Nitrogen cycle budget

Figure 1. A simplified watershed nitrogen cycle, with major pathways (arrows) and their effects on the watershed hydrogen budget (numbers in circles) shown. Circled numbers represent the number of hydrogen ions transferred to the soil solution or surface water ( +1) or from the soil solution or surface water (-l)for every molecule of N03 or NH4 + that follows a given pathway. For example, nitrification follows the pathway for NH4 + assimilation into microbial biomass ( + l) and is leached out as N03 ( + 1), for a total hydrogen ion production of +2 for every molecule of N03 produced.

Figure 1.15 Schematic budget of the global nitrogen cycle in preindustrial times (black) and how it changed as a result of human intervention (red). Fluxes are in units of Tg N year and inventories (bold italics) inTg N. The flux estimates are based on Gruber and Galloway (2008).

Brandes, J. A., and Devol, A. H. (2002). A global marine fixed nitrogen isotopic budget Implications for Holocene nitrogen cycling. Global Biogeochem. Cycles. 16, 67.1-67.14. 

Walsh, J. J. (1996). Nitrogen fixation within a tropical upweUing ecosystem Evidence for a Redfield budget of carbon/nitrogen cycling by the total phytoplankton community. J. Geophys. Res. 101 (C9), 20607-20616. 

Alteration of Nitrogen Cycling in the East Asian Region Regional bio geochemical budget approach... 

Xing G. X. and Zhu Z. L., 2002. Regional nitrogen budget for China and its major watersheds. In Boyer E. W. and Howarth R. W. (Eds.), The nitrogen cycle at regional to global scale. Kluwer Academic Publishers, 405-427. 

According to the aim of the study, a data set of soil descriptors of d5mamic properties (Karlen et al, 2001) related to soil quality has been chosen, in conformity with the criteria proposed by Doran and Zeiss (2000). Since the main differences between the two soil management systems are supposed to be the input/output budget of nutritive elements (Intrigliolo et al, 2000) and the improvement of soil organic fertility and of environmentally linked attributes, the soil quality indicators chosen were related to soil carbon and nitrogen cycles (pools and processes) and to the availability of nutrients for the crop. 

---