Published: April 15, 2011 r2011 American Chemical Society 4715 dx.doi.org/10.1021/jf104389m | J. Agric. Food Chem. 2011, 59, 4715–4724 ARTICLE pubs.acs.org/JAFC Effect of Organic and Conventional Crop Rotation, Fertilization, and Crop Protection Practices on Metal Contents in Wheat (Triticum aestivum) Julia Cooper, † Roy Sanderson, ‡ Ismail Cakmak, § Levent Ozturk, § Peter Shotton, † Andrew Carmichael, † Reza Sadrabadi Haghighi, || Catherine Tetard-Jones, † Nikos Volakakis, † Mick Eyre, † and Carlo Leifert* ,† † Nafferton Ecological Farming Group, School of Agriculture, Food and Rural Development (AFRD), Newcastle University, Stocksfield, Northumberland, NE42 7XD, U.K. ‡ School of Biology, Ridley Building, Newcastle University, NE1 7RU, U.K. § Faculty of Engineering and Natural Science, Sabanci University, 34956 Istanbul, Turkey ) Agronomy Department, Islamic Azad University—Mashhad Branch, P.O. Box 91735-413 Mashhad, Iran ABSTRACT: The effects of organic versus conventional crop management practices (crop rotation, crop protection, and fertility management strategies) on wheat yields and grain metal (Al, Cd, Cu, Ni, Pb, and Zn) concentrations were investigated in a long- term field trial. The interactions between crop management practices and the season that the crop was grown were investigated using univariate and redundancy analysis approaches. Grain yields were highest where conventional fertility management and crop protection practices were used, but growing wheat after a previous crop of grass/clover was shown to partially compensate for yield reductions due to the use of organic fertility management. All metals except for Pb were significantly affected by crop management practices and the year that the wheat was grown. Grain Cd and Cu levels were higher on average when conventional fertility management practices were used. Al and Cu were higher on average when conventional crop protection practices were used. The results demonstrate that there is potential to manage metal concentrations in the diet by adopting specific crop management practices shown to affect crop uptake of metals. KEYWORDS: Metals, organic farming, cadmium, copper, aluminum, zinc, lead, nickel ’ INTRODUCTION Demand for foods produced using organic and other low- input crop production methods has increased rapidly over the last 20 years. 1,2 Organic farming standards prohibit the use of chemosynthetic pesticides and water-soluble mineral nitrogen, phosphorus, and potassium fertilizers and restrict the use of other mineral fertilizers. Fertilization therefore relies more on organic fertilizers, especially green and animal manures. The use of animal manures and copper (Cu) fungicides (which is permitted under organic farming practice) has resulted in concerns about higher loads of nutritionally undesirable metals such as cadmium (Cd), copper (Cu), lead (Pb), and nickel (Ni) as well as aluminum (Al) in organic crops. 3,4 Some metals (e.g., Cu) are essential micronutrients for plants and humans at low concen- trations but are toxic at higher exposure and dietary intake levels. 5,6 Crop-based foods account for over 80% of Cd and Pb intake. 7,8 The metal content of crops is reported to be affected by a range of factors, including soil type, 9-11 climatic conditions, 11,12 crop species, and variety choice. 5,13-16 The use of mineral phosphorus (P) and sulfur (S) based fertilizers and pesticides has been linked to increased levels of Cd in food crops. Similarly the use of Cu fertilizers and fungicides has been linked to an increased Cu content in both soils and food crops. 12,17-19 In a group of Swedish studies mineral P fertilizer use was linked not only to an increase in Cd concentrations in soils 20 and cereal grain 21,22 but also to increased Cd concentra- tions in kidneys and other tissues of pigs and dairy cows. 23,24 This has led to stricter monitoring of Cd concentrations in P-fertilizers in many countries 23,24 and efforts to breed crop varieties/ cultivars with low metal uptake efficiency (so-called pollution- safe cultivars or PSCs) in order to reduce metal intake via major food crops. 16 A range of survey and field experiment based studies have compared the cadmium content (and in some cases the content of other metals) in organic and conventional food products. The majority of studies reported significantly higher or trends toward higher Cd levels in conventionally produced crops. This included studies on wheat, oats, onions, tomatoes, lettuce, peppers, peach, lentils, and peas. 5,14,18,25 In contrast, a survey-based study by Jorhem and Slanina 11 reported inconsistent results for wheat, and a field experimental study by Rossi et al. 19 found significantly higher Cd levels in organically produced tomato. There are also some survey and experimental studies in which the Pb content in organic and conventional crops was compared. Rossi et al. 19 reported 4 times higher Pb concentrations in conventional compared to organic wheat produced in Italy, Received: July 9, 2010 Accepted: February 11, 2011 Revised: February 9, 2011