1996 Volume 65 Issue 2 Pages 327-332
Effects of nitrate concentrations and the ratio of NO3-: NH4+ in nutrient solutions on the oxalate content of spinach (Spinacia oleracea L. cv. Shoryoku) leaves were examined Solutions containing 0 to 100 ppm of NO3- were used to grow the plants. When the ni trate level of nutrient solutions was lower than 10 ppm, plants grew poorly and the total nitrogen and oxalate contents of the leaves were low.
When grown on the solutions containing different ratios of NO3- : NH4+, the total and watersoluble oxalate contents decreased as the ratio was decreased. The effects of different nitrogen sources and concentrations on the growth of plants varied depending on the seasons of the year. Generally when the ratio exceeded 1 : 3 (75% NH4+), plant growth was depressed. However, when the ratio was less than 3 : 1 (25% NH4+), the plants grew well. Thus, the oxalate content of spinach leaves can be reduced without depressing plant growth.