Rempelos et al. 2023 - Cd, Ni, and Pb in UK field vegetables under organic and conventional protocols

Rempelos and colleagues analyzed harvested potato tubers, cabbage heads, lettuce heads, and onion bulbs from the long-term Nafferton Factorial Systems Comparison trials in Northumberland, UK. The paper reports cadmium, nickel, and lead concentrations on a fresh-weight basis as main-effect means under organic versus conventional crop protection, mineral NPK versus cattle farmyard manure fertilization, and spring-bean versus winter-barley pre-crops. The source is routeable as summary-level vegetable occurrence evidence and as supply-chain evidence that fertilization regime can shift Cd and Ni in harvested vegetables.

Key numbers

All toxic-metal values below are Table 10 main-effect means +/- SE in ug/kg fresh weight. They are not individual sample results, and the crop-protection, fertilization, and pre-crop columns are separate main-effect summaries rather than additive treatment cells.

Crop protection and fertilization contrasts

Fertilization was the strongest agronomic toxic-metal lever in the ANOVA: mineral NPK fertilization increased Cd in all four crops and increased Ni in potato, cabbage, and onion. Section 3.6 reports relative Cd increases under NPK versus farmyard manure of 50% in potato, 46% in onion, 25% in lettuce, and 17% in cabbage; the potato figure is internally inconsistent with the Table 10 main-effect means above (39 vs 24 µg/kg fresh weight imply 62.5%), and the wiki reports the paper’s prose as written rather than substituting the computed value. Pb was not significantly affected by crop protection, fertilization, or pre-crop.

Pre-crop contrast

The pre-crop contrast had fewer years of data than the crop-protection and fertilization contrasts. Lettuce Cd was significantly higher after winter barley than after spring beans; potato and onion Cd showed trends toward higher concentrations after winter barley.

Methods (brief)

The Nafferton Factorial Systems Comparison trials were established at Newcastle University’s Nafferton Experimental Farm in Northumberland, UK, on a sandy loam Cambic Stagnogley/Stagnic Cambisol. The split-split-split-plot design used four replicate blocks and four replicate experiments to compare organic/conventional rotation, crop protection, and fertilization protocols. Harvested potato tubers, cabbage and lettuce head leaves, and onion bulbs were freeze-dried after harvest and shipped to specialist laboratories. Toxic metal and mineral nutrient analyses other than nitrogen were carried out by Sabanci University using methods previously described by the NFSC group.

Table 10 draws on different multi-year windows by crop: potato toxic-metal main-effect means for crop protection and fertilization span seven growing seasons (2004, 2005, 2006, 2007, 2010, 2011, 2012), cabbage spans six (2004-2009), and lettuce and onion span four (2004-2007). Pre-crop main-effect means are available for fewer years: four seasons for potato and two seasons for cabbage, lettuce, and onion.

Implications

Certification: This is useful summary-level evidence for UK-grown vegetables and for the agronomic lever that mineral NPK fertilizer, likely via mineral phosphorus fertilizer contaminants, can increase Cd and Ni in harvested crops. It should not be pooled as sample-level observations, but its mean +/- SE summaries are admissible as summary statistics with the source’s fresh-weight basis and multi-year main-effect framing preserved.

Courses: Strong teaching example for separating crop-production labels from the actual lever: the paper finds lower Cd and Ni primarily through the fertilizer contrast, not through crop-protection chemistry.

App: Route to vegetable ingredient pages as UK fresh-weight occurrence context for Cd, Ni, and Pb. Retain the summary-statistic basis so downstream pooling can use moment-matching rather than treating each table cell as an individual sample.

Wiki pages this source may touch

• potatoes
• cabbage
• lettuce
• onions
• vegetables
• root-vegetables
• leafy-vegetables
• cadmium
• nickel
• lead
• soil-to-plant-transfer

Verification notes

The PDF has author attribution and DOI 10.3390/agronomy13051225; no DOI conflict was observed. Brand and supplier names used for seed/transplant sources are omitted under the brand firewall. The source reports Cd, Ni, and Pb only; no arsenic, mercury, chromium, or aluminum concentrations are reported for harvested crops. All toxic-metal values are fresh-weight main-effect means from Table 10, not sample-level rows. Because the source does not publish individual concentration records in the PDF and states that data are available on reasonable request, sample_n is left null and the multi-year scope is described in sample_population and Methods.

Merge-enhance pass 2026-06-02 (Claude): the page is faithful to Table 10 across every cell of both contrast tables (crop-protection/fertilization and pre-crop). Audit subagent (Agent tool, general-purpose, agent ID a8740e5f581900d2c) returned REVISE on Check 1 because the in-prose potato Cd NPK-vs-FYM increase had been silently substituted with the value computed from Table 10 (62.5%, rounded to 63%) when the paper’s own Section 3.6 (p. 16) explicitly states 50% for potato — an internal inconsistency in the source between prose and table. Per Cochrane discipline (faithful reproduction with the inconsistency flagged, not silent substitution), the potato figure is reverted to the paper’s stated 50% and the inconsistency is now flagged inline. Section 3.6 is the correct reference for the per-crop percentages, not Section 4.3.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.