T. Shimomachi, Y. Kawahara, C. Kobashigawa, E. Omoda, K. Hamabe, K. Tamaya
In this study, the effect of residual salinity in polder soil on plants was investigated, in order to develop a value-added plant production method. Spinach plants were subjected to a saline environment by adding diluted artificial seawater to the soil of reclaimed land with 23.5 g m-2 ammonium sulfate at NaCl conversion concentrations of 0, 0.05 and 0.10 mol L-1. Diluted seawater equal to the amount of the maximum water holding capacity of the soil was added to the soil three weeks after germination. Afterward, the moisture content of the soil was maintained at about 40% during the experiment. The plants were harvested 4 weeks after starting the saline treatment. The growth of the plants, measured by parameters such as leaf width and number of leaves, was almost the same, and the fresh weight of both shoots and roots increased compared to the control plants at NaCl treatment concentration of 0.05 mol L-1. Na ion in spinach increased with increase in NaCl treatment concentration, but K, Ca, Mg and Fe ions showed little change. Spinach grown in polder soil contained a large amount of cations, soluble saccharide, L-ascorbic acid and polyphenol compared with field cultivated spinach. Essential amino acid content increased with increase in NaCl concentrations compared with the control. It is well known that the effect of γ-amino butyric acid (GABA), an inhibitory neurotransmitter in humans, has physiological functions such as relaxation, increasing immunity and reducing blood pressure. Spinach cultivated in polder soil contained extremely large amounts of GABA, about 200 times compared with field cultivated spinach regardless of NaCl treatment concentration. Nitrate ion and oxalic acid ion decreased at NaCl concentrations of 0.05 and 0.10 mol L-1 and that nitrate ion level was less than EU standards (250 mg/100 gfw harvested 1 April to 31 October and 300 mg/100 gfw harvested 1 November to 31 March). In conclusion, experimental results showed that spinach plants cultivated under the appropriate residual salinity in polder soil might have potential to increase the amount of production and nutrients and to decrease components harmful to humans at same time.
Shimomachi, T., Kawahara, Y., Kobashigawa, C., Omoda, E., Hamabe, K. and Tamaya, K. (2008). EFFECT OF RESIDUAL SALINITY ON SPINACH GROWTH AND NUTRIENT CONTENTS IN POLDER SOIL. Acta Hortic. 797, 419-424
DOI: 10.17660/ActaHortic.2008.797.60
controlled environment agriculture, polder soil, residual salinity, high quality spinach

Acta Horticulturae