Work

Circularity of potassium in a grassland-based dairy farm on a clay loam soil

Year: 2024

Type: article

Abstract: A proportion of potassium (K) exits grassland-based dairy farms in tradeable products. Potassium imports are typically needed to offset depletion of soil reserves. The objectives of this study were to (i) quantify K entering and exiting a grassland-based dairy farm including K lost to water, (ii) to relate the balance between K entering and existing the farm to soil K fertility status in order to (iii) design a better K fertilisation strategy for grassland under temperate climatic conditions. The quantities of K entering and exiting a grassland-based dairy farm (Solohead Research Farm; 52⁰51’N, 08⁰21’W) were determined each year between 2005 and 2022. Potassium losses to groundwater were measured during the winters of 2020/21, 2021/22 and 2022/23. Averaged over 18 years, K entering (kg ha −1 ± standard error) was 82 ± 11 and exiting was 41 ± 4. The annual average farm K balance was 41 ± 12 kg ha −1 and ranged between −36 and 136 kg ha −1 . Annual K loss to groundwater (mean ± SE kg ha −1 ) ranged between 6.9 ± 6.13 and 59 ± 7.4. Annual average soil test K (STK; following extraction using Morgan's solution (Na acetate + acetic acid, pH 4.8)) concentrations in paddocks across the farm ranged from 85 to 253 mg L −1 . The yearly change in average STK concentrations correlated with annual farm K balance in the preceding year (R 2 =0.59; P<0.001). Annual farm-scale K budgets were useful in quantifying K flows in products and losses. Potassium leaching to groundwater represented the majority (55 %) of K exiting the farm; exceeding export of K in milk and other products. Maintaining overall farm STK status required annual fertiliser K inputs of 22.5 kg ha −1 between 2016 and 2022. This study elucidates the challenges in managing soil K fertility on grassland based dairy farms.

Source: European Journal of Agronomy

DOI: 10.1016/j.eja.2024.127329

Authors: T. McCarthy, D.P. Wall, P.J. Forrestal, I.A. Casey, J. Humphreys

Institution: Teagasc - The Irish Agriculture and Food Development Authority

Language: English

Topic: Agricultural Science and Fertilization

Subfield: Soil Science

Field: Agricultural and Biological Sciences

Domain: Life Sciences

SDGs: Zero hunger, Life on land

Open Access status: hybrid

Estimated APC paid: $3,450