The nitrogen cycle in Khon Kaen province was estimated using Thai agricultural statistics, study reports of food consumption and human excreta discharge, animal feed consumption and animal excrement production, survey data on the utilization of crop residues, human excreta, garbage, animal excrement and food factory (rice mill, sugar mill, cassava chips and starch) waste, measurement data of crop residue production and nitrogen content of crop residues, animal excrement and food factory waste, and journal articles on N2 fixation and nitrogen losses from farmland.
Fig. 1 Nitrogen cycle-related to agriculture activity in 1990-92 and 2000-02 in Khon Kaen Province, Thailand (kg N ha-1 year-1). Values outside parentheses indicate nitrogen flow in 2000-02, and values inside parentheses indicate nitrogen flow in 1990-92. Values in italics are calculated by subtracting output from input.