A nitrogen budget of mainland China with spatial and temporal variation

Abstract

The present study evaluated nitrogen (N) input and output in mainland China using updated data of temporally and spatially-based land use maps and statistical data at national and provincial scales. The total N inputs increased from 3,081 kg km -2 in 1985 to 5,426 kg km -2 in 2007. Chemical fertilizer dominated the N input and showed an increasing trend. Biological N fixation was the second important N input till 1990 and atmospheric deposition became the second most important source after that, accounting for 24.0% in 2007. There was no net N input through food/feed import in 1985, but it accounted for 3.5% of the total N input in 2007. According to a mass balance model, we assumed total N input equal to output. The results showed that more than half of the total N was denitrified or stored in the system. Ammonia volatilization accounted for 18.9-22.9% of the total N input, and N export to water bodies accounted for 17.9-20.7%. About 5.1-7.7% of the N input was emitted to the atmosphere through biomass burning. When calculated per unit area, total N input, N export to water bodies, denitrification and storage could be very well explained by human population density. Nitrogen input and major outputs were also positively related to per capita gross domestic product and the percentage of total land area used as cropland. The N budget is compared to that of some other countries and the environmental impacts of the N cycle is discussed.

Spatiotemporal Variations in Nitrous Oxide Emissions from an Open Fen on the Qinghai–Tibetan Plateau: a 3-Year Study

“…The relatively low value of N 2 O emission rate in this study may be due to the relative stable water-logged conditions and light nitrogen loading about 5.88 kg N ha −1 year −1 , which was the average for the whole Qinghai-Tibetan plateau (Ti et al 2012). On the plateau, the mean N 2 O emission was relatively lower than those from alpine meadows and littoral zones in the same region (Du et al 2008;Chen et al 2011), however, much higher than those from steppes and grasslands of northern and western Qinghai-Tibetan Plateau, which is colder and drier (summarized in Table 4).…”

The composition, spatial patterns, and influencing factors of atmospheric wet nitrogen deposition in Chinese terrestrial ecosystems

“…It was estimated that the production of reactive N increased from 15 Tg N in 1860 to 156 Tg N in 1995, with a further increase up to 187 Tg N in 2005 (Galloway et al, 2008). On the one hand, atmospheric N deposition has a positive effect on maintaining plant productivity of terrestrial ecosystems through enhancing the N availability (Fleischer et al, 2013;Reay et al, 2008;Thomas et al, 2010;Ti et al, 2012); on the other hand, excessive N deposition has negative impacts on ecosystem health and services, such as N saturation (Aber et al, 1989;Kopacek et al, 2013), soil acidification (Bowman et al, 2008;Maljanen et al, 2013;Vitousek et al, 1997), and loss of biodiversity (Bobbink et al, 2010;Stevens et al, 2004).…”

Exploring the Trends in Nitrogen Input and Nitrogen Use Efficiency for Agricultural Sustainability

“…The N input from animal manure was calculated by estimating the manure production and accounting for the fraction added to croplands. Manure production was estimated by multiplying the number of livestock for each year by the average manure N production per head per year for each livestock type [18]. Annual N production of main livestock (donkeys, buffaloes, cattle, chickens, goats, horses, mules, pigs, and sheep) and the fraction of animal manure production available for croplands application were adopted from previous studies [18,[37][38][39][40][41] and are presented in Table 1.…”

“…We calculated the amount of various N inputs including planted seeds/tubers, atmospheric deposition, irrigation water, crop residues, animal manure, biological N fixation, and synthetic N fertilizer to the croplands and the NUE of crop production system based on 117 primary crops from 1961 to 2012 in China. Notably, compared with other studies [18][19][20], this is the first study to estimate the total N input and NUE by including all seven major N resources to croplands in China's crop production. Moreover, the Chinese government has issued a policy to reduce the use of fertilizers and pesticides in agriculture recently [22].…”

“…Generally, N inputs from planted seeds/tubers, atmospheric deposition, irrigation water, crop residues, animal manure, biological N fixation, and synthetic N fertilizer are considered the major sources of total N inputs to cropland. However, previous studies only included some of those N sources to estimate the total N input to cropland [18][19][20]. Furthermore, crop production and synthetic N fertilizer have increased substantially in China during the past decades [2], but the investigation on the partial factor productivity of applied synthetic N fertilizer (PFP N ) is limited in China.…”