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Braunschweig, Germany

Taylor M.D.,Waikato Regional Council | Lowe D.J.,University of Waikato | Hardi P.,Institute of Crop and Soil Science | Smidt G.A.,Jacobs University Bremen | Schnug E.,Institute of Crop and Soil Science

Enhanced weathering associated with the use of phosphate fertilisers has been identified in some of the major farming areas of New Zealand and an evaluation of its effects on soil properties and the implications for soil management are needed. We assessed changes in the character of volcanic glass shards in topsoils (0-10 cm depth) of two tephra-derived Andisols of differing ages (Udivitrands, Hapludands), and with and without long-term fertilisation, to test if fertilising accelerates the weathering of soil constituents. Using visual assessment based on scanning electron microscopy and electron microprobe analyses of glass shards from samples from paired sites, we showed that the average sizes of the shards and the sharpness of the glass-shard edges (angularity) diminished with the age of the soil, and that these decreases were more marked in the soils that had been fertilised. Silica polymorphs were observed only in the older soil (Hapludand) that had been fertilised. We concluded that the addition of phosphate-containing fertiliser enhanced the dissolution of volcanic glass, consistent with phosphoric acid and F--induced dealumination and desilication, and thus soil weathering has been accelerated. The Al and Si may subsequently coprecipitate as secondary minerals, such as allophane. However, silica polymorphs may form where Al activity is low. The occurrence of neogenic silica in topsoils (despite high annual rainfall that should result in desilication of the topsoil and reprecipitation of silica deeper in the soil) is explained by the seasonality of fertiliser application and the spring-summer climate, where the soil remains moist for periods sufficiently long enough for the dissolution of volcanic glass (and possibly of other aluminosilicates), the formation of Al-humus complexes, and the subsequent precipitation of silica in dry periods. Implications of the accelerated weathering for soil and land management are discussed. © 2016 Elsevier B.V. Source

Kratz S.,Institute of Crop and Soil Science | Schick J.,Institute of Crop and Soil Science | Schnug E.,Institute of Crop and Soil Science
Science of the Total Environment

68 rock phosphates and 162 P containing (organo-)mineral fertilizers sold in Germany were evaluated with regard to trace element contents. While Al, As, B, Be, Cd, Cr, Mo, Ni, Pb, Sb, Se, Tl, U, and Zn were higher in sedimentary than in igneous rock phosphates, the opposite was true for Co, Cu, Sn, Mn, Ti, Fe, and Sr. Comparing element concentrations to the currently valid legal limit values defined by the German Fertilizer Ordinance, it was found that some PK and many straight P fertilizers (superphosphate, triple superphosphate, partly acidulated rock phosphates) exceeded the limit of 50mgCd/kg P2O5. Mean values for As, Ni, Pb, and Tl remained below legal limits in almost all cases. While no legal limit has been defined for U in Germany yet, the limit of 50mgU/kg P2O5 for P containing fertilizers proposed by the German Commission for the Protection of Soils was clearly exceeded by mean values for all fertilizer types analyzed. A large share of the samples evaluated in this work contained essential trace elements at high concentrations, with many of them not being declared as such. Furthermore, trace elements supplied with these fertilizers at a fertilization rate leveling P uptake would exceed trace element uptake by crops. This may become most relevant for B and Fe, since many crops are sensitive to an oversupply of B, and Fe loads exceeding plant uptake may immobilize P supplies for the crops by forming Fe phosphate salts. The sample set included two products made from thermochemically treated sewage sludge ash. The products displayed very high concentrations of Fe and Mn and exceeded the legal limit for Ni, emphasizing the necessity to continue research on heavy metal removal from recycled raw materials and the development of environmentally friendly and agriculturally efficient fertilizer products. © 2015 Elsevier B.V. Source

Sulas L.,CNR Institute for Animal Production System In Mediterranean Environment | Piluzza G.,CNR Institute for Animal Production System In Mediterranean Environment | Rochon J.J.,Institut Universitaire de France | Goby J.P.,Institut Universitaire de France | And 4 more authors.
Grass and Forage Science

This study reports the leaching of nitrogen (N), phosphorus (P) and potassium (K) from beneath grazed leguminous swards established at two Mediterranean and two north-western European sites. The purpose of the experiment was to provide scientific evidence on whether moderately extensive systems of animal production based on legumes could be environmentally sustainable, to comply with the Water Framework Directive. There were differences in the legume species and the grazing animal between sites, reflecting differences in local management and climatic conditions. There were also differences in the methods used to assess nutrient leaching, again reflecting soil and hydrological conditions present. There were no general differences between the quantities of nutrient leached at Mediterranean and north European sites over the 3year experiment and these quantities, up to 6kgha -1year -1 for nitrate-N, were similar to those reported from earlier studies of leaching beneath grass-white clover swards at temperate sites. Temporal variability in leached nutrient concentrations and amounts was greater at the Mediterranean sites. There were no discernible differences in the effects of sward treatment on leaching. The proportion of N leached in organic combination or as ammonium was greater than with N-fertilized grass systems. The quantities of P leached were relatively high, ranging from 0·1 to 3kgha -1 year -1 for soluble reactive P, reflecting the practice of high levels of fertilizer application to these systems. Reduction of P transfer to water from these systems will be critical for future compliance with the Water Framework Directive. © 2012 Blackwell Publishing Ltd. Source

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