Effects of Brassicaceae Seed Meal Incorporation on Pre-plant Weed Emergence and Strawberry Productivity in Macrophomina Phaseolinainfested and Non-infested Soil

Field and greenhouse trials were conducted to assess the effects of Brassicaceous seed meals on weed growth and infectivity toward strawberry of the pathogen Macrophomina\ud phaseolina, the causal agent of charcoal rot disease in strawberry cultivation. In a field\ud trial, I assessed the effect of soil amendment with high-glucosinolate (303 Ilmole g-l)\ud Brassicajuncea seed meal (BjSM) (6.75 t ha-1) on weed emergence prior to strawberry\ud planting, on fruit and shoot biomass yield, and on levels of M. phaseolina in the soil and\ud in roots as determined by quanitative-PCR and a root plating assay. Whereas there was\ud no major evidence of disease suppression or improvement of fruit production in amended\ud soils, pruned biomass at the end of the fruiting season was higher in soils that contained\ud BjSM regardless of disease presence. In a greenhouse trial, fruit production and biomass\ud were significantly higher in anaerobic digestate amended soils irrespective of the\ud presence of BjSM or the pathogen. Weed biomass assessed in the field trial was\ud significantly lower in all soils that were treated with BjSM. Significant suppression of\ud weed emergence was similarly observed in a second year field trial in which composted\ud digestate (45 t ha-1) and a 1: 1 mixture of BjSM and Sinapis alba seed meal (15 t ha-1)\ud were incorporated into the soil at 19 weeks and 4 weeks prior to planting, respectively.\ud M. phaseolina DNA levels in experimental soils were found to be several orders of\ud magnitude higher than those found in commercial agricultural soils. These results\ud demonstrate that the incorporation of Brassicaceaous seed meals into soils controls pre-plant\ud weed emergence but did not prevent M. phaseolina infection of strawberry, perhaps\ud due to the extremely high density of the pathogen in the field site soil.California Strawberry Commission; Harmony Farm Supply and Nursery; the Laguna Treatment Plan