Effects Of Fertilizer Management On Macronutrient And Heavy Metal Balance In Soil-crop Systems

The combined application of organic manure and inorganic fertilizers was proved to be an efficient way of fertilizing plants in China. In this study, two field experiments in rice-rape cropping system and tomato-radish-pakchoi cropping system were conducted to characterize growth and yield responses of crops, macronutrient and heavy metal content and uptake of crops, runoff, macronutrient and heavy metal balance in cropping rotation influenced by commercial organic manure (COM) used as a partial substitute for chemical fertilizers. Four treatments as chemical fertilizers (T1), chemical fertilizers+lower rate of organic manure (T2), chemical fertilizers+medium rate of organic manure (T3), and chemical fertilizers+ high rate of organic manure (T4) were designed in the experiment. The doses of N, P2O5, and K2O of each treatment were equal, and each treatment had four replications. Cadmium distribution and accumulation in different genotypes of radish were also investigated. The major results were summarized as follows:1. The results indicated that market yield and biomass of rice and rape in El and E2-1 were not significantly different among the treatments with the equal doses of N, P, and K. Application of manure increased brown rice and grain yield of rice in E2-2. Market yield (expressed as fresh weights), shoot biomass of tested crops and biomass of radish roots (expressed as dry weight) were not significantly different among the treatments with the equal doses of N, P, and K in all three rotations except pakchoi yiled in the third rotation.2. These results indicated that COM used as a partial substitute for chemical fertilizers can meet for plant growth and maintain vegetable market yield. N content of brown rice increased in different raten of COM treatment, but P and K contents in brown rice increased only in medium rate of COM treatment. P and K content of rapeseed increased in different rate of COM treatment, but only low rate of COM treatment increased N content in rapeseed. Low rate of COM treatment increased N content in tomato fruit, P content of tomato fruit increased in medium rate of COM treatment and high rate of COM treatment. Application of COM decreased P content in tomato fruit. Medium rate of COM treatment improved N content in radish flesh root, different rate of COM all increased P and K content in radish flesh root. Application of COM decreased N content in pakchoi and increased P and K content in pakchoi expect P in medium rate of COM treatment.3. In rice-rape cropping systems, application of COM lessened P accumulation in soils and improved K accumulation in soils, while the case was opposite in the vegetable cropping systems.4. The results indicated that applicantion of manure decreased heavy metal content in plants. In brown rice, Cu content decreased in low rate of COM treatment and high rate of COM treatment, and Zn, Cd and Pb content decreased in low rate of COM treatment. Cd content of brown rice in all treatment of E1 and E2 were lower than limit (0.2 mg-kg-1) in cereals in China except medium and high rate of COM treatment of El. In rapeseed, Cu content decreased in different rate of COM treatment, Zn content decreased in medium rate of COM treatment, Cd content decreased in medium rate of COM treatment and high rate of COM treatment, and Pb content decreased in high rate of COM treatment. Cd and Pb content of rapeseed in all treatment of E1 and E2 were all lower than limit except four treatmens inE2-1. Different rate of COM decreased Cd contents in tomato fruit. Low rate of COM decreased Cu and Zn contents in radish fleshy root. Different rate of COM decreased Cu content in pakchoi. Low rate of COM decreased Cd and Pb content in pakchoi. Cd, Pb concentrations in tomato, radish and pakchoi were all lower than the limit of vegetable in China.5. It was also found that there were no zinc and copper deficit in rice-rape cropping system and tomato-radish-pakchoi cropping system with four treatments. Fertilization input plenty of Cd and Pb to soil while crops absorb little, so there was Cd and Pb accumulation in all treatments of two cropping systems, which should be noticed. It could be concluded that integrated fertilization with appropriate rate of COM and chemical fertilizers could not only remain the balance of Zn and Cu, but also minimize the risk of heavy metal pollution in the cropping system, which can be regarded as an effective manner for the construction of sustainable agriculture.6. There were significant differences in Cd accumulation of different radish variety growing on Cd contaminated soil. The Cd content of MEZ and BYDG were 0.0156 mg-kg-1 and 0.0596 mg-kg-1 respectively, which were lower than Cd limit (0.1 mg-kg-1) in radish. It showed that MEZ and BYDG can be planted in Cd slightly-contaminated soil.