic long-term incubations on field soil to mimic the conditions that eroded soil encounters in brackish sediments. The release of P from soil increased with the amount of labile organic C (acetate) addition and decreased with the soil/solution ratio. We deduce that in less-productive brackish systems, microbial Fe reduction allows for the maintenance of the coupled cycling of Fe and P and restricts the amount of P entering the oxic water. In more eutrophic systems, the formation of Fe sulfides as a result of SO4 reduction inactivates Fe, and leads to a higher release of P, thus generating an adverse feedback effect. The dependence of the fate of soil-bound Fe and P on the trophic status of the receiving water should be recognized in eutrophication management.

Conversion of dissolved phosphorus in runoff by ferric sulfate to a form less available to algae: Field performance and cost assessment.

Conversion of dissolved P by ferric sulfate into a particulate form sparingly available to algae was studied in 15 ditches in Finland using stand-alone dispensers for ferric sulfate administration. Ferric sulfate typically converted 60-70 % of dissolved P into iron-associated form, a process which required 250-650 kg per kg dissolved P. Mean cost was 160 EUR per kg P converted (range 20-400 EUR kg(-1)). The costs were lowest at sites characterized by high dissolved P concentrations and small catchment area. At best, the treatment was efficient and cost-effective, but to limit the costs and the risks, ferric sulfate dispensers should only be installed in small critical source areas.

Simultaneous bilateral cataract surgery: economic analysis; Helsinki Simultaneous Bilateral Cataract Surgery Study Report 2.

PURPOSE: To present an economic-analysis comparison of simultaneous and sequential bilateral cataract surgery. SETTING: Helsinki University Eye Hospital, Helsinki, Finland. DESIGN: Economic analysis. METHODS: Effects were estimated from data in a study in which patients were randomized to have bilateral cataract surgery on the same day (study group) or sequentially (control group). The main clinical outcomes were corrected distance visual acuity, refraction, complications, Visual Function Index-7 (VF-7) scores, and patient-rated satisfaction with vision. Health-care costs of surgeries and preoperative and postoperative visits were estimated, including the cost of staff, equipment, material, floor space, overhead, and complications. The data were obtained from staff measurements, questionnaires, internal hospital records, and accountancy. Non-health-care costs of travel, home care, and time were estimated based on questionnaires from a random subset of patients. The main economic outcome measures were cost per VF-7 score unit change and cost per patient in simultaneous versus sequential surgery. RESULTS: The study comprised 520 patients (241 patients included non-health-care and time cost analyses). Surgical outcomes and patient satisfaction were similar in both groups. Simultaneous cataract surgery saved 449 Euros (€) per patient in health-care costs and €739 when travel and paid home-care costs were included. The savings added up to €849 per patient when the cost of lost working time was included. CONCLUSION: Compared with sequential bilateral cataract surgery, simultaneous bilateral cataract surgery provided comparable clinical outcomes with substantial savings in health-care and non-health-care-related costs. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Simultaneous bilateral versus sequential bilateral cataract surgery: Helsinki Simultaneous Bilateral Cataract Surgery Study Report 1.

PURPOSE: To evaluate the refractive outcomes, complication rates, and changes in patients' functional state and satisfaction with simultaneous compared with sequential bilateral cataract surgery. SETTING: Helsinki University Eye Hospital, Helsinki, Finland. DESIGN: Clinical trial. METHODS: Consecutive patients scheduled for bilateral cataract surgery were enrolled based on appropriate inclusion criteria and randomized to be operated on in 1 session (study group) or sequentially (control group) 4 to 6 weeks apart. RESULTS: Four hundred ninety-one (94.4%) of the 520 patients completed the study. Of the eyes, 493 (247 patients) had bilateral surgery in 1 session and 506 (257 patients) in separate sessions. In the study group, 240 patients (96.0%) were treated per protocol. In the control group, 250 patients (97.3%) were treated per protocol. The refraction was within ± 0.50 diopter (D) of the target in 67.2% of eyes in the study group and 69.2% of eyes in the control group and within ± 1.00 D in 91.0% and 90.3%, respectively (P = .92). The only complication that affected postoperative visual acuity was chronic cystoid macular edema, which occurred in 1 eye in the study group (0.2%) and in 2 eyes (0.4%) of 1 patient in the control group (P = .57). Ninety-five percent of patients in both groups reported being very satisfied with surgery. CONCLUSION: The refractive outcomes, rates of complications, and patient-rated satisfaction were similar whether bilateral cataract surgery was performed simultaneously or sequentially. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Treating keratoconus with intacs corneal ring segments.

