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- Bergström, Lars, et al.
(author)
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Turnover and Losses of Phosphorus in Swedish Agricultural Soils: Long-Term Changes, Leaching Trends, and Mitigation Measures
- 2015
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In: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 44, s. 512-523
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Journal article (peer-reviewed)abstract
- Transport of phosphorus (P) from agricultural fields to water bodies deteriorates water quality and causes eutrophication. To reduce P losses and optimize P use efficiency by crops, better knowledge is needed of P turnover in soil and the efficiency of best management practices (BMPs). In this review, we examined these issues using results from 10 Swedish long-term soil fertility trials and various studies on subsurface losses of P. The fertility trials are more than 50 years old and consist of two cropping systems with farmyard manure and mineral fertilizer. One major finding was that replacement of P removed by crops with fertilizer P was not sufficient to maintain soil P concentrations, determined with acid ammonium lactate extraction. The BMPs for reducing P leaching losses reviewed here included catch crops, constructed wetlands, structure liming of clay soils, and various manure application strategies. None of the eight catch crops tested reduced P leaching significantly, whereas total P loads were reduced by 36% by wetland installation, by 39 to 55% by structure liming (tested at two sites), and by 50% by incorporation of pig slurry into a clay soil instead of surface application. Trend analysis of P monitoring data since the 1980s for a number of small Swedish catchments in which various BMPs have been implemented showed no clear pattern, and both upward and downward trends were observed. However, other factors, such as weather conditions and soil type, have profound effects on P losses, which can mask the effects of BMPs.
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| 4. |
- Blombäck, Karin, et al.
(author)
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Comparing measures for determination of phosphorus saturation as a method to estimate dissolved P in soil solution
- 2021
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In: Geoderma. - : Elsevier. - 0016-7061 .- 1872-6259. ; 383
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Journal article (peer-reviewed)abstract
- In response to concerns over the translocation of P from soils to P-sensitive water bodies, there is high demand for developing simple indicators for evaluating a soil’s risk of releasing P into solution. Many studies have shown that the degree of soil phosphorus saturation (DPS), calculated as the ratio of soil P concentration to soil P sorption capacity (PSC), is good predictor of a soil’s risk of releasing P in solution. In this study we compared four different DPS indices in how well they predicted dissolved P following extraction with either a 0.01 M CaCl2 (PCaCl2) solution or deionized water (PW). The first two indices were calculated from the ratio of extractable P to extractable Al and Fe using either acid ammonium oxalate (AlOX + FeOX) or ammonium lactate solutions (AlAL + FeAL). The second two DPS indices were calculated from the ratio of either Olsen-extractable P or AL-extractable P with sorption capacity estimated from the single point P sorption index (PSI). On a subset of 11 soils, we compared the different methods for estimating PSC with fitted Langmuir sorption maximum (Smax) using data from complete sorption isotherms. Both (AlOX + FeOX) and PSI were well correlated with Smax and hence regarded as good estimates for P sorption capacity. Conversely, (AlAL + FeAL) was not significantly correlated with Smax. P saturation calculated from PSI together with PAL or POls predicted PCaCl2 and PW best, whereas P saturation calculated from ammonium oxalate predicted PCaCl2 and PW the least. We did not find notable improvements in the regression models when we added a second explanatory variable (clay content, pH or total carbon) to the models. Our results show that multiple measures of P saturation provide similar predictions of a soiĺs potential for releasing dissolved P into soil solution. This provides flexibility in how P saturation indices are calculated to identify leaching prone hotspots.
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| 5. |
- Linefur, Helena, et al.
