Determining the appropriate soil cadmium (Cd) criteria for vegetable production is important for ensuring that the Cd concentrations of the vegetables meet food safety standards. The soil extractable Cd criteria for vegetable production are also essential for both food safety and environmental management, especially in areas with a high natural background level. In the present study, soil total and extractable Cd criteria were derived using the approach of species sensitivity distribution integrated with soil aging and bioavailability as affected by soil properties. A dataset of 90 vegetable species planted in different soils was compiled by screening the published in literature in five bibliographic databases using designated search strings. The empirical soil–plant transfer model was applied to normalize the bioaccumulation data. After normalization, the intra-species variability was reduced by 18.3 to 84.4%. The soil Cd concentration that would protect 95% (HC₅) of the species was estimated by species sensitivity distribution curves that were fitted by the Burr III function. The soil Cd criteria derived from the added approach for risk assessment were proposed as continuous criteria based on a combination of organic carbon and pH in the soil. Criteria for total Cd and EDTA-extractable Cd in the soil ranged from 0.23 to 0.61 mg kg^–1 and from 0.09 to 0.25 mg kg^–1, respectively. Field experimental data were used to validate the applicability and validity of these criteria. Most of the predicted HC₅ values in the field experimental sites were below the 1:1 line. These results provide a scientific basis for soil Cd criteria for vegetable production that will ensure food safety.

A field plot experiment in a calcareous soil with wheat and maize rotation was carried out for 2 yr. The study aimed to investigate the effects of biosolids (sewage sludge or chicken manure) application on nitrogen (N) and phosphorus (P) accumulation in soils and to develop a model for the effects of biosolids application on available P (Olsen-P) accumulation in soils, by which the quantities of biosolids that can be safely applied to agricultural soils were estimated. The results showed that heavy application of biosolids to agricultural soils based on the N requirement of a wheat-maize rotation cropping system will oversupply P. Soil total N was increased by 0.010 g kg-1 at application rate of 1 ton sewage sludge per hectare. The high ratio of N to P in grains of wheat and maize (from 4.0 to 7.6) and low ratio of N to P in biosolids (<2) led to more surplus P accumulated in soils. Although plant yields and P uptake by plants increased with increasing quantities of applied biosolids in soils, there was still an average 2.87 mg kg-1 increase in Olsen-P in the plough layer treated with biosolids for every 100 kg P ha-1 surplus. A predictive model was developed based upon the initial Olsen-P in soils, P input rates, crop yield, soil pH, and cultivation time. From the model, it is suggested that sewage sludge could be applied to calcareous soils for 12 yr using the recommended application rate (9 tons ha-1 yr-1). The field results will be helpful in achieving best management of biosolids application for agricultural production and environmental protection.