| Phosphogypsum is the waste produced from phosphorus chemical industry. It has not been well managed and reused and caused serious environmental pollution and land-occupation. In order to explore a new way to reuse or recycle the phosphogypsum wastes, the impact of different amounts of phosphogypsum wastes on the growth and yield of winter wheat, as well as N2O emissions from the wheat field soil was investigated with a combined lab incubation and field experiment.The key results are listed as following:(1) The lab incubation experiment showed that soil N2O emissions decreased with the increase of the amount of phosphogypsum added, where the effect was initial stronger but final weaker found depending on the amount of phosphogypsum. It was found that the optimal application rate of phosphogypsum was 2.80g/bottle for reducing N2O emissions while better mitigation of N2O emissions was obtained in treatments of 0.70g/bottle and 1.40g/bottle.(2) The field plot experiments (lasting for two years) demonstrated that the different effects of phosphogypsum on the growth and yield of winter wheat, and soil N2O emissions were obtained. Significant increase of the wheat 1000-grain-weight and yield was found at the treatment of 2100kg·hm-2 phosphogypsum, which was increased by 48.11% and 47.00%, respectively in the continuous two years. Compared with the treatment of compound fertilizer (900kg·hm-2) throughout the wheat growing season, soil N2O emission was reduced by 30.14% and 30.15% for the treatment of 2100kg·hm-2 phosphogypsum waste, where this N2O reducing effect was persistently observed at stage of the jointing, heading and filling of the growth of winter wheat. In contrast, a little reduction of soil N2O was found in treatment of 1050kg·hm-2 phosphogypsum waste.(3) In the case of application of phosphogypsum waste, both the fresh weight and yield of wheat showed a significantly negative correlation with the emissions of N2O. Phosphogypsum can not only significantly stimulate the growth of wheat, but also significantly reduce soil N2O emissions. Cost-profit and input-output analysis (from economy and environment) of the application of phosphogypsum was conducted based on the panel of Shanghai Energy and Carbon Emission Trading in March 2015. For the application of phosphogypsum waste of 2100kg·hm-2, the ratio of input to output of the winter wheat increased from 1:9.93 to 1:17.82, and the output can be increased by 79.46%. In the meantime, the N2O emissions can be reduced up to 161.71 kg·hm-2. The N2O emissions can be reduced by 76.48 kg with per ton of phosphogypsum waste generally, which is equivalent to 22944 kg of CO2 emissions reduction and the environmental benefits of RMB 1140.5. The similar pattern was observed for the second year.(4) Phosphogypsum could reduce activities of soil urease, sucrase, cellulose enzyme, and catalase in winter wheat soil. Consequently inhibition of nitrification and denitrification in soil and decreased soil N2O emission were observed. As a potential agricultural greenhouse gases mitigating agent, phosphogypsum wastes could obviously decline the N2O emission from the field soil and also stimulate the growth of wheat. It has a potential application value for the development of ecological agriculture and mitigating the greenhouse gases. |
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