(author)
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Lime placement on subsoil as a strategy to reduce phosphorus leaching from agricultural soils
- 2016
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In: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 32, s. 381-389
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Journal article (peer-reviewed)abstract
- Leaching of phosphorus (P) from agricultural land is a major contributor to eutrophication of surface waters in many countries, and effective mitigation options to reduce P in leachate are needed. In this study, intact columns (0.77 m deep) of subsoil from three Swedish agricultural soils (one sand and two clay) were used to examine whether placing quicklime (calcium oxide, CaO) on the subsoil could reduce P leaching over a 3-yr period. Leaching of particulate P (PP) was significantly less from clay soil columns with lime than from clay soil columns without (P < 0.001 and P < 0.05, respectively), with a relative reduction of 49 and 51% in the two soils. Leaching of dissolved reactive P (DRP) was less from sand columns with lime than from sand columns without, although not significantly so due to large variation in P leaching between columns. These results indicate that placement of lime on subsoil has potential to reduce P leaching, especially of PP from clay soils. However, more studies including both topsoil and subsoil and a range of soil types are needed to assess the full potential of this P mitigation option.
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| 6. |
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| 7. |
- Linefur, Helena, et al.
(author)
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The Role of Subsoil as a Source or Sink for Phosphorus Leaching
- 2015
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In: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 44, s. 535-544
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Journal article (peer-reviewed)abstract
- The importance of subsoil features for phosphorus (P) leaching is frequently mentioned, but subsoil effects are still poorly documented. This study examined whether the subsoil of four agricultural Swedish soils (two sand and two clay) functioned as a source or sink for P leaching by measuring P leaching from intact soil columns with topsoil (1.05 m deep) and without topsoil (0.77 m deep) over 3 yr. One sandy soil with high topsoil P content (Olsen P, 84 mg kg(-1)) and high subsoil sorption capacity (P sorption index [PSI], 3.7 mmol kg(-1)) had low leaching of dissolved reactive P (DRP) from full-length and subsoil lysimeters (0.12 and 0.08 kg ha(-1) yr(-1), respectively). The other sandy soil, with high Olsen P content in the topsoil and subsoil (27 and 19 mg kg(-1), respectively) and low PSI in the subsoil (1.4 mmol kg(-1)), had high DRP leaching from full-length and subsoil lysimeters (3.33 and 3.29 kg ha(-1) yr(-1), respectively). High P content at depth (Olsen P, 21 mg kg(-1)) in one clay soil resulted in relatively higher subsoil DRP contribution (89%) to total leaching than observed in the other clay soil (71%). These results indicate that the subsoil can act as source or sink for P leaching, depending on P content, degree of P saturation, and P sorption capacity, and therefore subsoil properties should be considered when selecting mitigation measures to reduce P leaching.
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| 9. |
- Linefur, Helena, et al.
(author)
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Topsoil and Subsoil Properties Influence Phosphorus Leaching from Four Agricultural Soils
- 2013
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In: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 42, s. 455-463
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Journal article (peer-reviewed)abstract
- Eutrophication, a major problem in many fresh and brackish waters, is largely caused by nonpoint-source pollution by P from agricultural soils. This lysimeter study examined the influence of P content, physical properties, and sorption characteristics in topsoil and subsoil on P leaching measured during 21 mo in 1-m-long, undisturbed soil columns of two clay and two sandy soils. Total P losses during the period varied between 0.65 and 7.40 kg ha(-1). Dissolved reactive P was the dominant form in leachate from the sandy soils and one clay soil, varying from 48 to 76%. Particulate P dominated in leachate from the other clay soil, where low pH (5.2) in the subsoil decreased aggregate stability and thereby probably increased the dispersion of clay particles. Phosphorus leaching was small from soils with high P sorption index (PSI) and low P saturation (<10% of PSI) in the subsoil, even though extractable P (Olsen P) in the topsoil was high, and large from a soil with low sorption capacity and high P saturation (>35% of PSI) in the profile. High sorption capacity in the subsoil was more important for P leaching in sandy soils than in clay soils with macropore flow, where the effect of high sorption capacity was reduced due to less interaction between percolating water and the soil matrix. The results suggest that P leaching is greatly affected by subsoil properties and that topsoil studies, which dominate current research, are insufficient for assessing P leaching in many soils.
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