Band-steaming a new solution for seedbank depletion in low competitive vegetables.

Weed competition is a major problem in organic agriculture, because the use of herbicides is prohibited. Vegetable crops are generally the most sensitive from this point of view, especially the sown ones, because they often need plenty of time for emergence. This often implies a large effort for hand weeding in the rows, which are very difficult to be treated physically in a selective way. Soil steaming could be a possible solution for preventive weed control/weed seedbank depletion in organic/integrated low-competitive vegetable crops, in order to reduce labor time for in-row hand-weeding. The effect of bioflash system (consisting in the distribution of steam and CaO) on weed seedbank was “exploited” to develop a new machine for “band-steaming”. In this case, steaming is performed just in strips, where the crop will be successively sown. Each strip corresponds to one crop row. The machine is drawn and is equipped with a water tank, a hopper containing the exothermic compound (CaO) and an industrial steam generator providing an outflow of about 1300 kg h-1. The steam generator unit is connected to a 5.10 m wide, PTO-driven rotary cultivator with 12 units. Each unit is connected to a steam pipe and is characterized by the rotating tool and a carter which bears the steaming bar. The tested working speed ranged from 0.2 to 0.5 km h-1. The steam injection is superficial in order to kill the weed seeds till a depth of about 5 cm. The prototype has been tested on carrot in four organic farms spread throughout Italy. The results are encouraging as the soil temperature peak was about 80 °C and the weed emergence reduction, 10 days after planting, ranged on average from 70% up to over 90%. On average the 50% of labour demand for hand weeding was saved (about 200 h ha-1). However the machine needs to be improved in order to make the steam injection more efficient and this treatment more sustainable (more effective and cheaper).