Fertiliser overuse in China harms ecosystems

Environmental Research Web: In order to meet its food needs China has encouraged extensive fertilization with synthetic nitrogen fertilizers. But now the loss of excess nitrogen to the environment is causing problems such as eutrophication of surface waters, nitrate pollution of groundwater, acid rain and soil acidification, greenhouse gas emissions and other air pollution.

"It took nearly 50 years to achieve food sufficiency in China," Xiao-Tang Ju of China Agricultural University and the Ministry of Education told environmentalresearchweb. "An unanticipated cost has been that massive fertilizer inputs have led to significant environmental degradation. China consumes more than 30% of the world’s nitrogen fertilizer with 9% of global arable land since the 1980s."

With that in mind, researchers at China Agricultural University, the Chinese Ministry of Education, the Chinese Academy of Sciences, Hebei Agricultural Univeristy, China, and the Agri-Food and Biosciences Institute in the UK have found that using 30-60% less nitrogen kept crop yields the same but halved nitrogen loss to the environment. The team studied two double-cropping systems – waterlogged rice/upland wheat in the Taihu region of east China and irrigated wheat/rainfed maize on the North China Plain.

All four crops showed different nitrogen behaviour, "depending on climatic, soil and management practices". The team calculated that the rice/wheat system had an annual nitrogen surplus of 87 kg per hectare. This system had large losses by denitrification, which the scientists reckoned could be reduced by improving carbon management and controlling the water regime.

…"A better nitrogen balance can be achieved without sacrificing crop yields but significantly reducing environmental risk by adopting optimum nitrogen fertilization techniques, controlling the primary nitrogen loss pathways and improving the performance of the agricultural Extension [advisory] Service," said Ju. "The over-application of nitrogen also represents an unnecessary economic expenditure for farmers."

A village in Tongshan County, Hubei (between Tongshan town and Hengshitan Zhen, seen from Highway G106), with a large pond of lotuses, shot by Vmenkov, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 3.0 License