Effects of band-steaming on microbial activity and abundance in organic farming soil

Band-steaming of arable soil at 80–90 °C kill off weed seeds prior to crop establishment which allows an extensive intra-row weed control. Here we evaluated the side-effects of in situ band-steaming on soil respiration, enzyme activities, and numbers of culturable bacteria and fungi in an organic field soil. The results showed that mechanical disturbance created by band-steaming could be neglected as a mediator of microbial changes. Also, soil pH and water content was unaffected by band-steaming. Effects of band-steaming on in situ soil respiration and basal respiration, respectively, were insignificant or slightly stimulatory (P < 0.05). Fluorescein diacetate hydrolysis and arylsulfatase activity were significantly (P < 0.001) inhibited by 25 and 38%, respectively, and only showed weak recovery during 90 days after band-steaming. Bacterial colony-forming units increased after soil steaming whereas the number of fungal propagules was reduced by 50% (P < 0.001). This reduction persisted at a level of 38% after 90 days (P < 0.001). Evaluated in relation natural environmental stresses, band-steaming showed ecologically tolerable short-term effects, but with weaker recovery potential and therefore possible long-term effects. However, band-steaming affects only a minor volume of the plough layer (<10%) and long-term effects may be minimal due to annual tillage (mixing) of the soil. In conclusion, the side-effects on soil microbiology may not disqualify band-steaming as an option in organic farming systems.