This study examined the effect of factory and slaked lime, cruciferous plants, poultry, liquid swine and liquid cattle manure on infection of soilborne pathogens, especially Aphanomyces spp., on sugarbeet and spinach in greenhouse and field experiments. Soil samples collected from infected fields were brought to the laboratory and used for current greenhouse experiments. Lime or manure were mixed with soil, filled into plastic pots and sown with sugarbeet or spinach seeds. After four weeks the infections of the plants were assessed by using a disease severity index (DSI). The study did also investigate how different placements of lime in soil effected soilborne pathogens, and how soil pH was affected by different lime applications.
The field experiments were carried out in 2003 on spinach fields at two commercial farms in southern Sweden. In late July, two weeks before seeding, liquid manure (swine, 20 ton/ha; cattle, 40 ton/ha) were applied and cultivated with a harrow or a plough. On one experimental site were cruciferous plants grown as precrop. Moving of the cruciferous plants was done about a week prior to tillage. The effect of the treatments on the infection of the soilborne pathogens was determined by counting the plant appearance in two occasions and by assessment of a disease severity index of the roots. Cattle manure reduced root rot the most and lowered the DSI from 40 to 30, but swine manure and cruciferous plants had also good effect on soilborne pathogens in the field experiment. Both plant appearance and spinach yield were benefited by cattle and swine manure.
All organic amendments and lime treatments suppressed the severity of root rot in the experiments. Liquid swine manure lowered the DSI in sugarbeet between 12% to 34% in the greenhouse experiments and the plants fresh weight increased with up to 239%. Six ton slaked lime per hectare had best effect on soilborne pathogens among the lime treatments and reduced the DSI up to 21% compared to the control. The limes placement in soil turned out to be of great importance on the effect of soilborne pathogens. According to this study should lime be applicated below seed depth for best effect against the soilborne fungi. The effect on soil pH by different lime applications was measured during 72 days. Slaked lime and factory lime increased the soil pH several pH units during the first days, which creates an unfavour...
