Bacterial bio surfactants stimulate the growth of beans and improve foliar-treated Fe absorption

Due to the eco-systemic hazardous effects of surfactants, biosurfactants are recommended as wetting agents to increase the efficiency of foliar application of nutrients. Moreover, some of them could act as plant growth promoting agents. The aim of the present study was to assess the biosurfactant effect on iron foliar nutrition and its effects on bean growth. Biosurfactant production was investigated in seven Bacillus isolates from compost. Among them, B. nealsonii 104C, with the ability to produce glycolipid biosurfactant, was selected for the greenhouse study. Three concentrations of Fe, including zero, one, and two percent, and two levels of biosurfactant (zero and 50 mgL-1) were tested in a factorial experiment with a randomized complete block design on the bean plants growing hydroponically. The results showed that foliar application of iron without adding biosurfactant at one and two percent concentrations increased the plant yield by 2.08 and 2.8 times, respectively. Zero, one, and two percent iron plus biosurfactant increased the yield up to 4, 3.3, and 4.2 times compared to the control. The highest bean height, total dry weight, leaf and stem weight, and number of pods were observed in the biosurfactant treatment plus 2% iron. It seems that biosurfactants could be used in the bean plant organic farming as an iron transition facilitator via foliar application or as a plant growth stimulator.