PURPOSE: To assess the safety and efficacy of Intacs inserts for the treatment of mild to moderate keratoconus. METHODS: In a nonrandomized prospective clinical trial, 50 eyes of 37 patients with mild to moderate keratoconus were implanted with asymmetrical pairs of Intacs segments. Patients were interviewed and observed preoperatively and 24 hours, 1 week, 1, 3, 6, and 12 months postoperatively. Main outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, satisfaction with vision and trouble with vision, Visual Function-7 score, and surgically induced change in corneal astigmatism. RESULTS: Of the 50 operations performed, 92% were successful. Mean follow-up was 6.3 +/- 3.2 months. In 4 (8%) eyes, both Intacs segments were removed. In addition, 7 refractive adjustments in 7 eyes were performed successfully to improve visual and surgical outcome. Both BSCVA and UCVA improved throughout follow-up. Visual functioning index improved from 61.6 +/- 21.1 to 80.8 +/- 22.5, and the percentage of satisfaction with vision improved from 24.3% to 87.5% at 12 months. Vector analysis of astigmatism correction showed that the mean change in corneal astigmatism was 2.9 +/- 2.9 D at 6 months postoperatively. By selecting patients in whom astigmatism correction was best (index of success >0.5), an analysis was performed to determine individual factors important in successful surgery. Preoperatively these 11 (22%) eyes did not differ significantly from the remaining eyes and the only significant value was low K readings in the flat axis. CONCLUSIONS: Asymmetric Intacs placement improves BSCVA and UCVA and reduces astigmatism in patients with mild to moderate keratoconus. The procedure of Intacs placement is safe and effective. The change in astigmatism correction is unpredictable.

Traumatic cataract and other adverse events with the implantable contact lens.

PURPOSE: To evaluate the surgical outcome and adverse events associated with implantation of the implantable contact lens (ICL) for the correction of high myopia or high hyperopia. SETTING: Helsinki University Eye Hospital, Helsinki, Finland. METHODS: In this nonrandomized prospective clinical trial, the ICL V4 was implanted in 26 eyes of 13 patients with normal enrollment criteria (younger than 45 years, a clinically clear crystalline lens) (Group 1) and the V2, V3, or V4 were implanted in 38 eyes of 22 patients with heterogeneous criteria (older than 45 years or opacities in the crystalline lens) (Group 2). The main outcome measures were lens opacity classification system (LOCS II) assessment and transparency analysis of the lens. RESULTS: In Group 1, microdensitometric assessment showed no decrease in crystalline lens transparency and no statistically significant increase in crystalline lens density at any follow-up examination (P>.05). The incidence of anterior subcapsular (AS) opacities was 7.7%, and no eye developed clinically significant cataract during the mean follow-up of 13.2 months +/- 12.3 (SD). No myopic eye lost a line of best corrected visual acuity (BCVA); 50.0% of hyperopic eyes lost 1 line of BCVA. Sixty-eight percent of myopic eyes and 75.0% of hyperopic eyes were within +/-1.0 diopter of the predicted refraction. In Group 2, the incidence of AS opacities was 47.4% and 10 eyes (26.3%) developed clinically significant cataract during the mean follow-up of 30.9 +/- 18.0 months. The visual and refractive results were similar to those in Group 1 at 1 month, but due to progressive AS opacities in the crystalline lens, 23.4% of eyes lost BCVA lines during the follow-up. Intraoperative complications were few and insignificant. CONCLUSIONS: Implantation of the ICL for correction of high myopia or high hyperopia appears to be a safe procedure with good visual and refractive results immediately. There was no decrease in the transparency or increase in the density of the crystalline lens with the latest generation of the ICL device in the normal group, indicating enhanced safety. Progressive lens opacification in the heterogeneous group shows there are risk factors for cataract formation; ie, type V3 ICL, preexisting lens opacities, and older patient age. Anterior subcapsular opacities are most likely the result of trauma.

Quality of vision after AMO Array multifocal intraocular lens implantation.

PURPOSE: To evaluate safety and efficacy of Array SA40N multifocal intraocular lens (IOL) (AMO) implantation in cataract surgery. SETTING: Helsinki University Eye Hospital, Helsinki, Finland. METHODS: In this prospective randomized comparative trial, 80 patients scheduled for cataract surgery were selected based on preoperative counseling and randomized to have multifocal or monofocal IOL implantation. Fifty-three eyes of 35 patients received a multifocal IOL and 67 eyes of 40 patients, a monofocal IOL. The incidence of complications and visual outcome in the multifocal and monofocal IOL groups were compared. Quality of vision was measured by comparing the severity of visual symptoms (glare, halos, and cataract symptoms score), changes in functional impairment measured by a 7-item visual function test (VF-7), changes in global measures of vision (trouble and satisfaction with vision), and range of accommodation and contrast sensitivity. RESULTS: Intraoperative and postoperative complications and adverse events were few and required no further surgical intervention. Both distance and near visual acuities were significantly better in the multifocal group than in the monofocal group; the difference was most prominent in distance corrected near acuity (P<.001). Thirty-five eyes (67.3%) in the multifocal group and 10 eyes (14.9%) in the monofocal group achieved a distance corrected near acuity of J6 (20/40) or better; 30 eyes (56.6%) and 19 eyes (28.4%), respectively, achieved a best corrected distance acuity of 20/20 or better. Glare symptoms decreased postoperatively in both groups but were slightly more common in the multifocal group. In contrast, halos were significantly more common at 1 month in the multifocal group (P<.001). Contrast sensitivity values were slightly lower with multifocal IOLs at almost all spatial frequencies, but the difference was not significant. The change in the quality of life postoperatively, measured with the VF-7, was significant and identical in both groups. CONCLUSIONS: Pseudophakic eyes with multifocal IOLs had better distance and near acuity and range of accommodation than eyes with a monofocal IOL. Slightly lower contrast sensitivity and increased perception of halos by subjects with the multifocal IOL appear to be an acceptable compromise to enhanced near and distance vision.