Phosphorus losses from agricultural land to surface waters

The number of horses in Sweden has increased in recent decades, reaching over 300,000 in 2009. The horses are kept on 300,000 ha representing 10% of total agricultural land in Sweden. This study characterised the potential risk of phosphorus (P) losses from a heavy clay soil used for horse grazing and feeding (paddock) and compared the losses with nearby arable land managed conventionally and losses from ungrazed pasture. Water-soluble phosphorus (WSP) concentration in surface soil (0-10 cm) from the paddock areas (mean 0.62 mg 100 g-1 soil) did not differ significantly from that in arable land, but differed very significantly (p2.5 livestock units ha-1) may pose a risk of high P losses to nearby water bodies

Impact of horse-keeping on phosphorus (P) concentrations in soil and water

Agricultural sources contribute significantly to the high phosphorus (P) loads in water, causing eutrophication in many of Europe’s water bodies. Consequently, priority has been given to reducing P leakage from sources, including soils used for animal farming. Horse farms use about 4 % of the total agricultural land in the EU, but have not so far been investigated thoroughly with regard to their impact on water quality. This study characterised the potential risk of P leaching losses from Swedish horse paddocks in a three-stage investigation of the soil and water P status. The study began with an analysis of eight years of drainage P data from a small catchment, a so called – ‘observation field’, dominated by horse paddocks (Paper I). In the following study (Paper II), soil P status was examined in different parts of the horse paddocks (feeding, grazing and excretion areas) to identify potential hotspots for high P losses within the paddock. In the third experiment (Paper III), topsoil columns (0 - 20 cm) from different segments of the paddock (feeding, grazing, and excretion area) were isolated and potential leaching losses of P from the soil columns were measured during simulated rainfall in the laboratory. The studies showed that: i) horse paddocks can pose a potential threat to water quality via leaching of excess P, ii) feeding and excretion areas are potential hotspots for significantly high leaching losses, and iii) paddocks established on sandy soils are particularly vulnerable to high P losses. Besides identifying P leaching problems, additional investigations were carried out to mitigate P losses from paddocks using organic bedding materials (e.g. wheat straw, wood chips and peat) (Paper IV) and to determine an environmentally safe load of horse manure for arable soils (Paper V). The main findings of these studies were: iv) of the three bedding materials, only wood chips could reduce P losses while the other two enhanced leaching losses, and v) the addition of composted horse manure up to 36 Mg ha-1 (22 kg P ha-1) did not increase P leaching from organic soil, but from the mineral soils, while 90 - 100 % of the added P from the compost was retained in the soils. Finally, proposals for better paddock management were outlined and the need for national rules/regulations for horse paddocks were stressed to avoid nutrient build-up and to reduce losses. In addition, to strengthen the understandings and conclusions, more field studies were suggested for future research

Sequential removal of nitrate and sulfate in woodchip and hematite – coated biochar bioreactor

Laboratory column experiments have been used to study the sequential removal of nitrate (NO3−) and sulfate (SO42−) from mine water, where NO3− was removed through denitrification and SO42− was removed through SO42− reduction and the subsequent precipitation of hydrogen sulfide (H2S) in a hematite-coated biochar (HCB) bioreactor. Denitrification and SO42− reduction were investigated in columns filled with pine woodchipsand pine woodchips + biochar, both with and without the addition of lactate. Experimental results indicatedthat a >90% NO3− removal from 50 mg L−1 NO3−-N was achieved at a hydraulic residence time of 5 dayswithout lactate addition, but that SO42− reduction was minimal after an initial startup period. Lactate wasadded to stimulate SO42− reduction, producing H2S with >90% SO42− removal from an initial concentration of 361 mg L−1 SO42−-S. Sulfate concentrations were reduced to a greater extent in the woodchip + biocharcolumn, and NH4+ production was enhanced in both columns after lactate addition. After treatment in the HCB columns, H2S and NH4+ were removed to >95%. X-ray photoelectron spectroscopy (XPS) indicated that S2−, S22−, S0 and NH4+ were accumulating in the HCB columns and surface-bound iron was converted from Fe(III) to Fe(II). The XPS results suggested that the reductive dissolution of hematite preceded the precipitationof H2S as FeS, pyrite and elemental sulfur on the HCB surfaces

Escola catalana

Resumen basado en el de la publicaciónDespués de un período de debate curricular -que pasó abajo con una gran indiferencia tanto por parte de la mayoría del profesorado como de los estamentos universitarios- se publicó provisionalmente, entre los de las otras áreas, los nuevos currículos correspondientes a las áreas de conocimiento del medio para la primaria y de ciencias sociales, geografía e historia para la secundaria obligatoria. Una vez leídos y analizados, se comentan que el resultado general es confuso y decepcionante.Universitat de Barcelona. Biblioteca del Campus de Mundet ; Passeig de la Vall d'Hebron 171; 08035 Barcelona; Tel. +34934021035; Fax +34934021034ES

Four soil phosphorus (P) tests evaluated by plant P uptake and P balancing in the Ultuna long-term field experiment

Soil phosphorus (P) availability was assessed with four different soil P tests on seven soils of the Ultuna long-term field experiment (Sweden). These four soil P tests were (1) P-H2O (water extractable P); (2) P-H2OC10 (water extractable P upon 10 consecutive extractions); (3) P-AL (ammonium lactate extractable P) and (4) P-CDGT (P desorbable using diffusive gradients in thin films). The suitability of these soil P tests to predict P availability was assessed by correlation with plant P uptake (mean of preceding 11 years) and soil P balancing (input vs. output on plot level for a period of 54 years). The ability to predict these parameters was in the order P-H2OC10 > P-CDGT > P-H2O > P-AL. Thus, methods considering the P-resupply from the soil solid phase to soil solution performed clearly better than equilibrium-based extractions. Our findings suggest that the P-AL test, commonly used for P-fertilizer recommendations in Sweden, could not predict plant P uptake and the soil P balance in a satisfying way in the analysed soils

Phosphorus Availability in Soils Amended with Wheat Residue Char

Plant availability and risk for leaching and/or runoff losses of phosphorus (P) from soils depends among others on P concentration in the soil solution. Water soluble P in soil measures soil solution P concentration. The aim of this study was to understand the effect of wheat residue char (biochar) addition on water soluble P concentration in a wide range of biochar amended soils. Eleven agricultural fields representing dominant soil texture classes of Swedish agricultural lands were chosen. Concentrations of water soluble P in the soils and in biochar were measured prior to biochar incorporation to soils in the laboratory. Experiments with three dominant soil textures- silt loam, clay loam and an intermediate loam soil with different rates of biochar addition (i.e., 0.5, 1, 2 and 4%; w/w) showed that the highest concentration of water soluble P was achieved at an application rate of 1%. At higher application rates, P concentrations decreased which coincided with a pH increase of 0.3 - 0.7 units. When the eleven soils were amended with 1% (w/w) biochar, water soluble P concentrations increased in most of the soils ranging from 11 to 253%. However, much of the water soluble P added through the biochar was retained (33 - 100%). We concluded that - wheat residue char can act as a source of soluble P; and low and high additions of biochar can have different effects on soil solution P concentration due to possible reactions with Ca and Mg added with biochar