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Fertilization affects soil processes in many ways that remain unclear. The effects of N, P, and K application on plant growth and Cu and Pb accumulation were thus evaluated in a soil-maize system using five treatments: N, P, and K application; N and P application; N and K application; P and K application; and control (no fertilization). Compared to the control, fertilizer application treatments, especially N application, significantly increased maize photosynthetic rate, which further improved shoot biomass production. Root growth, root and shoot Cu and Pb concentrations, and Cu and Pb mobility also significantly altered with fertilizer application. Shoot Cu contents, root Cu uptake and translocation factors were significantly increased in the N-fertilized treatments. The significant decrease of shoot Pb concentration and root Pb uptake and increase of Cu and Pb immobilization were observed in the P-fertilized treatments. No significant correlation was observed between K application and Cu and Pb accumulation in maize. Our results show that an increase in P application and decrease in N application is recommended to reduce agro-ecological risks associated with Cu and Pb in soil-maize systems. However, the mechanisms governing the relationship between nutrients and heavy metal transformation in soil-plant systems needs further research.

A long-term (33 years) experiments were conducted to investigate the effect of chemical fertilization on rice yield, yield trends, soil properties, agronomic efficiency of applied nutrients and nutrient balance for the double rice cropping systems in subtropical China. The treatments were different combinations of N, P and K fertilizers (N, NP, NK and NPK), double dose of recommended NPK (2NPK) and no fertilizer control (control). Compared with no fertilizer control, all fertilization treatments had no significant effects on soil pH and SOC contents (P > 0.05), but generally increased nutrients content when corresponding elements were applied. The impact of fertilizers on grain yields was 2NPK > NPK > NP > NK > N, and application of P fertilizer not only increased the rice yield, but improved yield stability. The trend of agronomic use efficiency of applied P was significantly positive (P < 0.05) only for the first rice crop, suggesting that P fertilizer played a less important role in the second rice season than in the first rice season. The study indicated that the current local fertilizer recommendations should be optimized for the consideration of differences in indigenous nutrient supplies in different rice seasons.