Penwith Farmscoper Report.

Published online
09 Aug 2023
Published by
Natural England
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This report discusses the assessment of how farm management influences nitrate concentrations in drainage water and its subsequent impact on wetlands was conducted using the Farmscoper model. Within this framework, the model compared the annual average nitrate concentrations originating from different farm systems against specific threshold levels crucial for preserving wetland health within Penwith Moors. The findings of the study reveal that nitrate concentrations stemming from arable land consistently surpass the higher threshold of 2 mg l-1 NO3-N. Similarly, grassland fields that receive 150 kg N ha-1 yr-1 or more from fertilizers, manure, and grazing excreta also tend to exceed the 2 mg l-1 threshold. To maintain concentrations below the lower threshold of 1 mg l-1, the implementation of a low-input grassland system with nitrogen inputs below 50 kg N ha-1 yr-1 is deemed necessary. Various factors such as rainfall and soil type introduce variations that impact denitrification and resulting concentrations. In this study, the modeling assumed full compliance with the Farming Rules for Water as a baseline scenario. The negligible effects arising from adherence to Nitrate Vulnerable Zone regulations and reasonable precautions within the FRfW are relatively minor, amounting to a maximum of 12% variation. Importantly, these assumptions do not alter the fundamental conclusions regarding appropriate farm management practices required to attain the desired target nitrate concentration thresholds.

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