Ability of some Norwegian soils to supply grass with potassium (K) - soil analyses as predictors of K supply from soil |
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Authors: | AF Øgaard T Krogstad T Lunnan |
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Institution: | Agricultural University of Norway, Department of Soil and Water Sciences, P.O. Box 5028, N–1432 Aas, Norway;The Norwegian Crop Research Institute, Løken Research Station, N–2940 Heggenes, Norway |
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Abstract: | Abstract. Uptake in grass crops of ammonium acetate lactate extractable K (KAL) and reserve K (interlayer K + structural K) in soil was studied in 16 field experiments at different locations on a range of mineral soil types in Norway. The K uptake from soil, both from KAL and reserve K, was considerable, often even at the highest level of K fertilizer. During three years, only on the sandy soils with a low level of acid soluble K (KHNO3 minus KAL) was there a yield response to K fertilization. The KAL values declined rapidly and flattened off at a 'minimum level' which differed with soil type. This minimum level for KAL is a useful parameter in fertilizer planning, because the grass usually took up the K in excess of the minimum level over two years. The minimum value of KAL was significantly correlated with the content of clay + silt in soil. The decrease in KAL during the growing season was closely correlated to the KAL value in spring minus the minimum value and, therefore, the amount of K supplied to the grass from the KAL fraction can be calculated. Furthermore, the KAL value for the following spring may be estimated. The release from reserve K was partially related to acid soluble K. |
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Keywords: | Available potassium potassium fertilizers application rates soil analysis grassland soils |
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