In this study, we estimated the appropriate nitrogen (N) recommendations of cucumber by evaluating the effects of soil incorporation of rye (Secale cereal L.) as a green manure crops on the growth and yield of cucumber under the greenhouse condition showing two different soil nitrate N levels. One, soil nitrate-N content before the experiment was 60 mg kg -1 , carried out in 2012 and the other showing a 227 mg kg -1 level was conducted in 2013. Six different N treatments were used as follows: No N fertilizer, rye, rye with urea 0.5 N, 0.75 N, and 1.0 N, and urea 1.0 N. The amount of N supply from soil incorporation of rye was 146 kg ha -1 in 2012 and 107 kg ha -1 in 2013. When soil nitrate N content before the experiment was 60 mg kg -1 , the growth and yield of cucumber did not differ between the rye + urea 0.5 N and the urea 1.0 N, which can reduce 50% of N fertilizer recommendation. In case of soil nitrate N content before the experiment was 227 mg kg -1 or beyond, no N fertilization can be recommended because there were no significant differences in the growth and yield of cucumber among all treatments including the rye. Lastly, when soil nitrate N content before the experiment was within range of 227 -60 mg kg -1 , N recommendations can be calculated through the equation Y = -3.34X + 227 (X: % of N recommendations, Y: soil nitrate N content). However, further studies on the relationship between soil nitrate N content and yield of cucumber are required.