To determine the available nitrogen (N) resource budgets and balance (application minus plant
uptake), we obtained data on inorganic fertilizers and livestock manure from statistical yearbooks for
Japan, the Republic of Korea (hereafter, Korea), and China. Uptake of N via crop production was also
calculated using national nutrient content factors. From the N budget and crop production data, we
calculated the N balance and use efficiencies. Japan used too much N, Korea balanced its use of
inorganic fertilizer but needed to improve when combined with manure use, and China had high
nutrient inputs and outputs in crop yield. To improve nutrient use efficiency and decrease the surplus,
we defined a manure budget based on nationally available N sources, with the goal of using manure
first, followed by inorganic fertilizer. Based on this analysis, Japan should apply inorganic N fertilizer
primarily then use livestock waste N to compensate for a soil N, Korea should develop forage crop
production and build recycling pathways within the country, and China should reduce its excessive use
of N.
Management of N appears to be acceptable and efficient. Japanese and Chinese N resource
budgets and outputs in crop production appear reasonable, but the high N surplus should be decreased
through more efficient use of inorganic N fertilizers. The present results suggest that increasing soil
fertility and improving the use of livestock manure will be the key for sustainability in all three
countries.
These countries has too enough nutrient budget and soil fertility data sets, therefore, they could
manage and control N use. However there would be difficulty to adopte for African countries. I will
touch to future needs for information of nutrient budget approach for enhancing African agriculture.