Effect of biofumigation and repeated biosolarization on soil fungal communities in pepper crops

Soil disinfestation (SD) with methyl bromide (MB) was a standard practice until its banning in 2005 to control soil-borne diseases and to prevent soil fatigue in pepper crops in Southeast Spain. This effect occurs when SD is not carried out between two consecutive crops in the same soil and it seems to be associated with a build-up of soil fungi at the end of the crop cycle. Alternatives to MB as biofumigation (B) and biosolarization (biofumigation with solarization, BS) were deeply studied since then. The effects of and the repetition of BS in the same plots with a gradual decrease in the amount of applied manure (a mixture of fresh sheep and chicken manures) were evaluated at two different locations during one and three years respectively. Soil fungal density was estimated in each plot before and after treatments where Aspergillus spp., Fusarium spp., Penicillium spp. and Rhizopus spp. were systematically present and clearly reduced after SD. B and BS reduced fungal density to the same extent as MB though no treatment eliminated them. The progressive reduction of manure applied did not lead to a lower efficacy than MB.