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Plant growth and nutrient uptake by plants have been shown to be affected by soil pH. However, the effects have not been evaluated with a mechanistic uptake model that can evaluate the relative influence of soil pH changes on changes in soil supply parameters that influence predicted P uptake. The objectives of this research were to verify the Barber‐Cushman nutrient‐uptake model under a range of soil pH conditions and to use the model to evaluate the influence of soil pH on the model parameters supplying P and K to maize (Zea mays L.) roots. A pot experiment was conducted to evaluate the accuracy of the model for predicting P and K uptake at soil pH levels of 3.8, 4.7, 5.7, 6.5, 7.6, and 8.3 in Chalmers silt loam (fine‐silty, mixed, mesic Typic Haplaquoll). This study showed that the nutrient‐uptake model accurately predicted the effect of the soil pH on P uptake (Y = 0.44 + 0.93X, r2 = 0.99) when the change of P from H2PO4 to HPO4 at the higher pH values was accounted for, and predicted K uptake (Y = 67 + 0.94X, r2 = 0.99) without modification for pH.

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The cadmium (Cd) accumulation capacity of various vegetables and the relationship between Cd concentrations in edible parts of vegetables and those in soils were assessed by conducting field experiments at Cdcontaminated sites in northern and central Taiwan. In addition, to thoroughly assess Cd concentrations in vegetables and to understand the food safety of vegetables in Taiwan, 2257 paired vegetable and surface soil samples were collected from major vegetable production areas for Cd concentration analysis. According to the bioconcentration factors calculated, the Cd accumulation capacity varied considerably among the vegetable species tested, and the order of the five vegetables with the highest capacities is peanut (Arachis hypogaea L.) > amaranth (Amaranthus tricolor L.) > spinach (Spinacia oleraceae L.) > gynura (Gynura bicolor DC.) > okra (Hibiscus esculentus L.), whereas the order of the five vegetables with the lowest capacities is bitter gourd (Momordica charantia L.) < cucumber (Cucumis sativus L.) < asparagus bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis (L.) Verdc.) < snap bean (Phaseolus vulgaris L.) < sponge gourd (Luffa cylindrica Roem.). We derived 29 soil-plant transfer models of Cd for individual vegetable species based on available pools of the Cd, manganese (Mn), zinc (Zn), copper (Cu) and iron (Fe) concentrations; soil pH; and cation exchange capacity (CEC). According to the derived models, the available Cd, Mn and Zn concentrations, and pH, served as the main factors affecting Cd concentrations in the edible parts of vegetables, whereas the CEC and available Cu and Fe concentrations are less important factors. The data of previous studies and those of this study from major vegetable production areas, including 30 vegetable crops, were used to evaluate the safety of vegetables in Taiwan. The results indicated that the percentage of vegetables with Cd concentrations exceeding the regulatory concentration was 0.54%; therefore, the food safety concern is low. However, 9.8, 1.0, 0.9 and 0.6% of amaranth, cabbage (Brassica oleracea L. Capitata Group), Chinese cabbage (Brassica pekinensis Skeels.) and carrot (Daucus carota L.), respectively, had Cd concentrations in the edible parts exceeding the regulatory concentration. Particular attention should be paid when planning production areas for these vegetables. We recommend cultivating peanuts in fields with a soil Cd concentration < 0.33 mg kg −1. The bioconcentration factors and soil-plant transfer models derived in this study might serve as assessment tools for planning farming areas for these vegetables.

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