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upland soil to find out crotalaria's optimal seeding rate. Crotalaria's plant height and number of leaves increased when the harvest time was later regardless of its seeding rate. Its nitrogen content of above-ground part was 19.8 g ha-1, and C/N ratio was 22.5. The highest nitrogen content (50.3 g kg-1) was found in flowers part, followed by its leaves, roots and stems. The green manure yields of crotalaria increased when the harvest time was later. The green manure yield of crotalaria was biggest in 50kg ha-1 which was low in seeding rate. It tended to decrease when the seeding rate was higher, and the nitrogen yield had the same tendency. Therefore, the appropriate seeding rate was 50kg ha-1 and the time for application to soil was considered to be the flowering stage. Key words: Crotalaria, Green manure crops, Nitrogen yield Crotalaria's green manure yield and nitrogen yield were biggest in 50 kg ha-1, and the yield tended to decrease when the seeding rate was higher