Summary
This narrative review synthesises evidence on the use of potassium-rich crop residues—particularly hulls, husks, and shells from tree crops including almond, cacao, coffee, pecan, and hazelnut—as organic soil amendments in agroecosystems. The review demonstrates that potassium ions solubilise readily from lignocellulosic pericarps into soil solution, driven primarily by water availability rather than decomposition rates, offering a means to meet crop nutrient demand whilst reducing reliance on synthetic fertilisers. The authors discuss how orchard floor management practices can be tailored to optimise the soil and plant benefits of this approach.
Regional applicability
The findings are most directly applicable to UK tree crop production (orchards, soft fruit systems) seeking to reduce synthetic fertiliser inputs and improve soil health through organic amendments. However, potassium release dynamics may differ under cooler, wetter UK climates compared to the semi-arid and tropical regions where many cited studies were conducted, requiring local validation.
Key measures
Potassium concentration in crop residues; potassium solubilisation rates from plant material into soil solution; effects on soil health, water retention, and crop yield; decomposition timescales
Outcomes reported
The review characterises potassium concentrations in lignocellulosic pericarps (hulls, husks, shells) from almond, cacao, coffee, pecan, and hazelnut, and synthesises evidence on how surface application of these residues affects potassium cycling, water dynamics, soil functionality, and crop yield in tree crop systems.
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