Tag: agriculture

Biogeochemical Flows, Nitrogen

Biogeochemical Flows: Nitrogen

Planetary Boundary

  • Global boundary: 62 Tg N/year
  • Source: *Steffen, W., K. Richardson, J. Rockström, S.E. Cornell, et.al. 2015. Planetary boundaries: Guiding human development on a changing planet. Science 347: 736, 1259855
  • Overall, the fixation of nitrogen through Haber–Bosch (120 Tg N yr−1) in 2010 was double the natural terrestrial sources of Nr (63 Tg N yr−1).
  • The overall magnitude of anthropogenic relative to natural sources of fixed nitrogen (210 Tg N yr−1 anthropogenic and 203 Tg N yr−1natural) is so large it has doubled the global cycling of nitrogen over the last century. 
  • The overall magnitude of anthropogenic relative to natural sources of fixed nitrogen (210 Tg N yr−1 anthropogenic and 203 Tg N yr−1 natural) is so large it has doubled the global cycling of nitrogen over the last century.
  • Source: Fowler, et al., The global nitrogen cycle in the twenty-first century, Philos Trans R Soc Lond B Biol Sci. 2013 Jul 5; 368(1621): 20130164.

Significance

The supply of Nr–reactive nitrogen (NH3, NH4, NO, NO2, HNO3, N20, HONO, PAN and other organic N compounds) is essential for all life forms, and increases in nitrogen supply have been exploited in agriculture to increase the yield of crops and provide food for the growing global human population. It has been estimated that almost half of the human population at the beginning of the twenty-first century depends on fertilizer N for their food. (Source: Fowler, et al.)

As nitrogen is a major nutrient, changes in its supply influence the productivity of ecosystems and change the competition between species and biological diversity. Nitrogen compounds as precursors of tropospheric ozone and atmospheric particulate material also degrade air quality. Their effects include increases in human mortality, effects on terrestrial ecosystems and contribute to the radiative forcing of global and regional climate. (Source: Lee, et al., see figure below)


Global N budget. Numbers represent global land N storage in TgN or annual N exchange fluxes in TgN yr−1 for contemporary (1991–2005 average) and preindustrial (1831–1860 average in parenthesis) times. See notes for this figure and the table below in:  Lee, et al., Prominence of the tropics in the recent rise of global nitrogen pollution.  Nature Communications (2019)10:1437 https://doi.org/10.1038/s41467-019-09468-4  and Supplementary Table 1 (modified below) and Supplementary Note 1 (https://doi.org/10.1038/s41467- 019-09468-4.)
Nitrogen Stores & Fluxes Published Estimates 1990’s Published Estimates 2000’s
Biological N Fixation 112; 139  
Agricultural 32 50-70
Preindustrial 58; 195  
Non-agricultural NA  
Natural 107; 128  
     
Atmospheric Deposition 59  
     
Haber-Bosch (Synthetic fetilizers) 100 120
     
Fluxes to the ocean 48 45
     
Fluxes to the atmosphere 189  
Denitrification N2 115 96
Other emissions 74 70
     
Fluxes to the land storage 60 27
     
Soils/litter storage 95,000  
     
Fluxes:  TgN/year    
Storage:  TgN    
Source: https://sedac.ciesin.columbia.edu/data/set/ferman-v1-nitrogen-fertilizer-application/maps

Biogeochemical Flows, Phosphorus

Biogeochemical Flows: Phosphorus

Planetary Boundary

  • Global P Boundary: 11 Tg P/year*
  • Regional (watershed) P Boundary: 6.2 Tg P/year*
  • Current global rate of P fertilizer to croplands* (primary source of P to regional watersheds): 14.2 Tg P/year*
    • Total P flow through international agricultural trade increased from 0.4Tg to 3.0 Tg between 1961-2011**
    • The fraction of P taken up by crops that is subsequently exported increased from 9% to 20% between 1961 and 2011**
    • Global P flows through international trade of agricultural products have become an important feature of the global P cycle, accounting for 20% of the P in global crop production, 17% of the P globally used as mineral fertilizer, and 27% of the P that was traded as mineral fertilizers in 2011.**
  • (Sources: *Steffen, W., K. Richardson, J. Rockström, S.E. Cornell, et.al. 2015. Planetary boundaries: Guiding human development on a changing planet. Science 347: 736, 1259855, **Nesme, T.,  G.S. Metson, and E.M. Bennett. 2018. Global phosphorus flows through agricultural trade. Global Environ. 50:133–141.Change 50:133–141. doi:10.1016/j.gloenvcha.2018.04.004 https://www.sciencedirect.com/science/article/pii/S0959378017310026

*Phosphorus and Agricultural Trade

Source: https://sedac.ciesin.columbia.edu/data/set/ferman-v1-phosphorus-fertilizer-application
Global phosphorus fertilizer application to cropland

Highlights

  • Critical element for all living organisms
  • Availability drives the productivity of many aquatic and terrestrial ecosystems worldwide
  • In agricultural systems, additional P can be supplied to soils as mineral fertilizer or manure to support crop growth and sustain high yields
  • Mineral P fertilizer production is dependent on the physical and economic availability of mined rock phosphate resources (non-renewable, diminishing, geopolitically concentrated)
    • The P cycle has been greatly transformed since the pre-Industrial era through increased agricultural mineral P fertilizer use
  • P losses to water bodies through runoff and erosion from fertilized agricultural soils and from the inadequate management of animal manure or human excreta has led to aquatic eutrophication
  • International trade of agricultural products (food, feed, fiber and fuel) are a key component of the global phosphorus cycle; agricultural flows of P are driven by trade of cereals, soybeans, and feed cakes
  • 28% of global P traded in human food, 44% in animal feed and 28% in crops for other uses in 2011