Effects of nitrogen forms and levels on the foliar nitrate-nitrogen contents of komatsuna (Brassica rapa L. var. pervidis Bailey) in hydroponics
2005
Mitsushio, H.(Saga Univ. (Japan). Faculty of Agriculture) | Nakahara, T. | Someya, T. | Inoue, K.
To produce Komatsuna (Brassica rapa L. var. pervidis BAILEY) with low nitrate content in hydroponics, the effects of the use of urea as a partial substitute of N03-N in media and low nitrogen concentration in media on the foliar nitrate contents were examined. 1.The partial substitution of N03-N by urea (6.50 mM urea and 1.50mM N03-N) in a medium reduced the N03-N content of the plant cultivated for 16 days after transplanting down to 77% of that of the control (7.00 mM N03-N and 1.00 mM NH4-N). Furthermore, the plants cultivated as above, transplanted in nitrogen-free solutions and grew for additional four days showed a reduced content of N03-N (22-28% of the control) and possessed a similar satisfactory appearance, though the final plant weight was smaller than that of the control. 2. Foliar N03-N content of the plant cultivated for 16 days after transplanting decreased down to 61 % of the control by cultivating in a medium containing reduced total nitrogen (3.50mM N03-N and 0.50 mM NH4-N) and further decreased to 23 % (6.17 mg/g dry weight) by the successive four days cultivation in a nitrogen-free medium containing trace elements only. It is noteworthy that the final dry weight of the plant of this treatment was almost equal to that of the control. These results suggest that Komatsuna with low nitrate content and good appearance can be produced by the partial substitution of N03-N by urea or by the use of relatively low nitrogen concentration media, followed by cultivation in nitrogen-free media for several days.
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