Effect of Sodium Selenate Supplied Condition by Fertigation on the Growth and Content of Minerals, Ascorbic acid, Nitrate, and Selenium of Some Western Vegetables

This study was conducted to investigate the proper supplied conditions of sodium selenate supplied by fertigation to improve functionality of major western vegetables; beet, broccoli, cabbage lettuce, celery, and parsley in highland. In this work, the growth and content of minerals, ascorbic acid, nitrate, and selenium were measured in western vegetables that treated sodium selenate by different concentration, treatment time and treatment frequency. While there was not different in early growth of some western vegetables among different concentration of sodium selenate; 1, 2, 5 and 20 mgㆍL-¹, at 20 days after treatment, the fresh weight was reduced 33% at cabbage lettuce, 47% at broccoli, and 74% at parsley compared control in 5 mgㆍL-¹ treatment. But the fresh weight of beet and celery reduced just 20% and 15% compared control in even 20 mgㆍL-¹. The ascorbic acid of cabbage lettuce, celery, and beet increased as sodium selenate concentration increased, so that of cabbage lettuce showed 1.2 times compared control in 20 mgㆍL-¹ treatment and also that of beet and celery increased 10%. But the ascorbic acid of broccoli and parsley was not influenced by treated sodium selenate. As the concentration of sodium selenate increased, the nitrate contents decreased regardless of crops compared control. This reduced effect of nitrate was highest in cabbage lettuce, followed by beet and celery. The mineral contents, such as K, Ca, and Mg, decreased in all crops, as the concentration of sodium selenate increased. The potassium content showed an obvious negative correlationship with the concentrations of sodium selenate regardless of crops, but the magnesium and calcium content did not show significant difference between treatments. The selenium content increased in proportion as increasing sodium selenate concentrations. The broccoli, celery and parsley treated 20 mgㆍL-¹ sodium selenate showed 24.4 times, 76.4 times, and 560 times higher than control, respectively. When the sodium selenate supplied to some western vegetables in different growth stage, the selenium content increased 1.3 times and 1.4 times higher in early stage than in late stage in cabbage lettuce and broccoli, respectively. However in parsley and celery, the selenium content showed the highest in middle stage. The selenium content increased in proportion as increasing the sodium selenate treatment frequency, but in above 10 times treatment, the increased effect alleviated in parsley, celery, and cabbage lettuce. On the contrary, the selenium content of broccoli increased constantly as treatment frequency increased.