Submitted to: Acta Horticulturae
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2014
Publication Date: 7/8/2014
Citation: Muramoto, J., Shennan, C., Baird, G., Zavatta, M., Koike, S.T., Bolda, M.P., Daugovish, O., Dara, S.K., Klonsky, K., Mazzola, M. 2014. Optimizing anaerobic soil disinfestation for California strawberries. Acta Horticulturae. 1044:215-220. Interpretive Summary: Soil-borne disease management without chemical fumigants remains a major challenge for strawberry production in California, and modifications to existing regulations are likely to intensify this challenge by further limiting availability of fumigants on a large percentage of strawberry acreage. Anaerobic soil disinfestation (ASD) was developed in Japan and the Netherlands as an alternative to soil fumigation and involves the generation of an anaerobic environment through a combination of flooding and addition of a carbon source to the soil system. Disease control is believed to result from the production certain volatiles that are generated by microorganisms that are active under anaerobic conditions. Anaerobic soil disinfestation has been consistently effective in the control of Verticillium wilt of strawberry when rice bran was used as the carbon input. However, the rates of rice bran required are high (9 ton per acre) and come with potential hazards due to the high nitrogen inputs, and therefore potential loss, associated with this input. Therefore, anaerobic soil disinfestation was conducted using a range of carbon inputs and rates in field trials conducted at multiple sites in California. Lower rice bran rates (6 ton per acre) or rice bran (4.5 ton per acre) plus molasses (4.5 ton per acre) as the carbon input used in ASD was as effective as the high rate of rice bran in controlling disease and increasing strawberry yields. The ASD treatments that included rice bran as a carbon source provided yields that were equivalent to pre-plant fumigation at multiple sites. In future trials, application methods will be modified to optimize ASD for the control of Fusarium wilt.
Technical Abstract: Anaerobic soil disinfestation (ASD), a biological alternative to soil fumigation, can control soilborne pathogens and nematodes in numerous crop production systems. To optimize ASD for California strawberries, a series of field and pot experiments have been conducted since 2003. Overall, ASD treatment was shown to be consistently effective at suppressing Verticillium dahliae and obtaining comparable yield with fumigant control in coastal California when 20t ha-1 of rice bran (RB) was pre-plant incorporated and at least 75mm of irrigation was applied in sandy-loam to clay-loam soils. However, due to economic and high nitrogen application issues associated with use of 20t ha-1 RB, there is interest in examining alternative C sources used in ASD. In the 2012-2013 season, we conducted non-replicated demonstration trials at 4 local farms in which sugarcane molasses (Mol) 20t ha-1 alone or in combination with RB (Mol 10t ha-1 + RB 10t ha-1) were tested. Although Mol has advantages over RB in terms of ease of application and lower N content, the anaerobic condition created by Mol did not last long and split applications were needed. Further, cumulative marketable fruit yield from Mol 20t ha-1 plots were as low as 70% of fumigated controls, whereas RB 20t ha-1 and Mol 10t ha-1 + RB 10t ha-1 plots had similar yields as the control. Lack of effectiveness in Mol-based ASD may be related to uneven distribution of Mol across the bed profile and low soil temperatures at trial sites. We also evaluated the potential for eliminating pre-plant fertilizer application when using RB-based ASD at one site. Pre-plant fertilizer increased fruit yield only ~5%, suggesting a possibility of reducing pre-plant fertilizer at ASD fields. Future studies should examine other C-sources including summer cover crops combined with a low rate of RB or Mol in ASD.