Response of soil exchangeable and crop potassium concentrations to variable fertilizer and cropping regimes in long-term field experiments on different soil types |
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| Authors: | S Andersson M Simonsson L Mattsson A C Edwards & I Öborn |
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| Institution: | Department of Soil Sciences, Swedish University of Agricultural Sciences (SLU), PO Box 7014, SE-750 07 Uppsala, Sweden, and; Nether Backhill, Ardallie (by Peterhead), Aberdeenshire AB42 5BQ, UK |
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| Abstract: | Annual potassium (K) balances have been calculated over a 40‐year period for five field experiments located on varying parent materials (from loamy sand to clay) in south and central Sweden. Each experiment consisted of a number of K fertilizer regimes and was divided into two crop rotations, mixed arable/livestock (I) and arable only (II). Annual calculations were based on data for K inputs through manure and fertilizer, and outputs in crop removal. Plots receiving no K fertilizer showed negative K balances which ranged from 30 to 65 kg ha?1 year?1 in rotation I, compared with 10–26 kg ha?1 year?1 for rotation II. On sandy loam and clay soils, the K yield of nil K plots (rotation I) increased significantly with time during the experimental period indicating increasing release of K from soil minerals, uptake from deeper soil horizons and/or depletion of exchangeable soil K (Kex). Significant depletion of Kex in the topsoil was only found in the loamy sand indicating a K supply from internal sources in the sandy loam and clay soils. On silty clay and clay soils, a grass/clover ley K concentration of ～2% (dry weight) was maintained during the 40‐year study period on the nil K plots, but on the sandy loam, loam and loamy sand, herbage concentrations were generally less than 2% K. |
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| Keywords: | Long-term field experiments potassium fertilizers exchangeable soil potassium potassium balance grass/clover ley potassium concentration |
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