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Abstract
Linz‐Donawitz (LD) slag, containing 29% calcium (Ca), 21% iron (Fe), and 5% magnesium (Mg), is a by‐product of the iron and steel‐making industry. It is produced in large quantities in Europe and poses a substantial disposal problem. A field trial was conducted to study whether LD slag could be used as a dolomitic liming agent for pastures. The effects of six LD slag rates (0, 1000, 1500, 3000, 5000, and 7500 kg LD slag/ha), with or without NPK fertiliser, on soil properties, pasture yield, and botanical composition were investigated at two locations, Derio and Abadiano (Bizkaia, northern Spain). Soil at Derio was a fine silty, mixed (acid), mesic Typic Udorthent and at Abadiano a fine loamy, mixed (nonacid), mesic Aquic Udifluvent. At Derio, the 3‐year trial was laid out on a newly established pasture of perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), and white clover (Trifolium repens L.), whereas at Abadiano the trial was on a resident pasture dominated by yorkshire fog (Holcus lanatus L.) and browntop (Agrostis tenuis Sibth.). Application of LD slag increased the soil pH linearly at both sites. At Derio, the 7500 kg slag/ha rate increased the soil pH from 5.3 to 6.4, whereas at Abadiano the pH was raised from 5.7 to 6.5 and from 5.8 to 6.7 with and without NPK fertilisation respectively. The increase in pH was accompanied by a decrease to less than 5% in the percentage of Al saturation in the cation exchange complex. At Derio, soil exchangeable Ca increased in comparison with the control, by a factor of 1.8 and 2.3, with and without NPK fertilisation, respectively. At Derio, pasture yield increased with slag application, the second year responses being the largest (41% increase with 3000 kg slag/ha). At Abadiano, pasture yield did not respond to slag, but the botanical composition changed, with the contribution of browntop and yorkshire fog decreasing, and the contribution of red fescue (Festuca rubra L.) and ribwort (Plantago lanceolata L.) increasing. According to the results, LD slag appears to be a useful liming material for correcting soil acidity on pasture soils. As a consequence, the agronomic use of LD slags will contribute towards solving the environmental problem of their disposal.