Ultrafine bubbles effectively enhance soybean seedling growth under nutrient deficit stress

Ultrafine bubbles (UFBs) exhibit a number of unique physical characteristics; however, reports on plant growth enhancement by UFB application are controversial. Here, we report experiments conducted to test whether UFB technology effectively promotes plant growth. We analyzed the effects of three experimental factors: water (UFB addition), hypoxia (aeration), and fluid movement (stirring) on the growth of soybean seedlings cultured hydroponically under low and high nutrition levels in a controlled environment room under artificial lighting for 8 days. When no nutrients were supplied, positive UFB water effects were evident, but low nutrition reduced UFB water-mediated growth enhancement and high nutrition totally obliterated any growth enhancement by UFB water. We concluded that UFB water-induced growth enhancement was effective and significant under nutrient deficit stress but no growth enhancement was observed, and even negative effects were evident, under favorable plant growth conditions.