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Potassium transformation in clay soil with contrasting K budgets in long‐term experiment
Author(s) -
Damar Hada,
Ziadi Noura,
Lafond Jean,
Parent LéonEtienne
Publication year - 2020
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.1002/agj2.20379
Subject(s) - soil water , agronomy , manure , environmental science , topsoil , potassium , hordeum vulgare , forage , fertilizer , crop rotation , crop , chemistry , soil science , poaceae , biology , organic chemistry
Canadian Shield clay soils are high in potassium (K) reserves. The differential contribution of soil K fractions to crop nutrition is an important issue for ley farming systems of Eastern Canada where nitrogen (N)‐based manure application rate leads to K surplus and redistribution. Our objective was to assess the long‐term change in K offtake, K budget, and K forms under a 3‐yr‐cycle ley farming system (barley [ Hordeum vulgare ]–mixed forage–mixed forage) initiated in 1989 and ended in 2016. The liquid dairy manure (LDM) supplied higher amounts of K than mineral fertilization (MIN) and led to larger K offtake across crop cycles. The cumulative K budgets averaged −579 kg K ha −1 cycle −1 for MIN and +69 kg K ha −1 cycle −1 for LDM. Despite cyclic variations, topsoil showed a surplus of exchangeable K (>100 kg K ha −1 ) at the end of experimentation under MIN and LDM compared to the initial state in 1989. Exchangeable and non‐exchangeable K fractions increased between 2001 and 2016 in 0‐ to 30‐cm depth even under K deficit (MIN), due to K release from slowly available forms and recycling from lower layers. There were no significant relationships between K budget and exchangeable K down to 90 cm. The approach relating soil exchangeable K and K budgets to support buildup and maintenance of soil fertility proved to be inappropriate in clay soils high in illite‐like minerals. Potassium dynamics in clay soils under ley farming highlighted the importance of considering non‐exchangeable and subsoil K in K fertilization recommendations.