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ARS Home » Pacific West Area » Wenatchee, Washington » Physiology and Pathology of Tree Fruits Research » Research » Publications at this Location » Publication #320454
Title: Carbon source and irrigation evaluation for anaerobic soil disinfestation in southern California

Author
item DAUGOVISH, OLEG - University Of California - Cooperative Extension Service
item SHENNAN, CAROL - University Of California
item MURAMOTO, JOJI - University Of California
item Mazzola, Mark

Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: 9/27/2016
Publication Date: 11/7/2015
Citation: Daugovish, O., Shennan, C., Muramoto, J., Mazzola, M. 2015. Carbon source and irrigation evaluation for anaerobic soil disinfestation in southern California. International Conference on Methyl Bromide Alternatives and Emissions Reductions. p. 12.1-12.3.

Interpretive Summary:

Technical Abstract: Water use efficiency and utilization of feasible carbon sources have been important factors for successful implementation and adoption of ASD in California and are the focus of current research. In the 2014-15 study at Santa Paula, CA we compared ASD with 9 t of rice bran bed-incorporated with either delaying irrigation for one week (ASD 1 wk delay), without irrigation (ASD w/o water) or immediate irrigation with 1,480m3/ha = 3 acre-feet (ASD reg). Glycerin was use as liquid carbon source treatment, and applied at 4% by volume via three drip lines per bed as a one-time injection. A no treatment control was included in this RCBD experiment with four replications. Delaying or avoiding irrigation would allow sufficient time for field irrigators to connect and check all drip lines, potentially minimizing water loss, thus making ASD application more user-friendly. Soil at the site was silty clay loam with pH 7.3 and ECe 0.7 dS/m. All three rice bran treatments induced strong anaerobic conditions which persisted for at least four weeks surpassing 120,000 cumulative Eh mV hours of anaerobiosis, more than twice the threshold previously developed for control of soil-borne pathogen Verticillium dahliae. Glycerin-based ASD created very strong anaerobic conditions in soil but only for three days after application and resulted in about 70,000 Eh mV cumulative hours. At this study site, significant soil-borne disease development or strawberry mortality were not observed. However, during the first three months after planting rice bran based ASD treatments reduced weed populations nearly 90% (mostly common lambsquarters, annual sowthistle and burning nettle), while glycerin treatment did not reduced weed density relative to the no treatment control. Plant performance was similar among ASD reg, ASD w/o water and ASD 1 wk delay treatments and improved early marketable fruit production compared to the control 100-118% (Figure 1). Glycerin treatment had no significant effect on early production (Dec 2014-Jan 2015) but provided yield improvement from February to May and 46% yield increase for the whole season (Figure 1). Delayed plant response to glycerin treatment is likely due to distribution of the glycerin solution near and below the drip lines used for application, a region of the soil profile not reached by strawberry roots during the first 2-3 months after planting. In contrast, rice bran was uniformly distributed throughout the bed profile, which resulted in immediate root contact with treated soil and accelerated plant growth and fruit production (data not shown). Even at the end of the growing season (June 2015), ten months after incorporation the following effects of rice bran on soil were observed: a) lower bulk density compared to untreated and glycerin treatments. b) lower ECe (measure of salinity) than in untreated and glycerin treatments (likely due to differences in infiltration and leaching). c) 30-35% greater volumetric water content at 8-16 cm soil depth at tensions from 0-80 CB, compared to untreated, indicating greater water holding capacity. d) 180 ppm residual Olsen P205 at 0-30cm (12 inch) soil profile in planting holes compared to 78 and 71 ppm in untreated and glycerin treatments, respectively. e) Similarity of microbial communities among all treatments with rice bran, which were distinctly different from those observed in control and glycerin treatments. The differential effects of carbon sources and application methods on physical, chemical and microbiological properties of soil have been also observed in other trials (data not shown) and emphasize the complex and interactive nature of changes in soil that lead to successful ASD. This study also showed that at least in clay loam soil, moisture at bedding may be sufficient for ASD and growers may save water and associated expenses, provided soil paramet