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 ± standard error) was 82 ± 11 and exiting was 41 ± 4. The annual average farm K balance was 41 ± 12 kg ha and ranged between −36 and 136 kg ha. Annual K loss to groundwater (mean ± SE kg ha) 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. The yearly change in average STK concentrations correlated with annual farm K balance in the preceding year (R=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 between 2016 and 2022. This study elucidates the challenges in managing soil K fertility on grassland based dairy farms.

中文翻译：

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黏壤土草地奶牛场钾的循环度


一部分钾（K）以可贸易产品的形式离开草原奶牛场。通常需要进口钾来抵消土壤储量的消耗。本研究的目的是 (i) 量化进入和离开草原奶牛场的钾，包括流失于水的钾，(ii) 将进入和现有农场的钾之间的平衡与土壤钾肥力状态联系起来，以便 ( iii) 为温带气候条件下的草地设计更好的施钾策略。 2005 年至 2022 年间，每年测定进出草原奶牛场（索罗黑德研究农场；北纬 52⁰51'，西经 08⁰21'）的钾量。在 2020/21、2021 年冬季测量了地下水中钾的损失/22 和 2022/23。 18 年平均来看，钾输入量（千克公顷±标准误差）为 82 ± 11，排出量为 41 ± 4。农场的年平均钾平衡为 41 ± 12 千克公顷，范围在 -36 至 136 千克公顷之间。每年地下水钾流失量（平均值±SE kg ha）范围在 6.9 ± 6.13 和 59 ± 7.4 之间。整个农场围场的年平均土壤测试 K（STK；使用摩根溶液（醋酸钠 + 醋酸，pH 4.8）提取后）浓度范围为 85 至 253 mg·L。平均 STK 浓度的年度变化与农场年度 K 相关。上一年余额（R=0.59；P<0.001）。农场规模的年度钾预算有助于量化产品中的钾流量和损失。钾渗入地下水占农场排出钾的大部分（55%）；超过牛奶和其他产品中钾的出口量。维持农场整体 STK 状态需要在 2016 年至 2022 年间每年投入 22.5 公斤公顷的肥料钾。这项研究阐明了草原奶牛场管理土壤钾肥力的挑战。