Interactions between nitrogen application and soil properties and their impacts on the transfer of cadmium from soil to wheat (Triticum aestivum L.) grain

Rapid urbanization, industrialization, and agricultural intensification have triggered soil and environmental pollution through excessive nitrogen (N) application and cadmium (Cd) contamination. There is still contradiction regarding the effect of N application and soil properties on grain Cd concentration in wheat (Triticum aesavum L.). Grain Cd concentration does not only rely on crop genotypic characteristics and soil geochemical properties but also to a large extent on N fertilizer application. Assessing and identifying the factors governing Cd phytoavailability in soil-plant systems is thus crucial. For this purpose, we developed and validated quantitative relationships of wheat grain Cd concentration with soil geochemical properties related to Cd phytoavailability (pH, Eh, CEC, EC), and N application rates and to investigate interactions between N application rates (0-300 kg ha(-1)), soil geochemical properties, and grain Cd concentration with data acquired from four field trials conducted in China during 2017-2018 using two wheat cultivars (Annong-1124 and Ningmai-15). The results indicated that N application rates significantly influenced soil properties (pH, Eh, CEC, and EC) and played a decisive role in the transfer of Cd from soil to wheat grain by increasing soil acidification, soil salinity, oxidation reactions, and exchange capacity. Soil geochemical properties were ranged from 5.49 to 6.02 (pH), 55.07 to 103.73 mV (Eh), 164.57 to 258.63 2 mu S.cm(-1) (EC), 19.2 to 23 cmol.kg(-1) (CEC), while grain Cd was ranged from 0.16 to 0.27 mg.kg(-1). Quantitative relationships were highly significant for both wheat cultivars with R-2 > 0.83. Validation results indicated a solid performance of quantitative relationships (RMSE < 3%, RRMSE < 8%, RE < 7%, and R-2 > 0.90) and confirmed their robustness as reliable predictors for assessing wheat grain Cd concentration. The finding of this work will further assist agronomist to assess the possible risk of elevated Cd content in these wheat cultivars arising from regional crop and soil management strategies, especially related to N. The findings will help to improve food security and soil sustainability without compromising the food safety-related risks.