Life Cycle Environmental Impacts Of Fertilization In Wheat, Maize And Vegetables Production In North China Plain

Nodaway, the China faces the huge challenge to achieve the self-sufficient food production and lowering the environmental burdens. The North China Plain, a main grain crop producing region in China, plays an important role in ensuring the food security, but which is also a high-risk region of environmental contamination mainly derived from the overuse of fertilizer in crop production. Therefore, it is urgently needed to analyze the resource and environmental cost of fertilization in North China Plain and explore optimized approaches for the sustainable development of agriculture in the study area, hence, supplying scientific basics for government to design improved policies. By using the LCA （Life Cycle Assessment） method and the database from farmers’surveys, this study aims to 1) compile the inventory of resource use and emissions of fertilization associated with the main crop production systems （winter wheat, summer maize, greenhouse- and open-field vegetables） in North China Plain, 2) identify the key factors leading to these emissions and 3) explore the availability of improving the potential to lower resource use and emissions of fertilization. The main results are shown as follows:1 The integrated environmental impacts of fertilization per ton of grain production can be in order of wheat （0.509） > maize （0.350） > open-field non-leaf vegetable （0.226） > greenhouse cucumber （0.203） > open-field leaf vegetable （0.176）. While the integrated environmental impacts of fertilization per ha can ranked as greenhouse cucumber （55.6） > open-field vegetables rotation （28.2） > wheat-maize rotation （5.4）.2 For producing per ton of crops, the aquatic eutrophication （83.5%-97.0%） was identified as the greatest environmental impact category for the main crops in North China Plain and closely followed by acidification （2.0%-7.1%） and the lower ones energy consumption and aquatic toxicity were overlooked; On per ha land, the aquatic eutrophication （87.3%-96.9%） was identified as the greatest environmental impact category for the main crop rotation systems in North China Plain and closely followed by acidification （2.0%-7.3%） and the lower ones energy consumption and aquatic toxicity were overlooked. Subsequently, More than 96% of aquatic eutrophication and acidification potential as well as over half of global warming potential originated from the crop cultivation within the crop life cycle. Furthermore, the NH₃, NO₃^--N and TP emissions from cropland were the main contributors, accounting for approximately 40%, 40% and 20% for wheat, maize and wheat-maize rotation, and around 10%, 30% and 60% for （greenhouse and open-field） vegetables. Above all, fertilizer N inputs were considered as the strongest contributors to the aquatic eutrophication in wheat, maize and wheat-maize rotation, while in vegetable production the strongest one was fertilizer P input. With regards to the acidification, the fertilizer N application was its main source in main crops production and crop rotation systems.3 Crop yields, fertilizer N, fertilizer P and fertilization method were identified as the key factors resulting in these integrated environmental impacts of fertilization in main crops production and different crop rotation systems in North China Plain. On a basis of per ton of grain, the integrated indicator values for all investigated crops gradually decreased as the crop yields increased, while the corresponding values increased as the fertilizer N and P inputs increased. On a basis of per ha, the relationship between crop yields and integrated indicator values were different among crops: cereal crop yields were also negatively related to the integrated indicator values, but there was no significant relationship between crop yields and integrated indicator values for vegetable systems, and the corresponding values increased as the fertilizer N and P inputs increased. The integrated environmental impact potential of deep fertilization was lower than the impact potential of surface fertilization in both of producing per ton of wheat and maize grain. There were significant differences in the integrated environmental impact potential among farmers.4 The balanced fertilization and improved fertilization method are the useful approaches to lowering the integrated environmental burdens of fertilization in the main crops production and different crop rotation systems in North China Plain. The integrated indicator values could be decreased by 19.0%-37.1% via the improvement of fertilization methods （e.g. surface application shifted to deep application or irrigation after fertilization）: the potential of decline were highest for wheat and lowest for maize. The integrated indicator values could be decreased by 18.4%-31.9% via the balanced N fertilization: the potential of decline were highest for greenhouse cucumber and lowest for maize. The integrated indicator values could be decreased by 7.0%-58.6% via the balanced P fertilization. In conclusion, the priorities to decrease the environmental impacts for cereal crops are the improvement of fertilization method, while for the vegetables the emphases should be laid on the balanced P fertilization. To improve crop yields constantly, to reduce fertilizer application rates to meet crop nutrient needs and reasonable fertilization method are important ways to ensure high yield at the same time low environmental impact potential.