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2.Influences of Compost and Organic Fertilizer on the Concentrations of Nitrate, Sugar, Ascorbic Acid and β-Carotene in Komatsuna (Brassica campestris L. rapifera group)

Shoji Nakagawa1, Hideharu Yamamoto2, Yuki Igarashi2, Yuriko Tamura1, Kiyoko Yoshida3 (1 Institute for Agro-Microbiology 2 Japanese Federation of MOA Nature Farming Branch Cooperatives 3 Kagawa Nutr. Univ.)

Amounts of nutritional constituents accumulated in komatsuna, which were grown under the applications of chemical fertilizers (CF) or organic fertilizers (OF, rice bran + okara) in virgin soils (VS) and soils in which composts had been applied for 12 y (CAS), were measured. The amounts of fertilizer applied was adjusted to give the same growth range of komatsuna for all treatments.

1) Nitrate concentrations of komatsuna grown in CAS were higher, and 0.8m3m-3 ethanol soluble total sugar (TS) concentrations tend to be lower than those grown in VS. In case of VS, nitrate concentrations of komatsuna grown under OF applications tend to be higher than those grown under CF applications, but in case of CAS, those grown under OF applications tend to be lower than CF applications. After 6 d of preservation, nitrate concentrations of komatsuna grown in CAS were higher, and total ascorbic acid (AS) and TS concentrations tended to be lower than those grown in VS.

2) Strong negative correlations were found in between nitrate concentrations and both of AS and TS concentrations.

3) The nitrate concentrations of komatsuna were determined by the nitrate concentrations in the soils, but in VS, they were also influenced by chloride concentration. Relatively high nitrate concentrations of the OF applied komatsuna in VS is due to low concentration of chloride in VS and OF.

4) There results indicate that the application of organic fertilizers and composts does not always improve the nutritional constituents of komatsuna, and the concentration of chloride in organic fertilizers and composts as well as soils may need to be considered in organic farming.

Keywords: komatsuna, compost, organic fertilizer, nutritional constituents, chloride