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Potassium balances for arable soils in southern England 1986–1999
Author(s) -
Heming S.D.
Publication year - 2004
Publication title -
soil use and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.709
H-Index - 81
eISSN - 1475-2743
pISSN - 0266-0032
DOI - 10.1111/j.1475-2743.2004.tb00390.x
Subject(s) - subsoil , topsoil , arable land , soil water , fertilizer , leaching (pedology) , agronomy , environmental science , potassium , soil science , agriculture , chemistry , ecology , biology , organic chemistry
. The behaviour of potassium (K) in a range of arable soils was examined by plotting the change in exchangeable K of the topsoil (Δ K ex ) at the end of a 3–5 year period against the K balance over the same period (fertilizer K applied minus offtake in crops, estimated from farmers' records of yield and straw removal). Based on the assumption that values for offtake per tonne of crop yield used for UK arable crops MAFF 2000) are valid averages, 10–50% of Δ K ex was explained by the balance, relationships being stronger on shallow/stony soils. Excess fertilizer tended to increase K ex and reduced fertilization decreased it, requiring between 1.2 and 5.4 kg K ha −1 for each mg L −1 Δ K ex . However, merely to prevent K ex falling required an extra 20 kg K ha −1 yr −1 fertilizer on Chalk soils and soils formed in the overlying Tertiary and Quaternary deposits, despite clay contents >18%. Whereas, on older geological materials, medium soils needed no extra K and clays gained 17 kg K ha −1 yr −1 . It is unlikely that the apparent losses on some soil types are anomalies due to greater crop K contents. Theory and the literature suggest leaching from the topsoil as a major factor; accumulation in the subsoil was not measured. Recommendations for K fertilization of UK soils might be improved by including loss or gain corrections for certain soil types.