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Sustainable intensification of China's agriculture: the key role of nutrient management and climate change mitigation and adaptation

DEV's Dr Yuelai Lu's latest publication 'Sustainable intensification of China's agriculture: the key role of nutrient management and climate change mitigation and adaptation' can now be found here.

INTORDUCTION

During the second half of the 20th Century the focus of China's agricultural policies was to expand food production faster than population growth and to maintain 100% grain self-sufficiency with little regard to the negative environmental consequences of these policies. However, since the year 2000 China's agricultural policies have progressively given greater attention to reducing environmental and ecosystem impacts, whilst maintaining high levels of food self-sufficiency (Qin et al., 2013), and in the past five years has been introducing measures to advance sustainable intensification.

On the food production front China has been very successful. Using only 7% of the world's arable land it meets most of the food needs of 22% of the world's current population. Per capita availability of grain in China increased from 326 kg in 1980 to 399 kg in 2008, meat from 9 kg to 42 kg, while the population increased from 987 million to 1.33 billion in the same period. Consequently, the number of undernourished people in China decreased by 16 million from 1995 to 2005, because of improved food supply and higher incomes, whereas in the rest of the developing world the number of undernourished increased by 48 million. This was possible because of China's exceptionally high growth in agricultural productivity, which averaged 4.6% per year over the period 1978 to 2010 – a sustained growth rate that few other countries have achieved. But although total factor productivity grew at about 2% per year over this period ( Ju et al., 2009), the partial productivity of the two key inputs for crop production namely synthetic nitrogen (N) fertilizer and irrigation declined or remained low, and improvements in livestock waste management failed to keep up with the huge residues being generated by the rapidly growing intensive livestock sector (Chadwick et al., 2015). Consequently N use efficiency fell by about 300% between 1979 and 2010 ( Ma et al., 2013) in part because of the overuse and mismanagement of synthetic N fertilizer and manure and was the primary cause of non-point source pollution ( Norse, 2005; Sun et al., 2012), and livestock wastes became a major cause of point source pollution ( SAIN, 2012b).

These environmental impacts of conventional intensification and the lack of response to them are the major reason why since the mid-2000s agriculture has surpassed industry as the largest polluter of the water system (MEP, 2010). For example, it discharges 44%, 57% and 67% respectively of the nation's total COD, N and phosphate (P) into water and causes widespread damage to drinking water supplies and fisheries. The over-use of N fertilizer on crops plus high ammonia emissions from the livestock sector has caused serious widespread soil acidification (Guo et al., 2010) and negative impacts on soil microbial and plant ecosystems. Finally, China's agriculture contributes around 20% (estimates vary from 17% to 22%) of the nation's total greenhouse gas (GHG) emissions, which are now the largest in the world, and most of them come from synthetic N fertilizer production and use (Zhang et al., 2013) or from the livestock sector (SAIN, 2011).

The economic costs of the environmental impacts of conventional intensification are considerable and knowledge of these should also favour policy shifts and technological innovation to speed up the shift towards sustainable intensification. These costs are at least US$ 32-67 billion and are equivalent to 3-7% of China's agricultural GDP (Norse and Ju, 2015). Nutrient (primarily N and P) mismanagement is a major cause of the economic damage, and hence is the main focus of this special issue. For example, the overuse of synthetic N fertilizer is very widespread on food crops and cotton and a major long-term cause of groundwater nitrate accumulation, eutrophication of surface water systems and of soil acidification (Norse et al., 2012).

READ MORE HERE.