Biochar, a green way to deal with burning and burying biomass, has attracted more attention in recent years. To fill the gap of the effects of different biochar on crop yield in Northern China, the first field experiment was conducted in farmland located in Hebei Province. Biochars derived from two kinds of feedstocks (rice straw and corn stalk) were added into an Inceptisols area with different dosages (1 ton/ha, 2 ton/ha or 4 ton/ha) in April 2014. The crop yields were collected for corn, peanut, and sweet potato during one crop season from spring to autumn 2014, and the wheat from winter 2014 to summer 2015, respectively. The results showed biochar amendment could enhance yields, and biochar from rice straw showed a more positive effect on the yield of corn, peanut, and winter wheat than corn stalk biochar. The dosage of biochar of 2 ton/ha or 1 ton/ha could enhance the yield by 5%-15% and biochar of 4 ton/ha could increase the yield by about 20%. The properties of N/P/K, CEC, and pH of soils amended with biochar were not changed, while biochar effects could be related to improvement of soil water content.

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Copper is a critical mineral resource and plays a crucial role in social and economic development. In China, the world’s largest copper consumer, copper footprints and embodied copper transfers among sectors have not been studied sufficiently. Combing an environmentally extended input-output model and complex network method, this paper systematically analyzes China’s copper consumption embodied in the final demand and the production process. The research shows that (1) from the perspective of the final demand, the Construction sector is the largest driver of copper consumption, contributing 3.27 Mt in 2020, followed by the Manufacture of General Purpose Machinery sector (1.31 Mt). (2) Structural path analysis (SPA) shows that mainly the Construction sector drives copper consumption from the Production and Distribution of Electric Power and Heat Power sector, followed by the Manufacture of Non-metallic Mineral Products sector, and so on. Conversely, the Production and Distribution of Electric Power and Heat Power sector is the main initial sector in the supply chain, driven by the Construction sector, the Manufacture of Non-metallic Mineral Products sector, the Smelting and Processing of Metals sector, and so on. (3) From the perspective of production, the Transport, Storage, and Postal Services sector is an important transfer station transforming resources from the upstream sectors to the downstream sectors along with the transfers of embodied copper. The Production and Distribution of Electric Power and Heat Power sector is an important supplier for the downstream sectors. The Construction sector is an important consumer for the upstream sectors. The sectors including the Smelting and Processing of Metals sector, the Manufacture of Chemical Products sector and the Manufacture of Non-metallic Mineral Products sector function well as transformers, suppliers and consumers in the process of embodied copper transfers. (4) From the perspective of production, the embodied copper flow system can be divided into four groups that are closely linked. E & C community is the core member of the whole embodied copper flow network. C and S community is the main consumer of embodied copper resources in the network, exporting a great deal of embodied resources from other communities. Finally, some policy proposals on the rational utilization of copper resources are put forward.