Purpose

Planting strategies can be effective mechanisms to reduce diffuse pollution from agricultural catchments reaching water bodies. Plants with antimicrobial properties such as mānuka (Leptospermum scoparium) demonstrated in controlled conditions the ability to inhibit nitrification and growth of pathogens in soils. This potential in a real on-farm setting was still to be investigated.

Methods

In a stock-excluded riparian area, planted with mānuka on a dry stock farm, synthetic excrement patches high in urea (950 kg N ha⁻¹ equiv.) and Escherichia coli (7.9 × 10⁹ cfu plant^-1) underneath mānuka saplings and pasture were applied. Soil was sampled at three depths over 21 days after the excrement application and analysed for total C and N, inorganic N, pH, soil moisture and E. coli.

Results

There was no significant difference between the pasture and mānuka for total C and N, C:N ratio, and soil moisture. E. coli was only different between both at 20–30 cm deep. NO₃⁻ - N and NH₄⁺ - N concentrations were significantly lower under mānuka compared to pasture for the upper two soil depths (NO₃⁻ - N: 109 mg kg⁻¹ vs 205 mg kg⁻¹ in the topsoil).

Conclusions

The results of this study indicate that mānuka may inhibit urease activity and nitrification and could reduce on-farm nitrate leaching, while also highlighting that field conditions make quantifying such phenomenon more complex.

中文翻译：

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mānuka（Leptospermum scoparium）对土壤中氮和大肠杆菌减少的影响：田间试验

目的

种植策略可以成为减少农业集水区到达水体的扩散污染的有效机制。具有抗菌特性的植物，例如 mānuka（Leptospermum scoparium），在受控条件下表现出抑制硝化作用和土壤中病原体生长的能力。这种在真实农场环境中的潜力仍有待研究。

方法

在无牲畜的河岸地区，在干牲畜农场上种植了 mānuka，在 mānuka 树苗下种植了高尿素（950 kg N ha ^-1 equiv.）和大肠杆菌（7.9 × 10 ⁹  cfu 植物^-1）的合成排泄物补丁和牧草被应用。在粪便施用后的 21 天内，在三个深度对土壤进行取样，并分析总碳和氮、无机氮、pH、土壤水分和大肠杆菌。

结果

在总 C 和 N、C:N 比和土壤水分方面，牧场和 mānuka 之间没有显着差异。大肠杆菌仅在 20-30 厘米深时才不同。NO ₃ ^- - N 和NH ₄ ⁺ - N 的浓度在mānuka 下显着低于上部两个土壤深度的牧场（NO ₃ ^- - N：109 mg kg ^-1对比表土中的205 mg kg ^-1）。

结论

这项研究的结果表明，麦卢卡可能会抑制尿素酶活性和硝化作用，并可以减少农场硝酸盐的浸出，同时也强调了田间条件使这种现象的量化变得更加复杂。