Nitrate surveillance: Summary

Every Member State is required to monitor and report levels of nitrate in specified foodstuffs as part of the European Commission regulation and the UK also requires this information as part of the collection of data to support the review of retained EU law in the UK and inform the setting of policy around maximum nitrate levels. The requirement to carry out monitoring for nitrate in lettuce, spinach and rocket is being met by the UK Nitrate Surveillance Programme. Results are presented for the period between 1st April 2021 and 31st March 2022. A total of 202 samples were collected within the sampling period, comprising of 130 lettuce, 9 rocket, 26 spinach samples. A further 37 samples categorised at “Other Green Leafy Vegetables”, which comprised of samples including mustard, mizuna, celery, Pak Choi and cabbage. The lowest average nitrate concentration was recorded in summer-grown iceberg lettuce (935.2 mg/kg), and no iceberg samples exceeded the maximum nitrate concentration. The highest average nitrate concentration was seen in winter grown non-iceberg lettuce grown under protection within the lettuce group (3242.2 mg/kg), and in winter-grown rocket overall (4271.2 mg/kg). The number of samples exceeding the maximum threshold increased this year to 7 samples – 2 samples of open-air non-iceberg lettuce sampled in the summer, 1 sample of protected non-iceberg lettuce in the summer, and 3 samples of spinach. A further 4 samples were within 10% of the maximum threshold. Consistent with previous years of this project, a strong correlation was found between nitrate concentration and sampling date, with samples collected later in the season showing greater concentrations, indicating potential interactions between nitrate accumulation and climate – particularly light levels and available soil moisture and the accumulation of nitrate in the soil through subsequent fertiliser applications with successive planting. Furthermore, there was significant interaction between nitrate accumulation, product type and cultivation type, which could be further explored to better identify risk factors associated with nitrate accumulation in leafy vegetables grown in the UK.